Modeling groundwater and heat flow subject to freezing and thawing

摘要

A newly developed FEFLOW plug-in module, piFreeze, provides simulation capabilities to cover freezing and thawing of subsurface water. The governing balance equations account for the respective volume fractions of frozen and liquid water and for the density difference between both phases. Extensions have been developed for both unsaturated and saturated conditions. Constitutive relations describe the temperature dependency of the heat capacity including the latent heat associated with the phase change, of permeability and fluid viscosity, and of the thermal conductivity. A flexible empirical expression describes the local freezing progress im terns of liquid/ice mass fractioning over a finite temperature range around the freezing point.Application potential for FEFLOW with piFreeze is seen wherever natural or artificially induced freezing and thawing processes significantly affect the groundwater flow, for example in mining, construction, permafrost conditions, and geothermal energy.