Numerical and Experimental Determination of Wavy Fin-Tube Shape Factor

Abstract

This paper presents the numerical and experimental investigations of a wavy fin-tube heat exchanger aimed at correctly accounting for all factors influencing the thermal performance of the exchanger. The shape factor for the complex heat conduction path in the wavy fin is determined by using computational analysis and validated experimentally by utilizing electrical analogy to obtain the electric resistance across the fin. This is used to back-calculate the conduction shape factor. In the experimental study, the potential difference, V and current, I, was measured using a high precision data acquisition unit. The results were used to calculate the shape resistance which was compared with that obtained from the numerical model. Grid independence tests were performed on the model and several analytically derived standard shape factor formulae were also used for comparison with the model outputs. The deviation of the numerical results from the analytical formulae for the cases studied was less than +1.2%. The agreement between the experiments and the numerical model was within +3.5%. The results demonstrated the adequacy of the numerical approach to modeling the wavy fintube heat transfer. Effects such as differences in fin shape, fin length and waviness of the fin design on the shape factor were determined and discussed.