• Journal of Advanced Marine Engineering and Technology
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• 제28권2호
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• pp.252-262
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• 2004

A model of simultaneous heat and mass transfer process in absorption of refrigerant vapor into a lithium bromide solution of water-cooled vertical plate absorber. which was considered to the change of refrigerant vapor pressure along the plate width direction. was developed to evaluate the compactness of plate absorber and supply basis data for optimal design of plate absorber. The effects of plate interval as well as the effect of capacity for one piece of plate absorber on plate absorber size such as plate height. plate heating area and plate absorber volume have been investigated. It is confirmed that there is exist an optimal plate interval minimizing plate absorber volume. And the smaller capacity for one piece of plate absorber. the smaller plate absorber volume is obtained.

• 설비공학논문집
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• 제14권3호
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• pp.240-246
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• 2002

Bypass air conditioning systems are divided into three types; an outdoor air bypass, a mixed air bypass and a return air bypass system. What makes the return air by pass system more effective is that it directs all of moist outdoor air through the cooling coil. The bypass air conditioning system can maintain indoor R.H (Relative Humidity) less than a conventional CAV (Constant Air Volume) air conditioning system by adjusting face and bypass dampers at part load. When a design sensible load (the ratio of sensible load to total sensible load) is 70 percent (at this time, RSHF (Room Sensible Heat Factor) . 0.7), indoor R.H was maintained 59 percent by the return air bypass system, but 65 percent by the conventional CAV air conditioning system (valve control system). The bypass air conditioning system can also improve IAQ (Indoor Air Quality) in many buildings where the number of air change is high.

• The Korean Journal of Physiology
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• 제27권1호
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• pp.37-49
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• 1993

Ventilatory responses to inhaled $CO_2$ were measured during continuous negative pressure breathing (CNPB) in awake dogs. End expiratory lung volume (EELV) decreased linearly with pressure level during CNPB (correlation coefficient= 0.81, p<0.005) during air breathing. When CNPB was applied during 5% $CO_2$ inhalation, the decrease in EELV was not significantly different (p<0.5) from that during air breathing. As a result of a lowered EELV, tidal volume ($V_T$) significantly decreased by 22% and breathing frequency ($f_B$) increased by 68% in the steady state during air breathing (p<0.0001). These responses were similar during 5% $CO_2$ inhalation, thus the $CO_2$ response curve measured during CNPB shifted upward without a change in sensitivity (p>0.05). These results indicate additive effects of CNPB and $CO_2$ inhalation. The degree of hyperventilation during CNPB at eupnea was estimated to be 63% of that during control ventilation and was significantly greater than zero (p<0.0001), which suggests an alveolar hyperventilation due to CNPB. These results suggest that the mechanical alterations associated with n decrease in lung volume could play an important role in ventilatory control independently of chemical regulation of breathing. Thus, exercise hyperpnea, which is associated with a lowered functional residual capacity (FRC), may in part be explained by this mechanical stimulation of breathing.

• 한국의류학회지
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• 제36권4호
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• pp.382-390
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• 2012

This study shows the optimum attachment of Two-Way Shape Memory Alloy (TWSMA) springs onto thermal liner and its sewing method for the mass production of fire fighter's intelligent turnout gear. SMA springs were attached to the fabric by four different methods and stitched by two different shapes (square and wave). The durability of the attached springs was tested by laundering up to 50 cycles. Examined were whether the springs would remain attached to the fabric after repeated laundering, the shape memory effect and reaction of the springs, and the anti-corrosiveness of the springs. A Human-Clothing-Environment simulator evaluated thermal insulation according to attachment methods, air layer volume, and stitch types. The findings showed that silicon attached springs remained intact after repeated laundering; in addition, repeated laundering did not influence the responsiveness and anti-corrosiveness of SMAs. Air volume had positive relations with the insulation. Attachment methods or stitch methods had limited impact on the thermal insulation. As a result, a wave type stitch with silicone attachment was suggested as the optimum method to attach the SMA springs onto the intelligent turnout gear for fire fighters.

• 한국유체기계학회 논문집
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• 제18권4호
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• pp.49-55
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• 2015

The pumped storage plant operates with quick change of the discharge as well as quick changes between pump mode and turbine mode. This study focuses on the cavitation analysis of a pump-turbine model because in turbo-machinery, cavitation can reduce the performance and shorten service life. The pump-turbine model system consists of 7 blades, 20 stay vanes (including tongue) and 20 guide vanes. This study adopts the Rayleigh-Plesset model as a cavitation model, which illustrates cavitation by using the air volume fraction method. The pump mode and turbine mode at the operating condition of partial loading, normal and excessive loading are analyzed to investigate the cavitation performance of the pump-turbine. It was observed that this pump-turbine design showed very good cavitation characteristics with no cavitation bubbles in all operating conditions. Overall value of air volume fraction of both mode at different operating condition are lower than 1, which confirms low possibility of cavitation occurrence at current situation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.1-4
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• 2008

Fuel cells have the potential of providing several times higher energy storage densities than those possible using current state-of-the-art lithium-ion batteries, but current energy density of fuel cell system is not better than that of lithium-ion batteries. To achieve the high energy density, volume and weight of fuel cell system need to be reduced by miniaturizing system components such as stack, fuel tank, and balance-of-plant. In this paper, the thin flexible PCB (Printed circuit board) is used as a current collector to reduce the stack volume. Two end plates are made from light weight aluminum alloy plate. The plate surface is wholly oxidized through the anodizing treatment for electrical insulation. The opening rate of cathode plate hole is optimized through unit cell performance measurement of various opening rates. The performances are measured at room temperature and ambient pressure condition without any repulsive air supply. The active area of MEA is 10.08 $cm^2$ and active area per a unit cell is 1.68 $cm^2$. The peak power density is about 210 mW/$cm^2$ and the air-breathing planar stack of 2 Wis achieved as a small volume of 18 cc.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2016년도 춘계학술대회
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• pp.93-95
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• 2016

최근 물동량 하락으로 인해 선박의 에너지 절감에 대한 선주들의 관심이 모아지고 있다. 선박용 HVAC은 선박 구조상 거주구역이 수밀형 창문으로 구성되고 폐쇄적이기 때문에 승무원의 쾌적한 환경 조성을 위해 사용된다. 또한 생활수준의 향상과 더불어 승무원들의 쾌적함에 대한 요구는 더욱 강해지고 있어 HVAC의 기능 향상이 요구되고 있다. 따라서 본 논문에서는 변풍량 방식의 선박용 HVAC 구조를 사용하여 HVAC 제어기능 향상 및 에너지를 절감할 수 있는 방법을 제시한다.

• Journal of Biosystems Engineering
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• 제40권3호
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• pp.232-237
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• 2015

Purpose: In Korea, wheat is dried using circulating cross-flow grain dryers. However, there is no research on wheat drying which can be utilized for the dryers. Therefore, this study developed and evaluated a simulation of the circulating cross-flow dryer, and examined the effects of various factors on drying performance. Methods: The simulation program was developed using drying models and was evaluated against wheat-drying experiments with a dryer having a 30-ton capacity. The influence of drying temperature, air volume, and grain falling rate on drying performance were examined through the simulation. Results: The experimental results validated the simulation program by showing the same root mean square error (RMSE) for moisture content (0.286%) and drying rate (0.056%/h) in both the experimental data and the simulation values. The appropriate wheat-drying parameter values, considering drying conditions, were determined to be $50^{\circ}C$ for drying temperature, $500m^3/min$ for air volume, and a grain falling rate of $36.0m^3/h$. Conclusions: The developed simulation program for circulating cross-flow dryers analyzed the influences of performance factors such as drying temperature, air volume, and falling rate on drying performance.

• 태양에너지
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• 제20권4호
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• pp.17-24
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• 2000

Thermal performance of a SAAHPS (Solar and Ambient-air-assisted Heat Pump System) located in KIER is simulated with TRNSYS 14.2. The SAAHPS is composed of dual evaorators, each of which is used as a solar fluid heat source and an air fluid heat source. Polynomial coefficients data for the SAAHPS is supplied with Frigosoft, a program widely used for heat pump modeling. In general, collector area and storage volume are 2 key parameters in SAAHPS thermal performance. A parametric study is performed in this study to assess sensitivity of collector area and storage volume in SAAHPS. We concluded that firstly collector area and storage volume are the primary variables in SAAHPS thermal performance, secondly COP of SAAHPS is higher than that of conventional heat pumps. Therefore. collector efficiency can be enhanced swith SAAHPS during a heating season.

• 한국세라믹학회지
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• 제23권4호
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• pp.41-46
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• 1986

When barium titanate was synthesized in solid-solid reaction the abnormal expansion occurred from 90$0^{\circ}C$ to 110$0^{\circ}C$. The equi molecular mixture of $BaCo_3$ and $TiO_2$ was sintered from 90$0^{\circ}C$ to 130$0^{\circ}C$ on the condition of air vacuum and $CO_2$ atomosphere. After that the specimens were tested closely with XDR Dilatometer and SEM The result indicated that: 1, Volume expansion to be synthesized barium titanate in solid-solid reaction was affected by atomosphere sintering. 2. The solid reaction ot fiorm barium titanate in vacuum atomosphere occurred faster than that in air atomosphere. In vacuum atomosphere the maxium volume expansion was about 30% at 90$0^{\circ}C$ for 2hrs, 3. The solid reaction to form barium titanate in 4CO_2$ atomosphere occurred slower than that in air atomosphere. In $CO_2$ atomosphere the maximum volume expansion was 13% at 100$0^{\circ}C$ for 2 hrs. 4. According to the result of x-ray the expanison was caused by the reaction to form $BaTiO_3$ and change $Ba_2TiO_4$ into 4BaTiO_3$.