An Experimental Study And Analysis Of The Influence Factors Of The Thermal Response Test In The Ground Source Heat Pump System

The ground source heat pump(GSHE) technology is a kind ofnew energy utilization technology with high efficiency and energy saving, which is widely used gradually with the serious global energy crisis and environmental problems. The design of buried heat exchanger(BHE) is the key to the design of GSHE system, and an accurate measurement of the soil physical parameters is the premise to ensure the accurate design of ground heat exchanger. The thermal response test(TRT) method is the most commonly used in engineering to measure the soil physical properties, but the accuracy of the parameter selection will affect the test results in TRT,such as soil initial temperature, heating power, velocity in pipe and test time, ect, Analysis of the impact of these parameters on the TRT result accuracy is of great significance for field test.The soil thermal physical property testing method and data processing method are analysised, the line-source model combined with least square method is selected to conduct soil thermal conductivity and the heat transfer capacity. And from the heat transfer theory and fluid mechanics,the main influence factors is temperature difference between and velocity, influence degree is 1 and 0.8, respectively.The platform for the summer thermal response test is set up according to the principle of thermal response test. The studying using the method of circulating water and water thermometer to measure the soil initial temperature, the error of circulating water method is small when the velocity in pipe is more than 0.4 m/s.The ? when the heating power if 4.14 KW is closest to the average ground thermal conductivity in summer when the stable inlet temperature is 36?,the results show that when the heating power increased by 15.7%, thermal conductivity(?)increased by 2.98% and heat transfer capacity(q) increase by 17.1%, respectively, so the heating power on thermal conductivity has little apparent influence, but the heat transfer capacity increases with it.It takes time to be stable for the process, based on test results of 72 h, relative error of ?is within 8.69% and the elative error of q is within 0.77% when the test time is 24 h, therefore the test time has less influence on ?and q. Comprehensive test precision, duration of thermal response test can be performed for 24 h.The velocity in pipe is controled by 0.2m/s to 0.8m/s, ? increased by 5.51%,the q increased by 8.02% and the temperature difference(?t) decreased by 31.92%when the velocity increased by 02m/s. So The influence of velocity of on q and ?t are more significant.In addition, this article in view of the recovery temperature, soil temperature can be restored to 65% within the 24 h, so the best soil recovery period is the first 24 h.But because of the different heat transfer capacity, the time of recovery rate reaches stability is different, If the heat transfer capacity reduce 27%, the time can be reduced by 31% when soil temperature recovered to 95%.