Study On Start-up Characteristics And Heat Transfer Performances Of Plate Pulsating Heat Pipe

Pulsating heat pipe as a new member of the heat pipe family, is considered as a possible potential heat transfer component for the micro-electronics cooling of high heat flux. As the internal operation mechanism of pulsating heat pipe is involved in two-phase system which embodies multi-disciplinary and multi-parameters, the investigation on pulsating heat pipes is still at a primary stage.In order to study the start-up characteristics and heat transfer mechanism of plate pulsating heat pipe, the experiments of aluminum-type pulsating heat pipe are carried out in this paper. The experiments have researched the influence which some important factors to the heat pipe's start-up and performance under different heating method (bottom heated and top heated). The results indicate that heating power and filling rate are the important factors for the start-up of the plate pulsating heat pipe. Different filling rate needs different start-up power. The methods of increasing the heating power and enlarging the heating area can make the start-up easier. The thermal resistances of plate pulsating heat pipe are related with the heating power, and the higher the heating power is, the smaller the thermal resistances are. But the best filling rate which the heat pipe needs is different with different heating methods. As the research indicates, the best filling rate for the bottom heated is about 31.4% while this number is 54.9% for the top heated, and the performance of the heat pipe in the case of the bottom heated is better than the other.Besides, the visualized experiments of plate pulsating heat pipe are also carried out in this paper. The experiments have observed the working fluid's oscillation characteristics at different running stages. The results show that the flow patterns of working fluid can be divided into:bulk flow,annular flow and mixed flow. The bulk flow is the major flow patterns in the start-up stage, while the annular flow is the major in the stable operation stage. The working fluid's flow pattern is affected by filling rate and heating power.At the end of this paper, the regularity of heat transfer is theoretical analyzed. A single gas-liquid plug model and a double gas-liquid plugs model are built with the method of momentum-mass-energy conservation, and the characteristics of the two models are comparatively analyzed. The theoretical model is also focused on the initial pressure, tube size and working fluid to the movement of the liquid plug. By the numerical calculation, it can found that the double gas-liquid plugs model is more reasonable than the single gas-liquid plug model. The range of motion of liquid slug is enlarging with the increasing of the initial pressure and tube diameter, and this is benefit for the heat transfer performance of the heat pipe.