Analysis In Heat Transfer Of U-Type Vertical Ground Heat Exchanger And Their Engineering Application

Energy source and environment become the important problems in every country all over the world with succeeding in applying the 2008 Olympic Games, and the utilization of clean energy becomes the important task for us especially. Ground-source heat pump systems have been widely applied to both residential and commercial heating and cooling in America and Europe as these systems can make significant contributions to reductions in electrical energy usage and have been recognized as an environmental-friendly alternative to conventional unitary system. However, this technology has seldom been adopted so far in our country. Many a work of research on GSHP and popularizing application need to be done. Vertical U-Tube ground-coupled heat pumps have become increasingly popular because of any outstanding advantage it has, such as: fewer area requirement, fewer limits, running steadily, better performance, lower costs on system maintenance etc.The characteristics of soil temperature distribution are studied at the beginning of the paper, and the computational model of original soil temperature field distribution is established for Guangzhou district. The temperature within 60m underground is simulated and the results are accorded with experimental data. Then, a three-dimensional model of the steady heat transfer around a single vertical U-tube for GSHP is established and the exit water temperature and the soil temperature distribution around the buried pipe running in winter are simulated, and the results are tallied with experimental data. In addition, the influencing factors based on the numerical method can be applied widely to confirm the extent of the buried-pipe outlet water temperature influenced by different circulate water storm and depth of well and different thermal conductivity of soil and rock around the buried-pipe and to analyze the influence of underground heat-exchanger's heat transfer by different back-filled materials and different operation ways and different distances between the buried-pipes. It can offer reference of GSHP system running high effectively in a long time.Besides, the influence of the different dynamic heating and cooling load were calculated and simulated for the GCHP system. Comparing all the actual data, the simulation work were preceded by means of the relative software to prove the feasibility of the system. First, DeST is used to calculate the annual dynamic load. On the basis of monthly total cooling and heating loads and monthly peak cooling and heating loads, the main impact factors of vertical U-tube heat exchanger size and performance are simulated and analyzed through GLHEPRO3.0, recommended by ASHRAE as a good designing and simulating software for GCHPS, to carry on the task of simulation for 30 years. The purpose of doing this is to give some concrete suggestion and reference for the promotion of GCHPS in our country.