Study On The Operating Characteristics Of The Heat Source Tower-underground Pipe Compound Ground Source Heat Pump System

Energy plays an important role in human development and progress.With the development of human society and economy and people’s increasing demands on the living environment,building energy consumption is growing rapidly,and the application of efficient energy use technologies to alleviate the energy crisis has become a major social issue.As a major energy producer and consumer in the world,my country should actively develop and use renewable energy and increase the use and development of renewable energy.As a new type of heat pump technology that utilizes shallow geothermal energy,ground source heat pumps have been widely used in many regions of our country.However,due to the differences in climate,underground heat exchangers have been widely used in the process of using ground source heat pumps.The amount of heat taken and discharged in the middle of the year is different.This long-term imbalance will cause the soil temperature to continue to rise or fall,and to deviate from the initial soil temperature,resulting in a decrease in the performance of the unit system.The solution of environmental protection to achieve soil heat balance and to solve its key problems is of great significance.Aiming at the problem of soil heat imbalance in ground source heat pump systems,the main research contents of this paper are as follows:First of all,in order to solve the problem of soil thermal imbalance,this paper proposes a heat source tower-buried pipe composite ground source heat pump system,which uses the time period when the unit does not provide cooling and heating during the transition season,and the buried pipe is installed through the heat source tower.The surrounding soil area is adjusted for heat balance.Mathematical models of heat source towers,buried pipe heat exchangers and heat pump units are constructed on the MATLAB platform,and the combined ground source heat pump system model is integrated.Two typical northern and southern cities—Nanjing and Shenyang were selected.The meteorological parameters and building load data generated by the software De ST were used to focus on the thermal imbalance rate and the change in soil temperature to study the soil thermal imbalance in these two cities.According to the conditions and causes,the various parts of the combined ground source heat pump system were systematically designed according to the building load of Nanjing and Shenyang and the heat balance of the soil.Secondly,in order to explore the operation law of the heat source tower—the buried pipe compound ground source heat pump system in the transitional season,this paper studies the influence factors such as outdoor air temperature,outdoor air relative humidity,soil temperature,air flow and water flow.The effect of system performance.The results show that the greater the temperature difference between the soil temperature and the outdoor air dry bulb temperature,the heat exchange can be greatly increased;while the increase in the relative humidity of the outdoor air will weaken the heat exchange effect of the system in the heat rejection mode,and in the supplementary heat mode The heat transfer effect of the system can be enhanced by the lower temperature;the increase of the water flow rate does not have much effect on the heat exchange effect in the heat rejection mode or the supplementary heat mode,and the increase of the air flow rate can be significantly enhanced.The heat exchange effect of the system is improved.Based on the above study of the operating rules,an appropriate time point was selected in the two cities as the operating point of the unit during the transition season.Finally,this article uses the built-in heat source tower-buried pipe compound ground source heat pump to explore the reliability,energy saving and economic advantages of the two cities compared to conventional ground source heat pumps in a ten-year cycle..The results show that the combined ground-source heat pump can maintain the soil temperature and ensure the thermal balance of the soil,and improve the stability of the long-term operation of the system.In a ten-year operating cycle,the compound ground source heat pump has better economic efficiency than the conventional ground source heat pump.