The Research Of Experiment And Numerical Simulation Of Heat And Moisture Transfer In Unsaturated Soil Under The Action Of Heat Source

In recent years,with the intensification of energy crisis and the worsening of environmental problems,new energy development and utilization technology has gradually become the focus of academic attention and research.Therefore,as a green low carbon,energy-saving and efficient shallow layer geothermal energy development and utilization technology,soil source heat pump technology has been developed and applied rapidly,but there are still many urgent problems to be solved in the optimization of the heat transfer efficiency of the buried pipe.There is a big difference between the heat transfer process and the heat conduction process of the buried pipe in the unsaturated soil,so it is a difficult problem to study.Based on the research of unsaturated soil heat and moisture transfer,a onedimensional soil column experimental platform was built for unsaturated soil heat and moisture transfer experiment.Through the analysis of the experimental results,the influence of 3 factors on soil moisture,heat and initial moisture content on the heat and moisture transfer of unsaturated soil is discussed.Numerical simulation of heat and moisture transfer in unsaturated soil was carried out based on Hydrus-1D software.The results show that:(1)In the 6 types of soil samples,fine sand,silt and clay have better heat transfer effect.Coarse sand and gravel sand have the following heat transfer effect,while the middle sand has the worst heat transfer effect.Under the influence of heat source,the relationship between temperature in the soil and the distance accords with the power function.(2)In addition,the higher the heat source temperature is,the more obvious the heat transfer and moisture transfer effect of the soil sample;the higher the initial water content,the more obvious heat transfer effect of the soil sample,but the change of wet transfer effect is little.However,the moisture transfer in the soil sample has obvious hysteresis compared with the heat transfer process.(3)In soil,the process of heat and moisture transfer is interacted and driven each other.The closer the distance from the heat source,the temperature gradient is dominant in the process of driving water migration;the farther the heat source is,the effect of the temperature gradient on the heat transfer process gradually decreases,and the influence of the humidity gradient on the heat and humidity migration process is gradually increased.(4)The simulation results show that in a certain range,the longer the heating time is,the greater the heat influence range is,the more obvious the moisture transfer effect is,the greater the value of the peak value of the soil moisture content.With the increase of heat source time,the peak value of water cut moves away from the heat source and the water accumulation area broadens obviously.At the same time,the higher the heat source temperature and the larger the initial moisture content,the better the fitting effect of heat and moisture transfer.