The structure of a moisture separator reheater is very complex, and the cycle steam is heated during the film condensation of heating steam inside the tube bundle.

Previous works proposed a thermal calculation model and a calculation algorithm of a reheater tube bundle and linearized the quality variation of the heating steam and two-phase flow, but did not consider the subcooling of a condensate film.

Kim Myong Chol, a researcher at the Faculty of Thermal Engineering, has proposed an improved thermal calculation algorithm considering the nonlinearity of the steam quality inside the tube bundle and carried out a quantitative evaluation of the factors affecting heat transfer to provide a theoretical basis for determining the optimum design parameters of a moisture separator reheater.

He found out that measures must be taken to prevent U-tube bundles from sagging down in the design and manufacture of reheater bundles.

For more information, please refer to his paper “Analysis of Heat Transfer Characteristics of a Moisture Separator Reheater Considering the Variation of Steam Quality Inside the Tube” in “Proceedings of KUTIC-2025”.

Friction torque and load capacity of bearings are very important performance indicators. The high speed and precision of machines presupposes the minimization of the friction torque of bearings, and the long service life is guaranteed by the maximization of the dynamic load capacity. However, the friction torque and dynamic load capacity increase and decrease respectively with the changes of the internal geometric parameters of bearings, so a machine with long service life and good friction characteristics can be realized only by multi-objective optimization of the dynamic load capacity and friction torque of bearings.

Many researchers studied to maximize the dynamic load capacity of bearings and to minimize their friction torque, but there is a lack of confidence in the optimization results due to the lack of correlation, many simplified parts and lack of enough constraints

Ball bearings are most widely used because of their small friction torque and relatively simple manufacturing process. Ri Jong Hak, a researcher at the Faculty of Mechanical Science and Technology, fully presented the constraints that reflect the actual conditions of ball bearings and developed a new mathematical model to simultaneously optimize the dynamic load capacity and friction torque. On this basis, he optimized them using the genetic algorithm and verified its accuracy by the FEM.

The proposed method can be applied to the determination of internal geometric parameters to simultaneously optimize the dynamic load capacity and friction torque of ball bearings.

For more information, you can refer to his paper “A Novel Methodology for Determining the Internal Geometric Parameters of a Ball Bearing in Consideration of Load Capacity and Friction Torque” in “Proceedings of KUTIC-2025”.

Dimethyl carbonate (DMC) is one of the most important chemicals, which has a wide application range. It is used as the raw material of polycarbonate (PC) plastics, the solvent of electrolyte for energy storage devices, the additives of diesel fuel, etc. The worldwide carbonate synthesis industry is currently dominated by the transesterification method with ethylene oxide as a starting material, which was commercialized in the 1990s. However, the starting material, ethylene oxide, is from the crude oil and causes environmental pollution during production, so recently, the synthesis of carbonate based on urea has attracted attention.

At present, the achievement on the synthesis of DMC from urea and alcohol mainly comes from the research on catalysts and the most widely-used catalyst is ZnO. The reaction of DMC synthesis using ZnO as a catalyst proceeds according to the heterogeneous catalytic mechanism. However, to date, the ZnO catalyst used in previous studies is mostly prepared by the sol-gel method.

Preceding studies imply that 4-needle like nano-ZnO demonstrates stronger catalytic activity than spherical or sheet ZnO crystals, which improves reactions.

On the basis of the analysis, Kim Myong Hyok, a researcher at the Faculty of Chemical Engineering, studied the catalytic use of 4-needle like nano-ZnO prepared by the combustion method to improve the reaction time and temperature of dimethyl carbonate (DMC) synthesis, and the catalyst recovery, aiming to improve the DMC yield.

48g of methanol and 1g of catalyst were put into the reactor and heated to the desired reaction temperature, and then a liquid mixture of methanol 80g and urea 12g was added to the reactor for 10min. Ammonia generated during the reaction was removed three times through the safety valve of the reactor.

When nano-ZnO was used as a catalyst, the optimum reaction time and temperature of the DMC synthesis reaction were 3h and 140℃, respectively, with a DMC yield of 65.1%. The catalyst was recycled up to seven times.

You can find the details in his paper “Improvement in the Yield of Dimethyl Carbonate by 4-Needle like Nano-ZnO”in “Proceedings of KUTIC-2025”.