In photocatalytic microreactors the catalyst layer is obtained by integration of nanostructure films of semiconductors. One of these nanostructures that have a good photocatalytic activity is ZnO nanowires. The photocatalytic degradation of methylene blue in a continuous flow microreactor with ZnO nanowires deposited film is simulated. A finite element model is developed using COMSOL Multiphysics version 5. 3 software to simulate the microreactor performance. The kinetic law of the photocatalytic reaction is assumed to be Langmuir– Hinshelwood. The kinetic constants kLHa and K are determined 1. 43×10-7 mol/m2s and 7. 5 m3/mol, respectively. The percent of average absolute deviation of the model in predicting the methylene blue outlet concentration obtained about 0. 12% mol/m3. The model showed a very good agreement with the published experimental data. The effect of microreactor depth, methylene blue inlet concentration and flow rate on the methylene blue degradation is also investigated. The simulation results showed that the microreactor with shorter depth and lower values of inlet concentration and flow rate has higher efficiency. Thiele modulus and Damkö hler number are both estimated lower than 1. It indicates that the photocatalytic reactions occur without internal and bulk mass transfer limitations.

In the present study, Choline hydroxide (ChOH) as an ionic liquid catalyst was used for transesterification of soybean oil into biodiesel in a microchannel reactor. The effects of three variables, i. e., reaction temperature, catalyst dosage, and total flow rate, on fatty acid methyl ester (FAME) content (wt %), were optimized using Box– Behnken experimental design. In order to predict the FAME content, a quadratic polynomial model was obtained. The optimal conditions from the model were reaction temperature of 53. 53 ° C, catalyst dosage of 2. 6 wt %, and total flow rate of 11. 82 mL/min. In these conditions, the predicted FAME content was 96. 45 wt % and the experimental FAME content was obtained as 97. 6 wt %. The proximity of the experimental results and predicted values showed that the regression model was significant. Using the ionic liquid catalyst in the studied microreactor for transesterification leads to diminishing the reaction time to the order of seconds compared to conventional batch systems. In addition, the reusability of ChOH catalyst was investigated. The results revealed that the catalyst had perfect utility after several runs without much loss in the activity.

The aim of this study is the numerical investigation of liquid-liquid extraction inside a spiral T-microreactor integrated with ultrasonic waves. The influence of low-frequency ultrasound (20.3, 42.3, and 61.61 kHz) and high-frequency one (1.7 MHz) on extraction efficiency is evaluated by CFD modeling. The organic-aqueous phase flow patterns inside the microreactor are graphically analyzed. The organic phase is regarded as a dispersed phase and the aqueous phase as a continuous fluid using the two-phase VOF. In addition, the SIMPLE algorithm is used for pressure and velocity coupling. The results obtained from the CFD simulation of aqueous-organic phase flow patterns are compared with the experimental results. The application of both types of ultrasounds showed a higher extraction efficiency compared to the condition of not applying it. The decreasing trend for extraction efficiency and ultrasound effect was observed for increasing flow rate. The extraction efficiency is less affected by increasing the power of low-frequency ultrasound up to the range of 600 mV, after which a sharp increase is observed up to 840 mV. In addition, in the range above 600 mV, the increase in extraction efficiency can be attributed to the formation of emulsion, which leads to a higher surface per unit volume and higher extraction efficiency. The results indicated that for low-frequency ultrasound, 20.3 kHz resulted in higher extraction efficiency rather than the other one. Comparing the extraction efficiency for applying high (1.7 MHz) and low-frequency ultrasound (20.3, 42.3, and 61.61 kHz) showed that 1.7 MHz has a considerable positive effect on its increase. Indeed, 1.7 MHz ultrasound resulted in the highest extraction efficiency compared to low frequencies, due to the ability of high-frequency ultrasound to induce micro-jets and micro-streams into the microreactor.

One of the newest technologies in small nuclear power plants is using heat pipe cooled microreactors. In these power plants, several heat pipes transfer the heat produced in the microreactor core to the working fluid inside the main heat exchanger. In this paper the thermodynamic simulation of the Brayton gas cycle is conducted for a nuclear power plant equipped with a heat pipe cooled microreactor with a thermal power of 5 MW using the THERMOFLEX code. The considered working fluid in the Brayton cycle in this case is the supercritical carbon dioxide, and this cycle includes the main heat exchanger, turbine, main compressor, recompression compressor, pre-cooler and high and low-temperature recuperators. The results of the thermodynamic analysis of the studied cycle showed an efficiency of 36.508 % for the considered power plant. Besides that, as the pressure ratio of the main compressor increases up to 3.15, the efficiency of the power plant increases. Whereas, at higher pressure ratios, efficiency decreases. Also, the main compressor power in the cycle was obtained as 2030.1 kW. In addition, when the re-compression compressor is designed with a mass fraction of 23%, the cycle will achieve its highest efficiency. Besides that, the turbine expansion power and shaft power were calculated as 5091 kW and 5040 kW, respectively.