Abstract
For efficient operations of aquifer thermal energy storage (ATES), a fundamentalknowledge of simultaneous movement of heat and water in saturated-unsaturated soil zone is required. The heat and water transfer experiments have been conducted using the soil column in which fine sand and coarse sand were layered. Changes in temperature, pressure head, and heat flux in the soil column were measured. A quasi-steady analysis of coupled flow was also done based on the theory suggested by Milly (1982), and total water and heat flux were divided into the components. Furthermore the thermal vapor diffusion coefficient DTυ of coarse sand was estimated.
As a result, the followings were clear. Firstly DTυ of coarse sand was much greater than examples suggested in the past, and varied with water content and temperature. So it was guessed that the water vapor transfer other than diffusion, i. e. the movement of air including water vapor, occurred in an unsaturated coarse sand layer, and DTυ of coarse sand must be corrected for such a vapor transfer. Secondly, in a low water content part in coarse sand layer, the heat flux due to the water vapor movement determined by the corrected DTυ occurred dominantly. So, for ATES, it must be considered the balance of the merit that heat loss from the aquifer would be small by the existence of a low water content layer, i. e., a low thermal conductivity layer, and the demerit that the heat loss by the heat flow with the water vapor flow would occur in a low water content layer.
