A household microwave oven can be modified not only to be able to regulate microwave power continuously (including the intensity of EM field in the cavity),but also to be able to fit three flasks into the cavity (each...A household microwave oven can be modified not only to be able to regulate microwave power continuously (including the intensity of EM field in the cavity),but also to be able to fit three flasks into the cavity (each flask can be connected to a reflux condenser outside the cavity).The microwave heating uniformity of the three flasks was tested using water (50g. and 30g.) and ethanol (40g.) respectively.The results showed that the heating uniformity of the three flasks was 89±5% (average±σ n-1 ,n=22) and the microwave leakage was below 1 mW/cm 2.The modified oven was used by 90 undergraduate students for chemical synthesis experiment (microwave synthesis of veratraldehyde). The reaction time was only 2～3min.and the average yield was 86±9% (n=90).The variation of the average yields of among student groups was only 2%.Through variance analysis,F1,showing the difference was not significant.This modified microwave oven is especially suitable for chemical synthesis experiment for undergraduate students and for microwave digestion in analysis labs.展开更多
Many microwave reactors widely used in laboratory are made from commercial microwave ovens.In this paper, the heating process inside the reactor was simulated in order to obtain the final temperature distribution in t...Many microwave reactors widely used in laboratory are made from commercial microwave ovens.In this paper, the heating process inside the reactor was simulated in order to obtain the final temperature distribution in the solution in a beaker.Maxwell’s equations and the heat transport equation (HTE) were coupled to calculate the temperature results by means of the finite element method (FEM).In the calculation, Debye’s equation and Huang’s method were used to describe the temperature and time dependence of dielectric properties.Due to the non-uniform distribution of fields in the cavity, the heating results varied significantly with the position of the beaker.This could be more obvious for a chemical reaction because of the non-equilibrium characteristics.It was also observed that the repeatability of experiments was poor even for a fixed position of the beaker due to the magnetron instability.Therefore, such chemical reactors made from commercial microwave ovens can hardly ensure the repeatability of experiments.展开更多
文摘A household microwave oven can be modified not only to be able to regulate microwave power continuously (including the intensity of EM field in the cavity),but also to be able to fit three flasks into the cavity (each flask can be connected to a reflux condenser outside the cavity).The microwave heating uniformity of the three flasks was tested using water (50g. and 30g.) and ethanol (40g.) respectively.The results showed that the heating uniformity of the three flasks was 89±5% (average±σ n-1 ,n=22) and the microwave leakage was below 1 mW/cm 2.The modified oven was used by 90 undergraduate students for chemical synthesis experiment (microwave synthesis of veratraldehyde). The reaction time was only 2～3min.and the average yield was 86±9% (n=90).The variation of the average yields of among student groups was only 2%.Through variance analysis,F1,showing the difference was not significant.This modified microwave oven is especially suitable for chemical synthesis experiment for undergraduate students and for microwave digestion in analysis labs.
文摘Many microwave reactors widely used in laboratory are made from commercial microwave ovens.In this paper, the heating process inside the reactor was simulated in order to obtain the final temperature distribution in the solution in a beaker.Maxwell’s equations and the heat transport equation (HTE) were coupled to calculate the temperature results by means of the finite element method (FEM).In the calculation, Debye’s equation and Huang’s method were used to describe the temperature and time dependence of dielectric properties.Due to the non-uniform distribution of fields in the cavity, the heating results varied significantly with the position of the beaker.This could be more obvious for a chemical reaction because of the non-equilibrium characteristics.It was also observed that the repeatability of experiments was poor even for a fixed position of the beaker due to the magnetron instability.Therefore, such chemical reactors made from commercial microwave ovens can hardly ensure the repeatability of experiments.
