Study on Water Temperature and Soil Temperature Field for Outlet of Double-U Buried Pipe Based on Soil Stratification
The outlet water temperature and the heat transfer of underground pipes under the conditions of soil stratification and groundwater seepage were studied.Based on the theory of porous media,a transient three-dimensional model of layered rock and soil mass was established.The effects of the initial temperature of the soil,the seepage of groundwater,and the type of backfill material on the water temperature and temperature field of soil at the outlet of the buried pipe were analyzed.The initial soil temperature and the groundwater seepage velocity are positively correlated with the outlet temperature of the buried pipe.The temperature field variation of the soil depends to some extent on the type of backfill material and the thermal physical properties.When the initial temperature of soil was 290.15 K,the outlet water temperature of the buried pipe reached 280.43 K after 30 days of heat pump operation.Among the three commonly backfill materials,sand's heat exchange effect is the best,and when clay is used as backfill material there is a obvious cold accumulation near the buried pipe.When the groundwater seepage velocity reaches 200 m/a,the outlet water temperature of the underground pipe is 280.85 K,which is 0.51 K higher than that when there is no groundwater seepage.So the existence of groundwater seepage can eliminate the cold energy of soil accumulation,and the distance between the buried pipes along the seepage direction should be appropriately increased when laying underground pipes.
vertical double U buried pipeoutlet temperaturebackfill materialsgroundwater seepagesoil temprature
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