The Simulation and Test Verification of The Ground Heat Exchanger With Different Start - Stop Cycles Under The Same Cumulative Heat Load

In order to study the variation law of the circulating water 's thermal parameters in the ground heat exchanger(GHE) and the distribution characteristics of the geothermal field around the GHE during the intermittent regulation, the heat transfer simulation and the heat transfer test of the GHE under the same cumulative heat load with different start and stop cycles were carried out. Firstly, the rock-soil thermal response test of a 120 m double U-shaped GHE is carried out to obtain the comprehensive thermal physical parameters of the rock - soil mass; Then, the heat exchange tests of the different start- stop cycles (test cycles: S = 1h, s = 2h, s = 4h and S = 8h) under the same cumulative heat load with start - stop ratio 1:1 and start - stop ratio 2:1 were carried out. Then, the heat transfer simulation and prediction of different start- stop cycles corresponding to the test conditions are carried out by using the thermal physical parameters obtained from the rock-soil thermal response test. The results show that the heat transfer test results are basically consistent with the model simulation results, so that the accuracy of model parameters and the reliability of test data are mutually verified; After long-term operation of the operation modes with different intermittent periods, the temperature of the rock - soil mass near the GHE fluctuates obviously periodically, and the temperature value in each intermittent period fluctuates along the same trend line with the time ,which directly affects the temperature of the circulating water in the heat exchanger. Finally, it is concluded that under the action of different start - stop cycles, the temperature of the rock - soil near the GHE fluctuates periodically, which provides a basis for optimizing the thermodynamic parameters of the circulating water through the intermittent operation of GHE, so as to improve the efficiency of system operation.