Heat transfer and pressure drop in microchannels with random roughness

• Numerical simulations of flow and heat transfer have been performed for flow over surface roughness.
• The surface roughness influence on fluid flow and heat transfer has been investigated.
• The lattice Boltzmann model has been used for energy transport for this simulation.
• It has been found that in the presence of the surface roughness there is heat transfer enhancement.
• The mechanism which causes this heat transfer enhancement is reviled.

The effect of surface roughness on heat transfer and fluid flow phenomena within a microchannel has been investigated by using the lattice Boltzmann method. The surface roughness has been generated by using Gaussian function. Gaussian function is an efficient and convenient method to create surface roughness.Influence of the roughness cut-off frequencies and the relative roughness height has been investigated. It has been found that there are two mechanisms which influence heat transfer and fluid flow phenomena. The presence of low velocity regions and heat transfer intensification near the roughness tips are discussed.Realistic and simplified roughness models have been considered. Their influences on fluid flow and heat transfer phenomena have been investigated. Results obtained by using the real roughness model have been compared with the results obtained by using the simplified roughness model. The results confirmed that the simplified roughness model can be used to mimic real roughness model. In other words, simplified roughness model can be used to investigate influence of surface roughness on heat transfer and fluid flow phenomena.