Comparison of heat transfer and pressure drop between analytical and computational approaches : a preliminary study for optimal heat exchanger design

Abstract

Extended surface areas are indispensable features for compact heat exchanger design. Even one of the simplest, plain-fin-and-tube heat exchangers are still widely studied and used due to their relatively-easy production compared to other types of fin geometries. However, this simplicity only means that there are fewer parameters to consider, compared to those louvered fins for example. Those parameters are the transversal and longitudinal pitches between tubes, fin pitch, fin thickness, inner and outer tube diameters and the number of tube rows, given whether an optimization scheme is required to find a design solution. In this study, the validity of analytical and 3D computational fluid dynamics solutions employing the aforementioned parameters was investigated as a preliminary step to optimal heat exchanger design. The causes of differences between analytical approaches and the associated experimental solutions from previous studies were also sought via simulations. For this purpose, geometric parameters extracted merely from the Reynolds numbers used in those studies, were used to construct a plain-fin-and-tube heat exchanger core. Care was taken so as to employ air velocities remaining in the laminar regime traveling between the fins. It was found that the bounds of the experimental parameters which had been used to define correlations, had a significant impact on the validity of the analytical approach. The three-dimensional model proved to generate viable results with respect to already-published experiments. Since this study constitutes the preliminary step for an optimization scheme, the findings are also accompanied by an extensive literature review on analytical and computational tools.