Theoretical model for thermal energy storage processes in soil (Q2706054)

The authors consider a mathematical model for long-term energy storage processes in soils. The model examines a helical heat exchanger buried vertically, which is modeled as a series of horizontal rings with a constant pitch between them. The following assumptions hold: (i) heat and moisture transfer take place by diffusion; (ii) variations of fluid temperature along the heat exchanger of the energy storage system are calculated according to a quasi-steady-state model of heat transfer between heat exchanger and soil; (iii) the mass flux of vapor phase by diffusion may be neglected. The authors develop a numerical method for solving the system of coupled heat and mass transfer partial differential equations, and discuss the accuracy of the method.