Measurements and predictions of the heat transfer at the tube-fin junction for louvered fin heat exchangers

The dominant thermal resistance for most compact heat exchangers occurs on the air side and thus a detailed understanding of air side heat transfer is needed to improve current designs. Louvered fins, rather than continuous fins, are commonly used to increase heat transfer by initiating new boundary layer growth and increasing surface area. The tube wall from which the fins protrude has an impact on the overall heat exchanger performance. The boundary layer on the external (typically, air) side of the tube is subjected to repeated interruptions at the louver-tube junction. This paper discusses baseline results of a combined experimental and computational study of heat transfer along the tube wall of a typical compact heat exchanger design. A scaled-up model of a multi-louver array protruding from a heated flat surface was used for the experiments. With the exception of the inlet and turnover louver regions, the results of this study indicate agreement with steady, three-dimensional computational predictions to within 5% for Re = 230 and 8% for Re = 1016.