이산화탄소를 냉매로 사용하는 냉장 시스템의 냉방 효율에 관한 실험적 연구

박서윤,한근희,문승현 한국에너지학회 2023 에너지공학 Vol.32 No.4

지구온난화에 대한 대처방안으로 자연 냉매 도입의 점증에 따라 본 연구는 자연 냉매 중 하나인 CO2를 사용하 는 showcase를 국내에 도입하는 과정에서 에너지 효율을 극대화하는 방법을 연구하였다. showcase 전단에 문을 설치하거나 냉기의 흐름을 유도하는 guide vane을 설치하였을 때 전력 사용량을 개방되어 있을 때 기준으로 비 교, 분석하였다. 실험 결과, 문을 설치하면 정상상태 운전에서 약 50%에 달하는 에너지 절약 효과가 나타났으나 guide vane의 경우에는 개방형과 큰 차이가 없어 정상상태에서 냉기의 흐름을 유도하는 것이 전력 사용량에 큰 영향을 미치지 못한다는 것을 알 수 있었다. 도어형의 경우 에너지 절감 효과와 더불어 단별 온도 차이가 줄어들 어 진열된 제품의 균일한 품질관리에도 유리한 것으로 나타났다. 또한 냉장 시스템의 정지 상태에서 초기 기동 을 할 때 상부에서 토출되는 냉기의 양이 많은 상황에서 투입되는 에너지는 정상상태에서 투입되는 에너지와 비교하였을 때 세 가지 경우 모두 더 많은 양이 투입되었으나, guide vane을 설치하였을 때는 개방형과 도어형에 비하여 상대적으로 적은 에너지가 투입되어 guide vane의 설치는 초기 기동 시에 효과가 있는 것으로 판단된다. The introduction of natural refrigerants is increasing as a countermeasure against global warming. In the process of introducing showcases using CO2 as a refrigerant, in Korea, we verified methods to maximize energy efficiency. A door was installed at the front of the showcase or a guide-vane was installed to guide the flow of cold air, and the power consumption was compared to the one when it was open. As a result of the experiment, installing a door showed an energy saving effect of about 50% in normal operation. But there was no significant difference in the case of a guide vane from an open type, which means inducing the flow of cold air had an insignificant impact on power usage in normal condition. Door type showed the temperature difference reduction between positions in addition to the energy saving effect. This effect gives large advantage for uniform quality control of displayed products. In addition, when the refrigeration system is initially started from a stop state, the amount of cold air discharged from the top became large and the amount of energy input was also greater than the energy input in all three cases compared to the one in the normal state. But the guide vane type showed relatively less energy input compared to the open type and door type. Finally, It was concluded that the door type has a large energy saving effect in the normal state, and the guide vane type has an effect in the initial startup state.

자연냉매를 사용하는 초저온용 이원 및 이단압축 냉동방식의 운전특성 비교

노건상 한국기계기술학회 2021 한국기계기술학회지 Vol.23 No.1

In this paper, the performance characteristics of a cryogenic refrigeration system used in fields such as HMR(Home Meal Replacement) that require ultra-low temperatures of -50℃ using natural refrigerants according to the recent enforcement of the Atmosphere Environment Conservation Act were investigated. For this purpose, a 2-stage compression refrigeration system using R744(CO2) and a cascade refrigeration system using R747/R404A and R747/R717(NH3) were applied. The COP(coefficients of performance) of each refrigeration system were compared according to changes in evaporation and condensation temperature, subcooled and superheated degree. Although the coefficient of performance of the 2-stage compression refrigeration system using R744 was superior to that of the cascade refrigeration system, 2-stage refrigeration system was considered that various problems should be solved in practical terms. In addition, the COP of R744/R717 for various operating conditions showed similar results to R744/R404A, so the possibility of alternativeness could be confirmed in the cascade refrigeration system.

자연냉매용 소형냉동장치에서의 단열모세관 길이 예측

임원택 한국기계기술학회 2019 한국기계기술학회지 Vol.21 No.3

This paper focuses on the simulation of refrigeration cycle equipped with the adiabatic capillary tube, which is widely used in small vapor compression refrigeration systems. The present simulation is based on fundamental conservation equations of mass, energy and momentum. These equations are solved through an iterative process. The adiabatic capillary tube model is based on homogeneous flow model. This model is used to understand the natural refrigerants flow behavior inside the adiabatic capillary tube. Transport properties and thermodynamic of natural refrigerants are calculated by using EES(Engineering Equation Solver) program. The operating factors considered in this paper include condensation temperature, evaporation temperature, inner diameter tube and sub-cooling degree of the adiabatic capillary tube. Our simulation results are summarized as follows: as the size of the inner diameter tube increases, the pressure drop in the capillary tube decreases while the length of the capillary tube increases. We found that R-290 decreases by 20-22% on average, and R-600a significantly decreases below 50%, while R-1270 increases 17-19% on average, compared to R-134a.

자연냉매의 마이크로 휜관 증발 열전달 특성

이호생(H. S. Lee),진병주(B. J. Jin),성광훈(K. H. Seong),윤정인(J. I. Yoon) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-

In this study, evaporation heat transfer experiments were performed in 12.7㎜ micro-fin tube using natural refrigerants. The test rig had a straight, horizontal test section and refrigerant was heated by water through an annulus surrounding test section. Evaporation heat transfer coefficient was increased with increasing quality, refrigerant mass flux. The local and average evaporation heat transfer coefficients in micro-fin tube were compared to those a bare tube. The local evaporation coefficients of R-22 and natural refrigerants for the micro-fin tube were 131% and 96~124% higher than bare tube. EF(enhancement factor) is defined as the ratio of the micro-fin tube heat transfer coefficient to that of a comparable bare tube at a similar mass flux, heat flux, pressure level, and inlet outlet quality. EF of R-22 and natural refrigerants are presented average 2.68 and 2.41 at the all refrigerant mass flux in the experiment range.

자연냉매의 마이크로 휜관 증발열전달 및 압력강하 특성

오승택(Seung-taek Oh),이호생(Ho-saeng Lee),백승문(Seung moon Baek),문춘근(Choon-geun Moon),윤정인(Jung-in Yoon) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

This paper presents the heat transfer and pressure drop characteristics of R-290 (Propane), R-600a (Iso-butane) and R-1270 (Propylene) as an environment friendly refrigerant and R-22 as a HCFC's refrigerant for evaporating. The test section is a horizontal double pipe heat exchanger. Evaporating heat transfer and pressure drop measurements were performed for 12.70, 9.52 mm micro-fin tube and compared with the results in smooth tube. The local evaporating heat transfer coefficients of hydrocarbon refrigerants were superior to those of R-22 and the maximum increasing rate of heat transfer coefficient was found in R-600a. The average evaporating heat transfer coefficients in hydrocarbon refrigerants showed 8.94 to 13.36% higher values than those of R-22. Hydrocarbon refrigerants have a higher pressure drop than that of R-22 with respect to refrigerant quality and mass flux. Also, the evaporating heat transfer coefficient and pressure drop of working fluids in smooth and micro-fin tube were compared. The heat transfer enhancement factor (EF) and penalty factor (PF) between smooth and micro-fin tube varied from 2.1~2.5 and 1.49~1.61 in all experimental conditions, respectively.

자연 냉매를 이용하는 이원 냉동시스템의 성능 예측

노건상 한국기계기술학회 2010 한국기계기술학회지 Vol.12 No.3

탄화수소계 냉매의 응축 압력강하에 관한 연구

이광배(Kwang-Bae Lee),이호생(Ho-Saeng Lee),김재돌(Jae-Dol Kim),윤정인(Jung-In Yoon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

Experimental results for pressure gradients of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during condensing inside horizontal double pipe heat exchangers are presented. The test sections which has one tube diameter of 12.7㎜ with 0.86㎜ wall thickness, another tube diameter of 9.52㎜ with 0.76㎜ wall thickness are used for this investigation. Hydrocarbon refrigerants have higher pressure drop than R-22 in 12.7㎜ and 9.52㎜. This results form the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.

프로필렌 냉매의 응축열전달 특성에 관한 실험적 연구

이호생,김재돌,윤정인 대한설비공학회 2004 설비공학 논문집 Vol.16 No.7

This paper deals with the heat transfer characteristics of R-1270 (Propylene), R-600a (Iso-butane) and R-290 (Propane) as an environment friendly refrigerant and R-22 for condensing. The experimental apparatus has been set-up as a conventional vapor compression type heat pump system. The test section is a horizontal double pipe heat exchanger. A tube diameter of 12.70 mm with 1.32 mm wall thickness is used for this investigation. The test results showed that the local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than that of R-22. The average condensing heat transfer coefficient was obtained with the maximum value in R-1270 and the minimum one in R-22. Comparing the heat transfer coefficient of experimental results with that of other correlations, the presented results had a good agreement with the Cavallini-Zecchin's correlation. It reveals that the natural refrigerants can be used as substitute for R-22.

탄화수소계 냉매의 증발 열전달 및 압력강하 특성

이광배,이호생,김재돌,윤정인 대한설비공학회 2005 설비공학 논문집 Vol.17 No.7

Experimental results for heat transfer characteristic and pressure gradients of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers are presented. The test sections which has one tube diameter of 12.70 mm with 0.86 mm wall thickness, another tube diameter of 9.52 mm with 0.76 mm wall thickness are used for this investigation. The local evaporating heat transfer coefficients of hydrocarbon refrigerants were higher than that of R-22. The average evaporating heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than R-22 in 12.7 mm and 9.52 mm. This results form the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.

탄화수소계 냉매의 응축 열전달 및 압력강하 특성

이호생,성광훈,Phan Thanh Tong,윤정인 대한설비공학회 2006 설비공학 논문집 Vol.18 No.12

Experimental results for heat transfer characteristic and pressure gradient of hydrocarbon refrigerants(R-290, R-600a, R-1270) and HCFC refrigerant(R-22) during condensation inside horizontal double pipe heat exchangers are presented. The test sections which have one tube diameter of 12.70mm with 0.89mm, 9.52mm with 0.76mm, 6.35mm with 0.13 mm wall thickness are used for this investigation, respectively. The local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than those of R-22. The average condensing heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than R-22 in 10.92mm, 8mm and 6.1mm inner diameters. These results from the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.