Study On The Characteristics Of Ground Thermal Response In Summer And Winter Time

Ground-source heat pump air-conditioning system is a rising energy saving and environment friendly technology with the emergence of world wide energy crisis and environmental problems, and the ground-source heat pump systems have advantages of energy saving and low operating cost etc, compared with the traditional air-conditioning systems. The parameters of soil thermal property are the key factor in the design of borehole heat exchanger in ground-source heat pump system. Under a certain cooling or heating load, the number and depth of the boreholes are based on the soil thermal property parameters to a great extent, and the ground's thermal conductivity. In the practice engineering use, it is tested soil heat response in summer to get the ground's thermal conductivity, and the same time it is assumed the thermal conductivity in winter is the same as in summer, as a matter of fact, the transfer direction of moisture is different in summer and winter, the heat exchanging rate per unit tube plays important role for thermal response testing, therefore, the situation for rate of containing water is varied. So the assumption is truth or not, it is to do some further studying.The main contents in this paper are following up. It is discussed the characteristics of soil parameters. On the basis of the heat transfer mechanisms and heat exchange models of the borehole heat exchanger, it is made a soil heat response theoretical model to analyses the principal of ground's thermal conductivity. By the heat response performance testing bed, it is studied the ground thermal response both in summer and winter. By adjusting the velocity of flow through rating pump, it is studied the relationship of velocity for ground thermal response. By adjusting the output energy of experimental machine, it is studied the characteristics of ground thermal response for different unit of tube length under varied different exchange heat. By testing the thermal response for U heat exchange under the same location but different depth, it is studied the diversity of ground's thermal conductivity under different location infinite. By using the line source model to analyze the data, it is deduced the ground's thermal conductivity under different conditions and made out the influence of different conditions for ground's thermal conductivity.After a series of theoretical analyzing and experimental testing, there are some conclusions are following. For the borehole tube and heat flux of surrounding ground, the heat exchanging rate per unit tube plays important role for thermal response testing. The ground's thermal conductivity of getting heat in winter is bigger than the one of dispersing heat in summer. For the testing location (Songjiang Shanghai), the former is the 1.15 times of latter. The velocity of tube does some influence for thermal resistance of drilling hole and the inlet and outlet temperature of U tube, and does not affect the ground's thermal conductivity. The ground's thermal conductivity in deeper region is some how bigger than lower regions. For the testing location, the ground's thermal conductivity increases by 3.0% of 60m depth than 40m depth.