• 대한치과기공학회지
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• 제16권1호
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• pp.5-11
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• 1994

On purpose of relative comparison of between air-vent attached pattern and non attached one, casting tests were accomplished by castability analysis unrig wax screen mesh pattern. Experimental specimens are divided Into 4groups. 1) Air-vent attached pattern with high casting pressure(coil spring type centrifugal casting machine 2.5turn). 2) Air-vent attached pattern with low casting pressure(coil spring type centrifugal casting machine 1.5turn). 3) Air vent non attached pattern with high casting pressure(coil spring type centrifugal casting machine 2.5turn). 4) Air-vent non attached pattern with low casting pressure(coil spring type centrifrgal casting machine 1.5turn). The main results are as follows : 1) The condition of high casting pressure no.1, no.3 were showed perfect castability. 2) The condition of low-casting pressure, there is a wide difference between no.2, no.4 group. Castability of no.2 group preferable to no.4 group(p<0.001). 3) Low casting pressure and complex shape cause the low-castability. So it is recommanded that use of air-vent in case of complex shaped wax pattern with low easting pressure.

• 설비공학논문집
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• 제20권5호
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• pp.334-341
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• 2008

The purpose of this study is to investigate the effects of changing air temperature and the changing on/off periods of the air-conditioner system. Adding to that, this paper discuss is to consider the effects of air temperature with the air-conditioner system upon the human thermal comfort. The experiment is conducted during the summer. The subjects(6 young females) are exposed to the following conditions: combinations of 2 Swing and 2 Linear air control Conditions. (2 Swing during 40 min, 4 Swing during 40 min, Linear 40 min, Linear 60 min in still air and RH 50%). From the experiment, the following results are obtained; the thermal sensation vote is neutral after 90 minute. The mean skin temperature ranged about $34^{\circ}C$ at all conditions. The skin temperature was greatly affected by 2 Swing big amplitude condition.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.77-84
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• 2002

For the purpose of obtaining a fundamental data which is needed to develope the port injection type charged LPLi engine system, we manufactured intake port injection system of liquid charging LPG and modified heavy duty single cylinder LPLi engine from heavy duty diesel engine. Engine output and emission characteristics were analyzed under variable air/fuel ratio and charging pressure. Since LPG is consisted of propane and butane, we investigated combustion characteristics using this two kinds of fuel. From the result of charging engine performance test, engine torque increase about 30% ∼ 40% with 0.3bar charging pressure. In low speed condition, as charging pressure increase, combustion stability improve ill lean bum condition, but, in high speed condition, combustion stability make worse in lean bum condition. We know that engine output decreased rapidly from the condition of air excess ratio 1.3. In addition, we measured emission characteristics under the lean bum and charging condition. From this experiment, we found that CO emission is out of the question in the range from stiochiometric to lean burn and charging condition, but charging pressure has influence on HC emission.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.94-110
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• 1997

In the present study, a mean torque predictive model has been proposed and experimentally validated. It includes induction air mass model, fuel delivery model and mean production mode. Air induction and fuel delivery model considering dynamic behaviors of air induction and fuel delivery were proposed to predict the air-fuel ratio excursions under transient condition. Torque function model reflects thermal efficiency, volumetric efficiency, friction and effect of spark timing. In the spark timing model, knock limit and acceleration retard are included. Experiments were carried out to validate the simulation model for the step changes of throttle at constant engine speed. The results show reasonable agreements between simulation and experiment at fully warmed condition. Using this model, fueling strategies are varied with fast throttle open and it can predict air-fuel ratio excursion and IMEP.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.252-257
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• 2007

The present study investigated the effect of air velocity on frost formation of slit fin-and-tube heat exchanger under frosting condition. The slit fin-and-tube heat exchanger with outer tube diameter 7.0mm and 1 row was used. Air side pressure drop, photographs of frost distribution, frost accumulation and frost thickness were presented with respect to the frosting time. In the early stage of experiment, the case with air velocity of 1.5m/s showed 403% higher for the air pressure drop than the case with the air velocity of 0.5m/s. As the frost was accumulated, the effect of air velocity on air pressure drop was decreased. In the end stage of test, air pressure drops of two cases were very close and air pressure drop for the air velocity of 0.5m/s was higher than that of 2.0m/s. It was also shown in the photographs of frost distribution, frost accumulation and frost thickness. From frost thickness, fanning friction factor was presented.

• 한국산업융합학회 논문집
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• 제24권4_2호
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• pp.467-474
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• 2021

The renewable energy is known as eco-friendly energy to reduce the use of fossil fuel and decrease the environmental pollution due to exhaust gas. Targets of solar collector in domestic are usually acquisitions of hot water and hot air. System of air-heating collector is one of the technologies for obtaining hot air in cases of especially heating room and drying agricultural product. The purpose of this study is to investigate the characteristics of thermal flow such as relative pressure, velocity, outlet temperature and buoyancy effect in air-heating collector using solar heat. The flow field of air-heating collector was simulated using ANSYS-CFX program and the behaviour of hot air was evaluated with SST turbulence model. As the results, The streamline in air-heating collector showed several circular shapes in case of condition of buoyancy. Temperature difference in cross section of outlet of air-heating collector did not almost show in cases of buoyancy and small inlet velocity. Furthermore merit of air-heating collector was not observed in cases of inlet velocities. Even though it was useful to select condition of buoyancy for obtaining high temperature, however, it was confirmed that the trade off between high temperature of room and rapid injection of hot air to room could be needed through this numerical analysis.

• 대한설비공학회지:설비저널
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• 제17권2호
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• pp.131-139
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• 1988

The thermoacoustic oscillation induced in an air column with variable cross section area is investigated theoretically and experimentally. The onset condition of the oscillation is derived by equating the acoustic power production to the power dissipation. The power production at the heater is predicted by using the efficiency factor obtained by heat transfer analysis for a single wire in a uniform cross flow and considering the interference between heater wires. The power dissipation is estimated by measuring the attenuating coefficient from the pressure decay curve. The theoretical prediction to the onset condition of the oscillation is confirmed experimentally. The effect of the variation of the column cross section area on the onset condition is presented.

• Journal of Information Technology Applications and Management
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• 제24권3호
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• pp.93-105
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• 2017

Demands of cosmetics are affected not only by the well-known elements such as brand, price, and customer's consumption capacity, but also by some latent factors, for example, weather and air environment. Due to complexity and dynamic changes of the above factors, their influences can hardly be estimated in an accurate way by the traditional approaches such as survey and questionnaires. Through modeling and statistical analysis of big data, this article studied the impacts of weather condition and air quality on customer flow and sales of the cosmetics distributors in China, and found several hidden influencing factors. It provided a big-data based method for the analysis of unconventional factors on cosmetics marketing in the changing weather condition and air environment.

• 설비공학논문집
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• 제25권9호
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• pp.499-505
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• 2013

R744 has been appropriated for substitute refrigerant, because of its high stability, and environment-friendly nature as a natural refrigerant. To analyze the cooling performance of a refrigeration system in a refrigerator truck using R744 according to the blocking ratio, an analytical model of the refrigeration system was developed under frost conditions, using EES. The performance of the refrigeration system was predicted with the indoor and outdoor air temperature, outdoor air velocity, and compressor speed. As a result, the system performance decreased, with the increase of frost growth. When the blocking ratio was 40.4% in the basic condition, the refrigeration capacity was decreased by 27.1%, compared to the non-frost condition.

• 아시안잔디학회지
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• 제15권3호
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• pp.111-118
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• 2001

본 연구는 주거지역으로 둘러싸여진 4ha 규모의 녹지를 대상으로 토지피복현황 및 수고의 차이가 기상완화효과에 미치는 영향을 파악하기 위해 녹지 내의 기온 및 상대습도분포를 관측하였다. 그 데이터를 바탕으로 녹지의 토지피복현황과 기온 및 상대습도분포, 토지피복비율 및 수목그루와 기상완화효과와의 관련성을 회귀분석 등에 의해 해석하였다. 그 결과, 고온역은 인공구조물과 나지 주변에 저온역은 수림지와 초지 주변에서 형성되었다. 상대습도는 기온분포에 거의 대응하는 형태로 고온역은 저습역이구 저온역은 고습역으로 나타났다. 토지피복비율별 기상완화효과를 보면, 수림지와 초지율이 증가하면 기온은 떨어지고 상대습도는 상승시키는 효과를 보였다. 또, 수목그루의 증가는 수고에 관계없이 모두 기상완화에 효과적이고 그 효과의 효율은 교목, 소교목의 순이다.