• 설비공학논문집
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• 제12권10호
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• pp.941-949
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• 2000

Pool boiling heat transfer coefficients (HTCs) of HCFC123, CFC11, HCFC142b, HFC134a, CFC12, HFC22, HFC125 and HFC32 on a horizontal smooth tube have been measured. The experimental apparatus is specially designed to simulate the real heat transfer tube with the use of the secondary fluid of water as a heat source rather than a conventional electric heat source. Data were taken in the order of decreasing heat flux starting at $80 ㎾/m^2\; and \;ending\; at\; 5㎾/m^2\;in\; the\; poo\;l temperature\; at\; 7^{\circ}C$, Test results showed that HTCs of HFC125, and HFC32 are 50~67% higher than those of HCFC22. It is also found that some of the popular pool boiling heat transfer correlations in the literature are not good to predict the HTCs of newly developed alternative refrigerants. A new correlation was developed by a regression analysis which is based upon the consistent data obtained in this study and it showed an excellent agreement with all experimental data having an absolute mean deviation of less than 10%.

• 설비공학논문집
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• 제5권4호
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• pp.306-317
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• 1993

In this study, a performance comparison of scroll compressor for various refrigerants(CFC-12, HCFC-22 and HFC-134a) has been numerically carried out. The thermodynamic properties have been calculated by using the recent experimental equations and the performance has been investigated qualitatively at the same geometric specifications and operating conditions of scroll compressor. The results are as follows; HFC-134a has the highest compression ratio of 5.40. The mass flow rate of HCFC-22, which affects the cooling capacity of refrigerant system, is higher than that of other refrigerants. HFC-134a has the highest adiabatic efficiency in comparison with CFC-12 and HCFC-22.

• 한국환경과학회지
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• 제22권9호
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• pp.1105-1113
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• 2013

This paper attempted to estimate the emissions of HFC-134a from scrap truck as a result of measuring the residual quantities of HFC-134a in air conditioner of scrap truck. We measured the residual amounts in the scrap truck of 138 by applying commercial recover for refrigerants. The average residual rate(disposal-phase emission factor) is reported to be $44.3{\pm}3.3%$ within a confidence interval of 95%. Recent year model trucks exhibit the higher residual rates. Little variation, however, is observed in regard to vehicle size. The HFC-134a emission quantity from scrap truck in 2011 is estimated to be 55,908 $tCO_2$-eq that demonstrates 21.4% increase to compare with that in 2007. As the numbers of truck have increased dramatically during the last two decades, the emissions of HFC-134a from scrap truck would increase sharply in the next coming years. HFC-134a is a very high GWP greenhouse gas. therefore have to reduce the emissions from the scrap truck and need to find ways to recycle. The chemical compositions of refrigerants from scrap truck are quite similar to those of new refrigerants, suggesting that the refrigerants from scrap truck could be reused as refrigerant.

• 설비공학논문집
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• 제14권6호
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• pp.468-476
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• 2002

This paper deals with heat and mass transfer characteristics and performance evaluation of a counter flow double-tube condenser for a multi-component refrigerant mixture. The local heat and mass transfer characteristics of ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a are evaluated for a counter flow double-tube condenser cooled by water. Then, the local values of vapor quality, thermodynamic states at bulk vapor, vapor-liquid interface and bulk liquid, heat flux and condensation mass flux are obtained. The heat exchange performance for ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a on the total pressure drop and the heat transfer characteristics are also compared with those for R404A, R410A, R502, R22, R32, Rl23 and R134a.

• 설비공학논문집
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• 제13권8호
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• pp.710-719
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• 2001

Pool boiling heat transfer coefficients (HTCs) of HCFC123, HFC134a, HCFC22, HFC407C, HFC410A and HFC32 wre measured on a horizontal smooth tube, 26 fpi low fin tube, Turbo-B and Thermoexcel-E enhanced tubes. AN experimental apparatus was designed such that all tubes heated by cartridge heaters could be installed at the same time to save the refrigerant. Data were taken in the pool of $7^{\circ}C$ with the heat flux decreasing from 80 kW/$m^2\;to\;5kW/m^2$. Test results showed that HTCs of pure refrigerants and those of a azeotrope were greatly influenced by reduced pressure. HTCs of HFC407C were 21~25% lower than those of HCFC22 due to mass transfer resistance. For all refrigerants, enhanced tubes with sub-surface and sub-tunnels showed the largest heat transfer enhancement. Especially the largest heat enhancement was obtained for HCFC123 whose reduced pressure is the lowest among al the refrigerants tested. This indicates that either Turbo-B or Thermoexcel-E enhanced tube would be the best choice when used with a low vapor pressure refrigerant.

• 한국추진공학회지
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• 제22권5호
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• pp.59-65
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• 2018

hydroxyl-terminated polybutadiene(HTPB) 추진제는 자연 저장 기간 동안 내부 시효성 물질들에 의한 물리 화학적 반응으로 인해 서서히 노화가 진행된다. 각기 다른 시간-온도 조건에서 이들 시효성 물질의 가속 노화 시험을 통해 자연 상태에서의 노화 특성을 모사할 수 있다. 본 논문에서는 장기 저장 기간 동안 느리게 진행되는 HTPB 추진제의 물리 화학적 반응에 의한 노화 특성을 HFC(Heat Flow Calorimeter)로 분석 평가하여 수행한 HTPB 추진제의 신개념 수명 예측 기술에 대하여 고찰하였다.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권4호
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• pp.176-183
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• 2004

Systematic methods to calculate thermodynamic properties of carbon dioxide, HFC-134a and HCFC-22 are presented. First, application of a basic method to identify the saturation state with given temperature or pressure is attempted and the feasibility of auxil­iary equations is tested. Next, detailed procedures are suggested to tell a phase when tem­perature/pressure and another property are specified. Finally the Newton-Raphson method is applied to calculate unknown thermodynamic properties fixing the state with the two inde­pendent properties specified. The procedures described here are utilized to develop a computer program, which is used to find the relation between temperature and pressure with maximum isobaric heat capacity for super-critical carbon dioxide.

• 설비공학논문집
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• 제22권3호
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• pp.139-148
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• 2010

A centrifugal compressor for HFC-134a has been newly designed and developed. Flow analysis using commercial programs was used to evaluate performance and internal flow of the impeller, inlet guide vane and diffuser etc. The purpose of this study is to establish the design theory necessary to the development of HFC-134a centrifugal compressors and to supply basic data related to design by reviewing design values and experimental values through the performance test. The compressor for HFC-134a was also investigated experimentally to check compression performance. The calculated data coincide the test results of compressor. The data obtained in the present study are useful for design of HFC-134a centrifugal compressors.

• 한국식품과학회지
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• 제42권5호
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• pp.605-612
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• 2010

황기열수추출물(WEH)과 홍국 70% 에탄올추출물(EEB) 및 Monascus pilosus 액침배양액(LBK)을 동결건조한 등량 혼합물을 일반 닭고기 베이스소스에 0.225% 첨가한 황기홍국소스(HBS)를 처리한 계육의 식이가 고지방-고콜레스테롤 병행식이 흰쥐의 ROS 생성 및 소거계 효소류의 활성에 미치는 영향을 조사하였다. 실험군은 정상군(NC), 고지방-고콜레스테롤 대조군(HFC), 고지방-고콜레스테롤 식이에 베이스소스를 처리한 계육을 15% 첨가한 식이군(HFC-BS) 및 고지방-고콜레스테롤 식이에 황기홍국소스를 처리한 계육을 15% 첨가한 식이군(HFC-HBS)으로 구분하여(5마리/군) 5주간 사육하였다. 체내 활성산소를 생성하는 xanthin oxidoreductase O type 활성은 HFC군에 비하여는 31.84%가 HFCBS군에 비하여는 24.57%가 각각 감소되었다. Superoxide dismutase 및 glutathione S-transferase 활성은 HFC-HBS군이 HFC군 및 HFC-BS군에 비하여 각각 25.17-64.50% 및 19.29-62.89%가 증가 하였다. 활성산소에 소거에 관여하는 glutathione의 함량은 HFCHBS군이 HFC군 및 HFC-BS군에 비하여 각각 53.30% 및 25.11%가 증가하였으며, 간조직의 지질과산화물의 함량은 각각 20.29% 및 24.19%가 감소되었다. Glutathione peroxidase 및 catalase 활성은 각각 41.29-41.87% 및 22.91-23.44%가 증가하였다. 이상의 결과 황기홍국소스를 처리한 계육은 고지방-고콜레스테롤 병행식이 하에서도 활성산소 생성계 효소 활성을 감소함과 동시에 소거계 활성을 높힘으로서 간조직 손상을 예방 및 치유하는 것으로 사료된다.

• 생명과학회지
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• 제22권4호
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• pp.478-485
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• 2012

본 연구에서는 함초분 섭취가 지질대사에 미치는 영향을 알아보고자 하였다. 흰쥐를 일반식이 대조군(CON), 고지방식이 대조군(HFC), 고지방식이에 함초분 첨가군(HFG)로 각각 구분하여 4주간 섭취시켰다. 체중은 HFG가 HFC에 비하여 9% 정도 낮았다. 분변칼로리 분석을 한 결과, HFG의 지방량(CON에 비하여 120%, HFC에 비하여 138)과 분변 칼로리(약 110%)가 높은 것으로 나타났다. 혈중 중성지방과 LDL-C는 HFG가 HFC에 비하여 낮았으며(각각 71.8% 및 58%), HDL-C는 HFG가 HFC에 비하여 152% 높았다. 간의 FABP 발현은 HFG가 HFC보다 197% 높았으며, CPT-1 역시 동일한 경향을 보였다. 이러한 결과는 함초분 섭취가 체중의 증가를 억제하였고, 간세포 수준에서의 지방대사를 개선하였다는 점을 시사한다. 이러한 결과를 함초분이 소화관에서의 지방흡수를 억제함으로써 항비만 효과를 가지는 것으로 제안하고자 한다.