Research On Heat-fluid-solid Coupling Heat Transfer And Heat Storage Mechanism Of Energy Storage Rock And Soil

In recent years,building energy consumption has accounted for a large proportion of total social energy consumption.As a system that uses shallow geothermal resources efficiently to heat and cool buildings,ground source heat pump has been widely recognized by the society for its low energy consumption and easy maintenance.The core equipment of ground source heat pump system is the buried pipe heat exchanger.The buried pipe mode and the heat transfer performance of the pipe body and the surrounding medium have been the research hotspots of the heat pump system.Compared with the vertical buried pipe,the horizontal buried pipe has the advantages of small initial investment cost and convenient construction.However,due to the shallow horizontal burial depth,the tube is basically located in the shallow soil,and its heat transfer performance is easily affected by the external winter and summer climate and soil hydraulic characteristics,resulting in the low heat transfer efficiency of the horizontal tube,which limits its application and promotion to a certain extent.In order to solve this problem,this paper carried out numerical simulation on the heat transfer performance of horizontal buried pipe in soil,and discussed the influence of different factors(different groundwater depth,different soil types,and different heat exchanger structures)on the heat transfer performance of horizontal pipe heat exchanger.The results show that increasing the buried depth of the horizontal tube can make the soil around the tube have higher moisture content,thereby enhancing the heat transfer performance of the horizontal tube heat exchanger and the surrounding soil,but it will increase the excavation cost in the early construction.At the same time,the heat transfer performance of horizontal buried pipe is affected by soil specific heat capacity,and the influence of thermal conductivity on it is also significant.When the comprehensive thermal conductivity and comprehensive specific heat capacity of soil are large,the horizontal pipe has better heat transfer performance.For different soil types,the heat transfer performance of horizontal tubes in loam is the best,followed by that in sand,and that in clay is the worst.In addition to the influence of soil hydraulic characteristics and soil types,the structure of horizontal pipe itself has a great influence on its heat transfer performance.The traditional arrangement of straight pipes is not easy to cause soil thermal accumulation.Under long-term operation,the distribution of soil temperature field around the pipe body is better,but its soil utilization rate is low,and the heat transfer is often difficult to meet the needs of building heating and refrigeration.The arrangement of horizontal ' slinky ' spiral buried pipe increases the land utilization rate to a certain extent.However,due to the small spacing of the pipe body and the serious thermal interference between the pipes,the overall heat transfer efficiency is greatly reduced,resulting in poor heat transfer effect.Compared with the above two methods,the horizontal ' spiral ' type spiral buried pipe has the advantages of the highest land utilization rate and the best heat transfer performance,and the thermal accumulation risk coefficient is within the controllable range under long-term operation.