• Proceedings of the KSME Conference
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• 2000.04b
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• pp.83-89
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• 2000

This paper presents a pressure drop correlation for evaporation and condensation of alternative refrigerant with oil in micro-fin tubes. The correlation was developed from a data base consisting of oil-free pure and mixed refrigerants in micro-fin tube; Rl25 R134a. R32 R410a(R32/R125 50/50% mass), R22, R407c(R32/R125/R134a, 23/25/52% mass) and R32/R134a(25/75% mass). The micro-fin tube used in this paper had 60 0.2mm high fins with a 18 helix angle. The cross sectional flow area $(A_c)$ was $60.8 mm^2$ giving an equivalent smooth diameter$(D_e)$ of 8.8mm. The hydraulic diameter $(D_h)$ was estimated to the 5.45mm. The new correlation was obtained by replacing the friction factor and the tube-diameter in Bo Pierre correlation by a friction factor derived from pressure drop data for a micro-fin tube and the hydraulic diameter, respectively. This correlation was also used to predict some pressure data with a lubricant after using a mixing viscosity rule of lubricants and refrigerants. As a result, the new correlation was also well predicted to the measured data within a mean deviation of 19.0%.

• Journal of Power System Engineering
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• v.19 no.6
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• pp.82-88
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• 2015

In this paper, cycle performance analysis of two-stage compression and one-stage expansion refrigeration system applied various refrigerants is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include degree of superheating and subcooling, compressor efficiency, evaporation temperature, condensing temperature, mass flow rate ration into inter-cooler, effectiveness of internal heat exchanger. The main results were summarized as follows : The COP of two-stage compression and 1-stage expansion refrigeration system increases with the increasing subcooling, mass flow rate ration of inter-cooler, evaporation temperature, but decreases with the increasing condensing temperature and superheating degree. Therefore, subcooling degree, mass flow rate ratio of inter-cooler of two-stage compression and 1-stage expansion using substitute refrigerant have an effect on COP of this system. The COP of alternative refrigerants was higher than the COP of R22 in this study, although the COP of some mixed refrigerants were lower than COP of R22.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.181-185
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• 2008

The new concept for liquefaction of natural gas has been designed and simulated in this paper. Conventional liquefaction cycles are usually composed with Joule-Thomson valves at lower temperature refrigerant cycle. The new concept of natural gas liquefaction is discussed. The main difference with conventional liquefaction process is the presence of the turbine at low temperature of MR (mixed refrigerant) cycle. The turbine acts as expander but also as an energy generator. This generated energy is provided to the compressor which consumes energy to pressurize refrigerants. The composition of the mixed refrigerant is investigated in this study. Components of the refrigerant are methane, propane and nitrogen. Composition for new process is traced with Aspen HYSYS software. LNG heat exchangers are analyzed for the new process. Heating and cooling curves in heat exchangers were also analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3253-3259
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• 2009

In this study, a computer simulation has been performed for the refrigeration cycle using mixed refrigerants in order to decrease the process stream temperature to $-20^{\circ}C$. Refrigerant supply temperature was assumed to be $-30^{\circ}C$ considering the temperature difference as $10^{\circ}C$ with process stream. Peng-Robinson equation of state model was selected for the computer simulation. A new alpha function proposed by Twu et al was used for an accurate prediction of pure component vapor pressure experimental data. One fluid mixing rules were used for the estimation of mixture vapor-liquid equilibria calculations. A commercial process simulator, PRO/II with PROVISION was utilized for the simulation of the overall refrigeration process. In order to minimize the compressor power consumption, we have optimized the two-stage compression system by varying the first stage compressor outlet pressure. Finally, we could obtain the minimum total power 755.7kW at the first stage compressor outlet pressure, 6 bar.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.126-132
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• 2014

The P-T characteristics of mixed refrigerant in thermostatic expansion valve sensing bulb were studied using R-134a and R-410A refrigerant. The characteristics of mixed refrigerant were investigated according to pressure variation and the variation of composition ratio of R-134A and R-410A in the temperature range of $-15^{\circ}C{\sim}15^{\circ}C$. The Thermodynamic characteristic values of the mixed refrigerants were identified using the characteristic value analysis program of mixed refrigerant(Refrop v9.0, NIST). The P-T characteristics in the case of the mixing ratio of 90:10 for R-410A and R-134A were the same result as R-22. And the physical properties showed similar results with R-22. The Maximum operating pressure(MOP) of mixed refrigerant showed a tendency to decrease with decreasing the mixing ratio of additive gases($N_2$ or He) gases. The characteristics in the case of the mixing ratio of 80:1 for mixed refrigerant and additive gases were the similar result as Reference refrigerant.(R-22 MOP, Sporlan company) In addition $N_2$ and He, both showed the same results. It was able to confirm that a MOP on the thermostatic expansion valve sensing bulb can be maintained by adjusting the mixing ratio of mixed refrigerant gases and additive gases.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.836-842
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• 2013

In this paper, the 20 kW Ocean Thermal Energy Conversion(OTEC) is newly proposed in order to select the refrigerant that makes the cycle performance be optimized and the performance of 20 kW OTEC applying 15 pure refrigerants and 16 mixed refrigerants is analyzed. The efficiency of system, the mass flow of working fluids and TPP, which is new concepts, are analyzed. In view of cycle efficiency, R32/R152a (87:13) is the highest efficiency among the refrigerants. At the mass flow of working fluid to make the 20 kW electricity, R717 is shown as the lowest value. And in view of TPP in this study, R32/R134a 70:30 is the most optimized refrigerant. The analysis can confirm that the refrigerant is different along with the part of the system, so it is necessary to select the optimized refrigerant for 20 kW OTEC.

• Journal of the Semiconductor & Display Technology
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• v.23 no.2
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• pp.6-11
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• 2024

This paper presents the design and experimental analysis of a cryogenic refrigeration system for -100 ℃, primarily intended for semiconductor etching process. The refrigeration system utilizes non-flammable mixed refrigerant Joule-Thomson refrigeration cycle, incorporating a precooling stage to enhance overall performance. The selected refrigerants for the system include R1234yf for the precooling stage, and Ar, R14, R23 and R218 for the main cooling stage of the Joule-Thomson refrigeration cycle. Design results according to the system constraints and experimental results are discussed, including lowest evaporation temperature, compressor isentropic efficiency and overall pressure tendencies. The achieved refrigerant fraction from optimal design is Ar: R14: R23: R218 = 0.15: 0.4: 0.15: 0.3, indicating COP of 0.1118 at the isentropic compressor efficiency of 50%. The experimental result shows the developed system reaches steady state in approximately 3 hours.

• Journal of the Korean Institute of Gas
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• v.15 no.6
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• pp.38-43
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• 2011

Natural gas liquefaction process runs under cryogenic condition, and it spends large amount of energy. Minimizing energy consumption of natural gas liquefaction process is an important issue because of its physical characteristics. Among many kinds of natural gas liquefaction processes, C3-MR(Propane Pre-cooled Mixed Refrigerant) process uses two kind of refrigerants. One is the propane as the pure refrigerant(PR) and the other is the mixed refrigerant(MR). In this study, to find the optimal compressing level, propane cycle is simulated on different pressure level. The case study result shows relationship between energy consumption and pressure level. As a result, the conclusion is that at a higher pressure level, process consumes lower energy. At 5 pressure-levels, energy consumption is 23.7% lower than 3 pressure-levels.

• Journal of Fisheries and Marine Sciences Education
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• v.14 no.2
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• pp.177-190
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• 2002

An experimental study was carried out to make clear heat transfer characteristics in flow boiling of binary mixtures of refrigerants R134a and R123 in a uniformly heated horizontal tube. Experiments were run at a pressure of 0.6 MPa both for pure fluids and mixtures in the ranges of heat flux $10{\sim}50{kW/m}^2$, vapor quality 0~100% and mass flux 150-600 $kg/m^2s$. Heat transfer coefficients of mixtures were reduced compared to 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. Total pressure drop during two-phase flow boiling in a horizontal tube consists of the sum of two components, that is, the frictional pressure drop and pressure drop due to acceleration. The frictional pressure drop is the most difficult component to predict, and makes the most important contribution to the total pressure drop. On the other hand, the acceleration pressure drop resulting from the variation of the momentum flux caused by phase change is generally small as compared to the frictional pressure drop. There is no significant difference in measured pressure drop between mixtures and pure fluids. The correlation of Martinelli and Nelson predicted most of the present data both for pure and mixed refrigerants within 30%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.312-319
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• 2006

In this study, performance of 2 pure hydrocarbons and 7 mixtures was measured in an attempt to substitute HCFC22 used in air-conditioners and heat pumps. The mixtures were composed of R1270 (propylene), R290 (propane), HFC152a, and RE170 (Dimethyl ether, DME). The pure and mixed refrigerants tested have GWPs of $3{\sim}58$ as compared to that of $CO_2$ and the mixtures are all near-azeotropic showing the gliding temperature difference (GTD) of less than $0.6^{\circ}C$. Thermodynamic cycle analysis was carried out to determine the optimum compositions and actual tests were performed in a laboratory heat pump test bench at the evaporation and condensation temperatures of 7.5 and $45.1^{\circ}C$ respectively. Test results show that the coefficient of performance (COP) of these mixtures is up to 5.7% higher than that of HCFC22. While propane showed 11.5% reduction in capacity, most of the fluids tested had the similar capacity to that of HCFC22. Compressor discharge temperatures were reduced by $11{\sim}17^{\circ}C$ with these fluids. There was no problem with mineral oil since the mixtures were mainly composed of hydrocarbons. The amount of charge was reduced up to 55% as compared to HCFC22. Overall, these fluids provide good performance with reasonable energy savings without any environmental problem and thus can be used as long term alternatives for. residential air-conditioning and heat pumping application.