Parametric study on thermal and hydraulic characteristics of laminar flow in microchannel heat sink with fan-shaped ribs on sidewalls - Part 2: Pressure drop

This second part of a three-part study concerns pressure drop of laminar flow in microchannel heat sinks with water and silicon used as fluid and solid for the computational domain. In the rectangular microchannel with width of 0.1 mm and depth of 0.2 mm, the repeating aligned or offset fan-shaped ribs are mounted to the channel sidewalls. To examine the influence of fan-shaped rib's geometry on thermal and hydraulic characteristics of laminar flow, three non-dimensional variables, representing the width (0.05-0.4 mm), height (0.005-0.025 mm) and spacing (0.2-5 mm) of fan-shaped ribs are designed. The present study firstly presents the pressure distributions in microchannels to analyze the local hydraulic characteristics, and then examines the local pressure and friction factor along the flow direction for different geometry of fan-shaped ribs. Results show that the fan-shaped ribs can lead to large increase of local pressure in comparison with the smooth microchannel, especially for the aligned fan-shaped ribs. Further, the effect of fan-shaped ribs' geometry on the average friction factor has been investigated. Results show that with the increase of fan-shaped ribs' width, the friction factor ratio of the studied microchannels to the smooth one firstly decreases and then increases. The increase of fan-shaped ribs' height and decrease of ribs' spacing can lead to the extreme increase of average friction factor, especially for the microchannels with aligned fan-shaped ribs. For Reynolds number ranging from 187 to 715, the microchannels with aligned fan-shaped ribs show the average friction factor 1.1-8.28 times larger than the smooth one, while those with offset fan-shaped ribs show 1.22-6.27 times higher. New pressure drop correlations for such microchannel heat sinks are developed, which fit the present data with a mean absolute error of 13.2% for the ones with aligned fan-shaped ribs and 13.5% for the ones with offset fan-shaped ribs.