• Clean Technology
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• v.20 no.3
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• pp.314-320
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• 2014

The purpose of this work is to optimize composition of mixture refrigerants used in the C3MR (Propane & Mixed Refrigerants) process by a statistical optimization technique. C3MR studied in this work is one of widely used commercial natural gas liquefaction processes with high efficiency. Process simulation was performed in a commercial process simulator and methane ($C_1$), ethane ($C_2$), propane ($C_3$), and nitrogen ($N_2$) were selected as mixed refrigerants. Using the process model, optimum composition of refrigerants mixture was determined via mixture design and central composite design to produce minimum energy consumption. As a result, it was confirmed that energy consumption is reduced down to 11.3% comparing to existing design. It was also compared with heat effectiveness through temperature profile of MCHE (main cryogenic heat exchanger).

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.677-684
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• 2013

A mixed refrigerant cycle (MRC) has been widely used in liquefaction of natural gas because it is simple and easily operable with reasonable equipment costs. One of the important techniques in MRC is selection of a refrigerant mixture and decision of its optimum mixing ratio. In this work, it is examined whether mixture components (refrigerants) and their mixing ratio influence performance of general MRC processes. In doing this, mixture design and response surface method, which are well-known statistical techniques, are used to find optimal mixture refrigerants and their optimal mixing ratio that minimize total energy consumption of the entire liquefaction process. A MRC process using several refrigerants and various mixing ratios is simulated by Aspen HYSYS and mixture design and response surface method are implemented using Minitab. According to the results, methane ($C_1$), ethane ($C_2$), propane ($C_3$) and nitrogen ($N_2$) are selected as best mixture refrigerants and the determined mixture ratio (mole ration) can reduce total energy consumption by up to 50%.

• 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.

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.1
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• pp.25-33
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• 2007

The investigation has been made into the prediction of heat exchange performance of a counter flow type double-tube condenser for natural refrigerant mixtures composed of Propane/n-Butane or Propane/i-Butane in a smooth tube and micro-fin tube. Under various heat transfer conditions, mass flux, pressure drop and heat transfer coefficient of the mixed refrigerants were calculated using a prediction method, when the length of condensing tube, total heat transfer rate, mass flux and outlet temperature of coolant were maintained constant. Also, the predicted results were compared with those of HCFC22. The results showed that the mixed refrigerants of Propane/n-Butane or Propane/i-Butane could be substituted for HCFC22, while the pressure drop and overall heat transfer coefficient of the refrigerants were evaluated together.

• Journal of the Korean Institute of Gas
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• v.20 no.1
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• pp.62-67
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• 2016

Natural gas, one of the cleanest fossil fuel, is liquefied to reduce its volume for the long distance transportation. Small size floating liquefied natural gas plant has small area that safe issue is highly considered. However, Dual Mixed Refrigerants (DMR) process has fire potential by using flammable refrigerants and N2 Expander process has low compressed energy efficiency which has high inherent process safety. Therefore, safe process with high compressed energy efficiency is constantly needed. This study suggested an alternative refrigerants to existing DMR process by using Hydrofluorocarbon which has high safety due to its non-flammable properties. As a result, it showed 34.8% lower compressed energy efficiency than DMR process that contains fire potential whereas 42.6% improved compressed energy efficiency than Single N2 Expander process. In conclusion, this research proposed safe process for small size floating liquefied natural gas plant while having high efficiency.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.3
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• pp.305-314
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• 1987

Thermodynamic analysis of a mixed refrigerant refrigeration cycle has been performed by computing thermodynamic properties of various refrigerants. The analyses are carried cut to identify the sources and distribution of the energy degradation by irreversible processes. Heat exchange process with the surroundings produces the entropy and the irreversible loss can be reduced by the mixed refrigerant whose phase change temperature varies during the phase change processes in the evaporator and the condenser. The concept has been applied to find the minimum compression work and thus the minimum energy loss in the overall system, specifically in the case of the mixed refrigerant of R12 and R114. Parametric studies have been added to recognize the various factors affecting the system performance.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.119-124
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• 2023

In this study, experimental approach of the measurement of condensation and evaporation heat transfer coefficients is discussed for mixed refrigerants using in the ultra low-temperature cooling system for semiconductor etching process. An experimental apparatus was described performing the condensation and evaporation heat transfer measurements for mixed refrigerants. The mixed refrigerant used in this study was composed of the optimal mixture determined in previous research, with a composition of Ar:R14:R23:R218 = 0.15:0.4:0.15:0.3. The experiments were conducted over a temperature range from -82℃ to 15℃ and at pressures ranging from 18.5 bar to 5 bar. The convection heat transfer coefficients of the mixed refrigerant were measured at flow rates corresponding to actual operating conditions. The condensation heat transfer coefficient ranged from approximately 0.7 to 0.9 kW/m2K, while the evaporation heat transfer coefficient ranged from 1.0 to 1.7 kW/m2K. The detailed discussion of the experimental methods, procedures, and results were described in this paper.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.3
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• pp.406-420
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• 1995

As concerns increase over the dangers of environmental destruction on a global scale, CFC regulations have finally been carried out and some CFC's are expected to be phased out by the end of 1995. The research for alternative refrigerants is very demanding. The major activities related to alternative refrigerants are focused on two different areas; one is the development of mixed refrigerants by using the existing refrigerants, and the other is the development of new HFC refrigerants. One of the most promising alternative refrigerant for CFC-12 is HFC-134a. HFC-134a has often been used as a replacement of CFC-12 for automotive air-conditioners. However, due to different thermodynamic properties of HFC-134a, performances of the replaced system are degraded compared with those of the CFC-12 system. Sometimes, the complete redesign of the system is required. In order to analyse and design the new system effectively, the developement of a system simulation program, in which HFC-134a can be selected as a refrigerant, is recommended. Therefore, the summary of this research is as follows : (1) The various thermodynamic properties of HFC-134a are ana lysed and programmed. (2) The model for serpentine heat exchanger is developed and programmed. (3) These subroutines are integrated to develop to develop an automotive air conditioning system simulation program which is verified by the test results. (4) The verified program is used to analyse the performance of a selected automotive air conditioning system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1033-1041
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• 2003

Two-phase flow pattern data during horizontal in-tube flow boiling are presented for pure and mixed refrigerants of R134a and Rl23, The flow pattern is observed through tubular sight glasses located at inlet and outlet of the test section, which is made of a stainless steel tube, 2m long with 10mm I.D., 1.5mm wall thickness. The obtained results are compared with the available various correlations for flow pattern. The flow pattern map of Hashizume was in good agreement with the present data except the region of low mass velocity. Weisman flow pattern map was also known to satisfactorily predict data for refrigerants in the region of annular flow. In this study, the flow pattern are simply classified into two groups; stratified(including intermittent, stratified and stratified-wavy) flow and annular flow. The transition quality from stratified to annular flow was obtained by modifying the liquid Froude number.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.90-95
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• 2000

Condensation heat transfer experiments for R-22 and R-407C refrigerants mixed with mineral oil and POE oil respectively were performed in straight and U-bend sections of a microfin tube. Experimental parameters were an oil concentration from 0 to 5%, a mass flux from 100 to $400 kg/m^2s$ and an inlet quality from 0.5 to 0.9. The enhancement factors for R-22 and R-407C refrigerants at the first straight section decreased continuously as the oil concentration increased. They decreased rapidly as the mass flux decreased and inlet quality increased. The heat transfer coefficients in the U-bend were the maximum at the $90^{\circ}$ position. The heat transfer coefficients at the second straight section within the dimensionless length of 48 were larger by a maximum of 33% than the average heat transfer coefficients at the first straight section.