Study On The Operating Characteristics Of The Vertical Buried U-tube GSHPS

Ground source heat pump technology known as the 21 st century’s most promising new technology air conditioning. Since the application of domestic ground source heat pump technology started late development stage of ground source heat pump technology in China is not mature, in terms of basic theory and techniques they use foreign theories.But the affected geographical factors, foreign technology may not be suitable in domestic application. Therefore, to carry out research on ground-source heat pump system, provide a theoretical basis and data is necessary to promote the use of GSHPS.In this paper, the experiment was tested by the energy efficiency of the monitoring system, has achived data online, real-time monitoring and dynamic analysis capabilities, through metering and data collection devices, using data transmission means. And it provided the basic data for testing and operating characteristics of vertical GSHPS research.This paper analyzed to investigate the following, mainly through the data monitored by energy efficiency monitoring system. First, studying the recovery properties of the soil, through the real-time test vertical GSHPS, in 90 m deep vertical borehole heat exchangers at the end of the performance and systems under different flow rates and operating modes of operation; Second, simulate ground heat exchanger performance and changes in ground temperature field of borehole heat exchangers by Fluent at different speeds and different inlet inlet temperature.The results showed that: underground initial temperature was gradually increased in the depth direction, under ground 15 m, soil temperature substantially unaffected by atmospheric temperature; Although the increase in the vertical U-tube heat exchanger inlet velocity will help improve the ground heat exchanger heat transfer per meter, but not the greater the velocity, the greater the system COP, the most system COP in summer and winter corresponding flow rate was 0.27m/s and 0.34m/s in this bench; Appropriate to increase the terminal load is conducive to increasing the system COP, fitting the data obtained after the mathematical relationship between summer and winter system COP and load are: y_win-sys=0.00554+0.16988 x and y_sum-sys =0.06897 +0.2138 x.Underground temperature field simulation results showed that: a vertical U-tube heat exchanger inlet at different flow rates, changes in circumstances and underground heat exchanger temperature field in different inlet temperatures, found that as the inlet temperature or inlet velocity increases, per meter heat transfer gradually increases and the outlet temperature increases; The per meter heat transfer in summer is 60.97W/m and 43.02W/m when the inlet velocity of is 0.34m/s and 0.11m/s but these values in winter is 27.3% and 30.9% less than these in summer.Underground temperature field simulation results show that:（1）As inlet velocity of vertical U-tube increased, per meter heat of the U-tube heat exchanger in winter and summer is gradually increased, and the increase is gradually reduced; As inlet temperature of vertical U-tube increased, per meter heat of the U-tube heat exchanger gradually increases in summer, winter situation is opposite.（2）In winter and summer, the bigger the inlet velocity of vertical U-tube or the longer the GSHPS run, the greater the impact on the underground field temperature; The higher the inlet temperature of vertical U-tube in summer or the lower the inlet temperature of vertical U-tube in winter, the bigger the difference of ground temperature and its initial temperature; Along with the distance from the center of the borehole, the influence to the ground field temperature of the vertical U-tube heat exchanger is gradually weakened.