The Study On Soil Average Temperature Of GSHP System With Deep Heat Exchanger Operating In Extreme Cold Area

With the improvement of living standards,people pay more attention to the indoor thermal comfort,and more energy is consumed in the construction industry.Using sustainable and non-polluting energy sources to replace conventional sources of heat and cold can effectively reduce the energy consumed by buildings in heating and cooling.Geothermal energy is one of them.Harbin is located in extreme cold area.when the ground source heat pump is used in Harbin,the temperature of the underground soil will reduce due to the uneven cooling and heating load,which will affect the work performance of the ground source heat pump,resulting in poor heating and cooling effects or wasting more energy.Harbin is located in the Songnen Plain and is a region rich in geothermal energy.This article will analyze the impact of increasing ground heat exchanger depth,ground source heat pump system operation on the average soil temperature.Considering that the depth of the ground heat exchanger used in this project is up to1200m,it is rare in extreme cold area.The initial soil temperature of 1200m depth was obtained through experiments,and the exothermic heat extraction of 600m and 1200m depth ground heat exchangers was studied experimentally.The experimental results show that the initial temperature of 1200m depth in Songbei Harbin is 45?,and the maximum heat intake of 600m deep ground heat exchanger is 72.07kW,and the maximum heat intake of 1200m depth is 161.49kW.Ground-source heat pump systems improve the indoor thermal environment of a building,mainly by transferring excess heat or cooling from the room to the soil temperature field.When the building cooling and heating load changes,the working performance of the heat pump will also change,and affect the underground soil temperature through the ground heat exchanger.DeST was used to calculate the whole year dynamic load of the building.Combined with the central heating period in Harbin,the whole year dynamic load of the building was calculated.According to the calculation results,the ground source heat pump system is used for building heating for 170 days.The thermal load index is 30.21 W/m~2,and the cooling load index is 15.03 W/m~2.With reference to the ground source heat pump system in this experiment,the simulation model is built in TRNSYS to simulate the effect of the ground source heat pump system operation on the underground soil temperature.In the study of 1200m deep ground heat exchanger,the temperature gradient is too large,so the simulation group number was simulated at intervals of 100m.In the simulated one-year results,with the increase of the depth of the ground heat exchanger,the decrease of the average soil temperature decreases;the system COP increases with the depth of the ground heat exchanger.During the 10-year simulation run,as the depth increased,the decrease in average soil temperature decreased.The soil temperature around the ground heat exchanger with a depth of less than 400m is reduced by more than 9°C,which seriously affects the operation of the ground source heat pump system.