Numerical analysis of airside characteristics in plain and wavy heat exchangers in the turbulent flow regime

Abstract

Numerical investigation has been performed to study heat transfer and pressure drop characteristics of plain fin and wavy fin heat exchangers in the external airside. The characteristics were studied using the dimensional parameters, friction factor and Colburn factor. The flow rate was varied over the range of 2000 < or = Re < or = 7000 in the turbulent and transitional regimes. The analyses were performed using a finite volume method. Comparisons with experimental data were performed to validate the numerical results. The geometrical parameters like the fin pitch, transverse pitch, wavy angle and wavy height were varied to study the effects of each individual parameter. Comparisons were also drawn to the laminar range, the effect of number of tube rows and the pattern in which the tube were arranged. The investigation shows that the effect of the number of tube rows on heat transfer coefficient is less after the number of rows is increased beyond four. It is observed that the reducing the fin pitch increases the heat transfer and pressure drop in both the configurations. The increase in transverse pitch resulted in a decrease in thermal and hydraulic characteristics. Response to the variation of wavy angle and wavy height was similar, as the wavy angle and wavy height were increased, the number of corrugations also increased resulting in higher heat transfer and a higher pressure drop. The critical balance between high heat transfer and low pressure drop was analyzed using the efficiency index for each parameter variation. The tube layouts in the staggered form were observed to be better than the in-lined layout for both the configurations.