• Title/Summary/Keyword: Zeotropic mixtures

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A Prediction Model for Condensation of Zeotropic Refrigerant Mixtures Inside a Horizontal Smooth Tube (수평평활관내의 비공비 혼합냉매의 응축에 대한 예측모델)

  • ;;小山繁
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.4
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    • pp.262-270
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    • 2001
  • This paper deals with a prediction method for the condensation of ternary refrigerant mixture inside a horizontal smooth tube. Based on some reliable assumptions, the governing equations for the local heat and mass transfer characteristics are derived, and the prediction for the condensation of ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a, including R407C, is carried out. The local values of vapor quality, thermodynamic states at bulk vapor, vapor-liquid interface and bulk liquid, mass flux etc. are obtained for a constant wall temperature and a constant wall heat flux conditions, and the effects of the composition of HFC32/HFC125/HFC134a on heat transfer characteristics are examined. The prediction result is also compared with experimental data for condensation of ternary refrigerant mixtures. The predicted wall temperature distribution has a similar trend with experimental data but the predicted local heat transfer coefficients are 20-30% higher than the experimental data.

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Heat and Mass Transfer Characteristics and Performance Evaluation of a Double-Tube Condenser for an Alternative Refrigerant (대체냉매의 2중관 응축기 열 및 물질전달과 성능평가)

  • 이상무;박병덕;소산번
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.6
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    • pp.468-476
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    • 2002
  • This paper deals with heat and mass transfer characteristics and performance evaluation of a counter flow double-tube condenser for a multi-component refrigerant mixture. The local heat and mass transfer characteristics of ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a are evaluated for a counter flow double-tube condenser cooled by water. Then, the local values of vapor quality, thermodynamic states at bulk vapor, vapor-liquid interface and bulk liquid, heat flux and condensation mass flux are obtained. The heat exchange performance for ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a on the total pressure drop and the heat transfer characteristics are also compared with those for R404A, R410A, R502, R22, R32, Rl23 and R134a.

Cooling Performance of Several $CO_2/propane$ Mixtures in an Air-Conditioning System (이산화탄소/프로판 혼합냉매의 냉방성능 특성)

  • Kim, Ju-Hyok;Kim, Min-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.1
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    • pp.47-54
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    • 2006
  • [ $CO_2$ ] and propane mixtures were chosen as promising alternative refrigerants and their performance potentials were evaluated experimentally in an air-conditioning system. Pure $CO_2$ and 85/15, 75/25 and 60/40 binary blends by the charged mass percentage of $CO_2/propane$ were selected as working fluids. The effect of the inlet temperature of the secondary fluids and degree of superheat on the cooling performance was tested and discussed. The charging amounts of refrigerants were adjusted to make the system show the maximum COP. Comparisons among different refrigerants were carried out on the same compressor speed basis for a given operating condition. In addition, the temperature gliding effect of zeotropic mixtures on the system performance were analyzed based on the drop-in test results.

Influence of Charging Amounts on the Cooling Performance of $CO_2/Propane$ Mixtures and Concentration Shift Behavior (이산화탄소/프로판 혼합냉매의 냉방성능에 대한 충전량의 영향 및 순환성분비 변화 특성)

  • Kim, Ju-Hyok;Hwang, Yun-Wook;Kim, Min-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.11
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    • pp.851-858
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    • 2006
  • [ $CO_2$ ] and propane mixtures, which are environmentally benign, nontoxic, low in price, and compatible with materials and lubricants, were considered as promising alternative refrigerants. A fully instrumented air-conditioning system was developed for a precise performance evaluation of pure $CO_2$ and $CO_2/propane$ mixtures. In this paper, the effect of the charging amount and circulation concentration on the cooling performance of the system using $CO_2$ and propane mixtures was tested and discussed. Pure $CO_2$ and 85/15, 75/25 and 60/40 binary blends by the charged mass percentage of $CO_2/propane$ were selected as working fluids. An optimum charging amount was proposed as a parameter instead of the degree of subcooling, which can not be well defined in the transcritical cycle, to properly compare the performance between the transcritical and subcritical cycles.

Vapor-Liquid Equilibria of Carbon Dioxide and Propane Mixtures (이산화탄소와 프로판 혼합냉매의 기상-액상 평형)

  • Kim, Ju-Hyok;Kim, Min-Soo;Kim, Man-Hoe
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.11
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    • pp.859-866
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    • 2006
  • This paper presents the vapor-liquid equilibrium (VLE) data measured for carbon dioxide and propane mixtures. Their mixtures were considered as promising alternative refrigerants due to good thermophysical properties and negligible environmental impact. The isothermal VLE data were measured at eight temperatures ranging from 253.15 to 323.15 K in the circulation type equipment with a view cell. The binary system was found to be a zeotropic mixture in the tested temperature range and could be correlated with sufficient accuracy by using the Peng-Robinson equation of state (PR EoS) with the van der Waals one fluid mixing rule. A comparison with published experimental VLE data has been carried out by means of the PR equation of state. In addition, the phase behaviors of carbon dioxide and propane mixtures were analyzed based on the measured VLE data.

Condensing heat transfer characteristics of hydrocarbon refrigerants in a horizontal tube (탄화수소 냉매의 수평 원관내 응축열전달 특성)

  • Jang, Yeong-Su;Kim, Min-Su;No, Seung-Tak
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.12
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    • pp.1656-1667
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    • 1997
  • Condensing heat transfer characteristics of hydrocarbon refrigerants are experimentally investigated. Single component hydrocarbon refrigerants (propane, isobutane, butane and propylene) and binary mixtures of propane/isobutane and propane/butane are considered as test fluids. Local condensing heat transfer coefficients of selected refrigerants are obtained from overall conductance measurement. Average heat transfer coefficients at different mass fluxes and heat transfer rates are shown and compared with those of R22. Pure hydrocarbon refrigerants have higher values of heat transfer coefficient than R22. It is also found that there is a heat transfer degradation for hydrocarbon mixtures due to composition variation during condensation. Measured condensing heat transfer coefficients are compared with predicted values by available correlations. An empirical correlation for pure and mixed hydrocarbon is developed, and it shows good agreement with experimental data.

Drop-In Evaluation of Thermodynamic Performance of R-22 Alternative Refrigerant Mixtures (R-22 대체용 혼합냉매의 Drop-In 열역학적 성능 계산)

  • Ju, J.M.;Kim, C.N.;Park, Y.M.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.8 no.3
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    • pp.423-436
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    • 1996
  • Thermodynamic performance of eight zeotropic R-22 alternative refrigerant mixtures selected by AREP(R-22 Alternative Refrigerants Evaluation Program) and R-32/R-125/R-134a(23%/25%/52%), namely R-407C were evaluated by the "drop-in" simulation method. An existing air conditioner was selected and its design data were used for the simulation. "ARI Test A" air conditions were applied. The degree of vapor superheat at the compressor inlet fixed at $5^{\circ}C$ for all the mixtures. The results of the simulation were compared with those of R-22. COPs of all mixtures except for R-32/R-227ea(35%/65%) and R-32/R-125/R-134a(10%/70%/20%), were higher than that of R-22 by 2%~8%, while the capacities were all lower than that of R-22 by 13%~27%. COP of R-32/R-134a(40%/60%) was 2.4% higher but the capacity was 15% lower than those of R-22. In the case of R-32/R-134a(30%/70%), COP and capacity were 5.5% higher and 15% lower than those of R-22, respectively. Among the ternary mixtures, R-407C and R-32/R-125/R-134a(30%/10%/60%) showed the best performance. COP of R-407C was 2.4% higher than those of R-22 but the capacity was 15% lower.

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A Study on Heat Transfer Characteristics in Flow Boiling of Pure Refrigerants and Their Mixtures in Horizontal Tube (수평 전열관내 유동비등하는 순수냉매와 혼합냉매의 열전달 특성에 관한 연구)

  • 임태우;한규일
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.2
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    • pp.144-151
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    • 2003
  • An experimental study was carried out in a uniformly heated horizontal tube to examine heat transfer characteristics of pure refrigerants, R134a and R123, and their mixtures during flow boiling. The flow pattern was also observed through tubular sight glasses with an internal diameter of 10 mm located at the inlet and outlet of the test section. Tests were run at a pressure of 0.6 MPa and in the heat flux ranges of 5~100 kW/$m^2$, vapor Quality 0~100 percent and mass velocity of 150-600 kg/$m^2$s. The observed flow patterns were compared to the flow pattern map of Kattan et al., which predicted well the present data over the entire range of mass velocity employed in this study. Heat transfer coefficients of the mixture were less than the interpolated values between pure fluids both in the low quality region where the nucleate boiling is dominant and in the high quality region where the convective evaporation is dominant.

Evaluation of Condensation Heat Transfer Correlations for Microfin Tubes

  • Han, Dong-Hyouck;Lee, Kyu-Jung
    • International Journal of Air-Conditioning and Refrigeration
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    • v.15 no.4
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    • pp.163-168
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    • 2007
  • The feature of six existing condensation heat transfer correlations for microfin tubes were evaluated with the consideration of vapor quality, mass flux, geometries, and various refrigerants. The Kosky and Staub [15] and the Jaster and Kosky [16] correlations for smooth tube were used for the evaluation of the heat transfer enhancement factor (EF). For the prediction of zeotropic mixtures, most correlations show discrepancy with previous measurements. The Yu and Koyama [4] and the Shikazono et al. [8] correlations do not consider spiral angle effect. The Han and Lee [10] correlation shows fin height growth deteriorates heat transfer. Experimental verification to develop reliable condensation heat transfer correlation for microfin tubes is still needed with the consideration of geometrical effects and working conditions.