The Research On Optimization Design And Operation Of Ground Heat Exchanger For Ground Source Heat Pump

Ground source heat pump is an energy-saving aircondition system of green environmental protection, which has been promoted to utilize in China. The development situation and technology bottleneck restricting the development for ground source heat pump are summarized, and the design method of ground heat exchange is also analysised in this paper.Summarizing the test methods of ground thermal properties and methods of data handling, a simple test method of ground thermal properties is provided and its merit and demerit is analysised by the experiment. The main tasks of design for ground heat exchanger includes the choice of buried way of pipe, the design depth of borehole, the design flow of U-tube, the design inlet temperature of U-tube and the length of ground heat exchanger. The effect of depth of borehole, the flow rate of borehole and the inlet temperature of ground heat exchanger on the heat transfer performance of borehole was comprehensively analysized by the Quasi-three dimensional heat transfer of borehole which was built in this article. The hourly simulation model for annual running of ground heat exchanger is set up to simulate the operations of ground heat exchangers which were designed by different design decision. The results show that the different buried ways used in ground heat exchanger have a little effect on energy consumption of heat pump for the same building. The different thermal conductivity of backfilling materials has little influence on the energy consumption of heat pump, and it only affect the design length of ground heat exchanger. Meanwhile, the relationship between outlet temperature of U-tube and design load is analysised when the ground source heat pump is under dynamic load.The conception for the cost of heat transfer which can use to evaluate the economic of ground heat exchanger was presented and its specific formula is deduced in the article. Based on the cost of heat transfer and the simulation model, the optimization design process of ground heat exchanger is presented, and the design software that was written by C# language can provide to use for designer. Finally, the choice standard of buried way of pipe based on the energy consumption of heat pump and initial cost of ground heat exchanger is deduced, and the recommended value of design parameter of ground heat exchanger is provided according the simulated result.