Ground Source Heat Transfer Characteristics Of Borehole Heat Exchanger Vertically

Along with the rapid growth of China’s economic and the determination of the road of sustainable development, ground source heat pump (GSHP) technology with energy-saving and environmental benefits, has been given more and more attention. Ground source heat pump technology, which make use of the low energy of the soil, save part of the high energy, reduce heat loss in energy conversion and fuel combustion pollution of the environment, and thus is known to be a kind of green air conditioning technology with sustainable development.Ground heat exchanger (GHE) is the only heat transfer equipment between soil and ground-source heat pump. Research on the heat transfer performance of ground heat exchanger is the focus and difficulty of the ground source heat pump technology, it also plays an important role in improving the energy efficiency and the economics of GSHP system. The heat transfer process between GHE and soil is very complex, The effect of the heat transfer process also can be affected by a lot of factors. Because of these reasons, exploring the mechanism of different factors on the heat exchanger performance is of great value.This article use vertical GHE as the main research object, study a variety of factors impacted heat transfer performance of GHE, by using a method which combined theoretical analysis, numerical simulation and engineering experiments together.Based on the analysise of the advantages and disadvantages of existing pipe model,the text analyzed the heat transfer process of vertical U-shaped heat exchanger in the soil, created physical and mathematical models of a vertical U-shaped heat exchanger heat heat transfer process. The text used the MATLAB software to write a program to simulate the calculation.Based on the simulation of the model,the influencing effect to heat performance of GHE by different factors, such as soil and backfill materials thermal conductivity,the inlet temperature and velocity of flow can be simulated. The soil temperature field of the model also can be simulated. The experiments showed that the model has good calculation accuracy, the relative prediction error coefficient of the model is4.35%.The text also studied the heat transfer performance of GHE by using a large-scale GSHP test system. The GHE system in the test consists of six heat exchangers constitute in different forms and different sizes (Including single-U GHE, double-U GHE, triple tubes GHE). Through the experiment test,different heat transfer performance of GHE influenced by different factors, including the form of GHE, the size of GHE, the heat load conditions, different operation mode of heat pump system can be analyzed.Some valuable experimental data can be used in the further study of the GHE heat transfer performance.The thesis can provide theoretical and experimental data for further research in heat transfer performance of GHE, Some useful and guiding results in the design of GSHP project also can be drawn.