地埋管传热仿真实验平台建设与传热性能研究OA

To investigate the variation patterns of heat transfer performance in ground heat exchangers(GHEs),a laboratory-scale thermal simulation platform was constructed based on the principle of heat transfer similarity.This sandbox experimental setup includes two sets of double U-tube boreholes,enabling the simulation of various geological conditions such as initial ground temperature and groundwater flow velocity,as well as operational conditions including single versus double U-tube configurations and heat rejection versus heat extraction modes.Comparative experiments were conducted on the heat transfer performance of GHEs in both dry and water-saturated strata using this platform.The results indicate that under summer heat rejection conditions,variations in the thermal conductivity of the stratum alter the ratio of heat exchange per meter between double and single U-tube GHEs.This ratio is higher in dry strata with lower thermal conductivity and decreases when the stratum becomes water-saturated due to increased thermal conductivity.The smallest ratio is observed under winter heat extraction conditions.During summer operations,a lower initial ground temperature leads to a greater enhancement in GHE heat exchange.Specifically,a 3℃ increase in the initial temperature of the bottom stratum reduces heat exchange by 6.5％.When the dry stratum becomes saturated with water,the heat exchange of the GHE increases by more than twofold.Additionally,increasing the groundwater flow velocity from 0.22 m·d-1 to 0.35 m·d-1 improves heat exchange efficiency by 13％,indicating a significant enhancement in heat transfer capacity.