• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.497-501
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• 2009

Effect of angle of supply air on cooling and heating performances of office space is studied by numerical simulation. For a constant air volume(CAV) air-conditioning system, air is supplied vertically($90^{\circ}$) and horizontally($10^{\circ}$). Due to buoyancy, the supply angle affects the performance of cooling and heating. In cooling, since the cold supply air tends to move downward due to its high density, horizontal supply angle is better for uniform temperature distribution. In heating, however, vertical supply angle is preferred for better mean and uniform temperature distribution.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.64-68
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• 2009

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (HRS) with an exergetic equivalent cooling power of 9kW at 4.5K without liquid nitrogen $(LN_2)$ pre-cooling has been manufactured and installed for such purposes. In this proceeding, we will present the commissioning and initial operation results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.6
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• pp.615-631
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• 2012

This study provides an evaluation for capability of Integrated Climate and Air quality Modeling System (ICAMS) on future regional scale climate projection. Temperature and precipitation are compared between ground-level observation data and results of regional models (MM5) for the past 30 years over the Korean peninsula. The ICAMS successfully simulates the local-scale spatial/seasonal variation of the temperature and precipitation. The probability distribution of simulated daily mean and minimum temperature agree well with the observed patterns and trends, although mean temperature shows a little cold bias about $1^{\circ}C$ compared to observations. It seems that a systematic cold bias is mostly due to an underestimation of maximum temperature. In the case of precipitation, the rainfall in winter and light rainfall are remarkably simulated well, but summer precipitation is underestimated in the heavy rainfall phenomena of exceeding 20 mm/day. The ICAMS shows a tendency to overestimate the number of washout days about 7%. Those results of this study indicate that the performance of ICAMS is reasonable regarding to air quality predication over the Korean peninsula.

• Journal of ILASS-Korea
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• v.3 no.1
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• pp.10-18
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• 1998

To investigate the in-cylinder phenomena in a SI engine with 3 valves and pent-roof type combustion chamber, flow fields, fuel distributions, and flame propagations were measured in a single c!'tinder visualized engine. Flow fields were visualized by PTV system during the intake and compression process. Fuel distributions were measured by PLIF at the various engine conditions including the cold and hot engine conditions and the effect of air-shrouded injector on the fuel distribution was investigated also. In addition, flame propagation patterns were characterized.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.98-103
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• 2019

With the increasing need for environmental protection, it is particularly important to improve the energy saving and reliability of refrigerators. Generally, the cold air flowing into the freezer compartment transits to the bottom of the refrigerating compartment, which can lead to uneven temperature distribution. This paper proposes two design solutions for improving the temperature distribution problem. Of these, the optimal refrigeration design was selected and tested using Computational Fluid Dynamics (CFD) modeling and simulation. The results showed improved uniformity of the temperature distribution inside the refrigerator, thus benefitting food storage while reducing energy consumption.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.1
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• pp.72-82
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• 2008

Benzene is a very harmful and toxic compound known as human carcinogen by all routes of exposure. Owing to the risky feature of benzene, several countries such as Japan, UK and EU have established the ambient air quality standard and protect from that risk of it. Korea also has designated it as one of the criteria air pollutants and established the concentration limit ($5\;{\mu}g/m^3$) in the air and is going to apply the standard from 2010. Benzene is emitted from various sources such as combustion plants, production processes, waste treatment facilities and also automobiles. Mobile source is known as one of the major emission sources of benzene. In this study, we estimated the domestic emissions of benzene from mobile source and compared the results with those of advanced countries. Mobile source was divided into 2 categories, Le., on-road source and non-road source. The total emissions of benzene from mobile source were estimated as 3,106 tons/yr and 1,612 tons/yr was emitted from on-road source and 1,494 tons/yr was from non-road source. Emission ratio of benzene from on-road source showed that 80.0% was from passenger cars, 10.1% was from taxis, 7.2% was from light-duty vehicles, 2.5% was from heavy-duty vehicles and 0.2% was from buses. In the case of non-road source, the distribution showed that 66.3% was from construction machineries, 14.5% was from locomotives, 11.7% was from ships, 7.1% was from agriculture equipments and 0.5% was from aircrafts. The cold-start emissions were estimated as 942 tons/yr and this value was almost 1.5 times greater than that for hot engine emissions (608 tons/yr). In addition, the fuel-based distribution was 65.9%, 31.1% and 2.8% from gasoline, LPG and diesel vehicles, respectively. The emission ratio from mobile source occupied 65% and 30% of total benzene emissions in USA and UK, respectively. In case of Korea, the emission ratio of benzene from mobile source occupied 29% (15% from on-road source, 14% from non-road source) which showed similar value with UK.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.8
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• pp.419-428
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• 2017

In this study, energy loss due to ventilation load in the dock system was analyzed through simulation. Also, flow generated in the dock system of the warehouse was measured using manufactured measuring devices. Numerical simulation was conducted by simulating the most common picking tasks by examining the actual working environment. Incompressible and unsteady turbulent flows were assumed, and the turbulence model was the k-e standard model. Proper grid was selected through grid dependency test. Measurement was conducted using Honeywell and Vaisala sensors, and flow and temperature inside the warehouse were measured and compared with simulation results to validate simulation. When comparing amount of loss occurring in two hours and amount of loss occurring in 15 minutes, docking time of the former was eight times longer but energy loss was 3.8 times lower. Ventilation load occurring during the initial period after opening docking system accounted for a large proportion of total ventilation load. Also, comparing the load when the dock was closed and the load when the truck was parked, ventilation load was significantly higher than load due to heat conduction from the wall. Therefore, in improving the docking system, it is effective to reduce the gap by improving compatibility of the docking system and truck, rather than wall material.

• Journal of the Korean Solar Energy Society
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• v.28 no.6
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• pp.48-57
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• 2008

The research analyzed the distribution of the indoor temperatures of a radiant floor cooling system through mock-up experiments. It investigated the temperature difference of feed water, the vertical temperature difference of indoor air, the temperature difference of floor surface, and so on. The following is the results of the research. First, the research shows that the difference between indoor temperature and outside temperature was the smallest when the temperature of feed water was set at 16$^{\circ}C$. In addition, the temperature changes according to indoor positions (wall, room, floor, and ceiling) were the most uniform. Thus, the research found that the cold water temperature of 16$^{\circ}C$ is the most proper. In addition, it confirmed that the feed water temperature of 18$^{\circ}C$ is effective because the temperature can lower the temperature of a room to 13.55$^{\circ}C$, which is lower than the temperature of a non-cooling mode. Second, an investigation on the temperature distribution of vertical air in indoor space shows that the temperature distribution had a difference of 0.2 to 1.9$^{\circ}C$ on the average, which satisfies the range of 3.0$^{\circ}C$ in the standard of ISO.

• Journal of Power System Engineering
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• v.11 no.2
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• pp.20-25
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• 2007

The performance of air-to-air heat exchanger has been investigated with rotating porous plates newly developed in this study. With an equal interval of 18 mm, the rotating porous plates are installed inside the heat exchanger where the hot and cold airs enter at opposite ends. When flowing in opposite directions by the separating plate installed in the center of the rotating porous plates, the airs give and receive the heat each other. Dry bulb temperature is set by adjusting heat supply at heater. In order to measure the temperature distribution of the hot air side inside heat exchanger, the thermocouples are inserted between the plates. The first location of thermocouple is 10mm downstream from the inlet of heat exchanger, and succeeding ten locations are aligned at an equal interval of 18mm. From the experiment of air-to-air heat exchanger with the rotating porous plates, the heat transfer rate increased as both air flow rate and RPM of the rotating porous plate increased. It was found that the overall heat transfer coefficient increased with the increase in RPM of porous plate at the conditions of the same air flow rate.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.489-496
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• 2004

The effect of airconditioning and heating system when aircurtains installed in subway electrical rolling stock at entrance door. It blocks cold/hot air of outside. It is good for health with its blocking effect against dusts exhaust fumes, odor bugs and smoke from outside. It always maintains clean and pleasant atmosphere inside. It helps you to have health with its ever-equal temperature distribution at inside. It saves lots of maintenance cost for heating/cooling (about 86$\%$) since it cuts the loss of hot air under heating as well as of cold air under air-conditionin. Customers can feel pleasant go in and out (better than before) with the door. It is an indispensable product for the employers to cut the cost. It makes customers feel pleasant near doors, since it isnt influenced by temperature difference of cold/hot air when the door opens/closes. In electrical rolling stock passenger temperature is a lot different from that the door opens/closes. One of the main aims is to create an acceptable thermal environment without draught problem. Temperature, gradients when aircurtains installed in subway electrical rolling stock at entrance door have been studied. And the temperature measured at 0.1, 0.5, 1.3, 1.7m above the floor. It has been found that temperature, with large fluctuations caused more draught influence.