Based on a practical project in shanghai

this paper will give a yearly test on single U-shaped ground heat exchanger of ground-source heat pump in central air conditioning system

and analyzes the change of surface ground temperature field

inner ground temperature field and outer ground temperature field of the pipes. The test results show that: throughout the year

temperature fluctuation is larger in the shallow soil (more than 25m depth）which is outside the tube group

and time of the highest temperature of the shallow soil appears later than that on the ground . In the inside tube group

the soil temperature will increase along with the system’s continuous and steady operation. Thus

it makes the temperature difference smaller between the surface of the ground heat exchanger and soil temperature around

which leads to the heat exchange capacity decline. Through the contrast analysis，this paper also found that

for buildings where ground source heat pump is used and its cooling load is greater than the heating load ， the impact of the system's continuous and steady operation on the heat transfer between buried pipes and soil is significantly higher in the summer than that in the winter. At the same time

the experiment results prove that

increasing borehole spaceand intermittent operation of the ground source heat pump system are very important to enhance the heat exchange between the buried tube heat exchanger and soil.