Quantitative measurement of energy utilization efficiency and study of influence factors in typical microwave heating process

• Energy efficiency issues of microwave heating were quantitatively addressed.
• Microwave heating process was divided into two physical stages to study.
• Medium type, position, geometry and output power all affect the energy efficiency.
• We provide a feasible way to assess general microwave heating processes.

Microwave heating technology has been used in many fields as a means of selective, volumetric, and instantaneous heating. In the process, input electrical energy is first converted to microwave energy, which is then absorbed by a dielectric medium and changed into thermal energy (effective heat). The energy utilization efficiency of this process is of particular concern because it provides an important index of economic performance. A good understanding of these efficiencies via quantitative measurements is necessary to optimize the microwave heating process and to use it more effectively. The research reported here divided the microwave heating process into two stages, measured their energy utilization efficiencies in detail, and studied the effects of various factors. It was found that the heating body position in microwave cavity, the heating medium type, the microwave output power and the geometry parameters of heating medium like volume can all significantly influence the energy efficiencies. But even for the best optimized microwave heating process, the total energy efficiency can only amount to about 0.8. This work built up a general idea for understanding the issue of energy utilization efficiency in microwave heating processes through a quantitative method, and provided a feasible way to assess energy utilization characteristics of any microwave heating process or to test microwave absorption abilities of different media.