ELECTROMAGNETIC DRYING OF WET MATERIALS WITH MICROWAVE LOW PENETRATION DEPTH IN CONDITIONS OF HEAT REMOVAL BY RADIATION AND CONVECTION. I. WARM UP PHASE

• Main Authors: Vladimir V. Salomatov, Vadim A. Karelin, Vasiliy V. Salomatov
• Format: Article
• Language: Russian
• Published: Tomsk Polytechnic University 2019-10-01
• Series: Известия Томского политехнического университета: Инжиниринг георесурсов
• Subjects: microwave energy; drying; capillary-porous massif; heat radiation; convection; a.v. lykov heat and moisture transfer equations
• Online Access: http://izvestiya.tpu.ru/archive/article/view/2297/2076

The relevance of the research is determined by the need to develop mathematical models of microwave heating and MW-drying of wet materials to obtain technologically optimal and cost-effective modes. Due to the complexity and non-linearity of the processes taking place inside wet materials during microwave processing, it is extremely important to build models that would allow one to construct analytically approximate solutions in order to find the main laws and characteristic features of the processes under consideration. The aim of the research is to state the first stage of the microwave drying of wet material – the warm-up phase. The search for analytical solution for the temperature of the layer at different points in time allows us to determine the beginning of the next stage – drying. The object of the research is a flat layer of wet material – coal, sand, wood and other capillary-porous arrays, which are affected by microwave radiation. Such materials have a high dielectric constant and, as a result, they very efficiently absorb microwave radiation, which is almost 100 % converted to thermal energy. The methods are associated with mathematical modeling, which are based on Maxwell electrodynamics equations and heat and moisture transfer of A.V. Lykov. In this article, the Maxwell problem is solved independently on the problem of heat and mass transfer; therefore, the flux density of the absorbed microwave radiation is assumed to be known. Also, one of the features of this problem is the consideration of materials with a small depth of absorption, whereby the source term in the system of equations for heating is in the boundary condition. As a result of the research the problem of heat transfer at a given power source of heat was solved using asymptotic procedures. The authors have obtained approximate analytical solutions for the first of the three characteristic stages of microwave drying under conditions of low penetration depth of microwaves: the warm-up stage of a moist material. The constructed solutions were analyzed.