Heat transfer studies were carried out in a laboratory scale gas-solid fluidized bed with 0.1m ID x 1 m length column, using three sizes of local sand particles of 301, 454, and 560 µm. the bed region was heated bya horizontal heat transfer probe. It was made of copper rod (15 mm ODx50 mm long) and insulated at the ends by Teflon. A hole was drilled at the center of the rod to accommodate a cartridge heater 200 W (6.5 mm OD x 42 mm long). Three bed inventories of sand 1.5 kg, 2.0 kg, and 2.5 kg, four superficial air velocities of 1.0 m/s, 1.25 m/s, 1.5 m/s, 1.75 m/s were used. Three heat fluxes of 1698.9, 2928.4, 4675.7 W m-2 were employed. The data obtained showed how the heat transfer coefficient effected by the above operating parameters. The heat transfer coefficient is directly proportional with air superficial velocity as well as the bed inventory and heat fluxes but inversely proportional with sand particles size.

1. INTERNATIONAL JOURNAL OF ADVANCED RESEARCH
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 39-46 © IAEME
IN ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 5, Issue 7, July (2014), pp. 39-46
© IAEME: http://www.iaeme.com/IJARET.asp
Journal Impact Factor (2014): 7.8273 (Calculated by GISI)
www.jifactor.com
39
IJARET
© I A E M E
STUDY THE EFFECT OF DIFFERENT OPERATING PARAMETERS ON
HEAT TRANSFER COEFFICIENT IN GAS-SOLID FLUIDIZED BED USING
HORIZONTAL HEAT TRANSFER PROBE
Basma Abdulhadi Beddai1, A.V.S.S.K.S. Gupta2, M.T.Naik3, Ammar Arab Beddai4
1Center for Energy Studies, College of Engineering, JNTUH, Kukatpally, Hyderabad, A.P
2Mechanical Engineering, College of Engineering, JNTUH, Kukatpally, Hyderabad, A.P
3Center for Energy Studies, College of Engineering, JNTUH, Kukatpally, Hyderabad, A.P
4Material Engineering, Technical College- Baghdad, Iraq
ABSTRACT
Heat transfer studies were carried out in a laboratory scale gas-solid fluidized bed with 0.1m
ID x 1 m length column, using three sizes of local sand particles of 301, 454, and 560 μm. the bed
region was heated bya horizontal heat transfer probe. It was made of copper rod (15 mm ODx50 mm
long) and insulated at the ends by Teflon. A hole was drilled at the center of the rod to accommodate
a cartridge heater 200 W (6.5 mm OD x 42 mm long). Three bed inventories of sand 1.5 kg, 2.0 kg,
and 2.5 kg, four superficial air velocities of 1.0 m/s, 1.25 m/s, 1.5 m/s, 1.75 m/s were used. Three
heat fluxes of 1698.9, 2928.4, 4675.7 W m-2 were employed. The data obtained showed how the heat
transfer coefficient effected by the above operating parameters. The heat transfer coefficient is
directly proportional with air superficial velocity as well as the bed inventory and heat fluxes but
inversely proportional with sand particles size.
Keywords: Heat Transfer Coefficient, Gas- Solid Fluidized Bed, Horizontal Probe, Fluidization,
Horizontal Probe.
1. INTRODUCTION
Fluidization is a unit operation, and through this technique a bed of particulate solids,
supported over a fluid-distributing plate (often called the grid), is made to behave like a liquid by the
passage of the fluid (gas, liquid, or gas–liquid) at a flow rate above a certain critical value. In other
words, it is the phenomenon of imparting the properties of a fluid to a bed of particulate solids by
passing a fluid through the latter at a velocity which brings the fixed or stationary bed to its loosest

2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 39-46 © IAEME
possible state just before its transformation into a fluidlike bed[1].There exist high heat transfer rate of
fluidized beds and immersed surface, and little temperature variation across the bed, and can be
obtained higher heat transfer coefficients compared to a conventional fluidized beds. Due to these
advantages, this technology has been applied commercially in various processes, such as fluidized
bed combustor, fluidized bed reactor, fluidized bed dryer, etc[2].Three modes of heat transfer are
important with respect to surfaces immersed in fluidized beds: (1) Convection by particles carrying
heat conducted through the gas layer in contact with the exchange surfaces; (2) convection by gas,
and radiation. Many processes utilizing fluidized beds operate at temperatures below 500 oC where
the radiation component is of secondary significance. Gas convective heat transfer becomes
significant when the superficial gas velocity is higher or the particle size is large[3].
40
Kunii and Levenspiel pointed out that heat transfer in fluidized beds is a two part concern:
one deals with the bed to surface heat transfer such as heat transfer tubes and the other deals with the
gas to particle heat transfer [4].Kiang et al.measured heat transfer coefficients using 19 mm diameter
and 57.2 mm high vertical probe located along the axis at various levels in a 102-mm diameter and
3.66-m-high cold CFB riser. Axial variation of heat transfer coefficients in the range of 45 to 230
W/m2.K were reported. B. V. Reddy, P. K. Nag investigated the effect of operating parameters on the
axial and radial variation of the heat transfer coefficient in circulating fluidized bed column. They
proposed an empirical model with help of dimensional analysis to predict the heat transfer coefficient
to a bare horizontal tube in a CFB riser column and they observed a good agreement between the
model results and the experimental data.Noor M. Jasem et al. investigated the steady state heat
transfer between gas and solid and the surface immersed in gas- solid CFBs. They used a bed column
of 76 mm in inside diameter and 1500 mm in height fitted with a horizontal heating tube with outer
diameter 28 mm heated electrically with different power supplies (105 W). The fluidizing medium
was air at different velocities (4.97, 5.56 and 6 m/s). They employed three different size of sand
particle (i.e 194, 295 and 356 μm). They used initial bed heights with different values (15, 25 and 35
cm). They found that the heat transfer coefficients increase with fluidized air velocity and, through
clear, with heat flux, but, they show an inverse dependence on particle size, and direct proportional
with initial bed height which representation the bed density [5-7].
Sung Won Kim et al. carried out an experiments in a FBHE made of transparent acrylic plate.
The effect of gas velocity on the average and local heat transfer coefficients between a submerged
horizontal tube and a fluidized bed has been determined in a fluidized-bed-heat-exchanger of silica
sand particles. They measured the heat transfer coefficient around the tube circumference by
thermocouples and an optical probe. They concluded that the average heat transfer coefficient
exhibits a maximum value with variation of gas velocity, the local heat transfer coefficient exhibits
maximum values at the top of the tube and the average heat transfer coefficient increases with
increasing gas velocity toward a maximum value of the coefficient[8].
Vanderschuren and Delvosalle (1980), Delvosalle and Vanderschuren (1985), as well as
Molerus (1997) reported that particle–particle and particle–surface collisional heat transfers may
play significant role in fluidized beds under certain conditions. Therefore, because of intensive
motion of particles in the turbulent fluidized regime, it appears to be of interest of modeling and
investigating heat transfer processes induced by particle–particle and particle–surface collisions in
order to study these phenomena separately of the remaining thermal characteristics of the bed [9].
D. Karageorgieva, and R. Stanev studied the influence of some factors on total heat transfer
coefficient and the convective heat transfer one in low temperature circulating fluidized bed. They
compared their data with that in the literature, they found a very good agreement between them [10].
The heat transfer characteristics between a circulating fluidized bed and a surface immersed
inside it were investigated by M. A. Al Busoul. He presented a statistical model describing the
mechanism of heat transfer and the relation between the heat transfer coefficient and the main
parameters of the bed. The proposed model yields a satisfactory representation of heat transfer

3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 39-46 © IAEME
process in the circulating fluidized bed.Heat transfer from an immersed heating surface to a liquid-solid
41
and liquid-liquid solid fluidized beds were studied by Balasim A. Abid et.al. The experiments
were carried out in a (0.22) m column diameter fitted with an axially mounted cylindrical heater
heated electrically. They developed new correlations to predict the heat transfer coefficients in
liquid-solid and liquid-liquid-solid fluidized beds. They compared the obtained heat transfer
coefficients with those estimated from other correlations reported in the literature. The comparison
showed a good agreement with the data obtained for the gas-liquid-solid fluidized beds using low-density
particles[11], [12].
Qin-Fu Hou, et al. investigated heat transfer characteristics of different powders in gas
fluidization were by means of a combinedapproach of discrete element method and computational
fluid dynamics. The results confirmed that the convective heat transfer was dominant, and radiative
heattransfer becomes important when the bed temperature is high. However, conductive heat transfer
also played a role depending onthe flow regimes and material properties[13].
Many investigations were done to study the effect of particles sizes on heat transfer
coefficient and they obtained that the heat transfer coefficient decreases with increasing particle size
[14-16].
Experiments were carried out by NimaMasoumifard, et al. in a fluidized bed in order to
verify the influence of the axial position, particle diameter and the superficial gas velocity on the
heat transfer coefficient from a small horizontal tube (Dt = 8 mm) immersed in the fluidized bed. The
solid particles used were 280, 490 and 750 μm diameter sand particles, fluidized by air. They showed
that the heat transfer coefficient was increased with increasing the gas velocity, up to a maximum,
and then decreases with a slight slope. The heat transfer coefficient was found to decrease by
increasing the particle size. The probe position had less influence on the heat transfer coefficients [17].
P. Neto et al. studied the heat transfer in a laboratory scale bubbling fluidized bed with
54.5mm ID, using five different sizes of silica sand particles of 107.5, 142.5, 180, 282.5, and 357.5
μm.The bubbling bed region was heated by a 2 kW electrical resistance and the heat was transfer
towards membrane cooling wall placed above the free surface bed. They found that there were two
heat transfer mechanisms are responsible for the thermal energy transportation towards the
membrane cooling walls (1) the convective heat transfer from the mainly fluidized air flow, (2) the
heat carried by the bed solid particles in the to-and-from movement created by their upward
projection, due to the bursting bubbles reaching the bed surface, their collisions against the
membrane walls and subsequent return to the hot bubbling bed [18].The objective of the present study
is to investigate in detail heat transfer and to ascertain the effect of important parameters on the heat
transfer coefficient between the horizontal heat transfer surface and the fluidized bed in a lab-scale
fluidized bed system.
2. EXPERIMENTAL SETUP
Laboratory scale fluidized bed setup can be shown in fig. 1, the experiments were conducted
in a 0.1 m ID and 1 m height mild steel fluidization column. Air was supplied by a compressor. The
air flow was measured by a rotameter. The air was passing through the plenum chamber filled by
glass beads to maintain uniform distribution of air through bed,with a height of 0.1m and upper
diameter of 0.1m and bottom diameter of 0.015m. The air was distributed by a perforated plate of
mild steel with a diameter of 0.1m and a thickness of 0.003 m will consists of 256 holes of 2.7 mm
diameter drilled on a 7.5 mm square pitch. An ultrafine mesh was fixed on the distributor plate to
prevent bed particles leakage. There were 10 pressure ports in the fluidized column for pressure drop
measurements. The heat transfer section consisted from horizontal heat transfer probe.

4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 39-46 © IAEME
42
Fig. 1: Experimental setup of fluidized bed column, 1-compressoe, 2-Valve, 3-air rotameter,
4-plenum chamber, 5- Horizontal heat transfer probe, 6-thermocouples, 7- digital screen,
8- DC power supply, 9-five U manometers.
An ultrafine mesh was fixed on the top end of the column to avoid escaping the particles
from the top. Local sand of three different sizes 301μm, 454μm, and 560 μm were used as the bed
material. Three bed inventories of sand 1.5 kg, 2.0 kg, and 2.5 kg, four superficial air velocities of
1.0 m/s, 1.25 m/s, 1.5 m/s, 1.75 m/s were used. Three heat fluxes of 1698.9, 2928.4, 4675.7 W m-2
were employed.
The local heat transfer coefficient along the probe were estimated from the equation:

5. (4)
The probe average heat transfer coefficient was estimated from the local heat transfer coefficients:
(5)
3. RESULTS AND DISCUSSION
3.1 Effect of air superficial velocity on heat transfer coefficient
Fig. 3 shows the effect of superficial gas velocity of 1.0, 1.25, 1.5, 1.75 m/s on the surface-to-bed
heat transfer coefficient in the fluidized column at heat fluxes of 1698.9, 2928.4, 4675.7 W m-2,
1.5 kg bed inventory and 301μm particles size. From the figure, it is noticed that the heat transfer
coefficient increased with increasing the fluidization velocity. The increase in heat transfer may be
due to enhanced turbulence in the column for higher velocity which in turn causes for intermixing of
solids and gas solid suspension.

6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 39-46 © IAEME

7. 43
Fig. 2: Effect of gas superficial velocity on heat transfer coefficient at I=1.5 kg, dp=301μm and
three different heat fluxes
3.2 Effect of bed inventories on heat transfer coefficient
The effect of bed inventories on heat transfer coefficient can be shown in fig. 4. Inventory in
the bed was varied as 1.5, 2.0, and 2.5 kg. It is observed that increase in the inventory of sand in the
column increases the bed temperature and heat transfer coefficient. This is because sand particles
concentration increases with increase bed inventory. Consequently, more quantity of particles in the
lower splash region promotes more heat transfer through conduction because of which bulk
temperature of bed was observed to be higher than that of lower inventory. W/m2
Fig. 3: Effect of bed inventories on heat transfer coefficient at q=1698.9 W m-2, dp=301μm and four
different gas superficial velocities
Fig. 4: Effect of bed inventories on heat transfer coefficient at q=2928.4 W m-2, dp=301μm and four
different gas superficial velocities
h W/m2. oC
Ug m/s
q=1698.9 W m-2
q=2928.4 W m-2
q=4675.7 W m-2

8. h W/m2.oC
Ug m/s
I=1.5kg
I=2.0kg
I=2.5kg

9. h W/m2.oC
Ug m/s
I=1.5kg
I=2.0kg
I=2.5kg

10. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 39-46 © IAEME
300
280
260
240
220
200
180
160
0.95 1.15 1.35 1.55 1.75 1.95
Fig. 5: Effect of bed inventories on heat transfer coefficient at q=4675.7 W m-2, dp=301μm and four
44
different gas superficial velocities
3.3 Effect of sand particle size on heat transfer coefficient
Fig. 7, 8, and 9 show the effect of particle size on the heat transfer coefficient between the
heat transfer probe and the bed particles. Sand particles size of 301, 454, and 560 μm were used.It is
found that the heat transfer coefficient decreases for large particles mainly because of the higher
thermal resistance offered by the particles. Also with increase of particle size, the gas gap thickness
between the surface and particles increases resulting in a decrease of the heat transfer coefficient.
Moreover the smaller particles can increase the effective heat transfer area covered by particle itself.
220
200
180
160
140
120
Fig. 6: Effect of particles size on heat transfer coefficient at q=1698.9 W m-2, I=1.5 kg, and four
different gas superficial velocities
280
260
240
220
200
180
160
140
120
Fig. 7: Effect of particles size on heat transfer coefficient at q=2928.4 W m-2, I=1.5 kg, and four
different gas superficial velocities
h W/m2.oC
Ug m/s
I=1.5kg
I=2.0kg
I=2.5kg
100
0.9 1.1 1.3 1.5 1.7 1.9
h W/m2.oC
Ug m/s
dp=301μm
dp=450μm
dp=560μm
100

11. h W/m2.oC
Ug m/s

12. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 39-46 © IAEME
0.9 1.1 1.3 1.5 1.7 1.9
45
300
280
260
240
220
200
180
160
140
120
100
h W/m2.oC
Ug m/s
dp=301μm
dp=450μm
dp=560μm
Fig. 8: Effect of particles size on heat transfer coefficient at q=4675.7 W m-2, I=1.5 kg, and four
different gas superficial velocities
3.4 Effect of heat fluxes on heat transfer coefficient
The variation of heat transfer coefficient for different heat flux conditions against gas
superficial velocity for a particular bed inventory is shown in fig. 3. The heat transfer coefficient is
high for higher values of heat flux and it is decreasing with the decrease in heat flux. For higher heat
flux condition, the bed temperature increases. This is due to increase of amount of the heat which
transferred to the fluidized bed system, which in turn tends to enhance the heat transfer coefficient.
4. CONCLUSIONS
The main focus of this study was the effect of different operating parameters on heat transfer
coefficient in gas-solid fluidized bed. Following conclusions obtained from the experimental results:
1. Heat transfer coefficient is found to be increasing with increase air superficial velocity.
2. Heat transfer coefficient is directly proportional to the heat fluxes and bed inventory.
3. Smaller particles size yield higher heat transfer coefficient and vice versa in present heat
transfer studies.
4. The data show trends similar to those in published literatures.
REFERENCES
[1.] C.K. Gupta, D. Sathiyamoorthy, Fluid Bed Technology in Materials Processing, 1999 by
CRC Press LLC.
[2.] Zhu Xuejun, Ye Shichao, Pan Xiaoheng, The local heat transfer mathematical model
between vibrated fluidized beds and horizontal tubes, Experimental Thermal and Fluid
Science 32 (2008) 1279–1286.
[3.] A. Stefanova, H.T. Bi, C.J. Lim, J.R. Grace, Heat transfer from immersed vertical tube in a
fluidized bed of group A particles near the transition to the turbulent fluidization flow
regime, International Journal of Heat and Mass Transfer 51 (2008) 2020–2028.
[4.] K. Pisters, A. Prakash, Investigations of axial and radial variations of heat transfer
coefficient in bubbling fluidized bed with fast response probe, Powder Technology 207
(2011) 224–231.
[5.] R. Sundaresan, Ajit Kumar Kolar Core heat transfer studies in a circulating fluidized bed
Powder Technology 124 (2002) 138– 151.
[6.] B. V. Reddy, P. K. Nag, Axial And Radial Heat Transfer Studies in a Circulating Fluidized
Bed, International Journal of Energy Research, VOL. 21, 1109-1122 (1997).

13. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 7, July (2014), pp. 39-46 © IAEME
46
[7.] Noor M. Jasem, GhassanFadhil. M. H., Hafidh H. Mohammed, Experimental Study Of The
Effect Bed Density On Heat Transfer Coefficients In Towers With Gas Solid Circulating
Fluidized Bed, Al-Qadisiya Journal For Engineering Sciences 2009 Vol. 2 No. 3.
[8.] Anusaya M. Salwe, Local heat transfer coefficient around a horizontal heating element in
gas-solid fluidized bed, International Journal of Application or Innovation in Engineering
Management (IJAIEM), Volume 2, Issue 6, June 2013 ISSN 2319 – 4847.
[9.] Z. Sule, B.G. Lakatos, Cs. Mihalyko, Axial dispersion/population balance model of heat
transfer in gas–solid turbulent fluidized beds, Computers and Chemical Engineering 34
(2010) 753–762.
[10.] D. Karageorgieva, R. Stanev, Heat Transfer in Low Temperature Circulating Fluidized Bed,
Journal of the University of Chemical Technology and Metallurgy, 41, 1, 2006, 69-74.
[11.] M. A. Al Busoul, Bed- to- Surface Heat Transfer Coefficient ion Circulating Fluidized Bed,
heat and mass transfer 38 (2002) 295-299.
[12.] Balasim A. Abid, Majid I. Abdul-Wahab, Asrar A. Al-Obaidy, Heat Transfer from an
Immersed Heater in Liquid – Liquid – Solid Fluidized Beds, Eng. Tech. Journal, 2009
Vol.27, No.10.
[13.] Qin-Fu Hou, Zong-Yan Zhou, Ai-Bing Yu, Computational Study of the Effects of Material
Properties on Heat Transfer in Gas Fluidization, Industrial Engineering Chemistry
Research 2012, 51, 11572−11586.
[14.] A.V.S.S.Kumara Swami Gupta, Some Heat Transfer and Thermodynamic Studies of
Combined Cycle Power Generation, Thesis 1999.
[15.] JamalMane'e Al-Rubeai, Nabeel Majid Aliwi, A Study of Chaotic Behavior of Heat
Transfer In Gas-SolidFluidized Bed, Eng. Tech. Journal, Vol.28, 2010, No.10.
[16.] Tahseen Al-Hattb and Riyadh S. Al-Turhee, Effect of Particle Size,Flow Velocity And Heat
Flux on Heat Transfer Coefficient in Fluidized Bed Column, The Iraqi Journal For
Mechanical And Material Engineering, Special Issue (B).
[17.] NimaMasoumifard, NavidMostoufi*, Ali-AsgharHamidi, RahmatSotudeh-Gharebagh,
Investigation of Heat Transfer between a Horizontal Tube and Gas–Solid Fluidized Bed,
International Journal of Heat and Fluid Flow 29 (2008) 1504–1511.
[18.] P. Neto, A. M. Ribeiro, C. Pinho, Heat Transfer abovethe Free Surface ofa Bubbling
Fluidized Bed: A Simple Global Correlation, International Review of Chemical Engineering,
Vol. 1, 2009, N.1.
[19.] Mamdoh Al-Busoul, Aiman Al-Alawin and Hamza Al-Tahaineh, “Influence of Air-Fuel
Ratio and Particle Size on Fluidized Bed Combustion of the El-Lajjun Oil Shale”,
International Journal of Mechanical Engineering Technology (IJMET), Volume 4,
Issue 5, 2013, pp. 130 - 138, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.
[20.] M. Sreekanth, “Measurement of Devolatilization Time and Transient Shrinkage of a
Cylindrical Wood Particle in a Bubbling Fluidized Bed Combustor”, International Journal of
Mechanical Engineering Technology (IJMET), Volume 4, Issue 3, 2013, pp. 244 - 258,
ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.
[21.] Phairoach Chunkaew, Aree Achariyaviriya, Siva Achariyaviriya, James C. Moran and
Sujinda Sriwattana, “Operating Parameters Effects on Drying Kinetics and Salted Sunflower
Seed Quality Utilizing a Fluidized Bed”, International Journal of Advanced Research in
Engineering Technology (IJARET), Volume 4, Issue 6, 2013, pp. 256 - 268, ISSN Print:
0976-6480, ISSN Online: 0976-6499.