Study And Numerical Analysis Of Soil Temperature Field Of Soil Source Heat Pump Heat Exchanger In Cold Region

With the advancement of social and economic development in China,people have higher demand for healthy and comfortable living environment today,leading to the growth of energy demand for air conditioning and heating year by year.Due to the unbalanced energy consumption structure in the past,the short supply of energy is becoming more and more severe.Since the traditional heating methods no longer meet the requirements of the current times,the use of renewable energy for cooling and heating has become the trend for future development.With the advancement of science and technology,the application of ground source heat pumps(GSHP),an air conditioning heating technology that makes use of renewable and clean energy,has gradually become mature and attracted the attention of more and more researchers.Among them,improving heat exchange efficiency of the heat exchanger and minimizing the impact on the ground temperature field are the main directions of the researchers.This paper looked into the operation of GSHP in severe cold areas based on the project located in Lanxi County,Heilongjiang Province.First,thermal response experiment was carried out on the borehole to obtain the soil thermophysical parameters and the heating capacity of the borehole.Then,the author obtained the operation data of the project during the winter heating period from the monitoring system,and summarized the rules on the changes of soil temperature and other parameters before and after the GHSP heating period in severe cold area.The author also proposed suggestions on adjustment of the operation strategy based on the change of temperature during the soil recovery period.A three-dimensional heat transfer model for the GSHP single U-tube was established.The author proved the effectiveness of the model with the experimental results,and compared the different impact of intermittent and continuous operation strategies on the ground temperature field.Finally,the author set up the heat transfer model of the nest of tubes,and analyzed the effect of different tube spacing on ground temperature field and the efficiency of the heat exchanger in the central area.The author adopted this simulation to compare and analyze the changes in the radial temperature and ground temperature field after long-time operation under continuous and intermittent modes.The results showed that after long-time operation,the average ground temperature fell by 1.09% under the intermittent operation mode and 3.7% under the continuous operation mode.After the heat exchange,the temperature influence radius of intermittent mode is much smaller than that of continuous operation mode.Through the simulation results of the nest of tubes,it was found that single tube spacing did have an effecton the ground temperature field and heat transfer efficiency in the central area.After 6 months of simulated operation,the average ground temperature with the single tube spacing of 5m,6m,and 7m decreased by 10.41%,9.44%,and 8.46%,respectively.The efficiency of the heat exchanger in the central area increased by 17.34% and 29.5% compared to the model with a spacing of 5m.By carrying out experimental research,this paper put forward the operation rules of GSHP in severe cold areas.Based on numerical simulation,the influence of different operation strategies of the single U-tube and different borehole spacing of nest of tubes were analyzed.Through this research,this paper hopes to provide references for the operation strategy,borehole layout,and ground temperature change of GSHP in severe cold areas.