Numerical Simulation Of The Flow And Heat Transfer Performance In A Gravitational Heat Pipe

There are a lot of merits of gravitational heat pipes, such as high efficiency in heat transfer performance, high heat transfer limits, excellent environmental suitability and reliable working performance. Thus, it is used more and more nowadays, especially being used in energy conservation, new energy exploitation and utilization. The working fliud flowing inside a gravitational heat pipe is liquid-vapor two-phase flow pattern. The flow and heat transfer performance is a complex process, which involves not only the two phase flow and boiling but also the condensation and heat transfer, so it hasn't been totally recognized by people untill today.Founding mathematic models is one of the most important methods for heat pipe research, which can not only obtain dependable forecast under different operating conditions but also provide theoretical guidance for design and application of heat pipes. After a simple retrospect of the development history and application of the heat pipes, the current situation of research on the process of the flowage and heat transfer inside a gravitational heat pipe was introduced, and then the foundational theories such as operating principles, heat transfer limits and resistance inside a gravitational heat pipe were illustrated in this paper. On the basis of learning a plenty of theoretical and experimental results on heat pipes of forefathers, the flow and heat transfer performance inside a gravitational heat pipe was analyzed, then several reasonable assumptions were made and a mathematical model based on two-dimensional coordinate system was developed to simulate and analyze the process of the flowage and heat transfer inside the gravitational heat pipe.According to the mathematical model which was built before, a Semi-Implicit Method for Pressure-Linked Equations (SIMPLE method for short) was used to solve the governing equations.At the same time, a C program was compiled to do numerical calculation of the heat pipe which is operating steadily at some working conditions. As a result, the distribution of temperature and pressure field was calculated and the flow patterns of vapor and liquid film inside the heat pipe were readily obtained. With the purpose of testifying the rationality of the mathematical model and the numerical calculation, the numerical results were compared with the forefathers'experimental ones. Then, the parameters such as the working temperature, density of heat flow in evaporation region, the length of the condenser and evaporator, and the diameter of the gravitational heat pipe were changed to get variable working conditions. The influence of the above parameters to the operation of the gravitational heat pipe was calculated separately, in order to provide theoretical basis for both parameters optimized for optimum design and the enhancement of heat transfer efficiency of a gravitional heat pipe.