Experimental and numerical analysis of an energy-efficient direct-insertion microwave heating system based on a TM01 mode circular waveguide

Traditional thermal processing technologies for food and industrial applications suffer from high energy consumption, low energy utilization efficiency and large carbon emissions, making it urgent to develop novel heating technologies with high energy efficiency and low carbon characteristics. Although microwave heating is a clean and energy-efficient technology, temperature-dependent dielectric variations can cause impedance mismatch and energy loss. To address this issue, a TM01 mode circular waveguide-based direct-insertion microwave heating device is proposed, enabling stable and efficient performance across varying dielectric properties. Firstly, a dielectric-filled waveguide is developed to enable efficient conversion from coaxial TEM mode to circular waveguide TM01 mode. Secondly, the internal dielectric is extended to achieve direct-contact coupling with the load, enhancing microwave energy transfer efficiency. Then, the system is applied to continuous-flow processing, where it achieves a stable microwave energy utilization efficiency of approximately 96%, with only 4% deviation from simulations. The heating efficiency further exceeds 98%, reaching 98.45% for mineral water. Finally, energy balance calculations further validate the results, while LCA and carbon emission analysis confirm its low-carbon and sustainable performance. The device features a compact structure and high flexibility, supporting modular integration and array-based deployment for diverse industrial food processing scenarios. It also provides theoretical reference and engineering basis for the development of industrial microwave heating equipment with high adaptability, low energy loss and high energy efficiency.