Study On The Thermal Transfer Performance Of Vertical U-tube Ground Heat Exchanger In Chongqing

Energy is the human basis of the survival and development. As the largest developing country in the word, the economic of china grow rapidly in recent years, accompanied by serious environmental problems. How to improve the use of energy levels, reduce energy consumption to the environment pollution and improve the living environment has become the hard task. Ground source heat pump came into being because of its energy saving, low cost, wide application, etc, and is becoming an important way of the current HVAC energy conservation.The performance of underground heat-exchanger is the most important in a GSHP system. Previous studies have yielded fruitful results, but there are many constraints to promote the application of ground source heat pump problems to be solved. So the paper researched the single and double U-tube ground heat exchanger performance and the thermal short circuit of the vertical pipe.The paper firstly tested the soil thermal properties of a ground source heat pump system in chongqing, obtain the local thermal conductivity of the rock conditions and corresponding drilling pipe heat resistance and other basic data. On this basis, the heat transfer capacity of single and double Vertical U-tube geothermal exchangers and temperature difference between inlet and outlet and capability of heat exchanging per meter in different preserved pipe of one hundred depth double U-tube geothermal exchangers was analyzed by the experiment data and CFD simulation. Then the paper developed software for scientific guiding the project of GSHP.Conclusions of this paper are shown that the thermal interference of the double U-tube heat exchanger is much higher than the single U-tube heat exchanger, so it is much more necessary to study the thermal short circuit of double-U-ground heat exchanger; The efficiency of thermal transfer per meters of the double U-tube heat exchanger can be increased by about 20%-40% than the single U-tube heat exchanger; The hot short-circuit can be reduced in the case of the up-pipe insulation, which can promote the thermal performance of double U-tube heat exchanger by about 25%-35%, So it is very important to preserve back water pipe, and the length of preserved pipe should be equal to the sum of length of saturated heat transfer area and heat transfer area of underground heat exchanger. The results also indicated that the efficiency of thermal transfer per meters in cyclical loads was higher than that in continuous loads with the same length of preserved pipe.