The Research For The Characteristics And Determining Method Of The Initial Soil Temperature Of The Ground Source Heat Pump System

Shallow geothermal energy is a clean, sustainable energy, ground source heat pump is a good technology to use the shallow geothermal energy. The initial soil temperature influenced by the air temperature and solar radiation varies with depth and time. The initial soil temperature o has an important influence on the efficiency of the ground-source heat pump system. The initial temperature of the soil is the initial conditions of the dynamic heat transfer calculated of the underground heat exchanger, is also one of the basic parameters in the theoretical calculations. The initial soil temperature here generally refers to the initial average temperature of the soil.Due to the affect of thickness of the crust,rock properties, groundwater, topography and precipitation, the soil temperature distribution in the different regions. The soil temperature affected by the solar radiation.has characteristics of diurnal variation and annual variation.And the amplitude of the diurnal variation of temperature affect the depth of less than lm, the amplitude of the year-on-year changes in temperature affect the depth of up to5～～25m.In order to get accurate initial soil temperature, this paper shows some initial soil temperature models, and a initial soil temperature model is established to reflect the changes of soil temperature with time and depth. Verified, the paper shows that the model can reflect the variation of soil temperature in the heated layer and the warming layer accurately. Although this model is not accurate in epilimnion, but still be able to draw a more accurate soil initial average temperature. In a word, the model has good applicability in the region.The paper also experimental platform to study three experimental methods to determine the initial temperature of the soil, they are the wall temperature sensing method, the static water temperature method and the circulating water temperature method. This paper analyzes the static accuracy of the water temperature method. and the scope of application of the three methods is showed in this paper. This paper analyzes the different ground heat import and export average temperature obtained by different flow rates. The average water temperature of input and output ground heat pipe is closet to the original soil temperature at the flow velocity of0.843m/s. The static water temperature method and the wall temperature sensing method measured initial soil temperature distribution, It also shows three mathematical methods to get the initial average temperature of the ground. They are arithmetic average method, weighted average method and integral average method. It is found that the initial average temperature of the ground getting by three mathematical treatment under10meters or deeper have the same stability. The arithmetic average method is the most simple, so it is recommended for engineering application and scientific research.