Numerical analysis on heat transfer performance of oscillating flow in wavy channel

Abstract

This study focuses on the unsteady characteristics of heat transfer process and its augmentation in wavy channels working in an acoustic resonator with a standing wave imposing the oscillating flow. A two-dimensional numerical model is developed after a careful verification with the published experimental results. Forty cases, involving fifteen wavy channel structures along with a comparative parallel channel working in different driving ratios, were established considering the heating and cooling process in different heat exchangers. The dynamic characteristics of temperature and velocity field, redevelopment of boundary layer, spatial and time-spatial averaged Nusselt number are presented to depict the heat transfer performance in oscillating flow. The results show that the viscous boundary layer follows a procedure of generating, expanding, separating and merging in each acoustic cycle. Thermal boundary layer keeps a longer stability after experiencing the redevelopment, during which heat transfer augmentation occurs. However, heat transportation will be inhibited when thermal boundary layer separation happens. Besides, the heat transfer enhancement capacity of wavy channel compared with parallel channel can reach to 1.10 in both hot and cold side under driving ratio of 0.83 %. The optimal dimensional height of the wavy channel normalized by thermal penetration depth is also found to be located between 2–3. At last, the heat transfer performance is correlated with the change of amplitude height of wave, Reynolds and Prandtl number considering the heating and cooling processes. This study will provide numerical heat transfer data of oscillating flow using wavy channel and help the design of compact heat exchanger in thermoacoustic system.