The Simulation And Analysis Of An Over-length Gravity Heat Pipe’s Extracting Geothermal Technology

Over-length gravity heat pipe which is used to extract geothermal is built based on the advantages of the heat pipe. But this installation does not have a good effectiveness when it runs. In this paper, the FLUENT simulation software is used to simulate this over-length gravity heat pipe extracting geothermal,which length is 3000 m. Through the results of the simulation, analyzing the shortcomings of this installation and putting forward some measures to improve it. The FLUENT simulation software is used again to simulate the improved over-length gravity heat pipe. The improved simulation results can provide a reliable forecast for the improved over-length gravity heat pipe extracting geothermal installation and a theoretical guidance. The main research content of this paper is as follows:(1) The mechanism of convective heat transfer in gravity heat pipe is reviewed, and the working principle of the over-length gravity heat pipe is introduced. On the basis of this theoretical knowledge, summarizing the differences and relations between the over-length gravity heat pipe and the ordinary gravity heat pipe.(2) Using FLUENT simulation software which is belong to the CFD(Computational Fluid Dynamics) to simulate the over-length gravity heat pipe. First of all, the heat pipe is modeled and divided by the Gambit which is the pre-processing software. Secondly, the boundary conditions are set up in FLUENT, and the VOF model is used to calculate the flow and heat transfer in the gravity heat pipe. Because the evaporation and condensation models are not available in the FLUENT, the UDF(user-defined-function) can be used to define the evaporation and condensation models. The simulation results show that when the steam rises to the 2893 m, the steam begins to condense and the distance of the steam rising is 520 meters.(3) Optimal design of the over-length gravity heat pipe, according to the simulation results, the over-length gravity heat pipe extracting geothermal installation is improved in this four aspects. First, enhance the boiling heat transfer. Second, make the adiabatic section adiabat. Third, change the way of the liquid back. Fourth, put the pump in the right place.(4) Simulate the improved over-length gravity heat pipe, according to the simulation results, forecast the running condition and the output of the steam. This can judge the feasibility of the optimal measure. The result is that the output of the steam increases obviously.