Heat transfer in the microchannels with fan-shaped reentrant cavities and different ribs based on field synergy principle and entropy generation analysis

Abstract

This study numerically investigates performance analysis of three types of microchannels and the results obtained are compared with the open literature. The results show that the effect of different types of ribs on the overall performance is evident. The thermal enhancement factor η of the microchannels F–R (with rectangular ribs) is always the lowest, depending on the range of Reynolds number. Furthermore, different comprehensive performance criteria, based on the first and second law of thermodynamics, are proposed to assess the relative merit of each microchannel. The microchannel F-Trp (with trapezoidal ribs) is appeared to be the most promising configuration when Re<300, while the microchannel F–C (with circular ribs) has the best performance when Re>300. According to field synergy principle, the heat transfer enhancement can be attributed to the good synergy between velocity vector and temperature gradient. Moreover, thermal boundary is disturbed after adding ribs and temperature different between the channel wall and fluid is small, thus the corresponding of irreversibility (entropy generation) reduces and heat transfer rate improves. The present study aims to provide alternative ways to evaluate the heat transfer performance of microchannels.