Comparative analysis on performance of microchannel heat exchanger with symmetrical and asymmetrical louver fins.

The parallel-flow microchannel heat exchanger is the most commonly used outdoor heat exchanger in automobile air conditioning system, symmetrical louver fins have the problem of large wind resistance, so the improvement of its comprehensive performance is important for the system. This study uses the validated simulation model to explore the improvement effects of various fin parameters. The j factor and f factor are calculated to draw JF factor graphs to compare the performance. Contours are drawn to reflect the heat transfer process and flow condition inside the fins. For heat exchangers with symmetrical louver fins, the thermal and hydraulic performance is significantly affected by the fin pitch and fin height. Furthermore, this study proposes three new asymmetrical fins. The result indicates that the two types of fins with gradient height louver and gradient angle louver show favourable comprehensive performance. Their JF factors are enhanced by 9.6% and 18.3% respectively, compared to the standard symmetrical fins when the air inlet velocity was 4.5 m/s.