Theoretical Study On Ground Heat Exchanger And Economy Evaluation Of Ground-source Heat Pump

Ground-source heat pump (GSHP) system has been identified as a most environment-friendly and efficient heat pump system. The more use of GSHP will reduce the wastage of mineral fuel,which will help our country adjust the energy structure and reduce the amount of exhaust gas released to protect the natural environment and achieve the goal of sustainable development. To perfect heat-transfer model for ground heat exchanger is one of key problems about GSHP popularization and application. Based on the summarization of current research situation of ground heat exchanger model theory oversea and home, this paper mainly research thermal behavior of a single vertical U-tube heat exchanger in the ground. And for the theoretical model, a transient one-dimensional line source model outside borehole and a three-dimension heat transfer model inside borehole are presented. Calculates and analyses the U-tube heat exchanger heat flux and the temperature field of the soil around borehole and. Analyses the influencing effect to heat flux and the temperature field of the soil by different factors, such as the depth of U-tubes, the inlet temperature, flow of mass, properties of soil and distance between two tubes of the U-tubes. By numerical computing, obtain a lot of data of heat flux of the U-tubes and temperature field of the soil. By detailedly analyzing the data, hope to guide the GSHP practice.Based on a actual project, Value Analysis method is selected to evaluate economy character compared GSHP system with routine air-conditioning systems. Choose the important factors such as expense, system performance, social benefit to be appraising targets. By the Value Analysis method, function-coefficient and cost-coefficient are calculated. Then value-coefficient is calculated. Uses value-coefficient to evaluate econmy character of all systems. It shows that the expense of GSHP system is highest, but its performance and social benefit is best. So GSHP system will be a more popular air-conditioning system.