Research On Soil Temperature Field Around Heat Exchanger Of Ground Source Heat Pump

The development of ground source heat pump technology is very fast in recent years owning to its energy-saving and environmental protection and the research in this field gradually in-depth. Recently the research of soil heat exchanger mainly concentrated in the modeling, analysis and calculation for a single pipe based on the theory of line heat source, cylindrical heat source theory and the theory of energy balance.For this reason, establishing the model of the underground pipe group under the ground water seepage according to the theoretical of inner heat source and the heat moisture transfer theory of soil. Analysis the soil thermal conductivity, specific heat capacity and the impact of groundwater seepage on the soil temperature field around the tube group by using Fluent software. The results showed that:both soil thermal conductivity and specific heat capacity have influence on the heat transfer and heat transfer radius of pipe. With the thermal conductivity increase, the temperature variation amplitude decreases, the heat transfer radius increases; with the specific heat capacity increased, reducing the magnitude of the temperature change, thermal effect radius reduced. In contrast, the thermal conductivity play a leading role on temperature change and heat capacity play a leading role on heat transfer radius of the pipe; The temperature distribution around pipe in a circular symmetry without seepage and the distribution of temperature field is oval when there is seepage. Groundwater flow enhances the flow direction of the thermal interference, weakened the thermal interference in direction of perpendicular to the flow direction.Groundwater flow can carry away heat or cold energy effectively from heat exchanger transfer to the soil, to weaken or eliminate the energy accumulation of the soil around the buried pipe caused by uneven load and the greater the flow rate, the more obvious effectiveness is.The spacing and arrangement of heat exchanger is designed in Shenyang (cold area B), Beijing (cold area C) and Nanjing (hot summer and cold winter area). Calculating annual load by DeST then comparing the heat accumulation and impact area for the three cities caused by different pipe spacing and arrangement through 1yesrs of simulation in the conditions of dynamic load, and the best buried pipe method were obtained.In actual projects, the temperature imbalance will be alleviated mostly owing to the imbalance of heating and cooling load if the groundwater flow is effectively used and the arrangement of multiple boreholes is reasonable. The results of this paper may provide reference for the practical design and operation of ground source heat pump in engineering.