Investigation on effect of surface roughness on mixed convective heat transfer in microchannels

In this thesis, the effects of geometrical parameters such as surface roughness and microchannel dimensions on mixed convection heat transfer in microchannels were investigated. The contribution of combined natural and forced convection effects to total heat transfer was investigated experimentally in rectangular multiple microchannels fabricated using stainless steel material. The experiments were conducted with microchannel heat sinks having three different average surface roughness values of 1.1 μm, 1.8 μm, and 3.0 μm, three microchannel widths of 300 μm, 500 μm and 700 μm and two microchannel heights of 300 μm and 450 μm. During the manufacturing process, surface roughness values were controlled by changing electro-erosion fabrication parameters, and detailed surface maps were generated for the microchannel heat sinks. In the experiments using pure water as the working fluid, constant heat flux was applied to the bottom surface of the microchannel heat sink. The experiments were conducted in the range of 10–80 Reynolds numbers to ensure mixed convection conditions. In conclusion, it was determined that surface roughness had a significant effect on mixed convective heat transfer. Also, the causes and level of surface roughness effect were discussed.