Numerical simulation of laminar heat transfer in microchannels with rough surfaces characterized by fractal Cantor structures

The topography of rough surfaces is characterized by using a Cantor set structure. Based on this fractal characterization, a model of laminar heat transfer in rough microchannels is developed and analyzed numerically. The effects of the Reynolds number, relative roughness, and fractal dimension on laminar heat transfer are all investigated and discussed. The results indicate that the local Nusselt numbers after the entrance region are no longer constant but tend to experience fluctuation along the rough microchannels. Differing from the smooth microchannels, the average Nusselt number increases nearly linearly with the Reynolds number and is larger than the classical value. For higher values of relative roughness, the flow-over roughness induces flow separation, which plays an enhancement on laminar convective heat transfer. Moreover, the laminar heat transfer in microchannels is also enhanced by roughness with a larger fractal dimension yielding more frequent variation in the surface profile even though at the same relative roughness.