• 한국태양에너지학회 논문집
• /
• 제23권2호
• /
• pp.71-79
• /
• 2003

The goal of this paper is to measure and compare the performance of solar heat pump for refrigerants. To accomplish the goal, solar heat pump with aluminum roll bond type evaporator and indoor heat exchanged(condenser) was built. The test results showed that the COP and heating capacity of HFC-32/125/134a(23/25/52 wt%, $CH_2F_2/CF_3CHF_2/CF_3CH_2F$) were higher than those of HCFC-22$(CHClF_2)$. A study proved that best conditions to use heating system that is about $40m^2$ and $80m^2$. The COP range of the whole system was from 4 to 6 according to the solar collector's area variation. Hydrochlo-rofluorocarbon HCFC-22$(CHClF_2)$ is included in the compound to be controlled. HFC-32/125/134a(23/25/52 wt%, $CH_2F_2/CF_3CHF_2/CF_3CH_2F$) is the most suitable replacement HCFC-22$(CHClF_2)$ in solar heat pump application. The solar heat pump system was designed to show the best efficiency that the room temperature make $18\sim20^{\circ}C$ and $23\sim25^{\circ}C$ in Seoul during the fall season.

• 생명과학회지
• /
• 제22권5호
• /
• pp.671-680
• /
• 2012

홍마늘 추출물과 녹차, 식이섬유 및 녹차 식이섬유를 혼합한 3종의 복합물(R+T, R+F 및 R+TF)을 이용하여 고지방-콜레스테롤을 급이한 흰쥐에 대해 항비만 효과를 $in$ $vitro$ 및 $in$ $vivo$에서 측정하였다. 녹차 복합물(R+T) 및 녹차 식이섬유 복합물(R+TF)은 홍마늘 추출물(RG)보다 총 페놀 함량이 1.9~2.0배 높았으며, 콜레스테롤 흡착활성은 9.5~11.5배 높은 활성이었다. 실험군은 6군(정상군, 고지방-콜레스테롤 식이 급이군(HFC), R+T 급이군(HR+T), R+F 급이군(HR+F) 및 R+TF 급이군(HR+TF))으로 나누어 각 추출물을 식이에 1% 수준으로 4주간 급이 하였다. 실험군에서 최종 체중은 대조군에 비해 유의적인 감소를 보였으나, 식이효율은 대조군과 유의차가 없었다. 간장의 중량은 정상군에 비해 대조군이 2.0배 정도 증가되었으며, HR+T군과 HR+TF군에서 유의적으로 감소하였다. 내장지방과 부고환 주변지방 함량은 복합물 첨가군에서 대조군에 비해 유의적으로 감소하였다. 비만도 지수는 대조군에 비해 HR+TF군에서만 유의적으로 감소하였다. 총 지질, 총 콜레스테롤, 중성지질, LDL- 및 VLDL-콜레스테롤 등의 혈중 지질성분과 동맥경화 지수, 심혈관 질환 위험지수는 대조군에 비해 홍마늘 추출물 및 복합물 첨가군에서 유의적으로 감소하였으나, HR+T군, HR+F군 및 HR+TF군간에는 비슷한 수준이었다. GPT 활성은 복합물 첨가군간에 유의차가 없었으나, 홍마늘 추출물 첨가군보다는 유의적으로 낮은 활성이었다. 지질과 산화물 함량은 대조군에 비해 홍마늘 추출물과 복합물 첨가군에서 유의적으로 감소되었다. 항산화 활성은 HR+T군에서 가장 높았다. 따라서 홍마늘 복합물의 체내 지질 개선 및 항비만 효과는 시료 중의 녹차나 식이섬유의 총 페놀 함량 및 콜레스테롤 흡착활성에 기인된다고 생각된다.

• 조명전기설비학회논문지
• /
• 제25권5호
• /
• pp.22-33
• /
• 2011

An induction motor operated with a conventional direct self controller(DSC) shows a sluggish response during startup and under changes of torque command. Fuzzy logic controller(FLC) is used in conjection with DSC to minimize these problems. A FLC chooses the switching states based on a set of fuzzy variables. Flux position, error in flux magnitude and error in torque are used as fuzzy state variables. Fuzzy rules are determinated by observing the vector diagram of flux and currents. This paper proposes hybrid fuzzy controller for direct torque control(DTC) of induction motor drives. The speed controller is based on adaptive fuzzy learning controller(AFLC), which provide high dynamics performances both in transient and steady state response. Flux position, error in flux magnitude and error in torque are used as FLC state variables. The speed is estimated with model reference adaptive system(MRAS) based on artificial neural network(ANN) trained on-line by a back-propagation algorithm. This paper is controlled speed using hybrid fuzzy controller(HFC) and estimation of speed using ANN. The performance of the proposed induction motor drive with HFC controller and ANN is verified by analysis results at various operation conditions.

• 설비공학논문집
• /
• 제11권4호
• /
• pp.472-483
• /
• 1999

The evaporation heat transfer and pressure drop characteristics for HFC-l34a in flat plate type heat exchangers with enhanced beads were experimentally investigated. Three plate type evaporators with different geometric condition of U-turn area were tested. Mass fluxes were tested over the range of 83kg/$m^2$s to 166kg/$m^2$s, and heat fluxes were varied from 4㎾/$m^2$ to 12㎾/$m^2$. Evaporation temperature was 5$^{\circ}C$ with inlet qualities of 0.1 to 1.0. There was no notable difference in the heat transfer coefficient by geometric variation of U-turn area, but the third plate with cross-ribbed channel at U-turn area was better than others in the evaluation using volume goodness factor comparison. Also, the mixtures of HFC-l34a and PAG oil was tested to determine oil effects on heat transfer and pressure drop. As oil concentration was increased, heat transfer coefficient was increased by 22~48% up to the 3wt.%, but decreased by 14~22% at the 4wt.%. The pressure drop was increased by the maximum of 100% as oil concentration was increased.

• 한국기후변화학회지
• /
• 제7권3호
• /
• pp.283-288
• /
• 2016

In this study, applicability of GHG ETS Offset Program in Korea for a refrigerant sector was analyzed by reviewing foreign management policy and project status in progress related to refrigerants in the disposal stage. In order to derive the implication of the domestic Offset Program, it was looked into approved offset projects and certified offset credits current state in Korea. Offset Program has approved 22 methodologies up to the present, so it is necessary to enhance the accessibility to GHG reduction in various industrial sector including the refrigerant sector by developing appropriate methodologies. In this study firstly, it was investigated that management regulation of countries are managing the refrigerants in the disposal stage such as United States, Japan, Australia. Secondly, of CDM methodologies there were two methodologies associated with the refrigerant reduction(treatment), which were decomposition HFC-23 and destruction of HFC-134a. Also there were a non-registered methodology about destruction of HFC-134a of end of life vehicles. Lastly, in California according to Compliance Offset Program, there was Compliance Offset Protocol in ODS Projects that provided eligible conditions. Based on the review, it was examined the possible conditions for domestic offset project for refrigerant sector

• Journal of Advanced Marine Engineering and Technology
• /
• 제22권2호
• /
• pp.210-218
• /
• 1998

Experimental results for forced convection condensationof Refrigerant-22 and ternary Refrigerant-407c(HFC-32/125/134a 23/25/52 wt%) considered as a substitute R-22 inside horizontal micor-fin tubes are presented. The test section was horizontal double-tubed counterflow condenser with a length 4000 mm micro-fin tube having 9.53 mm OD., 0.2 mm fin height and 60 fins. The refrigerants R-22 and R-407c were cooled by a coolant circulated in a surrounding annulus. The range of parameters of mass velocity was varied from 102.1 to 301.0kg/($\textrm{m}^{2}.s$) with inlet quality 1.0. Both refrigerant R-22 and its alternative refrigerant R-407c were tested within the same range of parameters. At the given experimental conditions for R-22 and R-407c the pressure drops for R-407c were considerably higher than those for R-22 at micro-fin tubes. Over the mass velocity range tested the PF(penalty factor)was lower than the increasing ratio of heat transfer area by fins. Based on the data correlation was proposed for predicting the frictional pressure drops for R-22 and R-407c for a duration of condensation inside a horizontal micro-fin tube.

• Journal of Advanced Marine Engineering and Technology
• /
• 제32권1호
• /
• pp.50-56
• /
• 2008

Experimental results for forced convection condensation of Refrigerant-22 and ternary Refrigerant-407C(HFC-32/125/134a 23/25/52 wt%) which is being considered as a substitute R-22 inside a horizontal micro-fin tube are presented. The test section was horizontal double-tube counterflow condenser with a length 4,000 mm micro-fin tube, having 8.53 mm ID, 0.2 mm fin height and 60 fins. The range of parameters of mass velocity were varied from 102.1 to 301.0 kg/(m2.s) and inlet quality 1.0. At the given experimental conditions. the average heat transfer coefficients for R-407C were lower than that for R-22 at a micro-fin tube. Over the mass velocity range tested. the PF(penalty factor) for R-22, R-407C were lower than the increasing ratio of heat transfer area by fins, and the EF(enhancement factor) for R-22, R-407C were higher than the increasing ratio of heat transfer area by fins.

• 청정기술
• /
• 제22권3호
• /
• pp.154-160
• /
• 2016

가스 하이드레이트 형성을 이용하여 담수를 생산하고자 하는 어떠한 공정이라도 가스 하이드레이트 형성속도는 경제적인 관점에서 매우 중요한 공정변수일 수밖에 없다. 이에 본 연구에서는 촉진제를 사용하여 R-134a(또는 HFC-134a) 가스 하이드레이트의 형성속도를 향상시키고자 하였는데 최종목표가 음용수 생산이므로 촉진제로 세가지 다른 형태의 식용 계면활성제를 선정하여 사용하였다. 음이온성인 카라기난(κ-carrageenan), 양쪽성인 레시틴(lecithin), 그리고 비이온성인 폴리소르베이트 80(polysorbate 80)이 그것이다. 식용 계면활성제의 농도를 변화시키면서 R-134a 가스 하이드레이트 형성속도가 어떻게 변하는지 관찰하였다. 어떠한 경우이든 식용 계면활성제의 첨가가 R-134a 가스 하이드레이트 형성속도를 향상시키는 것으로 관찰되었으며 그 효과는 폴리소르베이트 80 > 카라기난 > 레시틴의 순서를 보였다. 이론적인 설명을 위해 범밀도함수(DFT) 이론을 기반으로 한 분자모델링을 이용하여 각 식용 계면활성제를 구성하고 있는 원자들의 전하를 계산하였고 실험으로 관찰된 촉진제 효과가 계면활성제 내의 수소결합을 할 수 있는 산소들의 수와 그 산소들의 원자전하 값들이 음수인 정도에 비례하는 관계가 있음을 알 수 있었다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제31권6호
• /
• pp.715-722
• /
• 2007

Experiments were conducted for the investigation of pressure drop inside horizontal micro-fin tubes during the condensation of R-22 and ternary refrigerant. R-407C(HFC-32/125/134a 23/25/62 wt%) as a substitute of R-22. The condenser is a double-tube and counterflow type heat exchanger which is consisted with micro-fin tubes having 60 fins with a length of 4000mm, outer diameter of 9.53mm and fin height of 0.2mm. The mass velocity varied from 102.1 to $301.0kg/(m^2{\cdot}s)$ and inlet quality was fixed as 1.0. From the experimental results. the pressure drop for R-407C was considerably higher than that for R-22. The value of PF(penalty factor) for both of refrigerants was not bigger than the ratio of micro-fin tube area to smooth tube area. Based on the experimental data. correlation was Proposed for the prediction of frictional pressure drop during the condensation of R-22 and R-407C inside horizontal micro-fin tubes.

• 설비공학논문집
• /
• 제12권3호
• /
• pp.315-324
• /
• 2000

R-410A, R-407C, and four refrigerant mixtures composed of R-32, R-l34a, R-l43a, R-l52a, R-600(butane), and R-600a(isobutane) were tested in an attempt to replace R-22 used in most of the residential air conditioners. The performance evaluation was carried out in a psychrometric calorimeter test facility using a residential spilt type air conditioner under the KS rating conditions. Except for the lubricant and hand-operated expansion valve, the other parts of the air conditioner were the same with the commercial system. Performance characteristics were measured; COP, capacity, compressor power, and VCR. R-410A was shown to have 5.5% higher COP and 3.5% lower capacity than R-22. R-32/134a/600a (42.8/ 46.0/11.2 wt%) mixture have the best performance among the four refrigerant mixtures composed of hydrofluorocarbon and hydrocarbon. This inixture have 3.0% lower COP and 1.6% lower capacity than R-22.