• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.6-9
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• 2008

The efficiency and life time of the proton exchange membrane (PEM) fuel cell system is critically changed with its humidity which should be maintained properly during dynamic operation. Membrane humidifier is required to regulate proper humidity level for the design point of the PEMFC system. In this study, we presented the performance of the cylindrical membrane humidifier which is operated as water-to-gas. Dry air pressure, liquid water flow temperature, and air flow rate were chosen as the operating parameters. Humidity level is expressed with dew point.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2385-2389
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• 2008

This is the experimental research that tries to explain a variety of RH is how to affect the cell performance and the flooding phenomenon of proton exchange membrane fuel cell (PEMFC). A value of PH changes to 0%, 50% and 90% as its variation, either stoichiometric flow rate changes to 1.5, 2 and 4. Into the comparison between theoretical and experimental value, this study analyzes that a variety of PH is how 10 affect flooding in the cathode of the proton exchange membrane fuel cell. The effect of air stoichiometry, air humidity and different flow fields are also discussed in this paper This study has accomplished the measurement of performance as the variety of RH in the cathode of proton exchange membrane fuel cell, moreover it has recorded the visualization of flooding in the cathode with a high-speed micro camera.

• 동력기계공학회지
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• 제21권1호
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• pp.50-56
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• 2017

To increase the enthalpy exchange efficiency of ERV elements, the moisture exchange character must be improved. The moisture exchange efficiency depends on material characteristics. The material used for ERV is Hwang-to paper based on Han-ji which is Korean traditional paper. The paper has excellent performance in moisture exchange and heat transfer compared with polymer and other papers. To have an anti bacteria performance and to improve moisture exchange performance of Han-ji, Hwang-to is added to the Han-ji. The enthalpy exchange efficiency of the Hwang-to paper shows 5% greater than that of the conventional paper. In case of Escherichia Coli, the reduction rate of bacteria is 96.6% and in case of Pseudomonas, the reduction rate of bacteria is 97.5%. The ERV element made of Hwang-to paper has a great possibility as an ERV element.

• 한국환경과학회지
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• 제21권1호
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• pp.11-21
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• 2012

This study investigated the characteristics of selected volatile organic compounds(VOCs) in newly-finished residential buildings, before the occupants moved in. This investigation was carried out by measuring the indoor and outdoor concentrations of selected VOCs before the occupants moved in and by utilizing an indoor mass balance model. Among 25 target VOCs, five aromatics(benzene, ethyl benzene, toluene, m,p-xylene, and o-xylene) were detected in all samples of both indoor and outdoor air. Toluene was most abundant VOC in the indoor air of new apartments, with a median value of 168 mg $m^{-3}$. Unlike other VOCs, halogenated compounds would not be significantly emitted from building materials. The indoor air concentrations of all selected VOCs, except for 1,3,5-trimethyl benzene, exhibited significant correlations each other, while for outdoor air concentrations, five aromatics only were significantly correlated between them. The emission rate of toluene was higher for the current study(median value, 76.8 mg $m^{-2}\;h^{-1}$) than for a previous study, while the emission rates of limonene, a-pinene and b-pinene(geometric means of 2.4, 13.8 and 9.6 mg $m^{-2}\;h^{-1}$, respectively) were lower and the emission rates of m,p-xylene and 2-butanone(geometric means of 10.9 and 21.3 mg $m^{-2}\;h^{-1}$, respectively) were similar. Although there were a few exceptions, the emission strengths are likely proportional to indoor temperature, and appear to reversely proportional to air exchange rate.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.221-221
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• 2000

The heat exchange part in a modern multi-type air-conditioning system employs multiple-pass heat exchangers. The heat-transfer performance of an each pass in such an exchanger depends strongly on the length of the two-phase region and the mass flow of the refrigerant. The total length and diameters of the pipes, the exit conditions, and the arrangement of each pass as well as the geometrical shape of the distributor at the branching sections are considered to be major factors affecting the heat-transfer performance. The refrigerant commonly used in these systems is HCFC-22. The two objectives of this paper are to investigate the characteristics of the refrigerant flow rate and the superheat in the evaporator of a multi-type air-conditioning system for a single or simultaneous operating conditions and to control the superheat and the refrigerant flow rate of the evaporator.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.172-179
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• 2004

Average Bi-directional flow tube was suggested to measure single and two phase flow rate. Its working principle is similar with Pilot tube, however, it makes it possible to eliminate the cooling system which is normally needed to prevent from flashing in the pressure impulse line of Pilot tube when it is used in the depressurization condition. The suggested instrumentation was tested in the air-water vertical test section which has 80mm inner diameter and 10m length. The flow tube was installed at 120 of L/D from inlet of test section. From the test, single air and water flow rate was measured successfully. For the emasurement of two phase flow rate, Chexal drift-flux correlation was used. In the test a new correlation of momentum exchange factor was suggested. The test result shows that the suggested instrumentation using the measured void fraction and Chexal drift-flux correlation can predict the mass flow rates within $10\%$ error of measured data.

• 설비공학논문집
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• 제12권9호
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• pp.825-834
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• 2000

A heat exchanger analysis is performed to investigate the heating characteristics of cryogenic nitrogen by ambient air for the purpose of cryogenic automotive propulsion. The heat exchanger is a concentric triple-passage for supercritical nitrogen, and the radial fins are attached on the outermost tube for the crossflow of ambient air. The temperature distribution is calculated for the nitrogen along the passage, including the real gas properties of nitrogen, the fluid convections and the conductions through the tube walls and the fins. Since the wall temperature of the outer (ambient side) tube is very low in most cases, a heavy frost can be formed on the surface, affecting the heat exchange performance. By the method of the similarity between the heat and the mass transfer of moist air, the frost growth and the time-dependent effectiveness of the heat exchanger are calculated for various operating conditions. It is concluded that the frost formation can augment the heating of nitrogen during the initial period because of the latent heat, then gradually degrades the heat exchange because of the increased thermal resistance. Practical design issues are discussed for the flow rate of nitrogen, the velocity and humidity of ambient air, and the sizes of the fin.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.115-118
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• 2010

공기 가열 장치는 크게 연소식과 열교환식 2가지가 있으며, 본 논문은 공기를 오염시키지 않은 열교환 방식인 청정 공기 가열 장치의 설계 방법을 기술하였다. 가열 장치는 크게 연소기 (Burner), 가열로 (Furnace), 열교환기 (Heat Exchanger), 배기구로 구성되어 되며, 가열되는 공기 유량과 입/출구 온도값으로부터 가열원인 연소기의 열용량과 연소기 연료인 LNG의 소요량을 구한다. 열교환기 내부에서 연소기의 뜨거운 연소가스와 가열되는 차가운 공기간의 열매체를 통한 간접 열교환이 이루어지므로, 가열되는 공기의 입/출구 온도에서 열교환기의 용량, 크기, 작동 최대 온도를 얻을 수 있게 된다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.333-339
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• 2000

This study was performed to investigate the performance of heat recovery device attached to exhaust gas funnel connected to combustion chamber of greenhouse heating system. The experiment heat recovery system is mainly consisted of LPG combustion chamber and two heat recovery units; unit-A is attached directly to the exhaust gas funnel, and unit-B is connected with unit-A. Heat recovery performance was evaluated by estimating total energy amount by using enthalpy difference between two measurement points together with mass flow rate of gas and/or air passing through each heat recovery unit depending on 5 different flow rates controlled by voltage meter. The results of this experimental study, such as heat exchange behavior of supply air pipes and exhaust air passages crossing the pipes, pressure drop between inlet and outlet, heat recovery performance of exchange unit, etc., will be used as fundamental data for designing optimum heat recovery device to be used for fuel saving purpose by reducing heat loss amounts mostly wasted outside of greenhouse through funnels.

• 수산해양기술연구
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• 제59권2호
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• pp.155-163
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• 2023

This study deals with the maximum thermal load analysis and optimal capacity determination method of tank culture system for applying seawater source heat pump to save energy and realize zero energy. The location of the fish farm was divided into four sea areas, and the heat load in summer and winter was analyzed, respectively. In addition, two representative methods, the flow-through aquaculture system and the recirculation aquaculture system were reviewed as water treatment methods for fish farms. In addition, the concept of the exchange rate was introduced to obtain the maximum heat load of the fish farms. Finally, power consumption for heat pumps was analyzed in the view point of sea areas, tank capacity, and exchange rate based on the calculated maximum thermal load.