• 대한기계학회논문집B
• /
• 제22권3호
• /
• pp.408-415
• /
• 1998

This study presents experimental results on the shut-down and start-up characteristics of a residential split-system air-conditioner with capillary tube, using R410A as a R22 alternative refrigerant. During shut-down, the transient characteristics are evaluated by measuring the high side and low side pressures and temperatures of the system. The dynamic behavior of the system after start-up is also investigated at the high temperature cooling test condition. All experiments are performed in psychrometric calorimeter. The cooling capacity, power consumption, dehumidification capacity and cycle characteristics after start-up are analyzed.

• 한국압력기기공학회 논문집
• /
• 제13권1호
• /
• pp.69-74
• /
• 2017

In the fire protection system or fire fighting water supply system, the jockey pump is generally installed for the prevention of the pressure decrease of pipes, the frequent driving of the fire pump and protection the pipes from the water hammer. In this paper, the pressure-rise in fire fighting water distribution pipes in condition of pipe pressurization by the surge tank at the start-up and the sudden-stop of the fire pump without additional installation of jockey pump is considered by using simple formula calculations and the evaluation of water hammer occurrence in condition of pipe pressurization by the surge tank is included. As a result, the pressure-rise of pipes is less than the pipe design pressure at the condition of pump's start-up and sudden stop, and the possibility of water hammer occurrence is remarkably low due to pressurization of the pipes by the surge tank.

• 한국소음진동공학회논문집
• /
• 제20권2호
• /
• pp.153-159
• /
• 2010

This work focuses on finding a method to reduce the noise of a hermetic reciprocating compressor during start-up using an acoustical analysis. The noise of compressor during start-up, which is a higher level than that of a normal operating condition, has transient and non-stationary characteristics. The acoustical analysis of compressor cavity is performed to find an effective method to reduce the noise level. In the acoustical analysis, the shape variations of frequency response function in the neighborhood of resonances are tested for three parameters: the height of remained oil, the suction position of refrigerant and the position of driving part. As a conclusion of this result, to reduce the emission noise of compressor during start-up, the height of remained oil should be kept at 16 mm, the refrigerant should be sucked at the cross point of nodal lines of X and Y directional cavity modes, and the driving part should be positioned in the center of cavity.

• 한국안전학회지
• /
• 제27권4호
• /
• pp.83-89
• /
• 2012

In order for start-up establishment to enter the business market, it has to get over the first mover advantage of the existing establishment. As a result, its working condition deteriorates and a great deal of occupational accidents take place. Based on 2009 standard, the occupational accident rate of start-up establishment is 1.28%, which is two times higher than existing establishment and the gap between manufacturing and service industry has been getting wide. For the characteristic of injured person in start-up establishment, it is showed that the occupancy rate of women and people with less than 30 age starting out in a career is high and the occupancy rate of occupational accident for holiday and night work is high. Therefore, the act for occupational accident prevention is needed in the early period of business and underprivileged group for occupational accident.

• 전력전자학회논문지
• /
• 제5권5호
• /
• pp.427-434
• /
• 2000

본 논문은 유도전동기의 직접벡터 제어 시스템에서 전동기가 기동 시 토크 충격없이 부드럽게 기동할 수 있는 기동기법을 제시한다. 정지모드에서는 고정자 전류만으로 고정자자속을 계산하는 방식을 사용하며, 기동 후 직접 벡터제어 모드에서는 프로그램어블 3-단계 저역필터로 고정자자속을 계산한다. 정지모드에서 직접벡터제어 모드로 변환 시 3-단계 저역필터의 시간지연으로 고정자 자속이 급격히 감소되어 토크 역시 갑자기 감소된다. 본 논문에서는 전동기가 기동 시 토크 충격을 방지하기 위한 고정자 자속의 피이드포워드 제어 기법을 제시하고, 시뮬레이션 및 실험을 통하여 이 기법의 타당성을 확인한다.

• 한국자동차공학회논문집
• /
• 제16권3호
• /
• pp.66-72
• /
• 2008

Fuel reforming technology for the fuel cell vehicles could be adopted to internal combustion engine for the reduction of engine out emissions. Since syngas which is reformed from fossil fuel has hydrogen as a major component, it has abilities to enhance the combustion characteristics with wide flammability and high speed flame propagation. In this paper, syngas was feed to 2.0 liter gasoline engine during the cold start and early state of idle condition. Not only cold start HC emission but also $NO_x$ emission could be dramatically reduced due to the fact that syngas has no HC and has nitrogen up to 50% as components. Exhaust gas temperature was lower than that of gasoline feeding condition. Delayed ignition timing, however, resulted in increased exhaust gas temperature approximated to gasoline condition. It is supposed that the usage of syngas in the gasoline internal combustion engine is an effective solution to meet the future strict emission regulations by the reduction of cold start THC and $NO_x$ emissions.

• 한국압력기기공학회 논문집
• /
• 제7권3호
• /
• pp.1-7
• /
• 2011

The analysis shows that the vibration is one of the main reasons of turbine failure. Especially, the problems caused by vibration occur right after retrofit of the turbine-generator and restarting the turbine. Through the case study of high vibration caused by after the turbine trip and restart, turbine vibration was identified to be influenced by startup condition. Turbine startup at high casing temperature right after unscheduled turbine trip cause radial expansion in rotor by contraction in axial direction, while casing continues to contract by steam flowing into casing. Consequently, gap between rotor and casing decrease until to metal contact to cause high vibration. Through the case study of high vibration of turbine-generator system after generator retrofit, it was identified that generator replacement could cause high vibration in turbine-generator system if the influence of generator replacement on entire system was not considered properly. To prevent startup delay caused by high vibration, it is important to keep the gaps at the design standard and start the turbine after thermal equilibrium.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
• /
• pp.169-178
• /
• 2001

Among the recent research ideas to reduce hydrocarbon emissions emitted from SI engines till light-off of catalyst since cold start are those exploiting non-thermal plasma technique and photo-catalyst that draws recent attention by virtue of its successful application to practical use to clean up the atmosphere using the feature of its relative independence on temperature. Based on the previous research results obtained with model exhaust gases using an experimental emissions reduction system that utilizes the non-thermal plasma and photo-catalyst technique, further investigation was conducted on a production N/A 1.5 liter DOHC engine during cold start to warm-up. For the effects of non-thermal plasma-photocatalyst combined reactor, 10% concentration reduction was achieved with the fuel component paraffins, and the large increase in non-fuel paraffinic components and acetylene concentrations were similar to those of base condition. However the absolute value was locally a bit higher than those of base condition since the products was made from the dissociation and decomposition of highly branched paraffins by plasma-photocatalyst reactor. Olefinic components were highly decomposed by about 75%, due to these excellent decompositions of olefins which have relatively high MIR values, and the SR value was 1.87 that is 30% reduction from that of base condition, then, the photochemical reactivity was lowered.

• 한국융합학회논문지
• /
• 제12권2호
• /
• pp.163-171
• /
• 2021

본 연구는 국내 신진디자이너의 패션스타트업에 대한 정부 지원 프로그램이자 시설 중 하나인 패션창작스튜디오의 패션스타트업 기업의 운영 현황과 창업자의 특성을 분석하였다. 이를 위해, 부산패션창작스튜디오의 패션스타트업 창업자 32명을 대상으로 설문 조사를 하였다. 그 결과 첫째, 패션창작스튜디오의 패션스타트업 기업 창업자들의 82%가 20대에 창업경험을 가지고 있었고, 60%가 3~5년 이하의 패션 실무경력을 가지고 창업에 도전하는 것으로 나타났다. 둘째, 패션스타트업 기업의 유통채널은 오픈 마켓이 36%, SNS가 주요 홍보 매체로 80%에 이른다. 또한, 71%가 중국에 수출하고 있다. 마지막으로, 업체의 33%가 인플루언스를 통한 바이럴마케팅을 고려하고 있고, 50%가 동남아시아에 수출을 계획하고 있다. 본 연구결과는 지원 프로그램이자 시설인 패션창작스튜디오를 활용하여 패션스타트업 기업의 성공적 창업과 운영 방향성을 제시하는데 연구적 의의가 있다.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
• /
• pp.157-160
• /
• 2008

Solar receiver in the solar power tower system has a similarity to a boiler of the thermal power plant in many aspects. However Boiler is operated long time without stopping while solar receiver repeats start and stop every day. The objective of this study is to investigate start-up characteristics of solar receiver. The experimental device was constructed in a bench scale. Basic experimental condition of water/steam was set by 25 bar and $223^{\circ}C$. Initially, the heat was added into risers only, then another experiment with input into drum additionally was done. When the heat flux was valid only risers, it took about 300 minutes until the water temperature in drum reached $223^{\circ}C$. Water temperature of drum was increased by $44^{\circ}C$/hr with 91.14 g/s of water circulation. With additional heat input into drum, 200 minutes was required to reach $223^{\circ}C$. In this case temperature was increased $66^{\circ}C$/hr with 96.5 g/s of water circulation.