Compact Microwave Continuous-Flow Heater

Abstract

Microwave continuous-flow heating has been proven to reduce the time of chemical reaction, increase the conversion rate, and improve product purity effectively. However, there are still problems such as relatively low heating efficiency, unideal heating homogeneity, and poor compactness, which brings further drawbacks like difficulty in fabrication and integration. In this study, a compact microwave continuous-flow heater based on six fractal antennas is proposed to address the problems above. First, a multi-physics simulation model is built, while heating efficiency and the volumetric coefficient of variance (COV) are improved through adjusting the geometric structure of this heater and the phase assignment of each radiator. Second, an experiment is conducted to verify the simulation model, which is consistent with the simulation. Third, a method of fast varying phases to achieve greater heating efficiency and heating homogeneity is adopted. The results show that the single-phase radiator improved efficiency by 31.1%, and COV was significantly optimized, reaching 64%. Furthermore, 0–100% ethanol–water solutions are processed by the heater, demonstrating its strong adaptability of vastly changing relative permittivity of liquid load. Moreover, an advance of this microwave continuous-flow heater is observed, compared with conventional multi-mode resonant cavity. Last, the performance of this microwave continuous-flow heater as the chemical reactor for biodiesel production is simulated. This design enables massive chemical production in fields like food industry and biodiesel production, with enhanced compactness, heating efficiency, and heating homogeneity.