Study On Uncertainty Of The Rock-soil Thermal Response Test In Ground-Coupled Heat Pump System

Ground-coupled heat pump technology currently has got widely promoted because of its energy-saving and environmental advantages. The rock-soil thermal properties test is the basis and guarantee of the technology. Obtain the accurate parameter of the rock-soil thermal properties can improve the accuracy of the system design with this technology, which can avoid the overlarge capital investment of the system or the poor effect of system operation., There are many uncertain factors in the rock-soil thermal response test because of the complicated situation in situ. At present the rock-soil thermal properties test remains to be optimized so as to improve the accuracy and reliability of the test result.This paper optimizes the current rock-soil thermal properties test through the following steps. First present the suggested model through comparing the heat transfer models of analyzing the rock-soil thermal properties test data and introduce the principle and the equipment of the rock-soil thermal response test. Then a program was compiled in Matlab software platform with the two-variable parameters estimation method and the Nelder-Mead algorithm. The program can inversely calculate the parameter of the rock-soil thermal properties. The software of Rock-soil thermal properties Analysis in Ground-coupled heat pump (GTA) was generated base on the program so that the experiment test data can be conveniently calculated. At last this paper presents an improved compound line-source model. Combining the superposition principle this model can deal with the situation of power fluctuation or power off in the rock-soil thermal response test. Base on the compound line-source model a new inversion calculation method was presented for analyzing the test data in rock-soil thermal response test with variable heat flux. A Matlab program was compiled, which can automatically analyze the thermal response test data in the variable heat flux situation and inversely calculate the parameter of the rock-soil thermal properties.Considering the uncertainty of test result because of the complicated situation of the rock-soil thermal response test, the paper presents the uncertainty analysis method base on the rock-soil thermal response test. The method analyzed the major factors that influence the test result. The intervals, averages and standard deviations of the parameters of the rock-soil thermal properties were given in the paper. This study improves the reliability of the rock-soil thermal response test and provides a more effective guidance for the design of the ground-coupled heat pump system.