Study Of Heat Transfer Mechanism Based On Field Synergy Theory And Entransy Dissipation Evaluation In A Pulsating Flow

Heat transfer in pulsating flow has been the focus of heat transfer academia because of its advantage in heat transfer efficiency and removing dirt. Yet, its mechanism has not be known clearly. So the mechanism of heat transfer in pulsating flow was studied based on field synergy theory numerically, then, different heat transfer case in pulsating flow was also evaluated based on entransy dissipation theory.Heat transfer in pulsating flow in a triangular channel was investigated on the case of A=0.2,Re=300 and 450, 0.24≤f≤1. the results shows that Nu number first increases then decreases as f increases, there is a optimal frequency in which Nu number reaches its maximum. Nu number improves to 150% at Re=300,f=0.5 Hz compared with the steady flow case.Dimensionless synergy equation and dimensionless synergy number Fc was established for this experiment. Fc number was calculated numerically corresponding with experimental case. The results shows that Fc number of pulsating flow improves notably compared with steady flow. The changing tendency of Fc number and Nu number was the same when f increases. when Nu number reaches its maximum, Fc number too. because of the strong mixing caused by the repeating sequence of vortex generation, growth, expansion and ejection from the groove to the main stream, There are two high Fc zone in the pulsating flow, which improve the synergy quality of the hole field and make the convection term of energy equation larger notably. That is why heat transfer in pulsating flow was significantly improved compared to the steady flow.entransy dissipation was calculated corresponding with experimental case. The results show that entransy dissipation significantly decreases in the pulsating flow. contrary to Nu number and Fc number, as f increases entransy dissipation decreases then increases. when Nu number and Fc number reach their maximum entransy dissipation reaches its minimum. So heat transfer in pulsating flow has double advantages.