Comparing Microwaves to Conventional Heating - Sponsored Whitepaper

Comparing Microwave to Conventional Heating and Drying Systems Industrial Product Processing For Cooking, Heating & Drying Applications

Microwave Drying The mechanism for drying with microwave energy is quite different from that of conventional drying. In conventional drying heat is transferred to the surface of the material by conduction, convection or radiation and into the interior of the material by thermal conduction. Moisture is initially flashed off from the surface and the remaining water diffuses to the surface. This is often a slow process in conventional drying and the diffusion rate is limited, requiring high external temperatures to generate the temperature differences required.

In conventional or surface heating, the process time is limited by the rate of the heat flow into the body of the material from the surface as determined by its specific heat, thermal conductivity, density and viscosity. Surface heat is not only slow, but also non-uniform with the surfaces, edges and corners being much hotter than the inside of the material. Consequently, the quality of conventionally heated materials is variable and frequently inferior to the desired result.

Microwaves are not forms of heat but rather forms of energy that are manifested as heat through their interaction with materials. Microwaves initially excite the outer layers of molecules. The inner part of the material is warmed as heat travels from the outer layers inward. Most of the moisture is vaporized before leaving the material. If the material is very wet and the pressure inside rises rapidly the liquid will be removed from the material due to the difference in pressure. This creates a sort of pumping action forcing liquid to the surface, often as vapor. The result is very rapid drying without the need to overheat the atmosphere and perhaps cause case hardening or other surface overheating phenomena.

Mechanism of Heating Microwave energy does not heat the room; only the desired material with no harmful greenhouse gas emissions from the heat source. The energy is mainly absorbed by a wet material placed in the cavity. Water, fat and sugar molecules in food materials absorb energy from the microwave in a process called electromagnetism; a phenomena associated with electric and magnetic fields and their interactions with each other and with electric charges and currents.