Jo Nov 7, 2025
The shell and tube heat exchanger among a variety of heat exchangers is widely used in many industrial applications for its advantages of long lifetime, simplicity of manufacture and wide operation range. In multi-channel systems including the shell and tube heat exchanger, flow distribution significantly affects their performance and lifetime. When a heat exchanger is designed, flow distribution is usually assumed to be uniform, but flow maldistribution may be an inevitable occurrence in practice. In particular, flow distribution in the tube-side of a single-pass shell-and-tube heat exchanger (SSTHX) with axial connections of bonnet nozzles is extremely non-uniform.
Generally, flow uniformity in multi-channel systems like heat exchangers has been realized in a limited flow regime (e.g. laminar flow or turbulent flow).
Pak Sin Myong, a section head at the Faculty of Heat Engineering, has proposed an innovative header baffle to effectively uniformalize flow distribution in the tube-side of a single-pass shell-and-tube heat exchanger (SSTHX) with axial connections of bonnet nozzles, even within the extensive range of Reynolds number.
He simulated the flow in the SSTHX using the commercial CFD code-ANSYS Fluent, and modeled the tube bundles as a porous medium. In the new structure of SSTHX, flow distribution was uniformalized ideally from extreme laminar regime to strong turbulent regime (Reynolds number of 40-80 000) although pressure loss was significantly increased (about 35%).
The effects of structural and thermo-hydraulic factors on flow uniformity were very small.
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Jo Nov 6, 2025
The high-pressure common-rail fuel injection system starts and finishes fuel injection by the high-speed solenoid valve of the pilot injector, and eliminates anomalous injection caused by pressure fluctuations and the breakdown of pumps caused by high injection pressure during high-speed flow in large quantity. In addition, it achieves stable injection at relatively high injection pressure in different situations. It can also improve diesel combustion and performance, reduce NOx in the exhaust gas emissions and diesel engine noise, and improve cold start performance and exhaust gas emission.
The fuel injection of a common-rail system is performed by the electrical signal of the high-speed solenoid valve. In other words, the high-speed solenoid valve determines the start, finish and quantity of fuel injection.
Therefore, researchers involved in the development of high-pressure common-rail systems in many countries have paid great attention to high-speed solenoid valves.
Ri Tong Hyon, a researcher at the Faculty of Electrical Engineering, has built a mathematical model of the high-speed response solenoid valve for a common-rail injector, investigated the influence of various parameters on the dynamic response of the high-speed response solenoid valve, and determined the optimum parameters.
In other words, he has investigated the effects of the inner and outer diameters of the stator outer core, the number of windings turns, the suction current, the outer diameter, thickness and inclination angle of the armature, the drive voltage, the spring preload, the elastic coefficient and the eddy current on the response characteristics of solenoid valves, and determined the optimum structural parameters and structural design.
As a result, he has managed to accurately calculate the dynamic response characteristics of a high-speed solenoid valve in the mixture of various fields.
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Jo Nov 5, 2025
Oungum is a musical instrument which was initiated, led to completion and named by Chairman
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Jo Nov 4, 2025
Accurately estimating ship emissions inventories in port areas provides scientific assurance for the building of green ports.
Ship emissions inventories using automated identification system (AIS) data are widely used to predict and estimate ship pollutant emissions in the seas and rivers for their high spatiotemporal resolution, but they still have considerable uncertainties.
Over the past decade, many studies have focused on addressing these uncertainties, and improving the accuracy of ship emissions inventories has constantly been a hot issue. The most notable sources of uncertainty in the ship emissions inventories using AIS data are the uncertainties related to model input data, prediction of propulsion power, emission factor and fuel information.
Yun Un Hyok, a section head at the Faculty of Shipbuilding and Ocean Engineering, has proposed an improved load-factor-based power model considering the impact of hull shape on the ship’s resistance, and applied it to the estimation of ship pollutant emissions in a certain port area.
The total ship emissions estimated using the proposed method were 1.27×104, 6.33×104, 1.91×103, 1.76×103, 3.11×103 and 7.52×103t of SO2, NOx, PM10, PM2.5, HC and CO, respectively.
According to the results of comparison with traditional power models, the total emissions from ocean going vessels (OGVs) in the sailing mode was 89% and 104% of those using Propeller Law and Admiralty Law power models, respectively. These differences were greater for NOx than for other pollutant species and also greater for bulk carriers and tankers than for other subtypes of vessels.
Although the proposed improved load-factor-based power model still has some uncertainties, it is believed to be worth employing to estimate regional ship emissions inventories in the future, because it can accurately estimate ship emissions inventories by analyzing the impact of hull shape on ship resistance with few ship parameters.
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Jo Nov 3, 2025
We should have a state-oriented attitude and patriotic stand towards the science and the era rather than wishing for any academic degrees or titles, honor or great scientific and technological successes. This is the remark made by Merited Scientist, Candidate Acad., Prof. Ph.D. Ri Mu Chol, an institute head of Bioengineering Institute, to the students taking the first step of research.
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Jo Nov 2, 2025
November has two seasonal divisions―riptong and sosol.
Riptong refers to the beginning of winter while sosol indicates the start of snowfall. The former falls on 7th or 8th and the latter falls on 22nd or 23rd of November.
What is important in the Korean people’s dietary practices was to make kimchi and to steam soybeans for making soybean paste of the next spring.
Regarding kimchi as important food supply for winter, the Korean people have long attached great importance to preparing kimchi. The materials and recipes were different in different parts of the country.
At this time every year, people made whole cabbage kimchi and other kinds of kimchi of different tastes and aromas peculiar to different localities including watery radish kimchi, wrapped-up kimchi and leaf-mustard kimchi.
The housewives of several families cooperated to make kimchi in turn and they regarded offering their fresh kimchi to their neighbours first as a moral practice.
Steaming and making balls of soybean for making soybean paste in the next spring was also an old custom handed down from generation to generation.
The folk games of this season include some indoor games like yut-game, paduk, Korean chess, etc. suitable for cold weather conditions and some outdoor games including kite-flying, shuttlecock, etc. enjoyed by children.
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