The Study On Temperature Field And Design Of Geothermal Heat Exchanger Cluster Under Groundwater Seepage

After the energy crisis in the 1970 s,energy conservation and environmental protection have been the hot issues concerned by all countries.As a new low-carbon and energy-saving air-conditioning technology,ground source heat pump(GSHP)has great potential in the use of renewable energy.The related theoretical research and practical application are increasing.At present,the study of buried pipes is mostly based on pure thermal conductivity model.For the existence of underground seepage and stratification of rock and soil,it is often neglected or added to the comprehensive thermal conductivity of rock and soil as a positive factor.Some scholars have made some qualitative analysis on the heat transfer performance of underground heat exchanger considering the stratification of rock and soil when there is underground seepage.However,due to the complexity of the problem,there is not much in-depth theoretical analysis so far.What's more,most of the existing design and calculation software for underground heat exchanger do not consider the influence of groundwater seepage and stratification of rock and soil.In this paper,firstly,an analytical model considering the stratification of rock and soil under seepage is established with the temperature of borehole wall as the coupling parameter.And through the thermal property test of a ground source heat pump project in Nanchang City,the measured value of the effluent temperature of the buried pipe is compared with the simulated calculation results,the results are in line with expectations.Secondly,based on the established single-hole heat transfer model,the step load and superposition principle,the heat transfer model of the buried tube group with variable heat flow under the seepage is established.Then,with Microsoft Visual Studio 2012 as the development tool,the complex functions are calculated and processed by using MATLAB,a program for designing and data processing of vertical buried pipe heat exchanger is completed by using modularization and structured design principles.Combining with engineering examples,the actual engineering parameters are substituted into the design calculation program.The total length of buried pipe and the number of boreholes are calculated,and compared with the commercial software GLD2012.The results show that the program design calculation module is reliable.The outlet water temperature of the underground heat exchanger and the radial temperature distribution of the U-shaped underground heat exchanger are calculated,and compared with the measured values,the correctness of the heat transfer model of the tube group and the reliability of the program temperature calculation module are quantitatively verified.Finally,combined with engineering examples,the design and heat transfer performance of underground tube heat exchanger are quantitatively analyzed under different factors by using the program.