Mechanism Of Heat Transfer Enhancement In A Triangular Grooved Channel For Pulsating Flow

Heat transfer by pulsating flow is a common way of unsteady heat transfer. Since pulsating flow could change the flow field and the thermal boundary, which affects the heat transfer largely, the pulsating flow and its associated heat transfer problems had caught the attention and interest of plenty of researchers. However, the pulsating flow is a typical process of instantaneous and nonlinear, even though numerous studies had been carried out to inspect the pulsating flow field characteristics on heat transfer enhancement, the mechanism of how the pulsating flow effects the heat transfer is still open.This service was to investigate the mechanism of pulsating heat transfer enhancement in a triangular shape grooved channel, through both the experimental and numerical simulation methods. The main work and achievements were as follows:1. The removable heat exchanger for experimental study was designed, and also, the NI-DAQ muIti-function data acquisition instrument and the particle image velocimetry system were set up, in order to precisely control the parameters and achieve the data.2. The effects of pulsation frequency and pulsation amplitude on the thermal efficiency were investigated in the range of300≤Re≤900.The result indicated that the pulsating flow could enhance the heat transfer efficiently. It was measured that the heat transfer improved up to190%at Re=300and St=0.36, A=50%compared with the steady flow case.3. The experimental investigation showed that as the pulsation frequency increased, the heat transfer enhancement ratio first increased and then decreased. The existence of the optimum pulsation frequency for the maximum heat transfer enhancement was confirmed. 4. The instantaneous velocity and vortex were acquired with the particle image velocimetry system. The relation between the velocity and vortex was analyzed, and the motion characteristics of the vortex were intended to explain the mechanism of heat transfer enhancement by pulsating flow.5. The numerical simulation under the same condition of experiment was carried out, and the results were consistent with the experimental findings. In order to investigate the heat transfer characteristics furthermore, the effects of different channel height on heat transfer were also numerically studied.