Experimental study on heat transfer in soil during heat storage and release processes

The soil temperature distribution characteristics were experimentally studied, during heat storage and release processes in the fine-grained sand with different moisture content. Results showed that, the soil temperature distributions in the process of soil heat storage and release are almost symmetric under the same excess temperature. The excess temperature is the main factor affecting the soil temperature change, and the influence of the moisture content variation is almost negligible. At each set of excess temperature, the soil temperature change in heat storage and release processes have a good logarithmic relationship with the heat transfer time, radial distance and longitudinal distance. The soil temperature change shows a linear increase trend with the excess temperature, and the soil temperature disturbance in radial direction is far greater than that in longitudinal direction. Based on the hypothetical multivariate nonlinear power function regression model, the experience formula for predicting the soil temperature was proposed. The prediction deviation was within 10 %.