• 설비공학논문집
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• 제16권5호
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• pp.444-451
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• 2004

Flow condensation heat transfer coefficients (HTCs) of R22, R134a, R407C, and R410A were measured on horizontal plain and microfin tubes. The experimental apparatus was composed of three main parts; a refrigerant loop, a water loop and a water/glycol loop. The test section in the refrigerant loop was made of both a plain and a microfin copper tube of 6.0∼6.16 mm inside diameter and 1.0 m length. Refrigerants were cooled by passing cold water through an annulus surrounding the test section. Tests were performed at a fixed refrigerant saturation temperature of 4$0^{\circ}C$ with mass fluxes of 100, 200, and 300 kg/m2s. Test results showed that at similar mass flux the flow condensation HTCs of R134a were similar to those of R22 for both plain and microfin tubes. On the other hand, HTCs of R407C were lower than those of R22 by 4∼16% and 16∼42% for plain and microfin tubes respectively. And HTCs of R410A were similar to those of R22 for a plain tube but lower than those of R22 by 3∼9% for a microfin tube. Heat transfer enhancement factors of a microfin tube were 1.3∼1.9.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.607-612
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• 2003

• 한국산학기술학회논문지
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• 제3권3호
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• pp.210-215
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• 2002

본 연구에서 R410A를 사용하는 멀티에어컨 시스템의 성능(성능계수, 용량, 소비전력 등)을 정상 상태에서 모사할 수 있는 Multi_Cycle이라 명명된 컴퓨터 모사 프로그램을 개발하였다. 컴퓨터 시뮬레이션 프로그램을 검증하기 위해서 일련의 사례 연구를 수행하였으며, 이에 대해서 설명하였다. Mulli_Cycle은 실내기, 실외기, 압축기와 팽창 밸브 모사를 위한 부프로그램 및 냉매와 습공기의 열역학적 물성치와 전달 물성치 예측을 위한 부프로그램으로 구성되어있다. 멀티에어컨 사이클을 구성하고 있는 각 유닛의 복잡한 조자조건과 다양한 종류의 냉매를 고려해야 하는 멀티에어컨의 성능 분석시 Multi_Cycle의 사용은 많은 도움이 될 것이다. 나아가, Multi_Cycle은 멀티에어컨 시스템을 최적화하고, 경제적이고 효율적인 운전 조건을 확립하는데 매우 유용한 도구가 될 수 있을 것이다. Multi_Cycle의 주시뮬레이션 코드는 Digital Visual Fortran으로 프로그램 되었으며 그래픽 사용자 인터페이스(GUI)는 Visual Basic으로 프로그램 되었다.

• 대한기계학회논문집B
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• 제37권4호
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• pp.395-404
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• 2013

본 연구에서는 내경 5.0mm 원관을 납작하게 한 납작관에 대하여 R-410A를 사용하여 증발열전달 실험을 수행하였다. 실험은 포화온도를 $15^{\circ}C$로 고정한 상태에서 열유속을 $5{\sim}15kW/m^2$, 질량유속을 $200{\sim}400kg/m^2s$로 변화시키며 수행되었다. 실험결과 납작관의 종횡비가 증가할수록 열전달계수와 압력손실 모두 증가하였는데 특히 종횡비 4 인 경우 증가폭이 현저하였다. 납작관의 실험결과를 기존 상관식들과 비교한 결과 열전달계수는 Shah 상관식, 마찰계수는 Jung and Radermacher 상관식이 적절히 예측하였다.

• 설비공학논문집
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• 제16권10호
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• pp.895-900
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• 2004

With the phaseout of CFC and HCFC refrigerants, refrigeration and heat pump systems must be redesigned to match and improve system performance with alternative refrigerants. A generalized flow model for predicting mass flow rate through short tube orifices is derived from a power law form of dimensionless parameters generated by Pi-theorem. The database for developing the correlation includes extensive experimental data for R12, R22, R134a, R407C, R410A, and R502 from the open literature. The correlation yields an average deviation of $0.3\%$ and a standard deviation of $6.1\%$ based on the present database. In addition, rating charts for predicting refrigerant flow rate through short tube orifices are generated for R12, R22, R134a, R407C, R410A, and R502.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.221-226
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• 2008

A microchannel condenser as a part of a R410A residential air-conditioning system was examined experimentally and numerically in this study. The system was operated in separate environmental chambers and its performance was measured in ARI A, B, and C conditions. A numerical model for the microchannel condenser was developed and its results were compared with the experimental results. The model simulated the condenser with the assumption of the uniform air and refrigerant distribution, and with the consideration of the non-uniform air distribution at the face of the condenser and refrigerant distribution in the headers. In order to consider the non-uniform air distribution, air velocity contours were generated from the measured local air velocities at the face of the condenser. The simulation results showed that the effect of the air and refrigerant distribution was not a significant parameter in predicting the capacity of the microchannel condenser which was experimentally examined in this study. The comparison of the calculated and experimental results showed that the condenser capacity could be predicted well for every test condition. However, the prediction of refrigerant pressure drop deviated significantly from the measured values.

• 한국유체기계학회 논문집
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• 제18권3호
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• pp.12-19
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• 2015

As a means of improving cycle performance of a R410A air-conditioning system, a combined structure of compressor and expander was introduced. A vane rotary type expander was designed to share a common shaft with twin type rolling piston rotary compressor in a housing. Numerical simulation on the performance of the combined compressor and expander was carried out. At ARI condition, the volumetric and total efficiencies of the designed vane expander were 69.37% and 30.23%, respectively. With the application of this expander, the compressor input was reduced by 3.91%, and the cooling capacity was increased by 3.98%. As a result, COP of the air-conditioning system was improved by 8.2%. As the pressure difference between the condenser and the evaporator becomes large, COP improvement increases unless the mass flow rate in the expander exceeds that in the compressor.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2004년도 하계종합학술발표회논문초록집
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• pp.410-410
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• 2004

• 설비공학논문집
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• 제17권12호
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• pp.1106-1112
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• 2005

An experimental investigation was performed to develop an empirical correlation of R-410A flowing through short tube orifices working near the critical region. Tests were executed by varying upstream pressure from 2,619 kPa to 4,551 kPa, and upstream subcooling from 2.8 and $11.1^{\circ}C$. The experimental data were represented as a function of major operating parameters and short tube diameter. As compared to mass flow trends at normal upstream pressures, flow dependency on upstream subcooling became more significant at high upstream pressures due to a higher density change. Based on the database obtained from this study and literature, an empirical correlation was developed from a power law form of dimensionless parameters generated by the Buckingham Pi theorem. The correlation yielded good agreement with the data. Approximately $92\%$ of the data were correlated within a relative deviation of $5\%$.

• 설비공학논문집
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• 제13권5호
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• pp.377-387
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• 2001

This paper presents leakage characteristics of a scroll compressor applying alternative refrigerants of R22 such as R407c and R410a under actual operating conditions. Because leakage in a scroll compressor produce significant losses and degradation of performance, those should be clarified to design a high efficient scroll compressor with alternative refrigerants of R22. However, flank and tip leakage characteristics of a scroll compressor with alternative refrigerants are very limited in open literature. In the present study, both experimentation and modeling of the leakages in the scroll compressor were performed. As a result, it was observed that the leakages of the scroll compressor with R407c increased by 15%, and that with R410a increased by 76% as compared to the compressor applying R22 under standard load conditions due to a higher upstream pressure and a higher pressure difference between pockets.