On the heat and mass analogy of fin-and-tube heat exchanger

This study examines the heat and mass analogy of the fin-and-tube heat exchanger under dehumidifying process. A total of 36 fin-and-tube heat exchangers having plain fin geometry are experimentally examined. It is found that the ratio of hc,o/hd,oCp,a is in the range of 0.6–1.1 and is insensitive to change of fin spacing at low Reynolds number. However, it is noted that this ratio is not a constant throughout the test range. A slight drop of the ratio of hc,o /hd,oCp,a is seen with the decrease of fin spacing and with the rise of the Reynolds number. This is associated with the more pronounced influence during condensate removal. Moreover, during the dehumidifying process, the temperature gradient is directly responsible for establishing the concentration gradient, suggesting the heat transfer and mass transfer are not independent. Based on a simple analysis, one can easily find that the increasing rate of dcdT∣i slightly exceeds that of ΔcΔT. As a result, the ratio of hc,o/hd,oCp,a can be proved to be slightly decreased with the rise of the Reynolds number.