Ashrae rp 1301 quantification of ventilation effectiveness

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2. 1 Quantification of Ventilation Effectiveness for Air Quality Control in Plant and Animal Environments (ASHRAE RP 1301) FINAL REPORT0F0F0F0F 1 For American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc (ASHRAE) 1791 Tullie Circle, NE Atlanta, GA 30329-2305 Submitted by Xinlei Wang, PhD, Associate Professor Yuanhui Zhang, PhD PE, Professor Department of Agricultural and Biological Engineering University of Illinois at Urbana-Champaign 1304 W Pennsylvania Ave Urbana, IL 61801 August, 2008 1 The contents of this report are also included in a PhD Dissertation submitted to the Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign.

3. 2 Quantification of Ventilation Effectiveness for Air Quality Control in Plant and Animal Environments (ASHRAE RP 1301) By Xinlei Wang, Yuanhui Zhang and Sheryll Jerez EXECUTIVE SUMMARY Ventilation effectiveness refers to the efficiency of a ventilation system to provide fresh air to the occupants, and dilute and remove internally generated contaminants. In ASHRAE Standard 62, it is defined as the fraction of outdoor air delivered to the space that reaches the occupied zone. Standard 62, however, does not contain practical information on how to evaluate and measure the ventilation effectiveness of the system. Other researchers have developed and evaluated ventilation effectiveness measurement procedures applicable to ventilated airspaces. These methods, however, are applicable mainly for researchers, usually require sophisticated instrumentation, and are labor intensive. There is a lack of practical and economical methods that researchers and field engineers can use to quickly determine the effectiveness of a ventilation system. ASHRAE initiated this project to address the need to develop practical and economical measurement procedures to evaluate the ventilation effectiveness applicable for mechanically ventilated animal buildings. Our approach in accomplishing this main objective involved three tasks: examination of the available methods and procedures for quantifying the ventilation effectiveness, conducting laboratory experiments to determine how the ventilation parameters (i.e., types of ventilation system, level of ventilation rate, location of pollutants source) affected the ventilation effectiveness factor, and conducting field measurements to verify the practicality and applicability of the chosen method in a swine building. Our extensive literature review on the subject-matter was published in ASHRAE Transactions. From our literature review, the direct measurement of pollutants (particles and gases) was more applicable in animal building applications as opposed to using tracer gases. Using the tracer methods (tracer step-up, step-down, and pulse methods) would be difficult due to large areas of floor space, presence of unwanted openings, and the presence of several supply and outlet locations in animal buildings. The ventilation effectiveness index that was found to be more applicable in animal buildings was the contaminant removal effectiveness. The laboratory experiments confirmed the results of other researchers on the non-uniform spatial distribution of pollutants indoors. The type of ventilation system affected the spatial distribution of contaminant concentrations (total suspended particulate matter or TSP, and carbon dioxide), but not the average concentration in the room. The ventilation rate, however, did not substantially alter the spatial distribution of the pollutants, but it did significantly affect the average concentration. The location of the source also has a significant effect on the average

4. 3 concentration of pollutants in the room. Thus, in using the contaminant removal factor to evaluate the ventilation effectiveness, the choice of sampling locations would be an important factor in the measurement. Field experiments were conducted in a wean-to-finish commercial swine building with a tunnel- ventilation system during winter and summer seasons. The results of the experiments showed that the spatial gradient of pollutants differ between these two seasons, due to different airflow patterns in the building. Consequently, the sampling locations to evaluate the contaminant removal effectiveness would be different in winter and summer. During the winter, the sampling locations spread out crosswise within the building yielded a more representative pollutant concentration for the building. During the summer, the sampling locations were shown to best be spread out lengthwise within the building to obtain more meaningful estimates of the pollutant concentrations. From the literature review, we concluded that the contaminant removal indices are the most applicable methods for animal building applications. There are two indices to evaluate the ventilation effectiveness: the average contaminant removal effectiveness and the local contaminant removal effectiveness. Theoretically, these indices can be obtained by measuring these three contaminant concentrations: Ce in the exhaust air, Cs in the supply air, and Cp’s at the locations of interest, such as the worker’s breathing zone. The pulse tracer method and direct measurements of contaminants generated in the building can be applied to measure these concentrations and then calculate the indices. In real building applications, the evaluation of the ventilation effectiveness for the entire room involves measurements from at least three and up to more than ten sampling locations. The experimental data in the lab and in the field showed a high variability of concentration by sampling locations, which suggests that the conclusion that can be drawn from single or two- point location measurements will be highly suspect. It may not be impossible, but could be difficult and costly to measure the contaminant concentrations at multiple points, such as the 30- 50 points in this study. However, the number and location of the sampling points can be reduced to a minimum, if prior data on the spatial distribution of gaseous and particulate contaminants are available. The results of this research provide some recommedations for sampling strategies if a limited number of sampling locations are desired. The ventilation effectiveness in animal buildings can be determined by measuring the concentrations of particulate matter and gases at selected locations inside the building, upstream of the exhaust fans, and at the air inlet. A general guideline for measuring ventilation effectiveness in animal buildings is developed from this project (Appendix A), which defines the sample size (number of samples), the sampling location and frequency, and the sample handling. More sampling points are better than few points. It is shown that the sample size has an effect on the calculation of ventilation effectiveness (Appendix B). It is recommended that the specific sampling method should be decided by the users according to this guideline based on the availability of instruments and cost.

5. 4 TABLE OF CONTENTS 0H0H0H0HEXECUTIVE SUMMARY .......................................................................................64H64H64H64H2 1H1H1H1HTABLE OF CONTENTS...........................................................................................65H65H65H65H4 2H2H2H2HLIST OF FIGURES ...................................................................................................66H66H66H66H7 3H3H3H3HLIST OF TABLES...................................................................................................67H67H67H67H11 4H4H4H4HCHAPTER 1 – INTRODUCTION..........................................................................68H68H68H68H13 5H5H5H5H1.1 BACKGROUND.......................................................................................................................69H69H69H69H13 6H6H6H6H1.2 OBJECTIVES AND APPROACH............................................................................................70H70H70H70H13 7H7H7H7H1.3 ORGANIZATION OF REPORT ..............................................................................................71H71H71H71H14 8H8H8H8HCHAPTER 2 – LITERATURE REVIEW...............................................................72H72H72H72H15 9H9H9H9H2.1 INTRODUCTION.....................................................................................................................73H73H73H73H15 10H10H10H10H2.2 EXISTING VENTILATION EFFECTIVENESS CRITERIA..................................................74H74H74H74H16 11H11H11H11H2.2.1 Indices for Room Air Renewal..............................................................................................75H75H75H75H17 12H12H12H12H2.2.2 Indices for Contaminant Removal.........................................................................................76H76H76H76H19 13H13H13H13H2.3 MEASUREMENT TECHNIQUES...........................................................................................77H77H77H77H21 14H14H14H14H2.3.1 Tracer Step-Down Method....................................................................................................78H78H78H78H22 15H15H15H15H2.3.2 Tracer Step-Up Method.........................................................................................................79H79H79H79H23 16H16H16H16H2.3.3 Pulse Method.........................................................................................................................80H80H80H80H24 17H17H17H17H2.3.4 Particle Concentration Measurement ....................................................................................81H81H81H81H24 18H18H18H18H2.4 APPLICABLE VENTILATION EFFECTIVENESS INDEX AND MEASUREMENT METHODS .............................................................................................................................................82H82H82H82H25 19H19H19H19H2.5 CONCLUSIONS .......................................................................................................................83H83H83H83H26 20H20H20H20HCHAPTER 3 – LABORATORY EXPERIMENTS ................................................84H84H84H84H27 21H21H21H21H3.1 INTRODUCTION.....................................................................................................................85H85H85H85H27 22H22H22H22H3.2 EXPERIMENTAL DETAILS...................................................................................................86H86H86H86H27 23H23H23H23H3.2.1 Room Ventilation Simulator .................................................................................................87H87H87H87H27 24H24H24H24H3.2.2 Dust Generation and Distribution System.............................................................................88H88H88H88H30 25H25H25H25H3.2.3 Carbon Dioxide Generation and Distribution System...........................................................89H89H89H89H35 26H26H26H26H3.2.4 Temperature Measurement....................................................................................................90H90H90H90H35

6. 5 27H27H27H27H3.3 EFFECT OF THE VENTILATION SYSTEM AND VENTILATION RATE ON THE SPATIAL DISTRIBUTION OF TSP .....................................................................................................91H91H91H91H36 28H28H28H28H3.3.1 Experimental Setup ...............................................................................................................92H92H92H92H36 29H29H29H29H3.3.2 Dust Sampling System and Measurement Procedure............................................................93H93H93H93H40 30H30H30H30H3.3.3 Experimental Design.............................................................................................................94H94H94H94H43 31H31H31H31H3.3.4 Results and Discussion..........................................................................................................95H95H95H95H44 32H32H32H32H3.4 EFFECT OF THE VENTILATION SYSTEM AND VENTILATION RATE ON THE SPATIAL DISTRIBUTION OF CO2 .....................................................................................................96H96H96H96H58 33H33H33H33H3.4.1 Experimental Setup ...............................................................................................................97H97H97H97H58 34H34H34H34H3.4.2 Carbon Dioxide Concentration Measurement and Sampling Procedure...............................98H98H98H98H58 35H35H35H35H3.4.2 Calibration of the Carbon Dioxide Sensors...........................................................................99H99H99H99H60 36H36H36H36H3.4.3 Leak Test...............................................................................................................................100H100H100H100H62 37H37H37H37H3.4.4 Experimental Design.............................................................................................................101H101H101H101H63 38H38H38H38H3.4.5 Results and Discussion..........................................................................................................102H102H102H102H64 39H39H39H39H3.5 EFFECT OF THE SOURCE LOCATION ON THE SPATIAL DISTRIBUTION OF THE TSP AND CO2 CONCENTRATIONS...........................................................................................................103H103H103H103H73 40H40H40H40H3.5.1 Experimental Design.............................................................................................................104H104H104H104H73 41H41H41H41H3.5.2 Results and Discussion..........................................................................................................105H105H105H105H73 42H42H42H42H3.6 COMPARISON OF THE CONTAMINANT REMOVAL EFFECTIVENESS OF THE VENTILATION SYSTEMS...................................................................................................................106H106H106H106H78 43H43H43H43H3.7 CHAPTER SUMMARY AND CONCLUSIONS.....................................................................107H107H107H107H80 44H44H44H44HCHAPTER 4 – FIELD EXPERIMENTS ................................................................108H108H108H108H82 45H45H45H45H4.1 INTRODUCTION.....................................................................................................................109H109H109H109H82 46H46H46H46H4.2 EXPERIMENTAL DETAILS...................................................................................................110H110H110H110H82 47H47H47H47H4.2.1. Facility and Sampling Locations...........................................................................................111H111H111H111H82 48H48H48H48H4.2.2. Dust Sampling System ..........................................................................................................112H112H112H112H86 49H49H49H49H4.2.3. Ammonia Sampling System..................................................................................................113H113H113H113H89 50H50H50H50H4.2.4. Measurement of Temperature Spatial Distribution...............................................................114H114H114H114H90 51H51H51H51H4.2.5. Measurement of Ventilation Rate, Air Velocity, and Airflow Pattern..................................115H115H115H115H90 52H52H52H52H4.2.6. Data Analyses........................................................................................................................116H116H116H116H91 53H53H53H53H4.3. RESULTS AND DISCUSSIONS .............................................................................................117H117H117H117H91 54H54H54H54H4.3.1. Ventilation Rates...................................................................................................................118H118H118H118H91 55H55H55H55H4.3.2 Spatial Distribution of Indoor Temperature and Air Velocity ..............................................119H119H119H119H94 56H56H56H56H4.3.3 Spatial Variation of the TSP Mass Concentration.................................................................120H120H120H120H97

7. 6 57H57H57H57H4.3.4 Temporal Variation in the TSP Mass Concentration ..........................................................121H121H121H121H107 58H58H58H58H4.3.5 Spatial Variability of the Ammonia Concentration.............................................................122H122H122H122H113 59H59H59H59H4.3.6 Temporal Variation in Ammonia Concentration.................................................................123H123H123H123H121 60H60H60H60H4.3.7 Emission of Airborne Particulate Matter ............................................................................124H124H124H124H121 61H61H61H61H4.4 CHAPTER SUMMARY AND CONCLUSIONS...................................................................125H125H125H125H126 62H62H62H62HCHAPTER 5 – RECOMMENDATIONS............................................................. 126H126H126H126H128 63H63H63H63HREFERENCES...................................................................................................... 127H127H127H127H130 APPENDIX A: Guideline for Measuring Ventilation Effectiveness in Animal Buildings ……136 APPENDIX B: Effect of Sample Size on the Calculation of Ventilation Effectiveness ………140

8. 7 LIST OF FIGURES Figure 3-1. Room ventilation simulator....................................................................................28 Figure 3-2. Schematic of the full-scale test room location and configuration..........................29 Figure 3-3. Schematic of the air delivery and measurement systems (Wang, 2000). ..............30 Figure 3-4. Dust generator........................................................................................................31 Figure 3-5. Top view of the dust distribution system used for uniform dust source generation inside the test room................................................................................................32 Figure 3-6. Top view of the dust distribution system used for concentrated dust source generation inside the test room ..............................................................................32 Figure 3-7. Particle size distribution (PSD) curves of (a) all-purpose wheat flour and (b) swine dust...............................................................................................................34 Figure 3-8. Carbon dioxide generation system.........................................................................35 Figure 3-9. Elevation view of the ventilation system setup A (not drawn to scale).................36 Figure 3-10. Front view of the outlet covered with a plastic shutter (encircled).......................37 Figure 3-11. The perforated wall inlet used in ventilation system B. The outlet is on the opposite endwall. .............................................................................................38 Figure 3-12. Comparison of the air velocity distribution in the (a) tunnel-ventilated swine building when two exhaust fans were on and (b) test room at a ventilation rate of 0.76 m3 /s..................................................................................39 Figure 3-13. Sampling locations (circles) for spatial measurement of the TSP mass concentration inside the full-scale test room: (a) side view and (b) top view; All dimensions are in meters........................................................................41 Figure 3-14. Spatial distribution of air velocity at an elevation of 0.4 m and ventilation rate of 0.76 m3 /s.....................................................................................................42 Figure 3-15. A sketch of the filter holder and venturi assembly with the critical venturi located downstream of the filter................................................................43 Figure 3-16. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 2 m for: (a) case C; (b) case F; and (c) percent difference (PD) in concentration between cases C and F. ...................................45 Figure 3-17. Prevailing airflow pattern in the test room for (a) case C and (b) case F. ............46 Figure 3-18. Air velocity distribution (m/s) in the wall inlet for case F.....................................46

9. 8 Figure 3-19. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 1.2 m for: (a) case C; (b) case F; and (c) percent difference (PD) in concentration between cases C and F.. ....................................48 Figure 3-20. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 0.4 m for: (a) case C; (b) case F; and (c) percent difference (PD) in concentration between cases C and F. .....................................49 Figure 3-21. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 2 m for ventilation system A: (a) case A; (b) case B; and (c) case C.........................................................................................................52 Figure 3-22. Contours of the percent difference (PD) in mass concentrations between the two levels of ventilations rates for system A: (a) 0.11 vs. 0.27 m3 /s; (b) 0.11 vs. 67 m3 /s; (c) 0.27 vs. 0.76 m3 /s. .........................................................53 Figure 3-23. Comparison of the average TSP mass concentration (mg/m3 ) for cases A to C of ventilation system A at three elevations: case A – 0.11 m3 /s, case B – 0.27 m3 /s, case C – 0.76 m3 /s..................................................................................................54 Figure 3-24. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 2 m for ventilation system B: (a) case D; (b) case E; and (c) case F.. .......................................................................................................56 Figure 3-25. Contours of the percent difference (PD) in mass concentrations between the two levels of ventilations rates for system B: (a) 0.11 vs. 0.27 m3 /s; (b) 0.11 vs. 67 m3 /s; and (c) 0.27 vs. 0.76 m3 /s. ....................................................57 Figure 3-26. Comparison of the average TSP mass concentration (mg/m3 ) for cases D to F of ventilation system B at three elevations: case D – 0.11 m3 /s, c case E – 0.27 m3 /s, case F – 0.76 m3 /s.................................................................58 Figure 3-27. Sampling locations (circles) for the spatial measurement of the CO2 concentration (ppm) inside the full-scale test room...............................................59 Figure 3-28. Carbon dioxide sensor calibration setup showing the major components.............61 Figure 3-29. Typical calibration curve for the CO2 sensor.........................................................61 Figure 3-30. Leak test setup........................................................................................................62 Figure 3-31. Air leakage at different air static pressure drops. ..................................................63 Figure 3-32. Spatial distribution of the temperature (°C) in the test room at an elevation of 2 m: (a) case A- 0.11 m3 /s, ventilation system A (b) case B- 0.27 m3 /s, ventilation system A, (c) case C- 0.76 m3 /s, ventilation system A, (d) case D-0.11 m3 /s, ventilation system B, (e) case E- 0.27 m3 /s, ventilation system B, and (f) case F- 0.76 m3 /s, ventilation system B...............................................................................................65

10. 9 Figure 3-33. Spatial distribution of the CO2 concentration (ppm) at an elevation of 2 m for: (a) case C; (b) case F; and (c) percent difference (PD) in concentration between cases C and F. .................................................................68 Figure 3-34. Spatial distribution of the CO2 concentration (ppm) at an elevation of 2 m for cases A to C of system A: (a) case A-0.11 m3 /s; (b) case B-0.27 m3 /s; and (c) case C- 0.76 m3 /s.....................................................70 Figure 3-35. Spatial distribution of the CO2 concentration (ppm) at an elevation of 2 m for cases D to F of system B: (a) case D-0.11 m3 /s; (b) case E-0.27 m3 /s; and (c) case F- 0.76 m3 /s ....................................................72 Figure 3-36. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 2 m for: (a) uniform dust distribution source- case F; (b) concentrated dust source- case G; and (c) percent difference (PD) in concentration between (a) and (b)..........................................................................74 Figure 3-37. Spatial distribution of the average CO2 concentration (ppm) at an elevation of 2 m for: (a) uniform dust distribution source- case F; (b) concentrated dust source- case G; and (c) percent difference (PD) in concentration between (a) and (b). .............................................................................................77 Figure 4-1. Approximate growth curve of the pigs .................................................................83 Figure 4-2. Schematics of the building: (a) Three-dimensional view showing the 10 sampling locations in the middle section of the building; (b) Plan view showing the sampling locations for dust, ammonia, temperature, relative humidity, and air velocity ......................................................................................84 Figure 4-3. Schematic of the cross section of the swine building. ...........................................85 Figure 4-4. Front view of the swine building showing the drop-down curtain to provide ventilation during warm weather. ..........................................................................86 Figure 4-5. Schematic of the total suspended particulate matter sampling system..................87 Figure 4-6. Flow schematic and components of the UIUC-TSP isokinetic sampler................88 Figure 4-7. Schematic and components of the ammonia sampling system..............................89 Figure 4-8. Daytime, nighttime, and 24-h averages of ventilation rates, and the average daily outside temperature in December .................................................................92 Figure 4-9. Daytime, nighttime, and 24-h averages of ventilation rates, and the average daily outside temperature in June ..........................................................................93 Figure 4-10. Diurnal variation of the average ventilation rate in both December and June sampling periods............................................................................................94 Figure 4-11. Spatial distribution of the average TSP mass concentration (mg/m3 ) measured in December at elevations of (a) 1.6 m and (b) 0.8 m. ..........................................99

11. 10 Figure 4-12. Spatial distribution of the average TSP mass concentration (mg/m3 ) measured in June at elevations of (a) 1.6 m and (b) 0.8 m ..................................102 Figure 4-13. Air flow pattern over the pens, visualized with white smoke. ...........................102 Figure 4-14. Comparison of the TSP mass concentration in December measured at elevations of 1.6 and 0.8 m at the five cross sections (CS) in the building: (a) CS I, (b) CS II, (c) CS III, (d) CS IV, and (e) CS V.......................................105 Figure 4-15. Comparison of the TSP mass concentration in June measured at elevations of 1.6 and 0.8 m at the five cross sections (CS) in the buildings: (a) CS I, (b) CS II, (c) CS III, (d) CS IV, and (e) CS V. ...................................................106 Figure 4-16. Spatial distribution of the average TSP mass concentration (mg/m3 ) at 1.6 m from the floor during (a) daytime and (b) nighttime sampling in December .........................................................................................109 Figure 4-17. Spatial distribution of the average TSP mass concentration (mg/m3 ) at 1.6 m from the floor during (a) daytime and (b) nighttime sampling in June ..................................................................................................109 Figure 4-18. Spatial distribution of the average NH3 concentration (ppm) in December at elevations of (a) 1.6 m and (b) 0.8 m...................................................................114 Figure 4-19. Spatial distribution of the average NH3 concentration (ppm) in June at elevations of (a) 1.6 m and (b) 0.8 m...............................................................115 Figure 4-20. Comparison of the NH3 concentration in December measured at elevations of 1.6 and 0.8 m at the three cross sections (CS) in the building: (a) CS I, (b) CS III, and (c) CS V. .......................................................119 Figure 4-21. Comparison of the NH3 concentration in June measured at elevations of 1.6 and 0.8 m at the three cross sections (CS) in the building: (a) CS I, (b) CS III, and (c) CS V. .....................................................................................120 Figure 4-22. Comparison of the whole-day TSP mass concentration upstream of exhaust fan no. 5 (EX5) and exhaust fan no. 2 (EX2).........................................123 Figure 4-23. Relationship between the building ventilation rate (Qb) and the TSP mass concentration leaving the exhaust fans. ...............................................................123 Figure 4-24. Comparison of the average TSP mass concentration upstream of the exhaust fans and the average concentration indoors............................................126 Figure 4-25. Comparison of the average TSP mass concentration upstream of the exhaust fans and the average concentration at the five cross sections (CS) indoors: CS-I, CS-II, CS-III, CS-IV, and CS-V ..................................................126

12. 11 LIST OF TABLES Table 2-1. Selected field measurement techniques to quantify ventilation effectiveness.......22 Table 3-1. Particle densities of different types of dust............................................................33 Table 3-2. Experimental test cases to determine the effect of the ventilation system and ventilation rate on the spatial distribution of the TSP mass concentration............43 Table 1-3. Summary of the TSP mass concentration for test cases C and F...........................50 Table 3-4. Summary of the TSP mass concentration for test cases A to C.............................51 Table 3-5. Summary of the TSP mass concentration for test cases D to F. ............................55 Table 3-6. Experimental test cases to determine the effect of the ventilation system and ventilation rate on spatial distribution of the CO2 concentration...........................63 Table 3-7. Summary of the measured air temperature for test cases A to F. ..........................64 Table 3-8. Summary of the CO2 concentration for test cases C and F....................................69 Table 3-9. Summary of the CO2 concentration for test cases A to C of system A. ................71 Table 3-10. Summary of the CO2 concentration for test cases D to E of system B..................71 Table 3-11. Experimental test cases to determine the effect of the dust source location on the spatial distribution of the TSP mass concentration.....................................73 Table 3-12. Summary of the TSP mass concentration data for test cases F and G...................75 Table 3-13. Experimental test cases to determine the effect of the source location on the spatial distribution of the CO2 concentration.........................................................76 Table 3-14. Summary of the CO2 concentration data for test cases F and G............................78 Table 3-15. Average TSP mass concentrations and dust removal effectiveness for all test cases.......................................................................................................................79 Table 3-16. Average CO2 concentrations and CO2 removal effectiveness for all test cases. ...80 Table 4-1. Composition of the feed diet..................................................................................83 Table 4-2. Summary of the indoor temperature and air velocities at the ceiling inlet and indoors in December and June sampling periods............................................96 Table 4-3. Mass concentration (mg/m3 ) of the total suspended particulate matter (TSP) per sampling location.............................................................................................98

13. 12 Table 4-4. Comparison of the means of the TSP mass concentration (mg/m3 ) in each sampling location at elevations of 0.8 and 1.6 m in December and June............100 Table 4-5. Comparison of the means of the TSP mass concentration (mg/m3 ) in each cross section at elevations of 0.8 and 1.6 m in December and June....................100 Table 4-6. Paired comparison of the TSP mass concentrations (mg/m3 ) at elevations of 0.8 and 1.6 m........................................................................................................104 Table 4-7. Average daytime (AM) and nighttime (PM) mass concentrations (mg/m3 ) of the total suspended particulate matter per sampling location..........................108 Table 4-8. Paired-comparison of the daytime (AM) and nighttime (PM) total suspended particulate matter mass concentrations (mg/m3 ) per day ...................110 Table 4-9. Comparison of the daily TSP mass concentration (mg/m3 ) averaged over all 50 sampling locations. ............................................................................111 Table 4-10. Comparison of the daily TSP mass concentration (mg/m3 ) averaged over all sampling days..................................................................................................112 Table 4-11. Ammonia concentration (ppm) per sampling location. .......................................116 Table 4-12. Ratios of ammonia concentrations in each sampling location over the reference locations in December..........................................................................117 Table 4-13. Ratios of ammonia concentrations in each sampling location over the reference locations in June...................................................................................117 Table 4-14. Average daily NH3 concentration (ppm) and the corresponding building ventilation rate (Qb) in December and June.........................................................121 Table 4-15. Average TSP mass concentration (mg/m3 ) leaving the building at daytime (AM) and nighttime (PM) over 15 sampling days in June ..................................124 Table 4-16. Summary data of the building ventilation rate (Qb), indoor and exhaust concentrations, and emission rate ........................................................................125

14. 13 CHAPTER 1 – INTRODUCTION 1.1 Background Indoor air quality in animal buildings must be maintained at levels not detrimental to the health and well being of the workers and animals and one of the effective ways of achieving acceptable indoor air quality is through ventilation. Frequently, the method used to improve air quality in these environments is to simply increase the ventilation rate. The recommended air ventilation rates in confined animal buildings (2 to 60 air changes per hour) are usually based on empirical formulas by assuming that the environmental parameters (temperature, relative humidity and pollutants) are evenly distributed in the room. In reality, pollutants, especially particulate matter, are rarely uniformly distributed in the room. Thus, the indoor air quality is not guaranteed to be improved or maintained within the acceptable level by simply increasing the ventilation rate. Previous studies (Albright, 1990; Maghirang et al., 2001; Zhang, 2004) reported the influence of the distribution of the air in the thermal conditions and air quality in the space. In assessing the performance of the ventilation systems, therefore, it is necessary to take into account how effectively the ventilation system removes the aerial pollutants from the ventilated airspace. The effectiveness of the ventilation system can be characterized in two ways: (1) effectiveness of the system in distributing the clean outdoor air to the needed occupied zones; and (2) effectiveness of the system in removing the contaminants in the occupied spaces. The ventilation effectiveness factor and ventilation effectiveness map appear to be the most applicable and practical to quantify the effectiveness of animal building’s ventilation system. These methods, however, require measurement of the contaminant concentration at various locations within the room. Multiple point measurement in animal buildings is always a challenge since the pollutant concentration within the room can vary by as much as 30 times depending on the level of activities in the building. In addition, the effectiveness of the ventilation system in distributing the air within the room and evacuating the contaminants from occupied spaces is affected by several factors including the configuration of the ventilation system, presence of obstruction, location and strength of contaminant source, and indoor and outdoor conditions. Research is needed to quantify the effectiveness of ventilation systems in animal buildings as affected by ventilation configuration, contaminant source location and strength, presence of obstructions, ventilation rate and other factors. 1.2 Objectives and Approach The overall goal of this proposed research was to develop and evaluate practical methods and procedures to measure or predict the effectiveness of ventilation systems in removing contaminants from animal buildings. The specific objectives were as follows: 1. Analyze the existing ventilation effectiveness measurement techniques or procedures for production animal facilities;

15. 14 2. Develop a practical method of measuring the ventilation effectiveness in animal facilities; and 3. Validate the accuracy and simplicity of the method in a full-scale test room and in a commercial swine production building. Our approach was to first examine the methods and procedures of quantifying the effectiveness of ventilation systems that have been used by other researchers in ventilated airspaces. We particularly looked at the validity and applicability of the ventilation effectiveness factor approach discussed in Zhang et al. (2001). In order to verify the feasibility of the chosen method, we conducted wide-ranging experiments in a full-scale test room that involved measurements of concentration of particles and gases at multiple locations as affected by the types of ventilation system and levels of ventilation rate. Knowing that the ventilation effectiveness in production animal facilities are influenced by other variables such as the presence of animals and other obstructions, we also conducted experiments in an occupied wean- to-finish swine building during summer and winter seasons. 1.3 Organization of Report The other components of this report are organized in the succeeding four chapters. Chapter 2 summarizes the literature review on the ventilation effectiveness criteria and measurement methods applicable to animal buildings. This chapter constitutes the major components of a paper published in ASHRAE Transactions (Vol 113, Part 1, pages 400-407) and addresses specific objectives 1 and 2. The laboratory and field experiments that address specific objective 3 are in Chapters 3 and 4, respectively. Chapter 5 discusses the recommendations for researchers and field engineers for practices in evaluating the effectiveness of ventilation systems and air quality in animal production facilities.

16. 15 CHAPTER 2 – LITERATURE REVIEW 2.1 Introduction Ventilation is an air exchange and distribution process that brings clean outdoor air by either natural or mechanical means to occupied spaces, distributes it within the space, and exhausts hot, humid, and contaminated air from the building. It is the primary method for maintaining acceptable air quality in animal buildings. During summer, the major concern in animal buildings is heat build up and ventilation must be able to remove excess heat; while during winter, the major purpose for ventilation is to remove excess moisture and carbon dioxide (CO2) while at the same time conserve heat produced by the animals. Although animal buildings’ ventilation rates are modulated primarily to remove excess moisture, heat, and CO2, it has been found that the designed ventilation rates to remove these components are in general sufficient to maintain the levels of other contaminants (e.g. ammonia (NH3), hydrogen sulfide(H2S), particulate matter (PM)) below the threshold values. In certain situations (i.e. low ventilation rate during colder months, too much activity in the barns during feeding and animal stocking), however, the concentration of these contaminants exceeded threshold values (Zhu et al. 2000; Predicala et al., 2001; Wathes et al. 2003; Jerez et al. 2005). When one or more of these pollutants rise to a level that is too high, one of the control measures is to adjust the management practices, i.e. removing the manure inside more often, storing manure outside the buildings, and adding additives and chemicals to feed and to manure storage, respectively. Ventilation, however, is still seen as the primary method and frequently the only means available to remove airborne pollutants, especially gases. As in the case of other ventilated buildings, ventilation rates and air distribution are often varied to provide thermal comfort to the occupants and reduce the levels of the contaminants inside the building to a minimum. The desire for thermal comfort and acceptable indoor air quality usually provide conflicting constraints to the operation of the ventilation system. While higher ventilation rate may increase the removal of gaseous contaminants, albeit not necessarily PM, it may result in cold draft which affects the animals’ performance and growth, and may even be fatal for small animals. On the other hand, lower ventilation rate may not be sufficient to evacuate contaminants indoor. Assuming ventilation rate is enough to achieve optimum thermal and IAQ conditions inside the building, this doesn’t guarantee that air will be well-mixed inside the ventilated space. In some cases however, a well-mixed air is not desired, i.e. if the interest is in reducing the air contaminants in areas occupied by the animals and workers, it is more desirable to have more fresh air going into these areas than in unoccupied spaces. What makes a ventilation system effective as a control method not only depends on the level of ventilation rate but also on the resulting air distribution as affected by the location of the air inlets and outlets within the building. The effectiveness of animal building’s mechanical ventilation systems is usually characterized in terms of the air exchange capacity (by measuring the fan air speed) and air distribution (by measuring the inlet air speed and airflow pattern); these parameters are more apt for troubleshooting and are not sufficient to provide quantitative value of the system’s performance

17. 16 in relation to contaminant removal. Although researchers have made great stride in improving animal building’s ventilation system design and control, limited studies have been done on the evaluation of these systems in terms of contaminant removal effectiveness. Standard quantitative criteria and measurement methods that researchers can use to compare the ventilation effectiveness of different types of animal building’s ventilation system are also lacking. 2.2 Existing Ventilation Effectiveness Criteria Ventilation effectiveness is defined as the ability of a ventilation system to achieve its design goals (Persily 1994); the main goal being: (1) to provide fresh air to the occupants and (2) to dilute and remove the internally generated contaminants (Liddament 1993). ASHRAE Standard 62-2001’s definition of ventilation effectiveness addresses both objectives through prescription of required ventilation rates and is defined as the fraction of the outdoor air delivered to the space that reaches the occupied zone (ASHRAE 2001). But the same standard does not have practical information on how to evaluate and measure the ventilation effectiveness of the system; the information that was provided in Appendix E was derived from a two-zone model and defined ventilation effectiveness (Ev) as a function of mixing factor S and the recirculation factor R (Equation 2-1) without stating the procedures on how to measure these values. ( ) ( )SRSEv ⋅−−= 11 (2-1) There are many other ways to interpret the ventilation effectiveness of the system including how effective it is in providing acceptable velocities in the occupied zone and delivering comfortable temperature level for the occupants. The Air Diffusion Performance Index (ADPI) has been developed to quantify the ventilation performance based on air velocity and effective draft temperature (a combination of local temperature variations from the room average) (ASHRAE 2005). ADPI is only an indicator of thermal comfort of the occupants. In terms of indoor air quality, quantitative analysis of the ventilation system’s performance focuses on the abilities of the ventilation system to provide fresh air to the occupants and remove internally generated contaminants. The parameters that define these two objectives depend on the spatial application scale, i.e. local vs. global; and time scale of interest, i.e. steady state vs. transient. The local scale relates the ventilation effectiveness to specific zones of interest in the room while the global scale yields the performance of the whole ventilation system. Although majority of the work on ventilation effectiveness measurements was based on steady state condition, Sandberg (1981) emphasizes the importance of characterizing the effectiveness of the ventilation system in both transient and steady state conditions. In office and residential buildings, the steady state phase is more applicable since the concern is in longer term pollution level; transient phase is more important in industrial facilities especially when there is an accidental release of toxic gas to be able to know how rapidly the concentration can be brought back to a safe level. In animal buildings, contaminants are being generated all the time; thus, longer term pollution level is the primary concern. Discussion on this report focuses primarily on steady state parameters that may be relevant to animal building applications. The parameters were divided into two categories: (1) Indices for room air renewal, which are based on age of air and residence times; and (2) Indices for contaminant removal, which are based on the relation between the concentration of contaminants at the exhaust ports and at various locations in the room.

18. 17 2.2.1 Indices for Room Air Renewal Nominal Air Exchange Rate. Since the ventilation air not only dilutes but also acts as carrier of gaseous and particulate contaminants, its freshness can then be used, to some extent, as an indicator of the effectiveness of the ventilation system. In this regard, a number of indices that describes the freshness of the air, usually in “time” parameters, has been developed and introduced. The most commonly cited of these indices is the specific air flow rate or nominal air exchange rate (n) (air exchange frequency in Skaaret 1984). The nominal air exchange rate is the ratio of the supplied fresh air flow rate (Q) to the volume of the ventilated room (V); it is usually expressed in terms of air changes per hour (ACH), i.e. the higher η is, the fresher is the air in the room, VQ=η (2-2) Although this definition may mean that the room air is completely replaced with fresh air at a given ACH, this isn’t the case since the displaced air is always a mixture of fresh and old air. The nominal air exchange rate has been used in ventilation measurements in offices, residential housings, and other mechanically ventilated spaces (Howard 1966; Dols and Persily 1992; Chow and Wong 1999). While the nominal air exchange rate provides information regarding the total amount of outside air entering the building; it provides no information on the distribution of the outside air in the building. When room air is not perfectly mixed, the local exchange rate, ηp, can be used to measure the amount of ventilation that occurs at specific locations in the room. This concept was first introduced by Sandberg (1981) and is defined as the flow rate of air Qp entering a certain volume Vp irrespective of the time that air has been inside the buildings. ppp VQ=η (2-3) The definition of local exchange rate in equation 2-3 by Sandberg (1981) is difficult to measure physically. Offermanm et al. (1983) introduced a local ventilation exchange rate based on the mass balance equation for a small perfectly mixed volume element p in an imperfectly mixed indoor space and is defined as the change in pollutant concentration C divided by the area under the concentration curve, C(t), integrated over a period of one hour. In equation 2-4, Cp(0) and Cp (t) are the pollutant or tracer concentrations observed at point p at time t = 0 and at t, respectively. This latter definition of local exchange rate is easier to measure using the tracer- gas decay technique. ∫∫−=η t p tC C p dtCdC p p 0 )( )0( (2-4) Age of Air. The age of air, also called internal age, is the time that has passed since a molecule of air entered the ventilated space; the younger the air, the better is its dilution capability and the

19. 18 more efficient is the ventilation system. Since not all molecules of air arrived at a point at the same time, the age of air is characterized by statistical age distribution, which is defined by a whole range of parameters such as the mean value, variance, maximum value, skewness, etc. The most important and widely used parameter is the mean value, i.e. local mean age of air and room mean age of air. The ventilation effectiveness parameters that use the age of air concept were first introduced by Sandberg and Sjoeberg (1983) and were applied later by others (Skareet 1984 and 1986; Sherman and Wilson 1986; Breum 1988 and 1992; Haghighat et al. 1990; Olufsen 1991; Sateri et al. 1991; Persily and Dols 1991; Mundt 1994; Heiselberg 1996; Xing et al. 2001; Novoselac and Srebric 2003). The indices were derived by Sandberg and Sjoeberg (1983) by considering an ideal unidirectional parallel plug or piston flow of air. The commonly used indices are the nominal time constant, local mean age, and room mean age. The nominal time constant, τn, (also called transit time) is the average period of time in which air, once entering the enclosure will remain. Thus, it gives the average age of the air leaving the room and is the inverse of nominal air exchange rate, η, i.e. η==τ 1QVn (2-5) The nominal time constant can be measured by tracer decay method that will be discussed in the following section. It is not dependent on the flow pattern and it has been shown that even during poor mixing, τn is equal to the mean age of air at the exhaust, τe, i.e. τn = τe (Sandberg 1983; Skaaret 1984). The local mean age of air at an arbitrary point p, τp, is the average time that it takes for an air molecule, once entering the enclosure, to reach point p. When measured using the tracer decay technique, it is the area under the decay curve divided by the initial concentration and is given by Equation 2-6 (ASHRAE 2002): )0()( 0 ppp CdttC∫ ∞ =τ (2-6) where Cp(t) is the concentration of tracer at time t and Cp(0) is the initial concentration at time 0. The room mean age of air, <τ>, is the average of the local ages of all air particles in the room. For a piston flow, it is equal to τn/2. During complete mixing, the room mean age of air can be calculated from the contaminant or tracer concentration in the exhaust duct Ce (Seppanen 1986): ∫∫ ∞∞ ⋅⋅>=τ< 00 )()( dttCdtttC ee (2-7) Air Exchange Effectiveness. The air exchange effectiveness, <εa>, describes the replacement of room air with fresh air compared to an ideal plug (piston) flow pattern. It is the ratio of the room mean age for the piston flow to the room mean age for the real flow through the room and is given by Equation 2-8 (Etheridge and Sandberg 1996): >τ<τ>=ε< 2na (2-8)

20. 19 In ASHRAE Standard (ASHRAE 2002), the air-change effectiveness, designated with E, is defined and is twice the air exchange effectiveness, i.e. E = 2<εa>. The air exchange efficiency provides a measure of how quickly air in an enclosure is replaced under different conditions of mixing. The theoretical upper limit for <εa> is 1, which happens when the flow is piston-type, whereas for complete mixing, it is equal to 0.5. While the air-exchange efficiency may indicate a mixing problem within the space, it doesn’t indicate where the problem exists (Liddament 1992). Only by monitoring the mean age of air at specific locations (τp) within a zone can the location of poor mixing be identified. The local air exchange effectiveness, εp, defined by Equation 2-9 (Heiselberg 1996) accomplishes this purpose. pnp ττε = (2-9) The local air exchange effectiveness indicates the rate of ventilation supplied at different locations in the room and thus the air distribution. At complete mixing, values of τp is the same throughout the space and is equal to the inverse of τn, thus εa is 1. If there is non-uniform air distribution within a space, locations with poor ventilation will have local ages of air that are higher than the average. When there is short-circuiting airflow pattern, locations in the stagnant regions will have values of τp that are relatively large and εp will be smaller than 1. 2.2.2 Indices for Contaminant Removal Average Contaminant Removal Effectiveness. The air exchange efficiency and the air exchange rate are not adequate to quantify the ability of the ventilation system to remove contaminants from the space because they are only related to the ventilation air. When contaminants are introduced in the room, they are not well-mixed and their spatial distribution may not follow the room air since their release points are different from that of the air, which is released at the supply or inlet terminals of the building. In addition, contaminants may have different densities than the air due to temperature differences that allow them to setup their own motion, and their movement is also affected by the diffusion process; particles, in particular, possess inertia that affects their own movement. Thus, ventilation effectiveness parameters that are based on the ratios between concentrations of contaminants have been developed, the reference point being the exhaust concentration and are based on the premise that in order not to increase the contaminant concentration indoor, the exhausted concentration should be at least equal to the amount created in or brought to the room; these parameters only apply to steady- state conditions. The definition that is frequently encountered in literature is the average contaminant removal effectiveness, <εc>, and is defined by equation 2-10 (Malmstrom and Ahlgre 1982): ( ) ( )ssec CCCC −><= -ε (2-10) Using the steady state concentrations, Ce and Cs are the concentrations in the exhaust and supply air, respectively, and <C> is the mean concentration in the room. Equation 2-10 describes the overall performance of the ventilation system in removing contaminants indoor. For complete

21. 20 mixing, the contaminant concentration is uniformly distributed and <εc > is unity. When there is short circuiting, the room average concentration will be greater than that at the exhaust point and thus <εc > will be less than unity. The steady state concentration of the contaminant at the exhaust, Ce, is equal to the ratio of the contaminant injection rate q to the supplied fresh airflow rate Q; whereas the steady state average contaminant concentration <C> is the ratio of the volume of contaminant in the room (Vc) to the total volume of the room (V). Thus, substituting the values for Ce and <C> in Equation 2-10 gives the expression for <εc > in terms of the ratio between the nominal time constant for the ventilation air τn and the nominal time constant for the contaminant c nτ (Skaaret 1986), i.e. c nnc ττε =〉〈 (2-11) where c nτ is equal to the ratio of equivalent volume of contaminant in the room, Vc, to the contaminant injection rate, q; τn is defined by Equation 2-5. Evidently, the shorter the contaminant time constant is, the higher is <εc > which will happen only when there is short- circuiting of contaminants. A variation of the average contaminant removal effectiveness, is defined in equation 2-12 (Zhang et al. 2001), i.e. ( ) ∑= −−= N p sppsef VCCVCCV 1 ε (2-12) where Vp is the representative volume at location p and N is the number of measured locations and should be greater than 1. In their work, Equation 2-12 was called ventilation effectiveness factor and was derived by introducing the ratio Vp/V as a weighing factor for the mean concentration <C> described in Equation 2-10. As in other contaminant removal effectiveness parameters described previously, higher values of εf is desired. When εf is equal to unity, the ventilation system is as effective as a complete mixing system. Using complete mixing as the reference, the ventilation system is effective in removing internally generated contaminant if εf is greater than unity while a value less than unity suggests otherwise. The ventilation effectiveness factor has been applied in field measurements in a livestock building and it was found to be primarily affected by the ventilation system and the location of pollutant source, but less affected by the ventilation rate. Local Contaminant Removal Effectiveness. The average concentration of contaminants in Equation 2-10 can be replaced with the contaminant concentration at point p (Cp) resulting in the local contaminant removal effectiveness c pε , i.e. ( ) ( )spse c CCCCp −−=ε (2-13) Equation 2-13 is the definition of relative ventilation effectiveness given by Sandberg (1981) and it expresses how the ventilation capability of the system varies among different locations in the room. It is a measure of dispersion and its value is always positive and can be greater than unity. It is equal to unity when there is perfect mixing, i.e. the concentration throughout the room is uniform and equal to the exhaust concentration. In the case of displacement ventilation, the

22. 21 value of c pε depends on the location of the source. If the source is generated downstream from the measurement point p then Cp may equal Cs and the value of c pε is infinite; whereas when the pollutant source is upstream of the measurement point, Cp may be higher than Ce and c pε will be lower than unity. It can also be higher than unity when there is local exhaust system within the room. Absolute Contaminant Removal Effectiveness. If the maximum value of contaminant concentration Cm in the room is used as the reference instead of <C> then Equation 2-10 becomes the absolute contaminant removal effectiveness c mε (absolute ventilation efficiency in Sandberg (1983)), i.e. ( ) ( )smse c CCCCm −−=ε (2-14) The ventilation effectiveness defined above expresses the ability of the system to reduce contaminant concentration relative to the maximum concentration but it doesn’t tell the time it takes to achieve the condition. It is always equal to or less than unity no matter what type of ventilation system (e.g. piston flow, displacement flow) is used. The contaminant removal effectiveness indices defined in Equations 2-10 to 2-14 have been selectively used in test rooms (Sandberg et al. 1986; Sandberg and Blomqvist 1989; Breum 1992; Nielsen 1992; Mundt 1994; Heiselberg 1996; Novoselac and Srebric 2003; Chao and Wan 2004) and in real buildings (Persily and Dohls 1991; Sateri et al. 1991) to test the performance of different types of ventilation systems and determine the effect of the ventilation parameters on those indices. It has been found that these indices were strongly dependent on the type of ventilation system, contaminant source location, and the presence or absence of disturbance. In addition, the performance of the ventilation system depends on which indicator was used, i.e. for displacement ventilation, calculated contaminant removal effectiveness for occupied zones are sometimes higher than that of the whole room and vice versa; while for mixing ventilation, the local indices are usually the same or worse than that for the whole space (Novoselac and Srebric 2003). 2.3 Measurement Techniques Except for the ventilation effectiveness factor εf which was verified in the laboratory by measuring the airborne dust concentrations, the rest of the ventilation effectiveness indices presented in the previous section were all derived and applied using tracer gases. Use of tracer gas techniques proposed by Sandberg and Sjoberg (1983) to measure the ventilation effectiveness of the system has expanded its application from laboratory evaluations to measurements in real buildings, although laboratory studies still dominate the literature. The three most commonly used techniques are step-down, step-up, and pulse method. However, for applications in real buildings, only step-down and step-up are commonly used as shown in Table 2-1; they have been applied in exchange rate, age of air and air exchange effectiveness measurements. Field measurements of contaminant removal effectiveness are less frequently

23. 22 done compared to the indices for room air renewal. Although ASHRAE Standard 129 (2002) limits the standard methods to only tracer step-up and step down, the pulse method is also briefly described herein. 2.3.1 Tracer Step-Down Method The decay method is applicable for any space, mechanically ventilated or not and either with single or multiple supply and exhaust ducts, as long as uniform distribution of tracer can be achieved by whatever means. In this method, the tracer gas is injected into and dispersed throughout the space with the aid of mixing fans or portable oscillating fans to achieve uniform distribution – uniform distribution can also be achieved by injecting tracer at a constant rate. The injection point depends on the desired measurements, i.e. the tracer is injected into the supply air stream for the age of air measurements while for age of contaminants, tracer gas is injected at representative locations in the room. After uniform condition is achieved, tracer addition is stopped at t=0 and concentration is recorded as it falls at all measurement locations, either to zero (or background) or at least 95% of the uniform initial concentration. Table 2-1. Selected field measurement techniques to quantify ventilation effectiveness. Index* Technique Description of Bldg./Rm. and measurements Reference η, ηp Step-up with SF6 as tracer gas Office rm. , MV system, V=128 m3 , 5 SPs at different heights and inlet, exhaust, return Offermann & Int-Hout 1989 Step-down with CH4, SF6, CO, CO2, N2O as tracer gases Tightly sealed room, fan-induced air-change rate, V=66.5 m3 ; various SPs (unspecified Shaw 1984 τ, τn, τp, <τ>, <εa> Step-up with N2O as tracer gas Printing plant w/ displacement ventilation, V=1100 m3 , 5 SPs at diff. heights and inlet and exhaust Breum 1988 Step-up with SF6 as tracer gas Industrial hall, MV system, V=38,000 m3 , 3 exhaust ducts were sampled Raatschen and Walker 1991 Step-down with N2O as tracer gas Conference rooms and classrooms, MV system, V from 136 to 378 m3 , up to 5 SP at diff. heights and exhaust Olufsen 1991 <εc> (Equation 11) Step-up with CO2 as tracer gas 49 residential houses, combination of MV and NV systems, 11 SPs; measured tracer concentration variation with time Sateri et al. 1991 Step-down with SF6 as tracer gas Office/library bldg., MV system, V=164,400 m3 ; 9 SPs that include return ducts and outdoor location Persily and Dohls 1991 * At least one of the indices within each row was measured in each reference cited. Some authors measured other indices not cited in table 1. SPs = sampling points; Bldg. = building; Rm. = room; MV = mechanical ventilation; NV= natural ventilation; A = floor area The recorded decay of concentration with time gives the cumulative age distribution of the air. The nominal time constant τn is equal to the mean age of air at the exhaust while τp and <τ> are calculated by integrating Equations 2-6 and 2-7, with concentration values corrected for the background concentration. The nominal exchange rateη and local air exchange rate ηp are the reciprocals of τn and τp, respectively. Air exchange effectiveness can be directly calculated using Equations 2-8 and 2-9. The contaminant removal effectiveness defined in Equations 2-10 to 2- 14 can also be obtained by measuring the steady-state concentrations of the contaminants at the specified locations, with the contaminant released within the room. Since tracer decay method requires uniform distribution of contaminants in the space, applying this method in large building measurements may pose difficulty. Similarly, when mixing fans are used to achieve uniform distribution of tracer, the added mixing disturbs the natural airflow

24. 23 pattern. In small buildings where uniform tracer concentration can be easily achieved, it has these advantages: simple to implement, saves tracer gas, doesn’t require initial knowledge on how the air is distributed within the space, and it is already known at the outset that the desired equilibrium concentration after an infinitely long time is equal to the background concentration or zero (Olufsen 1991). 2.3.2 Tracer Step-Up Method The step-up method is the inverse of tracer gas decay. It is based on the assumption that at time zero (t=0), there is a step change in the supply concentration from the background (or zero) to some value Cx and this concentration must be maintained throughout the measurement period. This method is only applicable to buildings with single air inlet duct and it requires complete mixing of the tracer gas with the supply air. To ensure good mixing of the tracer with the incoming air, the tracer should be injected upstream of the inlet fans, if present, or within the supply duct several duct diameters away from the inlet or grilles. If the building has more than one inlet, each must be injected with the same tracer concentration within 15%, which is generally impractical especially if the air inlets have different airflow rates. At time t0, tracer gas is injected into the supply air at a constant rate, which depends on the ventilation rate Q and the concentration range of the measurement device (ASHRAE 2002), i.e. midCQq ×= (2-15) where Cmid is tracer concentration near the middle of the measurement range. Constant injection of tracer should continue until a steady-state concentration C(∞) is observed at all measurement points; the growth of tracer gas concentration is then recorded at different points. The equations for calculating <τ> and τp are shown in Equations 2-16 and 2-17: dt C tC p p p ∫ ∞ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ∞ −=τ 0 )( )( 1 (2-16) ( ) ( )dttCCdttCCt eeee )()()()( 0 −∞−∞=〉τ〈 ∫ ∞ (2-17) where Ce(∞) is the steady-state concentration at the exhaust. As in step down method, τn is the age of the air at the exhaust; η and ηp are the reciprocals of τn and τp, respectively. Equations 2- 8 and 2-9 are used to calculate <εa> and εp, respectively; the contaminant removal effectiveness indices can also be calculated using the steady-state concentrations at the locations specified in Equations 2-10 to 2-14 and as in step-down method, the contaminant must be released within the room. The step-up method should only be used when it is possible to achieve uniform and identical tracer gas concentrations in all supply inlets. In large buildings which have multiple supply inlets, it may be difficult to achieve uniform mixing especially if the inlets are not ducted through a single outdoor air source, which is the case in animal buildings. In addition, this

25. 24 method can give rise to large errors due to uncertainties in the values of the steady state concentrations. 2.3.3 Pulse Method Pulse method is a steady-state variant of step-down method. In this method, a small amount of tracer gas is injected in short duration (1 or 2 min) into the supply duct or at a point within the room. The time variation in tracer concentration at the exhaust and other locations of interest are then measured. Unlike the step-down technique, the measurement period begins when the tracer is injected and then waits until the concentration decays down to zero or background concentration. This method is relatively new compared to the other two methods and applications of this approach in both laboratory and field settings are still limited. The measured time variation of the tracer concentration gives the statistical density function of the age distribution. The local and room ages of air are calculated using Equations 2-18 and 2- 19, respectively. ∫∫ ∞∞ ⋅=τ 00 )()( dttCdttCt ppp (2-18) ∫∫ ∞∞ ⋅⋅=〉τ〈 00 2 )()( dttCtdttCt ee (2-19) As in the other two methods presented previously, the other indices can be derived from the calculated local and mean ages of air. 2.3.4 Particle Concentration Measurement Although the tracer methods are widely used, tracer gases may not best represent the particle contaminants that are also present indoors, especially the large and dense particles in animal buildings. Thus, test dust with properties close to the particles encountered in the space is used. Very few researchers (Breum et al. 1990; Zhang et al. 2001; Maghirang et al. 2001; Fisk et al. 2001) have done measurements of ventilation effectiveness using dust as contaminants and only the work of Breum et al (1990) was done in real swine building. The contaminant removal effectiveness defined in equations 2-10, 2-12 to 2-14 can be obtained using particles injected within the room by measuring these three dust concentrations: Ce in the exhaust air, Cs in the supply air, and Cp’s at the locations of interest. Normally, to be able to get <C> in equation 2-10, spatial distribution of contaminant is measured (Zhang et al. 2001; Maghirang et al. 2001). The spatial distribution of particles also provides useful information on whether the ventilation in an area close to the source of contaminant is sufficient or not.

26. 25 2.4 Applicable Ventilation Effectiveness Index and Measurement Methods As in other real building measurements, assessment of the effectiveness of animal building’s ventilation system is difficult due in part to the following: (1) several gaseous contaminants are already present in significant quantities in and around the building (e.g. NH3, CO2, H2S, CH4); (2) the building is not airtight and air enters and leaves the building not only through the designed openings; (3) the area is usually large and uniform concentration of tracer is difficult if not impossible to achieve; (4) several inlets and exhaust fans are usually present in one building and sampling the air at all of these points can be impractical; and (5) ventilation rate varies throughout the day or the measurement period. Despite of the aforementioned limiting factors, procedures can be employed to get around them to measure the ventilation system performance. Contaminants, especially particles, are not usually spread in the same way as supply air since they have different points of release. The air enters the building through the supply inlets while contaminants are generated inside. Furthermore, contaminants may also have different densities than the air which will allow it to generate its own motions; particles in particular possess inertia that dictates its movement with the air. Therefore, the age of air may not be sufficient as a parameter to quantify the ventilation system’s performance; it will only suffice if it can be established that the movement of both the contaminants and the air are the same. Ventilation effectiveness indices that involve measurement of contaminant concentrations, such as those defined in Equations 2-10 to 2-14, therefore, are more appropriate indicators of the systems performance. Measurement of the contaminant removal parameters mentioned above can be done either by using tracer gases (to measure the average contaminant removal effectiveness given in Equation 11) or direct sampling of the contaminant concentrations. If tracer method will be employed, i.e. to calculate the average contaminant removal effectiveness defined in Equation 2-11, the pulse tracer method is the most applicable measurement technique since it does not require tracer gas concentration to be uniformly mixed nor constant amount be constantly injected – conditions required by step-up and step-down methods but are difficult if not impossible to achieve in animal buildings since these buildings are usually long and wide and the ventilation rate constantly varies even throughout the day. SF6 is the ideal tracer gas for the tracer study since it is not typically found in the ambient air. However, the most limiting factor in its use is the cost of equipment to monitor the concentration in real time ($40,000 for a photoacoustic SF6 analyzer, California Analytical Instrument). CO2, on the other hand, can be easily measured with low- cost, accurate, and reliable photo acoustic infrared analyzers but measurements can be contaminated since it is originally present in the ambient air (~350 ppm) and is generated by the animals. Background concentration of CO2 both in the supply air and indoor air can be monitored, however, prior to the actual tracer measurements. NH3 is more difficult to use as a tracer gas since its source in the building varies and is not stable, i.e. the concentration can be easily affected by the presence of urine on the floor and by even slight agitation of the manure in the pit. The contaminant removal parameters can also be determined by measuring the concentration of the actual contaminants in the building instead of using any tracer. This may prove to be more practical but the generation rate of contaminants inside maybe unknown unless separate measurements are done. The contaminant generation rate is not really required unless mass

27. 26 balance of contaminants is desired; otherwise, measurement of contaminant concentrations is sufficient to be able to calculate the parameters in equations 2-10, and 2-12 to 2-14. Contaminant removal effectiveness can be calculated for PM, CO2, NH3, and H2S. 2.5 Conclusions When choosing an index that can be used to characterize the ventilation effectiveness of the real system, it should be measurable, applicable under different operating conditions, and practical in terms of the cost and effort that will be involved in the measurements. The following conclusions can be drawn from this work: • The quantitative measures of the ventilation effectiveness of the system consist of parameters for air renewal and contaminant removal. Majority of the work done involved the use of age of air concept in controlled airspaces to determine how other factors (obstructions, heat sources, types of ventilation system, etc.) affect the indices. Limited number of research has been done on the applications of the age of air concept and the contaminant removal indices in real buildings. • Tracer methods proved to be useful in the measurement of the ventilation effectiveness parameters. However, the application of these methods in real buildings is difficult due to factors such as large area of application, presence of unwanted openings in buildings, and presence of several supply inlets and exhaust locations. • In real building applications, evaluation of local indices involves measurements from at least 3 up to more than 10 sampling locations. In animal buildings, the number and location of sampling points can also be reduced to a minimum if prior data on the spatial distribution of gaseous and particulate contaminants are available. • The contaminant removal indices are most applicable for animal building applications. Pulse tracer method and direct measurements of contaminants generated in the building can be applied to measure these indices.

28. 27 CHAPTER 3 – LABORATORY EXPERIMENTS 3.1 Introduction In order to evaluate the effects of different variables (types of ventilation system, pollutant source location, and levels of ventilation rate) on the contaminant removal effectiveness parameter suggested in Chapter 2, tests were conducted under controlled conditions in our Room Ventilation Simulator (RVS). The laboratory experiments involve measurements of the concentrations of total suspended particulate matter (TSP) and carbon dioxide (CO2) at 45 sampling locations indoors. The spatial distribution measurement of these pollutants aids in determining the number and location of sampling points. The specific objectives of this study were the following: • Measure the spatial distribution of total suspended particles (TSP) and carbon dioxide (CO2) concentrations; • Determine the effect of the types of ventilation system on the spatial distribution of TSP and CO2 concentrations; • Determine the effect of the levels of ventilation rate on the spatial distribution of TSP and CO2 concentrations; • Determine the effect of source location on the spatial distribution of TSP and CO2 concentrations; and • Evaluate the ventilation effectiveness using the contaminant spatial distribution measured by the multi-point samplers 3.2 Experimental Details 3.2.1 Room Ventilation Simulator The experiments to determine the effects of ventilation rates and the type of ventilation system were conducted in a full-scale test room housed inside a room ventilation simulator (RVS). The RVS, shown in Figure 3-1, consisted of an outer room, an inner test room, and an air delivery and measurement system. The outer room was 12.2 m long, 9.1 m wide, and 3.6 m high. It was fitted with an air conditioning and heating system to simulate typical weather conditions during summer and winter; the temperature in the outer room can be set between -25 and 40°C. During the first set of experiments in December, the temperature in the outer room was set at 23°C. In another set of experiment in May, the ambient temperature in the outer room was 22°C. The inner test room, where the sampling systems were setup, was modular in its design, i.e. the inner walls can be reconfigured conveniently. This full-scale test room, shown in Figure 3-2, was 5.5 m long, 3.7 m wide and 2.4 m high. The other side wall of the test room was made of glass to allow measurement of airflow pattern with the particle image velocimetry (PIV). There were also glass slits on both end walls to transmit the light luminance. All walls except the glass were covered with black, non-reflective paint to create a good optical environment. The two

29. 28 plenums on either ends of the test room were used to provide uniform air into and out of the test room. The amount of air that goes into the room or the air exchange rate is controlled by an air delivery and measurement system attached to the test room. Figure 3-1. Room ventilation simulator (Wang, 2000).

30. 29 Figure 3-2. Schematic of the full-scale test room location and configuration (top view, not drawn to scale). The air delivery and measurement system, shown in Figure 3-3, consisted of a measurement chamber and a centrifugal fan. The speed of the centrifugal fan is controlled by a variable frequency controller. Housed inside the measurement chamber was a perforated plate. Three perforated plates with different hole diameters of about 17.5, 22.2, and 23.3 mm were used interchangeably to provide airflow rates of 0.11, 0.27, and 0.76 m3 /s, respectively. The perforated plates were calibrated in the fan test chamber in the Bioenvironmental and Structural Systems (BESS) laboratory and the calibration results are presented in Wang (2000). The pressure taps across the perforated plate were connected to an inclined manometer to measure the static pressure drop. The linear relationship between the static pressure drop and the ventilation rate for each perforated plate was sought during calibration.

31. 30 Figure 3-3. Schematic of the air delivery and measurement systems (Wang, 2000). 3.2.2 Dust Generation and Distribution System The dust generation and distribution system that was used in the study was developed by Wang (2000) and was used in his dissertation research. It consisted of a rotating dust generator and a distribution system. Figure 3-4 shows the dust generator with its components. The speed of the table was regulated by a voltage regulator and can be adjusted from 0 to 100% of the power supply. The plate had three gutters and only the inner gutter was filled with dust. The volume of the inner gutter was 11.30 cm3 and the dust supply rate was calculated from the volume of the gutter and the rotation of the plate. The compressed air was used to suck dust from the plate and carry it into the dust distribution system. A compressed air pressure of 379.2 kPa (55 psi) was maintained throughout the experiments. At this pressure, the dust supply tube had a sufficient vacuum to suck dust into it. The filter located before the pressure regulator in Figure 4-6 was used to remove water and oil.

32. 31 Figure 3-4. Dust generator. Two types of dust distribution system were used in the study. The first, which was used to generate uniform dust over the whole floor area, is shown in Figure 3-5. In this system, dust was distributed into the room from the floor through the 25 emission ports. This distribution system was also used in the study by Wang (2000). It consisted of a 19-mm diameter copper pipe as the main line and the five branches were also copper pipes with an inner diameter of 7.9375 mm. These pipes were located 12 mm above the floor. Each of the tube had five holes located on the bottom resulting in 25 total emission ports distributed uniformly over the entire floor area. The diameter of each port was 1.5875 mm. In order to maintain the same compressed air pressure at each port, the total opening area of the five ports in each branch was one-fifth of the cross sectional area of the tube. The compressed air pressure at both ends of the tube was 9.8 kPa. Shown in Figure 3-6 is the other dust distribution system that was used to emit dust at one location in the room to test the effect of the location of the source on the spatial distribution of contaminants. The emission port was about 3 mm in diameter and the copper pipe that was used was also elevated 12 mm from the floor. The location of the hole was about 0.46 m away from the glass sidewall and about 0.69 m away from the closest endwall.

33. 32 Figure 3-5. Top view of the dust distribution system used for uniform dust source generation inside the test room (Wang, 2000). Figure 3-6. Top view of the dust distribution system used for concentrated dust source generation inside the test room (not drawn to scale). All purpose wheat flour (ordinary all-purpose flour available in supermarkets) was used as test dust. In order to come up with this decision, the true densities of six types of dust were measured using a pycnometer (Model 1330, Micromeritics Instrument Corporation, Norcross,

34. 33 GA) and compared their density with the density of swine dust. Aside from the wheat flour, the other types of dust that were tested and their corresponding densities are presented in Table 3-1. In addition to the particle density, the particle size distribution (PSD) of each type of dust was also measured using a laser scattering particle size distribution analyzer (Horiba Model LA-300, Horiba, CA). Oat dust, which also had a particle density close to that of swine dust, was not used since about 90% of its feedstock was more than 100 µm in diameter and it will take enormous time to prepare enough samples for the experiments. The PSDs of both wheat flour and swine dust are shown in Figure 3-7. The PSD of the wheat flour ranged from 0.584 to about 400 µm, while that of the swine dust was from 0.584 to about 175 µm. Although flour contains size fractions larger than 175 µm, these particles constitute about 10% of the total amount of particles. Table 3-1. Particle densities of different types of dust. Test Dust Particle Density, g/cm3 Arizona fine test dust (ISO 12103-1 A2) 2.72 Arizona fine test dust (ISO 12103-1 A4) 2.73 ASHRAE 52 test dust 2.60 Oat dust 1.52 Johnson’s baby powder 2.86 Wheat flour 1.50 Wean-to-finish swine dust 1.45

35. 34 (a) (b) Figure 3-7. Particle size distribution (PSD) curves of (a) all-purpose wheat flour and (b) swine dust.

36. 35 3.2.3 Carbon Dioxide Generation and Distribution System The carbon dioxide generation system is shown in Figure 3-8. Carbon dioxide in a pressurized gas cylinder was used as test gas or tracer gas. The concentrations of CO2 that were used in the experiments were 20 and 100%. A flow meter was used to regulate the flow of gas that is distributed into the room. In order to distribute CO2 into the distribution line as quickly as possible, compressed air was used as the CO2 carrier. The flow rate of the compressed air was also regulated and maintained at 0.02 m3 /min throughout the experiments. Prior to each experimental run, the compressed air was filtered and the condensed air removed from the filter to prevent water from getting into the distribution lines. The same distribution systems shown in Figures 3-5 and 3-6 were used to inject CO2 into the test room. Figure 3-8. Carbon dioxide generation system. 3.2.4 Temperature Measurement The temperature in all sampling locations inside the test room, at the inlet and at the exhaust was monitored during all test runs using type T thermocouples. Two Personal Daqs (Model 56, IOtech, Cleveland, OH) data acquisition system were used to record the temperature. All thermocouples were calibrated prior to use using a block calibrator (Model PB-35L, Techne

37. 36 (Cambridge) Limited, NJ) and a CR23X datalogger (Campbell Scientific, Inc., Logan, UT) connected to a computer. 3.3 Effect of the Ventilation System and Ventilation Rate on the Spatial Distribution of TSP 3.3.1 Experimental Setup All experiments were conducted in the full-scale test room described in section 3.2.1. Two types of ventilation system were used in this study. The setup of ventilation system A in the room is shown in Figure 3-9. System A had a continuous slot inlet along one end wall and a square outlet in the midsection of the opposite end wall. The slot inlet was 140 mm wide but the baffle that directed the air toward the ceiling was only open by about 50 mm. The outlet was covered with a 1.07 x 1.07 m plastic shutter to simulate the field installation of an exhaust fan. Figure 3- 10 shows the outlet location on the endwall opposite the inlet. The plenum after the outlet was connected to the centrifugal fan of the air delivery and measurement system creating negative pressure inside the room. Figure 3-9. Elevation view of the ventilation system setup A (not drawn to scale).

38. 37 Figure 3-10. Front view of the outlet covered with a plastic shutter (encircled). In ventilation system B, the slotted inlet was replaced with a perforated endwall, as shown in Figure 3-11, and the outlet was the same as system A. The perforated wall was a peg board with 0.635 cm diameter holes in a 2.54 x 2.54 cm grid. The total open area of the wall was about 4.8% resulting in an open area of 0.30 m2 . System B was used to simulate a cross-flow type of ventilation. A similitude analysis using the inlet jet momentum number was done prior to deciding on using the whole endwall as the inlet for system B. From the result of the analysis, similarity in the inlet and outflow conditions between the test room and the tunnel-ventilated swine building described in chapter 4 cannot be achieved. In using the perforated endwall, however, the flow in the inner section of the room was comparable with the flow in the inner section of the tunnel-ventilated swine building discussed in Chapter 4, which was close to being fully developed as shown in Figure 3-12. In Figure 3-12a, two of the exhaust fans were in operation and there was a slight increase in the resulting velocity distribution toward the sidewall of the building which was also observed in the room.

39. 38 Figure 3-11. The perforated wall inlet used in ventilation system B. The outlet is on the opposite endwall.

40. 39 (a) (b) Figure 3-12. Comparison of the air velocity distribution in the (a) tunnel-ventilated swine building when two exhaust fans were on and (b) test room at a ventilation rate of 0.76 m3 /s.

41. 40 3.3.2 Dust Sampling System and Measurement Procedure The mass concentration of TSP was measured simultaneously at 45 sampling locations indoors, at three locations at the inlet, and at three locations in front of the exhaust fan opening. The sampling locations indoors were at three longitudinal sections of the room. Each section had 15 samplers located at three elevations. Figure 3-13 (a and b) shows the side and top views of the sampling locations. The samplers consisted of CPVC pipes and were connected to two air pumps. Thirty six of the samplers were connected to a 3.73-kW pump while the other nine samplers were connected to a 1-hp pump. A separate 746-W pump was used to measure the mass concentration at three locations along the inlet. The three samplers located at three different heights across the cross section of the outlet opening were connected to another 746-W pump. In the TSP mass concentration measurement, critical venturis were used in each sampler to maintain the sampling flow rate throughout each experiment. The critical venturi was located downstream of the filter to avoid clogging. In the preliminary studies, the sampling flow rate through each venturi was lower by about 10 to 15% of the calibrated flow rate at sampling locations farthest from the pump. Thus, prior to and after each sampling run, the sampling flow rate in each location was measured and the average value was used in the calculation of the mass concentration. Prior to selecting the sampling inlet that was used, the applicability of either isokinetic or calm air sampling to collect representative samples was determined by measuring the velocity at the sampling locations using a hot-wire anemometer. At a ventilation rate of 0.11 m3 /s, there was no measurable air velocity in all of the sampling locations indoors. At 0.27 m3 /s only 12 locations had a measurable air velocity with a maximum measured value of 0.20 m/s. The maximum measured velocity at 0.76 m3 /s was 0.60 m/s which occurred close to the outlet. In majority of the sampling locations, however, the air velocities were lower than 0.30 m/s as shown in Figure 3-14. Thus, if isokinetic sampling will be followed for the 0.76 m3 /s ventilation flow rate, several sizes of sampling heads would be needed and would be economically prohibitive.

42. 41 (a) (b) Figure 3-13. Sampling locations (circles) for spatial measurement of the TSP mass concentration inside the full-scale test room: (a) side view and (b) top view; All dimensions are in meters.

43. 42 Figure 3-14. Spatial distribution of air velocity at an elevation of 0.4 m and ventilation rate of 0.76 m3 /s. The readily available and affordable inlet for air is a 37-mm diameter cassette-type filter holder. Figure 3-15 shows the sketch of the 37-mm diameter sampler oriented horizontally with the critical venturi located downstream of the filter. The filter holder was open-faced. The filters that were used in all tests were dried in a dessicator for 24 hours and weighed using a precision electronic balance (readability of ±0.01 mg, Mettler Toledo, Columbus, OH) before and after each test run. Prior to each test, there was an initialization period of 30 min before the actual sampling of dust was done to allow the concentration in the room to achieve steady-state. During this stabilization and the actual sampling periods, the dust generation rate was maintained at 5 mg/s. The length of the stabilization period was determined by measuring the dust concentration at the sampling location in the midsection of the room. A laser particle counter (LPC) (Model CI-500, Climet Instruments, Redlands, CA) was used to monitor the total number of particles at the midsection of the room at 5-min intervals for 1 hour. After the stabilization period, the pumps were turned on. The sampling duration for all test runs lasted for four hours to be able to collect enough dust for mass concentration analysis. The dust mass concentration was the product of the mass of the collected dust and the sampling flow rate.

44. 43 Figure 3-15. A sketch of the filter holder and venturi assembly with the critical venturi located downstream of the filter. 3.3.3 Experimental Design Two types of ventilation systems, systems A and B described in Section 3.3.1, were utilized for this study. Each ventilation system was tested at three levels of ventilation rates resulting in six test cases. The ventilation rates that were used in the experiments were 0.11, 0.27, and 0.76 m3 /s; these ventilation rates satisfy the cold, mild, and hot weather ventilation rate requirements for about 60 prenursery pigs (MWPS, 1990). It should be noted that the test room represents one pen in the tunnel ventilated swine building described in Chapter 4. Also, the test room did not contain animals; the presence of animals could affect the airflow pattern due to their heat production and also the obstruction they pose. Each test case in Table 3-2 was repeated three times resulting in 18 total runs. The inlet air velocities for system A were measured at 12 locations along the length of the inlet; for system B, the wall inlet was virtually divided into 88 equally-spaced sampling locations. In all of the runs presented in Table 3-2, the 25-point dust distribution system shown in Figure 3-5 was used. The inlet velocities between the same level of ventilation rate for the two systems vary significantly with those of system B lower by as much as 73%. The measurement of inlet velocities upstream of the holes for system B was a challenge and the accuracy could be suspect. Table 3-2. Experimental test cases to determine the effect of the ventilation system and ventilation rate on the spatial distribution of the TSP mass concentration. Test case Ventilation system Ventilation rate m3 /s Inlet temp °C Room temp °C Inlet velocity m/s A A 0.11 24.5 24.1 0.52 B A 0.27 24.2 23.9 1.14 C A 0.76 23.9 24.0 3.89 D B 0.11 23.0 23.4 0.32 E B 0.27 22.7 22.4 0.82 F B 0.76 23.0 22.7 2.24

45. 44 3.3.4 Results and Discussion Effect of the Type of Ventilation System on the Spatial Distribution of the TSP Mass Concentration To compare the effect of the types of ventilation system on the spatial distribution of dust mass concentration, only cases C and F were considered. Figure 3-16 (a and b) shows the contours of the spatial distribution of the TSP mass concentration at 2 m from the floor for cases C and F, respectively. Most of the mass concentrations in case C were higher than 0.45 mg/m3 while in case F, the dust mass concentrations were less than 0.30 mg/m3 . In case C, the mass concentration was highest near the inlet and lowest close to the outlet. Since the air inlet in case C was located close to the ceiling, portion of the supply air short-circuited through the outlet. A portion of the supply air created one large recirculation zone as shown in Figure 3-17a resulting in higher concentration near the inlet. In case F, the concentration gradient varies crosswise, with the highest concentration near the glass wall (Figure 3-16b). This could be attributed to non-uniform air velocity distribution in the wall inlet for case F as shown in Figure 3-18, with the air velocity near the glass wall (length=0) lower than the other sections of the inlet.

46. 45 (a) (b) (c) Figure 3-16. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 2 m for: (a) case C (Ventilation system A, 0.76 m3 /s) (b) case F (Ventilation system B, 0.76 m3 /s); and (c) percent difference (PD) in concentration between cases C and F. The increasing level of blue denotes higher concentration.

47. 46 (a) (b) Figure 3-17. Prevailing airflow pattern in the test room for (a) case C (Ventilation system A, 0.76 m3 /s) and (b) case F (Ventilation system B, 0.76 m3 /s). Figure 3-18. Air velocity distribution (m/s) in the wall inlet for case F.

48. 47 Shown in Figures 3-19 and 3-20 are the spatial distribution of mass concentration at 1.2 m and 0.4 m from the floor, respectively. Similar to the distribution at 2 m from the floor, the concentration was also highest near the inlet for system C at 1.2 and 0.4 m elevations. For system F, the concentration also varied crosswise, i.e. the mass concentration at a specific width of the room was almost uniform lengthwise. In quantifying the spatial uniformity of mass concentration in the room, the concentration variation (Cvar) was defined and is expressed in Equation 3-1. It is the ratio of the difference between the maximum (Cmax) and minimum(Cmin) mass concentrations to the maximum concentration in percent. Cvar value ranges from 0 to 100. The higher the Cvar value is, the less uniform is the distribution. The Cvar values at different elevations for cases C and F are presented in Table 3-3. Cvar values for case C were all lower than those of case F suggesting that the spatial distribution in case C were more uniform than in case F. %100 max minmax var × − = C CC C (3-1) The percent difference, PD, defined in Equation 3-2 was also calculated to quantitatively compare the difference in the spatial distribution of cases C and F. At an elevation of 2 m and 1.2 m, the concentrations in the sampling locations were higher by almost 90% in case C than in case F as shown in Figures 3-16c and 3-19c. When closer to the floor or the dust source (0.4 m), about 7/8 of the space in the room in case C still had concentrations higher than those in case F (Figure 3-20c). These results suggest that at a high ventilation rate, ventilation system B removed more airborne particles than that of system A. 100%PD × − = CofonDistributiSpatial FofonDistributiSpatialCofonDistributiSpatial (3-2)

49. 48 (a) (b) (c) Figure 3-19. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 1.2 m for: (a) case C; (b) case F; and (c) percent difference (PD) in concentration between cases C and F. The increasing level of blue denotes higher concentration.

50. 49 (a) (b) (c) Figure 3-20. Spatial distribution of the average TSP mass concentration (mg/m3 ) at an elevation of 0.4 m for: (a) case C; (b) case F; and (c) percent difference (PD) in concentration between cases C and F. The increasing level of blue denotes higher values. Presented in Table 3-3 is the average concentration at each elevation for cases C and F. The average dust mass concentration in case F at three elevations was lower than the corresponding

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