Measurements of the Initial Ground Temperature in GSHP System

The initial ground temperature (IGT) is one of the most important parameters in designing a ground source heat pump (GSHP) system and evaluating its performance. In this paper, three initial ground temperature test methods are introduced. Except the shallow zone, the ground temperature distribution measured from direct and indirect testing method has very small difference. In direct test, the temperature sensor must be embedded when burying the tube in the borehole which is hard to operate in engineering applications. Thus the direct testing method is suggested to be applied in the scientific research. The indirect testing method could be used in engineering applications. The mean ground temperature could be calculated from temperature distribution except the shallow zone temperature. The results from three calculating methods have a quite small difference. Therefore, the arithmetic average method is suggested for scientific and engineering application to calculate the mean ground temperature. The mean ground temperature is also gotten in TRT conveniently. In the condition of velocity 0.7m/s, water was circulated in the tube system with no heat source for 30 minutes. The average water temperature could be regard as the mean ground temperature with sufficient accuracy.