The Modeling And Numerical Simulation On Transfer Process Of Vertical U-tube Heat Exchanger Used In Ground Source Heat Pump

Ground source heat pump technology is developed with the use of shallow geothermal energy, which is of low taste but very rich. Heat transfer to the surrounding soil through the buried pipe in the summer, and the heat is absorbed through the buried pipe in the winter. So the ground source heat pump technology is a kind of clean and renewable energy use. In the energy crisis and global climate change, countries increase emphasis on the use of ground source heat pump, achieved a large-scale commercial use, and achieved good economic and environmental benefits. In china, the use of ground source heat pump technology has been booming since 1990s.U-type vertical pipe heat transferring model and the process of construction of the numerical simulation of engineering applications has been the theoretical foundation and the key and difficult of the ground source heat pump technology. In the practical engineering principles, this paper developed the thermal parameters and engineering design calculations for solving the VB program, to establish a quasi-hole drilling dimensional steady heat transfer model, the limited drilling outside the established two-dimensional model of long-term heat. On the geometric configuration is known, back to the good thermal conductivity vertical filler pipe to simulate the devices, and validated with experimental data.First, we do rock thermal response experiment. The initial soil temperature measured 14.8℃, the test vehicle data using regression analysis of the average thermal conductivity of rock 1.58w/mk. With the VB program we developed, and combine with "ground-source heat pump system technical specifications", the design method can easily find the corresponding visual thermal parameters and engineering design calculations.Secondly, as the boundary walls of the borehole were drilled within the established quasi three dimensional model of steady-state thermal conductivity and drilling outside the limited long-term non-steady two-dimensional heat conduction model.Then determine the pipe heat transfer model for simulation. In the engineering of practical principles, simplified model conditions, to determine the depth of the two typical (3 m and 20 m) of the radial heat flow with constant thermal conductivity of two-dimensional numerical model, combining MATLAB PDETOOL tool to simulate the heat transfer process. Single U, the heat flux q=402w/m~2, running 300 hours after the heat-affected depth of 3 m radius of 3.84m, 20 meter depth of heat affected radius of 3.61 meters. In the heat flux q=443.89w/m~2, running 300 hours, the 3-meter radius of the heat affected depth of 4.13 meters, 20 meters depth of heat affected radius of 4.06 meters.Finally the experimental data measured to verify the simulation results. By the comparison of the temperature data at the depth 3 meters and 20meters, and radial 1m, 2m, 3m of the double U heat transfer we can know simulation data are smaller than the experimental data, and the error are between 6% to 7%. Therefore, the results of application of the model data can be corrected and we can get the satisfactory results.