Study Of Heat Transfer On Underground Heat Exchanger System Of Ground Source Heat Pump

In this paper by experiment and numerical simulation of soil source heat pump system researches on the heat transfer performance of buried pipes. Experiments reveal the soil physical parameters along with the change of soil moisture content and porosity, and the field soil of permafrost and frozen soil thermal physical property comparison test.Using three parameters of unsaturated porous media seepage physical model, the buried pipe temperature boundary coupling with soil temperature boundary, to get the permafrost and frozen soil under the condition of buried tube heat transfer characteristics.The thermal physical property of sand soil will directly affect the heat transfer of buried tube in the ground-source heat pump system, therefore, in this paper, the thermal physical properties of sandy soil and its influencing factors were investigated experimentally. The effect of moisture content and porosity of sandy soil on its thermal conductivity, specific heat, thermal diffusivity was analyzed. The results showed that the thermal conductivity of sandy soil increased and the specific heat capacity increased at prescribed porosity with increasing the moisture content; the thermal diffusivity reached maximum at5%of moisture content. At prescribed moisture content, thermal conductivity and specific heat capacity of sandy soil decreased linearly with increasing the porosity, in contrary, the thermal diffusivity linearly increased; at prescribed porosity, thermal conductivity and specific heat capacity of sandy soil increased linearly with increasing the moisture content, in contrary, above5%moisture content, the thermal diffusivity linearly decreased moisture content. The research conclusions could provide some basic data for the heat transfer of buried tube in the ground-source heat pump system.After frozen soil thermal conductivity increase, specific heat capacity decreases, increasing temperature conductivity, so on the freezing and frozen soil are simulated respectively.Frozen soil pressure is greater than the frozen pressure. Frozen water saturation coverage than the freezing water saturation change trend, because the water is free settling effect, in the underlying water saturation is close to1; Scope of frozen soil temperature changing trend is greater than than the temperature of the frozen soil. In the soil around a horizontal buried pipe, temperature、water saturation and pressure change in lateral migration is not very significant; On the contrary, on the vertical gradient, temperature、water saturation and pressure change is significant.