Numerical simulation of the flow and heat-transfer characteristics of an aligned external three-dimensional rectangular-finned tube bank

Abstract

Finned-tube heat exchangers are commonly used for air conditioning, refrigeration, and utility boilers to enhance the energy efficiency of heat transfer. Compared with the 2D continuous finned tube, the 3D discrete finned tube heat exchangers have more outstanding performance on enhancement of heat-transfer. Especially, the 3D rectangular fin is believed to have better heat-transfer performance compared with common 3D fins.In this study, the flow and heat-transfer characteristics of an aligned external rectangular-finned tube bank with six rows of tubes were numerically investigated. The performances of an external rectangular-finned tube bank and a smooth tube bank were firstly compared. This was followed by an analysis of the effects of the geometric parameters (transverse tube pitch, longitudinal tube pitch, fin height, fin width, and fin pitch in the axial direction) and the Reynolds number on the flow and heat-transfer characteristics of an aligned external three-dimensional rectangular-finned tube bank.The results indicated that the heat transferability and friction loss of the aligned external three-dimensional rectangular-finned tube bank were higher than those of the smooth tube bank, while the comprehensive performance of external rectangular finned tube bank was not always superior. In addition, increasing the longitudinal tube pitch, fin height and fin width or decreasing the transverse tube pitch and fin pitch in the axial direction caused the heat-transfer capability and flow loss of the external rectangular-finned tube bank to increase, which can provide theoretical guidance for the design of a 3D finned-tube heat exchanger. The correlations of the Nusselt number (Nu) and the friction factor (f) for the six-row tube bank were presented, which can be helpful to engineering applications of heat exchanger for clean gas situations.