A numerical study of vorticity-enhanced heat transfer
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In this work, we have numerically studied the effect of the vorticity on the enhancement of heat transfer in a channel flow. In the first part of the work, we focus on the investigation of a channel flow with a vortex street as the incoming flow. We propose a model to simulate the fluid dynamics. We find that the flow exhibits different properties depending on the value of four dimensionless parameters. In particularly, we can classify the flows into two types, active and passive vibration, based on the sign of the incoming vortices. In the second part of the work, we discuss the heat transfer process due to the flows just described and investigate how the vorticity in the flow improves the efficiency of the heat transfer. The temperature shows different characteristics corresponding to the active and passive vibration cases. In active vibration cases, the vortex blob improves the heat transfer by disrupting the thermal boundary layer and preventing the decay of the wall temperature gradient throughout the channel, and by enhancing the forced convection to cool down the wall temperature. The heat transxfer performance is directly related to the strength of the vortex blobs and the background flow. In passive vibration cases, the corresponding heat transfer process is complicated and varies dramatically as the flow changes its properties. We also studied the effect of thermal parameters on heat transfer performance. Finally, we propose a more realistic optimization problem which is to minimize the maximum temperature of the solids with a given input energy. We find that the best heat transfer performance is obtained in the active vibration case with zero background flow.