A review on coupled heat and water vapour transport in unsaturated soils

Coupled heat and water transport has found to be relevant in unsaturated soils because of increasing interest in disposal of radioactive wastes, geothermal energy, hydrology and agricultural problems. In an unsaturated soil, heat can be either latent or sensible or both and water may take the form of either liquid or vapour or both. The impact of thermal gradient on water vapour movement in terms of both vapour and liquid flow is essential and it requires accurate experimental quantification and representation for modeling of coupled heat and water vapour flow. Although it is possible to calculate the total water vapour flux, it is difficult to distinguish experimentally between liquid and vapour fluxes in unsaturated soils. This paper focuses on providing a critical review on heat and water vapour transport in unsaturated soils.