Research Of Soil Temperature Recovery Around Ground Heat Exchanger With Constant Heat Flux

Ground Source Heat Pump(GSHP) system uses the geothermal resources underground. It can transfer the potential energy from the low temperature to the high temperature by inputting small quantity of highly potential energy such as electricity. In this way, it can provide both cooling and heating.It not only has lower electric energy comsumption,but also runs more efficiently and steady,and has prominent environmental benefits,such as achieving the target of environmental protection and sustainable development by reducing the harmful gas exhaustion.especially Ground Coupled Heat Pump (GCHP),which is widely used in present projects.However,the soil that is the cold and heat sources of this kind of air-conditioning,influences the heat transfer performance of ground heat exchanger and the COP of system.so it is necessary to research changes of soil temperature in detail,especially its recovery after having heat exchange with ground heat exchanger around.This thesis brings in the finite linear heat source of variational heat flux with step load and superposition principle on the basis of the one of invariable heat flux.it can make the heat absorption and recovery stages equivalent to variations of heat flux for q and 0,and use the self-built platform of experiment to verify whether this model can be applied to the study of my thesis.Based on this,this paper will simulate the variation of underground soil with different conditions,different proportions of start-stop and different heat flux,and then particularly research the variations of soil temperature with thermo-physical properties of underground soil,such as density,specific heat and thermal conductivity,finally make some conclusions.By utilizing the on-site test data to verify the initial temperature model,it is concluded that the theoredical analysis is quite consistent with the experimental results,especially below 10 meters,the maximal relative error is only 3.7% which is in the 20m.so this can be applied to practical projects better.In addition,the finite linear heat source is also validated,which concludes that the theoretical value in half depth is in a agreement with the experimental results,relative error is about 15%,this is allowed in practical projects.As for other conclusions like the effections of soil thermo-physical properties and the soil recovery in different conditions,those are presented detailedly in Chapter Five due to more conclusions.This paper will contribute to improve the efficiency of heat transfer between heat exchanger and soil,reduce the initial investment,and have the certain practical significance.