Study On U-Shaped Underground Tubes Dynamic Performance And Heat Pump Energy-saving Performance Of The GSHP

The ground-source heat pump (GSHP) technology has been brought to the attention of the north America, European countries and Japan for a number of desirable characteristics, including good energy saving performance, less harm to environment, high efficiency, low maintenance costs, and low life cycle cost. They have broadened in application in these areas. There are some research works on GSHP having been done in our country since last century 80's. The research works were concentrated on feasibility of GSHP and modeling of borehole heat exchanger on small experimental systems. At present there is a lack of fundamental data of dynamic thermal transfer performance of ground loop exchanger and energy-saving performance of GSHP system. Therefore a research of GSHP system with vertical U-shaped underground heat transfer tubes is carried out theoretically and experimentally.Regarding the conditions of the soil and the climate, the national standards and national development plans, the experience of GSHP technology development in other countries, the feasibility of GSHP in our country is revalued by massive investigation.A transient, two-dimensional numerical model of the vertical ground heat exchanger is established. Based on the model the influences of tube material and tube geometry character, the thermal conductivity of the back-fill material and the soil, and the operation mode are analyzed. The soil temperature distribution around the borehole is analyzed too. And some theoretical conclusions of reasonable design for underground exchanger are made.Based on data of experiments and model, the exergy analysis method is introduced. The typical summer and winter performances of GSHP system are analyzed by the exergy analysis method. And some conclusions about3refrigerants selection for GSHP and the determination of evaporating temperature and condensing temperature are made. It is useful for optimization of the GSHP system performance.All the results are applicable to both the theoretical and the practical work.