地源热泵间歇运行地温变化特性及恢复特性研究

针对土壤源热泵运行过程中地下传热衰减问题,进行了热泵间歇运行实验,测试分析了热泵间歇运行过程中地温变化规律及其对换热率和机组性能的影响.建立基于渗流的三维非稳态传热模型,对地下垂直U形埋管与周围土壤的热湿耦合传递进行数值计算,模拟了热泵运行状态下地温变化及热泵停歇状态下地温恢复特性;数值分析了土壤导热系数、土壤孔隙率、不同回填材料及太阳辐射能对地温恢复过程的影响.实验与数值计算都表明,热泵可控间歇运行策略对于改善地下传热,提高热泵系统性能具有重要作用,探讨热泵可控间歇运行问题对于地热能高效一体化利用具有理论意义.

Study of characteristics of soil temperature variation and recovery under intermittent operation of ground-source heat pump

The analyses of the variation rule of the soil temperature and its influence on the heat exchange rate and unit performance are studied by using the intermittent operation experiment of the heat pump,which is aiming at the problem of the attenuation of the soil temperature during the operation.The 3-dimensional unsteady state heat transfer seepage model is developed according to the groundwater advection and heat-transfer process between the vertical U tube underground and its ambient soil,based on which,the temperature variation under the operation of heat pump and the soil temperature recovery characteristics under the intermittent operation are simulated,the soil temperature recovery process influenced by the thermal conductivity,soil porosity,different backfill materials and solar radiation energy is discussed.It is presented by both the numerical simulations and experiments that: the intermittent operation of the heat pump plays an important role in improving the heat transfer underground,enhancing the heat pump property and has theoretical significance to the utilization of the geothermal energy.