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R134a 및 R1234yf 적용 냉동시스템의 비가역성 분석
조홍현(Honghyun Cho),이호성(Hoseong Lee),박차식(Chasik Park) 대한설비공학회 2013 대한설비공학회 학술발표대회논문집 Vol.2013 No.6
In this study, the performance of mobile air conditioner(MAC) systems to which the refrigerants R134a and R1234yf were used was evaluated to compare the characteristic of automotive refrigeration cycles with refrigerant. The drop-in test on MAC were carried out under variable compressor speed from 800 to 2500 rpm. Performance test by using R1234yf and R134a in the same system revealed low the charge amount and mass flow rates for using R1234yf, that is, up to 10% and 17%, respectively. The irreversiblilty of evaporator in a R134a air conditioning system with compressor speed under idle condition was 36.8% which was maximum value, and that of compressor increased with compressor speed. The irreversibility of compressor and IHX in a R1234yf air conditioning system with IHX with compressor speed was 39.6%, 3.6% under idle condition, and those was 44.1%, 9.7% at the compressor speed of 2520 rpm.
이산화탄소 급탕 열펌프의 난방 성능에 관한 실험적 연구
조홍현(Honghyun Cho),조성욱(Sungwook Cho),백창현(Changhyun Baek),이응찬(Eungchan Lee),강훈(Hoon Kang),김용찬(Yongchan Kim) 대한설비공학회 2008 대한설비공학회 학술발표대회논문집 Vol.2008 No.2
In this study, experimental study on the heating performance of a CO₂ heat pump water heater with a variation of operating conditions such as refrigerant charge amount, outdoor temperature, compressor frequency, EEV opening and water mass flow rate. Based on the test results, the optimum charge amount was 1800 g. At the water mass flow rates of 75, 85, 95 ㎏/hr, the water heating temperature was 62, 67, 74℃ and COP was 2.6, 2.8, 3.0, respectively. Besides, the water mass flow rate and compressor frequency were varied to maintain above the water heating temperature of 60℃ with the decrease of outdoor temperature. So, The compressor frequency increased beyond 65 Hz and the water mass flow rate was 45 kg/hr at the outdoor temperature of -13℃, 65 ㎏/hr at -8℃, 75 ㎏/hr at -3℃ and 85 ㎏/hr at 2, 7℃. As the outdoor temperature decreased, the heating COP decreased by 2.5-39.8%.
이산화탄소를 적용한 상분리 사이클의 최적운전에 관한 실험적 연구
조홍현(Honghyun Cho),이호성(Hoseong Lee),김용찬(Yongchan Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The cooling performance of a transcritical CO₂ cycle can be significantly improved by using a multi-stage compressor because the CO₂ cycle has a large pressure difference. In this study, the performance of a phase-separate CO₂ cycle was measured and analyzed by varying the refrigerant charge amount, 1<SUP>st</SUP>-2<SUP>nd</SUP> EEV opening, and 1<SUP>st</SUP>-2<SUP>nd</SUP> compressor frequency. The cooling performance of the phase-separate CO₂ cycle was improved over 6.4% by optimizing the operating conditions, and the reliability of system increased significantly.
R1234yf와 R134a 냉매의 이젝터를 적용한 냉동사이클 성능에 대한 해석적 연구
조홍현(Honghyun Cho),박차식(Chasik Park) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.7
This paper presents a numerical study on the performance of a vapor compression cycle equipped with an ejector as an expansion device to improve the COP by reducing the expansion loss and compressor work. The simulation is carried out using a model based on the conservation of mass, energy and momentum in the ejector. From the results of the simulation, the vapor compression cycle equipped with an ejector showed a maximum COP improvement of 14.0% when using R134a refrigerant and 16.8% when using R1234yf. In addition, the performance of the system with an ejector represents the increased performance as the temperature difference between condensing and evaporating increased.
냉매 R1234yf 적용 자동차용 에어컨 Drop-in 성능 특성
조홍현(Honghyun Cho),이호성(Hoseong Lee),박차식(Chasik Park) 대한설비공학회 2012 설비공학 논문집 Vol.24 No.12
In this study, the performance of mobile air conditioner(MAC) systems to which the refrigerants R134a and R1234yf were used was evaluated to compare the characteristic of automotive refrigeration cycles with refrigerant. The experimental setup of a MAC consists of an belt driven compressor, a condenser, an evaporator and a block type thermal expansion valve. The drop-in test on MAC were carried out under variable compressor speed from 800 to 2500 rpm. Performance test by using R1234yf and R134a in the same system revealed low the charge amount and mass flow rates for using R1234yf, that is, up to 10% and 17%, respectively. The compressor discharge temperature of R1234yf is 8℃ lower than that of R134a. The cooling capacity with R1234yf system decreased by 4~7% compared with R134a system. In addition, The COP of R1234yf system is lower 3~4% than that of R134a system.
조홍현(Honghyun Cho) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Recently, many plants use a lot of energy and various efforts are being made to reduce it. Techniques for reducing heat energy used in plants and improving heat transfer performance in the heat exchanger are being applied. Some methods for improving heat transfer in the heat exchanger including heat transfer improvement through changes in the structure and shape of the heat exchanger and improvement through enhancement of thermal properties of the working fluid. When the thermal properties of the working fluid are improved by using various ionic liquids, the performance of heat transfer can be improved. In this review, performance improvement technology using these ionic liquids is presented.