A study of the heat transfer law of ground source heat pump with seasonal heat storage

Based on the method of finite element analyses a quasi 3-D unsteady-state heat transfer model was developed. Changes in soil temperature, transfer rate per unit borehole depth and thermal influencing radius for ground source heat pump with seasonal heat storage with the heat pumps operation time were analyzed by comparison with the experimental results. The effects of soil structure, inlet water temperature, inlet mass flux and operation models on heat transfer of soil and the issue of ground heat balance were investigated. The results indicate that soil temperature at the same radius of different depths increases with the soil thermal diffusivity, the thermal influencing radius increases with the operation time, and the inlet water temperature gradually tends to be steady. The fluctuation changes in the soil temperature and heat transfer rate under the intermittent operation model and the soil temperature of radial distance more than 0.3 m were fitted with two models, indicating that the mass flow rate of the inlet fluid was not too big under the requirement of the heat transfer rate of the system, the soil temperature is recovered after one cycle of operation (360 d) of the ground source heat pump system with seasonal heat storage, and the fluid inlet temperature should be more than 40 ℃.