Experiment Study On Heat Transfer Of Underground Heat Exchanger For Ground Source Heat Pump

Energy source and environment become an urgent problem for every country all over the world. Developing the new energy and renewable energy becomes our country's vigorous goal to develop the national economy and the construction well-off society urgent primary mission and the strategic target in the 21st century. The ground source heat pump is a kind of heating as well as air conditioning installment, which using the shallow layer ground resource to the building. It is obvious that this kind of technology is energy conservative, conforming to characteristic and the environmental protection requirement, which has drawn many countries'attention. Meanwhile, this technology is needed to meet the requirement of better life.The underground heat exchanger of GSHP is the heating source and cooling source of the system, it is the core of the GSHP and plays an important role in the system. As a matter of fact, better understanding of the underground heat exchanger and better heat transfer is the aim of engineers. Generally speaking, engineers enhance the velocity in tube to get better convection heat transfer, select the normal conductivity high tubing and the backfill material enhance heat transfer, these methods have the positive effects regarding the ground source heat pump system stable operation and the reduced heat exchanger quantity. From the perspective of enhance heat and operation management, this thesis apply the heat transfer performance research to the underground heat exchanger.The verification vehicle contains 60 kinds of structural type using underground heat exchanger ground source heat pump, which is established in the Energy Building of Beijing University of Technology, this research contains the heat transfer effect of underground heat exchanger, compares the effect due to different types of heat exchanger (Single-U and Double-U), and some testing comparisons have made between various material and different backfill material.In the operation management experiments, the thesis compares temperature change effect of the underground circulation liquid due to two different structures (Signal-U and Double-U) in the continuous operation mode. In the continuous operation, the temperature near the exchanger is worsening, and is bad for the system. By using the time-slot operation mode, the soil temperature have some recover time to enhance the heat transfer rate and reduce the numbers of exchanger, as a result, lower the soil resource and construction cost. This thesis also analyzes the temperature variation rule of underground circulation liquid in the time-slot operation mode. The matching condition of different structural exchanger, their different combinations, as well as the heat pump is also applied.In summary, this thesis does some research on the heat transfer performance of GSHP and different operation mode. The results are valuable references to the design and construct of GSHP project and are good supports to the extension of GSHP.