| Currently, the domestic and international energy situation has become increasingly serious. It’s extremely urgent to advance new technologies to improve the utilization ratio of energy in our country. Pulsating flow heat transfer enhancement, for its unique advantages, has won the favor of scientific researchers both at home and abroad. And in the course of industrial production and daily life, It has broadly prospects for application. However, it’s very complex to investigate the pulsating flow because of the huge influencing factors. Presently, research in pulsating flow is not comprehensive enough. So, to research it extensively and in-depth is particularly important.The existing mechanism for pulsating heat transfer enhancement is numerous, but lack of unity between them. Vortex is the basic action in pulsating flow behavior. It means that the influence of the pulsating parameters can be represented by vortex motion. Therefore, vortex motion can not only be the internal essence between the existing pulsating flow strengthening mechanisms, but also creates the possibility to put forward for a more instructive and general pulsating heat transfer mechanism. Thence, it is particularly important to study the vortex motion characteristics in pulsating flow and explore the intrinsic relationship between the elements of pulsating flow heat transfer mechanism.The main work and achievements are as follows:1. The pulsating heat exchanger was designed, with the Polyimide film heater used to supply constant heat flux from the groove surface to the fluid. And the pulsating flow convection heat transfer experimental system was set up. The temperature measuring system to this experiment was designed. Furthermore, synchronous data acquisition system between NI-DAQ multi-function data acquisition instrument and particle image velocimetry system (PIV) was set up.2. At530≤Re≤1400, the effect of pulsation amplitude and pulsation frequency on the vortex motion and thermal efficiency were studied in five different kinds of cases. Especially, it’s found that the motor period of the vortex will be changed by the pulsation amplitude and the heat transfer improved up to180%at Re=750and P=l/3compared with the steady flow case, when study the relationship between pulsation amplitude and heat transfer efficiency at/=1.2HZ.3. The fluid-structures in the corresponding cases were acquired using the particle image velocimetry system (PIV). Then, pulsating flow heat transfer enhancement mechanism was attempted to explain using the Motion characteristics of the vortex. |
