Thermal-Hydraulic Study of Multi-Louvered Fins in Compact Heat Exchangers and Recommendations for Improvement

In this paper the effects of geometric parameters of compact heat exchangers have been studied numerically and experimentally. Conservation equations of mass, momentum, and energy were solved using the finite volume method (SIMPLE) in various heat and flow conditions. Also, precise tests of automotive air conditioning condensers were carried out. The results indicate that an increase of fin pitch causes a decrease of pressure drop and thermal capacity. The louver angle has a smaller effect on varying pressure drop and heat capacity than the fin pitch. Expansion of louver angles in a specific range causes enhancement of heat transfer coefficient and thermal capacity. At low louver angles, flow is in the direction of the fin (duct-directed flow), but at high louver angles, flow is almost aligned with the louvers (louver-directed flow). The results show that fluid velocity is more effective than geometric parameters on thermal-hydraulic characteristics. The highest heat transfer occurs in the first row of louvers, and the second row causes a greater pressure drop. Therefore, fin efficiency can be enhanced by removing the second array of louvers, which is known as a semi-louvered fin; this is recommended strongly. It may reduce pressure drop more than 40%, which consequently increases the heat transfer coefficient and thermal capacity. The effect of the recommended fin is more significant at low Reynolds numbers, as it can increase thermal capacity more than 20%. The comparison of numerical analysis results and those obtained in the experiments shows 5% accuracy inflow properties and 7% accuracy in thermal characteristics, approximately.