Numerical Simulation And Experimental Study On Heat Transfer Characteristics Of U-tube Heat Exchanger And Soil Temperature Distribution

Ground-coupled Heat Pump system(GCHPS) is a kind of sustainable green building and energy conservation technology. It has been shown unparalleled advantage in today’s society which theme is building a conservation-oriented society and promoting energy conservation. However, the key technology of the application and promotion of GCHPS according to local conditions is the solution to the problem of heat transfer between the U-tube heat exchanger and the surrounding soil.This paper is based on the research achievements and experimental platform established in the subtropical region. Further study included numerical simulation and experimental study of heat transfer characteristics is carried out in this paper. The results provide relevant theoretical reference and experimental evidence to the application, promotion optimization design of GCHPS technology.First established the three-dimensional unsteady heat transfer models with the actual U-tube heat exchanger and tube group (2X2) consistent, taking into account the convective heat transfer of the models between the top and air. Soil temperature distribution and heat transfer characteristics such as heat exchange per borehole depth, thermal resistance and pressure loss in the U-tube are studied. The results show that the suitable velocity of this experimental platform is range of0.2m/s-0.6m/s. In addition, simulation the soil temperature distribution in the depth and radial direction of the U-tube heat exchanger and tube group (2X2) is done. The results show that circulating water outlet temperature under two modes are289K,281K. Circulating water temperature increment remains4-5℃. Temperature in radius regional beyond0.4m shows concentric shape. Temperature in radius regional within0.4m shows varying degrees of eccentric phenomenon. Trends of soil temperature distribution is basically the same except the top of the models. Thermal interference appears obviously among the heat exchangers after running two months.Respectively, heat exchange per borehole depth in different forms and tube spacing of U-tube heat exchanger is studied. Analyzed recovery ratio of water temperature and thermal interference radius. The experimental results show that the models can be used to simulate the heat transfer characteristics and the soil temperature distribution of U-tube heat exchanger and tube group (2X2).