Aero-thermal behavior and performance optimization of rectangular finned elliptical heat exchangers with different tube arrangements

Abstract

Tube arrangement largely determines the flow structure as well as aero-thermal performance in finned tube heat exchangers (FTHXs). Most of the previous studies did not cover both overall performance and local thermal flow characteristics due to the physical complexity. This work is related to the comparison of various aero-thermal behaviors of rectangular finned elliptical tube heat exchangers (RFETHXs) with different tube arrangements in a turbulent flow region, from basic characteristics to optimal structures. Using 3-D numerical simulation based on the validated standard k-ε model, the local thermal flow characteristic as well as overall dimensional and dimensionless performances of three arrangements is investigated. Then, using variance analysis, the contribution of each structural parameter of the three arrangements on overall performance is compared after the screening of the factor of longitudinal tube pitch. Using the same CFD data as variance analysis, an elliptical basis function (EBF) model of each type of arrangements is constructed to understand the distribution of j/f0.5 as well as PEC in the parameter range of this work. Moreover, optimal structural parameters of each arrangement are provided. It is observed that, each tube arrangement presents its own characteristic of flow separation and heat transfer coefficient distribution on fins. For the in-line and staggered row arrangements, the contributions of all the main factors and the two-way interactions on various overall performances are close, while the situation of the staggered column is different. The influence of two-way interactions is marginal in the staggered column structure, while it cannot be neglected in the two other arrangements in most cases. For j/f0.5, the optimal structural parameter combination of the in-line and staggered row arrangements is fin thickness 0.6 mm, fin pitch 2 mm and transverse tube pitch 54 mm, whereas that of the staggered column arrangement is 0.6 mm, 2 mm and 70 mm in turn.