After a spacious research and consideration on various approaches of thermal coupled formulations in porous media, a new mathematical form of coupled heat, moisture, and air transfer in unsaturated soil is proposed upon taking the effect of combined volumetric moisture content and temperature gradients and air pressure changes. In this matter, in the convective flows through the unsaturated heated soil, the effects of sensible and latent heat of vapor are also composed with the water and dry air fluxes. Thus in this aspect, some new material parameters are defined for the derived equations, which are related to thermodynamic specifications of soil and the soil-water characteristic curve. After that, the application of the model is presented with a numerical example of a ground heat exchanger which is buried in the earth vertically. It could be considered as an interior heating source which operates in extracting saved energy from the earth or emitting heat to the ground. Then, by using some thermal graphs, the influence of the different operating ratio is investigated which are compared with the full operating mode at all times. Meanwhile, the mode1 is verified by comparing its results against those established by other researchers. By the results, it was found that the volumetric water content and specific heat capacity are the main factors could be effective to generate directly the thermal and isothermal diffusivities and conductivities in terms of the thermodynamic properties.