Research On Soil Thermal-physical Test And Influencing Factors For Ground Source Heat Pump

As the ground source heat pump technology gradually become the focus in the direction of Energy-efficient building industry, it has been major developed and applicated. The accurate soil thermal physical parameters is not only the precondition for the design and analysis of ground heat exchanger, but also a key link of the energy saving in ground source heat pump system. In order to improve the accuracy of the soil thermal physical property parameters and point out the error source in the testing process and data processing, this paper take measures from the establishment of field geotechnical thermal physical experiments, also calculation and analysis for several factors which affecting the accuracy of the test results is necessary.Combining with the automatic control system and principle of thermal response test,the paper developed the geotechnical thermal response test equipment. Different heating power was set up in the thermal response test experiments, moreover, the data processing is based on the simplified calculation of one-dimensional heat conduction problem for thermal resistance. And this paper used the method of fitting formula of slope line heat source model for data processing and the analyzed the result of the different parameters of test Wells.Secondly, this paper mainly did a lot of data analysis and summary to show the impact factor of the soil thermal physical experiments such as the soil initial temperature, heating power, and measuring the length and so on. Test results show that the volumetric specific heat capacity increase with the rising of the initial ground temperature measurements. And every 0.5℃ deviation to calculate the initial ground temperature, the average volume heat capacity offset 5.2%; Thermal physical parameters vary under the same test holes in different heating power, the high power coefficient of thermal conductivity and thermal diffusivity of the calculation value is higher, the reason is associated with the geological conditions and the groundwater seepage; Different test length contrast test showed that big error calculation occurs when the test time is 20 hours, but after 40 hours time length in the test, the data precision can meet the engineering need.Influence factors analysis, this paper also studies the influence of tube well spacing on soil temperature field. The calculation of soil temperature rise based on the line heat source theory, it concluded that after 100 hours’ 7.5 kw power heating, the soil temperature rise at 1 m distance from the heating Wells is 0.81℃, It’s maximum heating radius is 1.87 m. In the last part, this paper takes the power-outage data processing method, testing environment influence and buried pipe form to analysis, looking on a reference and research value to the soil thermal physical parameters testing in the practical project.