Water Vapor Movement on Mass and Heat Transport in the Perspective of Water Vapor Buoyancy: A Review

In 1957, the governing equation of mass and heat transport in the soil or porous media was popularised, now commonly referred to as PdV theory. This governing equation helps to quantify and simulate the water, vapor and heat in porous media. But at the same time, due to the fundamental uncertainty parameter in the equation, it was continuously updated. The equation predicting vapor flux movement in the soil has been the subject of many investigations. The vapor enhancement factor (VEF) was introduced to overcome the issue. When VEF was introduced, a few researchers were able to quantify the factor, but could not provide the guiding mechanism representing the observation. In the latest review from a literature study, we found a new form of equation to improve the VEF. It comes from the basis of the universal gas law, which describes the volume expansion from liquid water to vapor, and also the vapor buoyancy. This study aims to review water vapor movement and vapor buoyancy phenomenon. Also, to identify the parameters of the equations that contribute to the vapor buoyancy effect. The water vapor movement should not be neglected in the governing equation because its contribution to the overall mass movement is significant. Vapor buoyancy is possible to become a mechanism out from VEF. The parameters that contribute to vapor buoyancy effect are gravity, soil temperature, vapor density and water salinity. Clearly, understanding vapor buoyancy effect helps us better predict the distribution of soil temperature and soil moisture content.