• 한국산업보건학회지
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• 제3권1호
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• pp.3-13
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• 1993

This study was conducted at seven degreasing processes in plating plants located in Seoul, Incheon, Ansan, and Taejeon areas from July 21 to august 27, 1992. This study was performed to assess the TWA exposures to trichloroethylene (TCE) and evaluate factors affecting TCE concentrations in degreasing process. Two-Point Eddy Diffusional Model suggested by Wadden et al. was employed to calculalte emission factors according to degreaser type. Results are summarized as follows. 1. The TWA exposures of the degreasing operators ranged from 1.4 ppm to 123 ppm, and those of three plants out of seven were exceeding 50 ppm of both the Korean and U.S. OSHA standards. Degreasing assistant of Plant B, was exposed to 59 ppm. 2. The average concentrations at the distance 0, 1.5, 3.0 m from the degreasers were 1.014, 24, and 18 ppm, respectively, and showed a signifficant difference by distance (p<0.01). 3. The emission of TCE was reduced by installing local exhaust systems, condensers, and refrigeration lines at the degreasers (p<0.01). 4. The major factors related to exposure of operators were workload (r=.9621. p<0.01) and dimensions of degreansing room(r=-.8667, p<0.05). 5. If the air in degreasing room is mixed violently by other factors in addition to diffusion, the emission factors can not be evaluated because the important hypothesis of the Two-Point Eddy Diffusional Model can not be accepted. 6. The ultrasonic degreaser without the local exhaust ststem, condenser, and refrigeration lines emitted TCE three times greater than the ultrasonic degreaser with condenser and refrigeration 1ines only.

• Journal of Advanced Marine Engineering and Technology
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• 제35권1호
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• pp.40-45
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• 2011

본 연구의 목적은 팽창장치 후에 설치된 액기분리기와 예냉 열교환기를 갖는 냉동시스템의 특성을 파악하고자 하는 것이다. 냉장고의 전형적 냉매인 냉매 R134a의 팽창공정 후 액기분리기에서 분리된 찬 증기를 이용하여 예냉 열교환기에서 팽창장치에 주입되는 냉매를 과냉시킨다. 분석결과 냉동능력은 8.9% 상승하였으며, COP는 1.4% 증가하였다. 이러한 성능 향상의 이유는 냉매 모리엘선도의 포화액선과 포화기체선의 기울기가 다르기 때문이다.

• 한국기계가공학회지
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• 제10권4호
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• pp.121-126
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• 2011

An accumulator placed on the refrigerant cycle pipe lines is a part to relax fluctuations of pressure within the pipe lines and stabilize refrigerants flowed into pipe. The accumulator has been mainly manufactured by the process of tube spinning using CNC(Computer Numerical Control) lathe. However, this process has the defects which are low productivity per hour and high cost. For that reason, tube end-forming using roll die is actively being developed, recently. The purpose of this study is to develope the tube end-forming process using roll die in order to manufacture the accumulator for the refrigeration pipe lines. First, the process design of tube end-forming was performed based on specification of product, and then was verified with FE analysis. Also, the effects of friction coefficient and revolution speed of roll die on forming load were investigated. The analytical results were applied in the final process design of tube end-forming. Finally, tube end-forming test was carried out to verify the validity of the FE analysis and the process design.

• 설비공학논문집
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• 제18권7호
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• pp.571-577
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• 2006

The characteristics of ice packing factor (IPF) at the ice slurry system using one line type are compared with the system using two lines type. The installation space for one transporting line is saved at the one line system. For the one line type, the ice packing factor is reduced along the downstream, but for the two lines type, the ice packing factor is fixed. For the one line system, mass flow rate in the main line is fixed along the down-stream, but for two lines system, the mass flow rate in the main line is reduced along the downstream. For one line system, along the down stream after IPF=0, the temperature at the main steam is increased, and the extracted mass flow is increased. The initial IPF, at which the IPF is not arrived at zero upto the final node, is proposed for the B area.

• 한국초전도ㆍ저온공학회논문지
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• 제11권1호
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• pp.64-68
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• 2009

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (HRS) with an exergetic equivalent cooling power of 9kW at 4.5K without liquid nitrogen $(LN_2)$ pre-cooling has been manufactured and installed for such purposes. In this proceeding, we will present the commissioning and initial operation results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1201-1206
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• 2008

Psychrometric chart displays graphically the thermophysical properties of moist air, so it is very conveniently used in air-conditioning and refrigeration. On general psychrometric chart, there are dry bulb temperature, web bulb temperature, absolute humidity ratio, relative humidity, specific enthalpy, specific volume, sensible heat factor, and enthalpy-humidity difference ratio. However, various state and process values besides aboves can be plotted on psychrometric chart. In this study, we developed the software drawing twenty kinds of lines, that is vapor pressure, mole fraction ratio of vapor, dew point temperature, degree of saturation, density, specific entropy, specific exergy, contact or bypass factor, uncomfort index, discomposition index, predicted mean vote index, predicted percent dissatisfied, and so on. We wish to this software is a help to design, analysis and education.

• Nuclear Engineering and Technology
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• 제40권6호
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• pp.467-476
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• 2008

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (RRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K without liquid nitrogen ($LN_2$) pre-cooling has been manufactured and installed. The main components of the KST AR helium refrigeration system (HRS) can be classified into the warm compression system (WCS) and the cryogenic devices according to the operating temperature levels. The process helium is compressed from 1 bar to 22 bar passing through the WCS and is supplied to cryogenic devices. The main components of cryogenic devices are consist of cold box (C/B) and distribution box (D/B). The C/B cool-down and make the various cryogenic helium for the KSTAR Tokamak and the various cryogenic helium is distributed by the D/B as per the KSTAR requirement. In this proceeding, we will present the commissioning results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• 설비공학논문집
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• 제12권5호
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• pp.448-456
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• 2000

For piping line systems associated with a double-acting reciprocating compressor, an analytical study has been made on the gas pulsation in piping lines and its effects on the compressor performance. The transfer matrix which relates mass flow rate to the gas pulsation downstream of the compressor valve can be obtained by an acoustic model for piping line systems which include snubber and after-cooler with the aid of four pole theory Since mass flow rate is affected by the pressure pulsation in the pressure plenum, while the latter being determined by the former, iteration in the calculation should be made for convergence. The gas pulsation in pipings is found to have an adverse effect on the compressor's performance, and the magnitude of the gas pulsation can be lowered by increasing snubber volume.

• 설비공학논문집
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• 제27권7호
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• pp.337-343
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• 2015

This paper investigates the ventilation characteristics in a two-dimensional underground network junction composed of four main lines interconnected by eight ramps. Simple one-dimensional models cannot be applied to network junctions since there are interferences of traffic piston effects in the main lines and at the ramps. A numerical algorithm was developed to analyze the pressure and airflow distributions iteratively. The Darcy-Weisbach equation was used to calculate the piston effects by traffic flows, and a Hardy Cross iteration was conducted for network analysis at the interconnected junction. The results show interesting ventilation characteristics and CO concentration distributions depending on system parameters such as vehicle speed, tunnel diameter, and other junction configurations.

• 한국잠사곤충학회지
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• 제46권2호
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• pp.65-71
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• 2004

누에유전자원의 장기 안전보존 기술 개발의 일환으로 우선 보존 중인 300여 계통에 대한 2년간 냉장에 의한 장기보존시험을 하였다. 보호 온도 별 냉장일수 및 중간처리 횟수를 달리한 6개 시험구로 잠종보호기간을 2000년 7월1일부터 2002년 5월1일까지 680일로 하였다. 시험구 별 배자검사 결과, 잠종보호기간 400일의 경우 시험구 별, 원산지 별로 배자발육 차이는 나타나지 않았으며 전체 배자발육 정도는 을A 수준이었다. 잠종보호기간 500일의 경우, 원산지 별, 시험구 별 차이를 보이며 전체 배자발육 정도는 을B 수준이었으며 잠란 상태는 양호하였다. 잠종보호기간 650일의 경우, 원산지 별, 시험구별 차이를 보이며 전체 배자발육 정도는 병A수준이었으며 잠란 상태는 양호하였다. 원산지 별로 보면 유럽종>옅대종, 한국종>일본종, 중국종 순으로 유럽종이 발육경과가 빨랐으며 시험구 별로 보면 대조구(A구)와 C구 2 시험구가 기타 시험구보다 발육정도가 빨랐으며 전체 시험구에서 D구와 F구가 개체 별로 발육정도가 안정된 상태였다. 최청기간 중 잠란의 외형적 성상조사 및 배자검사 결과, 계대보존 가능성(예상 부화비율)이 전체 6개 시험구 평균 61%로 높게 나타났다. 그러나 실제 부화된 계통은 시험구A, B는 전무하였고 시험구C 3계통, 시험구D 48계통, 시험구E 1계통, 시험구F 29계통으로 배자발육이 늦고 배자상태가 안정적이었던 D구와 F구가 가능성 높은 시험구로 나타났다. A~F 6개 시험구 중 D,F 2개 시험구의 성적이 우수하였는데 시험구 D, F의 $-2.5^{\circ}C$ 보호기간은 각 235일과 310일로 타 시험구보다 $-2.5^{\circ}C$ 접촉기간이 길었다. D, F 2개 시험구의 부화된 계통수는 각 48계통, 29계통으로 전체 조사계통의 15.6%, 9.4%를 차지하였다. D, F시험구의 평균부화비율은 각 54.5%, 71.6%였으며 평균사란비율은 각 33.0%, 25.0%였다 이상의 시험 결과를 보면 D, F 두 시험구 모두 최청사란비율이 일반계통보다 높게 나타나 월년잠종의 2년간 냉장보존을 위해서는 최청사란비율에 직접적으로 작용하는 최청 조건의 재검토가 우선적으로 필요함을 알 수 있었다.