Study of the enhanced heat transfer characteristics of wavy-walled tube heat exchangers under pulsating flow fields

Abstract

Heat exchangers have a very wide range of applications in many industrial fields, so the rational design and the performance are to improve the heat exchanger energy efficiency and reduce the production cost of an important means. In this paper, the heat transfer mechanism of pulsation is revealed by simulating and analyzing the effects of three pulsation parameters: volumetric flow rate, pulsation frequency, and pulsation amplitude on the flow and heat transfer of a wavy-walled tube heat exchanger, with the study focusing on the instability behavior that affects the heat transfer mechanism. The results reveal that the combined heat transfer performance of the wavy-walled tube heat exchanger is about 8.2% higher than that of the straight-walled tube heat exchanger. The flow field of the heat exchanger is more fully developed under the pulsating flow field, and its performance evaluation coefficients (PECs) are all greater than 1. It is also found that with the increase in the volume flow rate Qv, the heat transfer enhancement coefficient and PEC first increase and then decrease, and reach the maximum value near Qv = 2.0 m3/h; with the increase in the amplitude A, the vortex and heat transfer enhancement coefficient inside the heat exchanger increase, but the integrated heat transfer performance of the heat exchanger is gradually weakened; with the increase in the frequency fT, the heat transfer enhancement coefficient and PEC first increase gradually, but the increase gradually decreases and levels off in the later stages, reaching a maximum value near fT = 0.5 Hz. Meanwhile, the field coefficients of the wavy-walled tube heat exchanger were analyzed and found to be much smaller than 1, with an order of magnitude of 10−4, and the results also showed that the field coefficients were inversely proportional to the volume flow rate and directly proportional to the amplitude of pulsation and that the field coefficients showed a tendency of increasing and then decreasing with the change of pulsation frequency and reached a maximum value near fT = 0.5 Hz. This work provides an important reference for current manufacturing industries to optimize heat exchanger sizing and develop efficient thermal management systems.