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간접 냉동시스템용 2차 냉매 R744, R717과 브라인 성능비교
이문빈(Wen-Bin Yi),조환(Hwan Jo),전민주(Min-Ju Jeon),오후규(Hoo-Kyu Oh) 대한설비공학회 2013 대한설비공학회 학술발표대회논문집 Vol.2013 No.6
In this paper were compared heat transfer coefficient and pumping power with respect to secondary refrigerant (single-phase and two-phase) in the indirect refrigeration system. The operating parameters considered in the study include pump efficiency, flow velocity. The main results were summarized as follows: The R744(carbon dioxide) and R717(ammonia) were better than other secondary refrigerants of single-phase in heat transfer coefficient. And R717 is better than R744. The R744 and R717 were lower than other secondary refrigerants of single-phase in side of pumping power, and R717 is lower than R744. R717 is better than R744 in secondary refrigerant. But R717 has flammability, toxicity, potential metal corrosion. So, R744 is the most idealistic secondary refrigerant.
-30℃∼-50℃의 저온에서 이산화탄소의 증발 열전달 특성
오후규(Hoo-Kyu Oh),조환(Hwan Jo),손창효(Chang-Hyo Son),전민주(Min-Ju Jeon),이문빈(Wen-Bin Yi) 대한설비공학회 2013 대한설비공학회 학술발표대회논문집 Vol.2013 No.6
The evaporation heat transfer coefficients of CO₂ at low temperature of -30∼-50℃ were investigated experimentally The test section consists of a smooth, horizontal tube of inner diameter of 4.57 mm. Analysis was conducted for various mass fluxes (200~400 kg/㎡s), heat fluxes (10~30 kW/㎡) and saturation temperatures (−30~-50℃). With the increase of quality and heat temperature the evaporation heat transfer coefficient increased. And the increase of heat flux and mass flux, the evaporation heat transfer coefficient increased. The test results showed the heat transfer of CO₂ has a greater effect on forced convective boiling more than nucleate boiling.
과냉각도와 과열도 변화에 따른 R744-R404A용 캐스케이드 냉동 시스템과 R404A용 2단 압축 1단 팽창식 냉동 시스템의 성능 비교
오후규(Hoo-Kyu Oh),조환(Hwan Jo),손창효(Chang-Hyo Son),전민주(Min-Ju Jeon),이문빈(Wen-Bin Yi) 대한설비공학회 2012 대한설비공학회 학술발표대회논문집 Vol.2012 No.11
This paper were compared the performance characteristics of R744-R404A cascade refrigeration system and R404A two-stage compression refrigeration system. The operating parameters considered in this study include subcooling and superheating degree. The main results were summarized as follows: The COP of R404A two-stage compression refrigeration system is greater than that of the R744-R404A cascade refrigeration system. Whereas the R744-R404A cascade refrigeration system is environmentally friendly due to use the natural refrigerant. And it can be configured by selecting the proper refrigerant at high-temperature side and low-temperature side. From the above results, it is necessary to select the appropriate low temperature refrigeration system by considering the enviromental and performance aspects.