Abstract
In order to improve the efficiency of aquifer thermal energy storage [ATES], a fundamental knowledge of heat transfer in saturated-unsaturated soil zone is required. Experiments to determine the characteristics of heat transfer in saturated soil zone have been conducted. An insulated large column, filled with water or fine sand, was used in the heat transfer experiments. After estimating the loss of heat from the column, thermal conductivity and temperature changes in the soil column were examined.
Furthermore, experimental data were simulated, using the one-dimensional model of heat transfer considering the loss of heat. As a result, the following points become clear:
(1) In case of the experiments extending over more than several hours, the loss of heat from the column cannot be neglected.
(2) Under these experimental conditions, most of heat transfer in saturated soil can be explained only by the heat-conduction term, and the influence of natural convection on heat transfer can be neglected.
(3) The thermal conductivity of the saturated soil evaluated from these experiments is in good agreement with that measured independently by the twin transient-state cylindrical-probe method. Key words: aquifer thermal energy storage, heat transfer, thermal conductivity, natural convection
