• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.64-67
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• 2006

Drop-in tests were conducted using R290/R32 (31:69) or R290/DME (65:35) mixture in a ice-cream maker for possible replacement of R-502 and R-404A. At the standard room temperature ($20^{\circ}C$), the time required for initial ice-cream making was 4'7' for R290/32, 4'39' for R404A and 4'59' for R290/DME. The electric energy consumed was 436 kJ for R290/32, 425 kJ for R404A and 439 kJ for R290/DME. The mass flow rate as well as the temperature and pressure data are also provided.

• 대한기계학회논문집B
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• 제20권2호
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• pp.730-740
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• 1996

Boiling heat transfer coefficients of pure refrigerants (R22, R32, R134a, R125, R290, and R600a) and refrigerant mixtures (R32/Rl34a, R290/ R600a, and R32/R125) are measured experimentally and compared with Chen's correlation. The test section is a seamless stainless steel tube with inner diameter of 7.7mm and uniformly heated by applying electric current directly to the tube. Heat fluxes range from 10 to 30kW$^2$. Mass fluxes are set to 424 ~ 742kg/m$^{2}$s for R22, R32, R134a, R32/R134a, and R32/Rl25 ; 265 ~ 583kg/m$^{2}$s for R290, R600a, and R290/R600a. Heat transfer coefficients depend strongly on heat flux at a low quality region and become independent as quality increases. Convective boiling term in the Chen's correlation predicts experimental data of the pure refrigerants fairly well (relative error of 12.1% for the data of quality over 0.2). The correlation for pure substances overpredicts the heat transfer coefficients for nonazeotropic refrigerant mixtures.

• 한국산학기술학회논문지
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• 제18권2호
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• pp.719-725
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• 2017

최근 들어 국민 식생활 문화가 개선되고 생활수준이 향상됨에 따라 소프트 아이스크림, 슬러시와 같은 일회용 냉동 유제품의 소비가 급증하고 있다. 이들 냉동 유제품은 소형 냉동 시스템에서 만들어진다. 소프트 아이스크림 제조기의 냉매로 그간 R-502가 주로 사용되어 왔으나 오존층 파괴와 관련하여 R-404A로 대체되고 있다. 하지만 R-404A도 지구온난화지수(GWP)가 높아 지구온난화지수가 낮은 냉매로의 전환이 필요하다. 본 연구에서는 R-404A의 대체 물질로 R-290/R-32를 고려하였다. 냉각기 체적 2.8 리터인 소프트 아이스크림 제조기에 R-290/R-32를 적용하여 최적화를 수행하였다. 최적화는 적정 냉매량 및 팽창밸브의 개도를 찾는데 주안점을 맞춰 수행되었는데 최적 조건 (충전량 1000 g, 밸브 개도 "0" (제조사 세팅치))에서 아이스크림 제조 시간은 6분 24초, COP는 0.83으로 나타났다. R-404A에서 아이스크림 제조시간은 6분 22초와 R-290/R-32와 유사하고 COP는 0.90으로 R-404A에서 다소 높게 나타났다. 이는 본 실험에 사용된 압축기가 R-404A용이기 때문으로 향후 R-290/R-32용 압축기가 개발되면 소비동력은 개선되리라 예상된다. 본 연구 결과는 냉동식품 제조기를 비롯한 여타 냉동 사이클의 최적화에도 활용될 수 있을 것이다.

• 설비공학논문집
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• 제6권1호
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• pp.47-53
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• 1994

Cycle simulation of the air-conditioner was carried out using a number of candidate alternatives to R22;R32/R125/R134a(30/10/60, by mass percent), R32/R125/R134a(10/70/20), R32/R134a(25/75), R32/R134a(30/70), R32/R125(60/40), R290(propane) and R134a. In this study, we considered only the basic parts of the air-conditioner such as the compressor, the evaporator, the condenser and the capillary tube, for the purpose of analysis. The performance characteristics of alternatives considered here were examined by comparing with the case using R22 at the constant volumetric flow rate condition. The results of our analysis revealed that the use of refrigerant mixtures, R32/R134a(30/70) and R32/R125/R134a(30/10/60), was appropriate for the alternatives to R22 in view of the cooling capacity and the COP. For the case of using R134a and R290, the COP was observed to increase under the same volumetric flow rate condition, but the cooling capacity was substantially decreased. Therefore the use of R134a and R290 should be accompanied with increasing considerably the size of compressor in order to maintain the same cooling capacity of R22.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.410-413
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• 2005

Drop-in tests were conducted using R290/R32 (31:69) mixture in an ice-cream maker for possible replacement of R-502 and R-404A. Optimum refrigerant charge and TEV opening were obtained through a series of experiments. At the standard outdoor condition ($35^{\circ}C$ DT, $24^{\circ}C$ WT), the time required for initial ice-cream making was 6'22", which was approximately the same as that of R-404A. The electric energy consumed was 660 kJ, which was about 10% higher than that of R-404A. The compressor outlet temperature ($8^{\circ}C$) and pressure (2.52 MPa) were higher than those ($60^{\circ}C$ and 1.48 MPa) of R-404A. The reason could be the usage of the same R-404A compressor although the specific volume of R290/R32 is much larger.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.268-273
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• 2005

Because of environmental issues caused by CFC, HCFC or HFC refrigerants, new alternative refrigerants has gained a significant attention. This paper presents experimental information on heat transfer coefficient and pressure drop behavior during evaporation process of R32/290 mixtures in a horizontal smooth tube. A smooth tube with outer diameter of 5 mm and length of 5 m was selected as a test tube. Heat transfer coefficients and pressure drop characteristics were measured for a range of mass fluxes from 497 to 994 $kg/m^2s$, heat fluxes from 12 to 20 $kW/m^2$ and for several mixture compositions(100/0, 75/25, 58.4/41.6, 2s/75, 100/0 by wt% of R32/290). The differences of measured heat transfer characteristics among various R32/290 refrigerant mixtures were analyzed for various compositions.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.356-364
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• 2021

During the hydrogen fueling process, hydrogen temperature inside the compressed tank were limited below 85℃ due to the allowable pressure of tank material. The chiller system to cool compressed hydrogen used R407C, greenhouse gas with a high global warming potential (GWP), as a refrigerant. To reduce greehouse gas emission, it should be replaced by refrigerant with a low GWP. This study proposes a chiller system for fueling hydrogen with R290, consisted in propane, by applying the C3 pre-cooled system use d in the LNG liquefaction process. The proposed system consisted of hydrogen compression and cooling sections and optimized the operating pressure through exergy analysis. It was also compared to the exergy efficiency with the existing system at the optimal operating pressure. The result showed that the optimal operating pressure is 700 kPa in 2-stage, 840 kPa/490 kPa in 3-stage, and the exergy efficiency increased by 17%.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.10.2-10.2
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• 2005

• 설비공학논문집
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• 제8권2호
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• pp.254-266
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• 1996

Boiling heat transfer coefficients of pure refrigerants(R22, R32, R125, R134a, R290, and R600a) and refrigerant mixtures(R32/R134a and R290/R600a) are measured experimentally and compared with several correlations. Convective boiling term of Chen's correlation predicts experimental data for pure refrigerants fairly well(root-mean-square error of 12.1% for the quality range over 0.2). An analysis of convective boiling heat transfer of refrigerant mixtures is performed for an annular flow to study degradation of heat transfer. Annular flow is the subject of this analysis because a great portion of the evaporator in refrigeration or air conditioning system is known to be in the annular flow regime. Mass transfer effect due to composition difference between liquid and vapor phases, which is considered as a driving force for mass transfer at interface, is included in this analysis. Correction factor $C_F$ is introduced to the correlation for the pure substances through annular flow analysis to apply the correlation to the mixtures. The flow boiling heat transfer coefficients are calculated using the correlation considering nucleate boilling effect in the low quality region and mass transfer effect for nonzazeotropic refrigerant mixtures.

• 태양에너지
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• 제17권4호
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• pp.23-33
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• 1997

본 연구에서는 Rankine 사이클을 이용한 해양 온도차 발전 시스템을 컴퓨터로 모사했고 작동유체를 변화시켜 가면서 그 성능을 비교하였다. 증발기와 응축기는 UA(총괄열전달계수$\times$전열면적)와 LMTD(대수평균온도차) 방법으로 모사하였으며 터빈과 펌프는 등엔트로피 효율로 모사하였다. 작동유체로는 R22, R290, R1270, R134a, R125, R143a, R32, R410A 그리고 암모니아 등을 사용하였다. 모사 결과 OTEC 발전 시스템의 효율은 작동유체에 상관없이 거의 일정한 것으로 드러났다. 한편 증발기 출구에서의 과열도와 응축기 출구에서의 과냉도는 시스템의 성능에 거의 영향을 미치지 않는 것으로 나타났지만 터빈의 효율과 열교환기의 크기는 시스템 성능에 큰 영향을 미치는 것으로 나타났다. 마지막으로 따뜻한 표층수와 차가운 심해수 사이의 온도차가 $20^{\circ}C$이상일 때 실제로 전기를 생산할 수 있다는 사실을 확인했다.