42. Cooling tower fans Comparison - 2000 ton tower - 196 m³/ sec @ 160 Pa pressure drop Fan dia Nbr Blades Rpm Tip speed Sound Power Fan shaft Power Fan ft m/sec dB(A) kW US $ 14 6 270.8 60.5 100.3 59.3 2100 16 7 193.9 49.5 95.6 53.2 3600 18 5 186.8 54.2 99 46 13500 18 * 4 137 40 86.3 54.9 45000
43. Cooling tower fans Fan power vs cost – 2000 ton tower – 196 m³/sec @ 160 Pa pressure drop Fan dia Tower price Fan Power ft % kW 14 - - 16 + 1, 25 % - 11 % 18 +8 % - 22 %
44. Cooling tower fans Comparison - 5000 ton tower - 375 m³/ sec @ 160 Pa pressure drop Fan dia Nbr Blades Rpm Tip speed Sound Power Fan shaft Power Fan ft m/sec dB(A) kW US $ 22 6 226 44.2 106.3 106.3 9500 26 9 104.8 43.5 97.9 87.1 26000 26 6 89.7 37.2 90.6 104.2 60000 28 6 82.6 36.9 90 102.3 65000
45. Cooling tower fans Fan power – noise vs cost - 5000 ton tower – 375 m³/ sec @ 160 Pa pressure drop Fan dia Tower price Power Sound Power ft % kW dB (A) 22 106.3 26 + 7 % - 18 % 97.9 26 20% -2% 90.6 28 + 22% -4% 90
Step one to avoid recirculation is to make sure that the top of the cooling tower should be at least level with the enclosure. Today , we as engineers are still fighting daily with architects on this issue ! or the right measurements to avoid recirculation are it is completely overlooked
Often VFD’s are promted to save energy in applications using electrical motors. Are we saving energy when applying VFDs on cooling towers ? We know that by lowering the condensing temperature with 1°F , the chiller efficiency improves with 3% . At the same time are the fan kw of the cooling towers more or less 5 % of the motor kw of the chiller. In other words , we will not save energy when considering all elements when reducing the cooling tower fan speed by using VFD’s.
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Fans are selected for a given air flow and static pressure caused in the cooling tower. Fan design parameters or characteristiques include the diameter, speed , the number and the shape of the blades and blade width. The paramters have all their influence on cost , power consumption and noise.
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