Performance study of spiral finned tubes on heat transfer and wake flow structure

Abstract

Heat exchangers have been widely utilised in many industrial and residential sectors. In this paper, the turbulent flow of a heat exchanger with spiral finned tubes (SFT) is numerically simulated using a large eddy simulation (LES), which outperforms existing two-equation solvers in finding the details of flow structure around bluff bodies. This work aims to find the coherent structures around spiral fins using the Q-criteria and to obtain flow topologies playing an important role to improve the heat transfer of spiral finned tubes. The SFT shows three primary flow regions representing various vortex structures. The study also observes how turbulent flow changes with different Reynolds numbers and how turbulent coherent structure changes with varying Nu numbers on the fin surface. The result shows that the correlation coefficient reaches 0.81 by examining the correlation of the Nu number and the Q values over the time series at each sampling point. In addition, the modal information of temperature variation is estimated using dynamic mode decomposition analysis. The dynamic mode of temperature shows highly consistent with the Q criterion distribution.