Experimental investigation of thermal hydraulic performance of heat exchangers with different Reynolds numbers on both air-side and water-side

Steady state laminar flow and transition flow heat transfer performance of two types of wavy fin heat exchangers with different Reynolds numbers on both air and water sides was experimentally studied. The tubes and fins assembly was made of aluminum to eliminate any thermal contact resistance on the interface between the tubes and fins. A series of tests were conducted for air and water Reynolds number that ranged from 670 to 3432 and from 1952 to 5140 respectively. In order to reduce the testing time, Equipower heating method was adopted throughout the experiment. Results exhibited that transfer coefficient h increases sharply when the flow of water is transition, meanwhile the flow of air side is laminar or just reached the transition and the flow of the water side needed to be more intensive. But before the sudden changes of h, the h increases slowly with Re_w increasing at the same Re_a. When compared with the same Reynolds number on the air side, an improvement as high as 15% was observed for the h, but the pumping power was only increased by 5%. In addition, the thermal hydraulic performance of sharp corner wavy fin is better than that of the round corner wavy fin.