Soil-temperature recovery characteristics of ground heat exchange system

Develops two kinds of soil-temperature recovery models with and without considering the axial heat transfer and the influence of groundwater flow by the superposition principle of temperature field, which are for the load in protective engineering. Analyses the soil temperature recovery process by the pure conductive model with different depths, radii, operation modes and heat flow densities. Studies the influence of groundwater flow on the soil-temperature recovery process and heat affecting distance.The results show that the influences of ground surface temperature and heat transfer along the borehole are non-negligible to soil-temperature recovery. Soil-temperature recovery rate decreases with the increase of distance and operating cycle, while it increases with the groundwater flow velocity. Soil-temperature recovery rate has correlation with soil properties, outdoor meteorological parameters, system operation modes and so on, while it is independent on the heat flow density. For load imbalance area, the borehole spacing should be appropriately increased.