Heat and Mass Transfer for Compact Fin-and-Tube Heat Exchangers Having Plain Fin Geometry

摘要

The air side heat performance for four compact fin-and-tube heat exchangers having plain fin configuration under dehumidifying conditions were reported in this study. Tests were conducted in a circulation wind tunnel. It consists of a closed loop wind tunnel in which air is circulated by a variable speed centrifugal fan (7.46 kW, 10 HP). The air duct is made of galvanized steel sheet and has a 850 mm × 550 mm cross-section. The dry-bulb and wet-bulb temperatures of the inlet air are controlled by an air-ventilator that can provide a cooling capacity up to 21.12 kW (6RT). The air flowrate measurement station is an outlet chamber setup with multiple nozzles. As shown in Figure A-1, the test results indicate that the heat transfer coefficients are relatively insensitive to change of inlet condition. However, the pressure drops are strongly related to the inlet conditions and fin pitch. For a larger fin pitch like 1.78 mm, the pressure drops for RH = 90% are approximately 10-20% higher than those of RH = 50%. Further reduction of fin pitch to a smaller value of 1.22 mm would significantly increase the pressure drops. As seen in Figure A-1, the pressure drops for RH = 90% are approximately 20-45% higher than those of RH = 50%. Possible explanation of this phenomenon may be due to the effect of condensate retention.