Heat and Mass Transfer when Heating and Drying a Spherical Body in Continuously Acting HF and Microwave Electromagnetic Fields

A study is performed of heat and mass transfer in a spherical body when it is dried in continuously acting HF and microwave electromagnetic fields. A linear (with constant process parameters) problem of heating a spherical body with these types of energy is formulated and solved analytically under conditions of its convective drying with allowance for the convective exchange of heat and mass with the ambient gas environment, both in general and during the first period of drying. In the first case, the intensity of drying is specified as a function of time and expressed using an analytical solution to the problem of mass conductivity (moisture diffusion) under the condition that moisture evaporates near the surface of the body. In the second case, it is assumed that all the heat supplied to the body is spent on evaporating the moisture, and there is thus no heating of the body. The partial vapor pressure near the surface of the sphere is then equal to that of the saturated vapor at the temperature of the sphere’s surface, and the temperature dependence of the saturated vapor pressure is described by Antoine’s equation. Solutions to problems of heating are obtained for the local temperature and the average temperature over the volume of the sphere. The solutions are used to model processes of heat and mass transfer numerically under conditions of convection and a supply of electromagnetic energy. A numerical analysis is performed for the evaporation moisture from the surface of a spherical particle for a process with a constant intensity of drying. The findings allow calculations of the heating of spherical bodies with a supply of electromagnetic energy and convection.