Flow and heat transfer analysis of microchannels structured with rectangular surface roughness

Microchannels structured with hybrid rectangular surface roughness is numerically analyzed for thermal-hydraulic performances of laminar flow. The performances are compared between working fluids of air and water, and under different heating walls and roughness configuration conditions at constricted Reynolds number (Re-c) of 50-250. The results show that both constricted friction factor and Nusselt number of water are slightly higher than those of air. The performance index (eta) of air increases with increasing Re-c but is decreasing for water, and the average deviation between them is 11 %. The convective heat transfer with one rough heated wall is almost 40 % lower than that of two heated walls, whereas the constricted friction factor has negligible difference. The channel structured with regular surface roughness (constant roughness height and with air flow) shows about 14 % higher values of eta than those of the respective channel with hybrid surface roughness at Re-c = 200. Structured surface roughness with suitable configuration can be an innovative way to improve the heat dissipation for electronic cooling.