Thermal Budget of Multicomponent Porous Ices

A relation for the temperature evolution of multicomponent porous ices is derived from the energy equation of multicomponent systems. It is demonstrated that the predominant energy transfer mechanisms can be incorporated into an effective thermal conductivity (lambda-eff), which is strongly temperature dependent, and that the heat conduction equation can be written in a Fourier type form. The vapor of volatile ices significantly contributes to lambda-eff by the transfer of latent heat of sublimation but otherwise hardly affects the energy balance. The general results are applied to porous water ice, porous H2O-CO2 ice and porous H2O-CO ice. In all cases it is found that the major part of the deposited energy per unit volume is consumed for heating of the ice. Depending on the material parameters and temperature, energy is transferred mainly by solid state conduction or by the transport of latent heat due to sublimation-condensation processes.