• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.12
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• pp.875-880
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• 2012

The field of the large volume heat exchanger for wasted heat recovery ventilation system is being expanded enormously seeing as the fact that the quantity of reducing energies are huge due to the large volume heat exchanger for wasted heat recovery system at large buildings and factories, which consume large amount of energies while it has been arising huge amount of losses in Korea because of the lack of technology. To develop large volume waste heat recovery heat exchanger, rotor type heat exchanger was simulated for the surface corrugation. Based on the simulation results produced $30,000m^3/h$ grade waste heat recovery, heat exchanger was performed for the actual experiment. In addition, performance tests exceed the capacity of a large waste heat recovery heat exchanger performance test methods proposed.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.1
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• pp.83-89
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• 2002

The goal of this research is to understand the NOx emission in direct injected diesel engine with premixed hydrogen fuel. Hydrogen fuel was supplied into the test engine through the intake pipe. Amount of hydrogen-supplemented fuel was 70 % basis on heating value of the total input fuel. The effects of intake air temperature and exhaust gas recirculation(EGR) on NOx emission were studied. The intake air temperatures were varied from $23^{\circ}C$ to $0^{\circ}C$ by using liquid nitrogen. Also, the exhaust gas was recirculated to the intake manifold and the amount of exhaust gas was controlled by the valve. The major conclusions of this work include: ( i ) nitrogen concentrations in the intake pipe were increased by 30% and cylinder gas temperature was decreased by 24% as the intake air temperature were changed from $23^{\circ}C$ to $0^{\circ}C$; ( ii ) NOx emission per unit heating value of supplied fuel was decreased by 45% with same decrease of intake air temperature; and (iii) NOx emission was decreased by 77% with 30% of EGR ratio. Therefore, it may be concluded that EGR is effective method to lower NOx emission in hydrogen fueled engine.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.3
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• pp.233-240
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• 2004

This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space The system was introduced into a real building and was examined by the field measurement Judging from the measurements during three years(1999~2001), the state of the system operation was very stable through this period and it was clear that the system contributes to reduction of energy consumption for air-conditioning. Futhermore, a simulation model used the simple heat diffusion equation Was developed to simulate its thermal characteristics and performances The simulations resulted m air temperature in good agreement with the measurements. Also, from the result of numerical analysis, It is clear that the amount of heat supply by using this system is more than the amount of energy loss to the room above it. Therefore, it is concluded that this systems is very useful and the proposed numerical model can be used for the prediction of system thermal performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.1
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• pp.161-170
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• 1995

This study is concerned with the numerical analysis of performance on fin-tube heat exchanger under frosting condition. In this work, tube-by-tube method using LMED is employed. The present results are compared with O'Neal's experimental and numerical results. A standard evaporator model with 2rows-2columns is selected to investigate the effects of the various parameters such as fin pitch, air flow velocity, and humidity. The results show that frost thickness and the amount of frost per unit area decrease as fin-pitch becomes narrower. In the meantime, frost thickness and accumulation rate increase with higher inlet air humidity. It is shown that heat transfer rate increases during 30minutes and then it decreases. Heat transfer rate and the amount of frost increase with air velocity, however frost thickness does not increase over a certain velocity.

• KSTLE International Journal
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• v.1 no.1
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• pp.52-58
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• 2000

The velocity and motion of single air bubbles rising through lubricant have been experimentally investigated to test the effect of silicon defoamant The investigation reveals that the velocity is markedly retarded by the addition of small amount of silicone defoamant. This retardation of rising velocity of air bubbles is proposed by increasing of Drag force or reducing of Buoyancy force around the surfaces of the bubbles.

• Journal of the Korea Society of Computer and Information
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• v.23 no.1
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• pp.91-102
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• 2018

The purpose of this study is to develop an excellent bodice prototype that is adapted to the body shape of middle-aged women using 3D measurement data. In the evaluation of appearance, S pattern 4.00, B pattern 2.80, E pattern 2.40, L pattern 1.40 were shown in order, and the best fit of S pattern was evaluated as excellent. As a result of looking at the color distribution chart to find out the amount, E pattern and S pattern were not space in the front bust, armhole, and the back waist line. The B pattern and the L pattern were marked in blue because of insufficiency space in the back neck. As a result of evaluation the amount of air gap in the clothing, the air gap of the bust was 0.12, which is the largest pattern of B. Next, the L pattern appears as a tight circle with smallest air gap in the order of the S pattern 0.096, the E pattern 0.08, and the L pattern 0.003. The S pattern was evaluated to be the most appropriate for the body shape of middle-aged women. But the waist and back were slightly tight. Middle-aged women have larger shoulder-related items and larger waist circumference. Therefore, when you set the perimeter item, you should add 1-2cm of space amount and give extra space to the circumference area.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.11
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• pp.851-858
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• 2006

[ $CO_2$ ] and propane mixtures, which are environmentally benign, nontoxic, low in price, and compatible with materials and lubricants, were considered as promising alternative refrigerants. A fully instrumented air-conditioning system was developed for a precise performance evaluation of pure $CO_2$ and $CO_2/propane$ mixtures. In this paper, the effect of the charging amount and circulation concentration on the cooling performance of the system using $CO_2$ and propane mixtures was tested and discussed. Pure $CO_2$ and 85/15, 75/25 and 60/40 binary blends by the charged mass percentage of $CO_2/propane$ were selected as working fluids. An optimum charging amount was proposed as a parameter instead of the degree of subcooling, which can not be well defined in the transcritical cycle, to properly compare the performance between the transcritical and subcritical cycles.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.3
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• pp.191-208
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• 1998

Estimations of dry and wet depositions in Korea and the size distributions of yellow sand above Korea have been carried out using the Eulerian aerosol model with the simulated meteorological data from the SNU mesoscale meteorological model. The estimated particle size distribution in Korea shows a bimodal distribution with peak values at 0.6 pm and 7 pm and a minimum at 2 pm in the lower layer However, as higher up, the bimodal distribution becomes an unimodal distribution with a peak value at 4∼5mm. Among the total amount of yellow sand deflated in the source regions , the dry and wet deposition fluxes were about 92%, and about 1.3∼0.5%, repectively, and the rest(5∼6%) is suspended in the air, Most of dust lifted in the air during the clear weather is deposited in the vicinity of the source regions by dry deposition and the rest undergoes the long -range transport with a gradual removal by the wet deposition processes. Over Korean peninsula, the total amount of yellow sand suspended in the air was about 6∼8% of the emissions in the source region and the dry and wet deposition fluxes were about 0.005∼0.7% and 0.003∼0.051% of the total emitted amount, repectively. It is estimated that 2.7∼8.9 mesa-tons of yellow sand is transported annually over the Korean peninsula with the annual mean dry deposition of 2.1∼490 kilo-tons and the annual mean wet deposition of 1.5∼65 kilo-tons.

• Journal of Power System Engineering
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• v.7 no.4
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• pp.31-37
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• 2003

This paper is a study on application of warm air circulator by using the carbon heating element with particle type. The main variables are the input current and amount of carbon heating source for experimental characteristics. The experimental results are obtained as follows. As the input current and temperature are increased, the resistance of heat source is decreased about $20{\sim}25%$ by the effect of negative resistance. As the amount of heating source is small, Joule heat is large with the input current. When the amount of heating source is 300 and the input current is 15A, the value of Joule heat is about 4604.6kJ/h. The heat production efficiency of carbon heating source is larger about 10% than the sheath heater.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.114-120
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• 2006

The basic effects of hydrogen addition for engine performance and emission were investigated in single cylinder research engine. Seven commercial injectors were tested to choose a suitable injector for hydrogen injection prior to its engine implementation. The hydrogen fuel leakage and flow rate were evaluated for each injector and KN3-1(Keihin, CO.) showed the best performance for hydrogen fuel. At the higher excess air ratio(${\lambda}=1.7$, 2.0), the better combustion stability was found with hydrogen addition even though its effect was small at lower excess air ratio (${\lambda}=1.0$, 1.3). Stable operation of the engine was even guaranteed at ${\lambda}=2.0$, if the amount of hydrogen gas was near 15% of total energy. In the lean region, ${\lambda}>1.3$, thermal efficiency was improved slightly while it was not clearly observed at ${\lambda}=1.0$, 1.3. It is considered that, in some cases, high temperature environment due to hydrogen combustion caused further heat loss to surroundings. Except for ${\lambda}=1.0$, with larger amount of hydrogen addition, CO was reduced drastically but it was emitted more at the leaner region. Nitric oxides(NOx) was increased a little more with hydrogen addition at ${\lambda}=1.0$, 1.3. However, at ${\lambda}>1.3$ its relative amount of emission was low. In addition, the amount of NOx was continuously decreased with hydrogen addition, but, at ${\lambda}=2.0$ the amount of NOx was lowered to 1/100 of that of ${\lambda}=1.0$. THC emission was significantly increased as air/fuel ratio was raised to leaner region due to misfire and partial burn.