Effects of truncated and offset pin-fins on hydrothermal performance and entropy generation in a rectangular microchannel heat sink with variable fluid properties

Abstract

A rectangular microchannel with truncated and offset pin-fins is designed, and investigated using numerical simulation. The width (Wc) and height (Hc) of a single smooth microchannel are 0.1 mm and 0.2 mm, respectively. The pin-fin length, width and height (Hr) are 0.06 mm, 0.03 mm and 0–0.2 mm, respectively. The offset value (Wr) of two adjacent pin-fins in width direction of microchannel ranges from 0 to 0.07 mm. The effects of relative height (Hrc = Hr/Hc) and relative offset value (Wrc = Wr/Wc) on hydrothermal performance and entropy generation are analyzed. Results show that increasing pin-fin height usually results in both higher thermal enhancement and flow resistance. Increasing pin-fin offset value properly can enhance heat transfer, but extremely larger offset value leads to decrease of thermal enhancement. The microchannel with Hrc = 0.75 and Wrc = 0.6 yields the maximum overall thermal performance factor of 1.43. The minimum augmentation entropy generation number of 0.31 is obtained in microchannel with Hrc = 0.75 and Wrc = 0.4. From comparison of variable and constant fluid properties, variable fluid properties significantly affect flow and heat transfer performance. Particularly, fluid viscosity plays a key role in fluid properties while others have unobvious effect.