Study On The Heat Transfer Performance Of The Gravitational Heat Pipe Used Under Ground

Gravitational heat pipe is a new type of heat transfer equipment with high efficiency. It can transfer heat without any extra power, so it is used more and more nowadays, especially being used under ground. It can make full use of the geothermal energy efficiently.In order to make better research of the heat transfer characteristics and working condition of the gravitational heat pipe which is used under ground and improve the heat transfer character of the heat pipe, the working principle inside the heat pipe was analysed in this paper based on the research of plenty of theoretical and experimental study on the heat pipe, then reasonable assumptions were made and a mathematical model was set up for the internal flow and heat exchange in the heat pipe. A numerical simulation was done to the heat transfer performance of the heat pipe operating steadily under ground using the above model.According to the model which was built before, A C program was compiled to do numerical calculation of the heat pipe which is operating steadily at some working condition. The height of the liquid tank in the heat pipe, the wall temperature distribution from the condenser to the evaporator, the thickness of the liquid film, flowing speed of the vapor and the liquid film, the condensing heat exchange coefficient and the evaporating heat exchange coefficient along the heat pipe was calculated and gained in this paper, simulating the heat transfer characteristics of the heat pipe which is operating under ground. Then, the parameters such as the condensed temperature, the heat power, the mass of liquid filled in the heat pipe, the length of the condenser and evaporator, and the diameter of the heat pipe were changed to get variable working condition. The influence of the above parameters to the operation of the heat pipe was calculated separately. The change of the thickness of the liquid film and change of the heat transfer coefficient under variable parameters was calculated to get a conclusion of the change of the heat transfer performance under different conditions, and theoretical foundation was proposed for improving the parameters to make the heat pipe better operate, as a result of which the heat pipe will work at the most appropriate condition and operate efficiently.