Heat transfer and field synergy characteristics in a rectangular unit channel under mechanical vibration

Abstract

The internal heat exchangers of a vehicle in driving are excited by forced vibration due to road bumps. But the effect of this phenomenon on the thermal-hydraulic performance of the heat exchanger has not been systematically studied. To investigate the influence of this vibration on the heat transfer characteristics, a numerical model of the rectangular heat exchanger unit channel under vibration excitation was established and verified by experiments. It is found that compared to frequency, amplitude of vibration has a greater effect in enhancing heat transfer but when it is more than 4 mm, which leads to a rapid increase in the friction factor f. An index (j/js)/(f/fs) and a thermal-vibration performance factor (TVPF) considering the frequency and amplitude are proposed to evaluate the effect of vibration on the heat transfer, and it is indicated that for real vehicle operation, an amplitude of 2 mm and frequency of 25 Hz can effectively enhance heat transfer. Besides, it was found that the velocity gradient field perpendicular to the main flow direction caused by vibration synergizes with the temperature gradient field. This work is meaningful and of significance to the practical design of the actual heat exchangers in the automotive application.