Heat transfer enhancement, entropy generation and temperature uniformity analyses of shark-skin bionic modified microchannel heat sink

Inspired by the shark-skin bionic concept, four novel flow control devices are proposed in this study to further enhance thermal performance (TP) with low entropy generation (S/S₀), as well as to improve temperature uniformity. Then, the flow structures and heat transfer characteristics of water-cooled microchannel heat sink (MCHS) modified by the proposed devices (Model A, Model B, Model C and Model D) are investigated in laminar flow regime (Re = 50–700). Results show that the variation trends of TP for different MCHS increase as Re increases, and the TP of all cases ranges from 1.1 to 3.1. And, the S/S₀ of all MCHS maintain low at small Re, which increases quickly as Re further increases. When Re is small (Re = 50–250), the largest TP is obtained by Model B with the smallest S/S₀. As Re is larger than 500, the TP and S/S₀ of Model D both become the largest. The varied geometry of flow control devices pushes main flow towards to side walls, and the sequential contraction and expansion area of split passage enhance the fluid exchange. However, the secondary flow generated by flow control device is not intense enough to cool down side walls when Re is small. Therefore, the temperature uniformity of MCHS is improved significantly with the increase of Re. The temperature uniformity of Model D is inferior to that of Model C due to hot spots exist at the narrow split passage. Furthermore, at large Re, Model C is superior to others, because the significant improvement of TP is achieved herein with acceptable S/S₀.