PERFORMANCR EVALUATION AN AIR-COOLED OF AN AIR-COOLED HEAT EXCHANGER BASED ON ENTROPY GENERATION

Abstract

In this study, the performance of an air-cooled heat exchanger was evaluated based on entropy generation under variations in operating conditions. The entropy generation was taken into account the irreversibility associated with heat transfer only. The predictions were validated and showed good agreement with analytical results and experimental measurements. The results reveal that the difference temperature between the inlet hot water and the ambient air or the initial temperature difference (ITD) can be used as the parameter to determine the effect of operating conditions. The heat transfer and entropy generation number increase with increasing ITD. The entropy generation number slightly increases with mass flow ratio of water to air ( ) and the effecte is less as the ITD is reduced. The moderate ITD is required for the operation of the air-cooled heat exchanger. Its limiting temperature ( ) is obtained when the outlet air temperature is minimize. Working below this value results in over-sensitivity to small change.