• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.564-571
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• 2001

The present study investigated the effect of key parameters on the performance of a cascade system using R-22 and R-23 refrigerants. Experimental data for the cascade system have been compared with simulation results using thermodynamic analysis. The cascade system tested at the evaporating temperature of $-80^{\circ}C $ and the condensing temperature of$40^{\circ}C $. The key experimental parameters were the evaporating temperature of the HTC(-35, -30, -25, -20, $-15^{\circ}C $) and mass flux of the HTC(200, 250, 300kg/$m^2$s). As the evaporating temperature and the mass flux of the HTC were increased respectively, the COP and the refrigerating efficiency were increased and then decreased while the volume flow rate per unit refrigeration capacity showed the opposite trend. The maximum COP and refrigerating efficiency were obtained at the evaporating temperature of the HTC of $-25^{\circ}C $ and the mass flux of 250 kg/$m^2$s.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.5
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• pp.473-477
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• 2019

In this paper, cold heat price contained in the 1 ton/h of LNG has been evaluated using PRO/II with PROVISION release 10.2 from Aveva company when LNG is used to liquefy several refrigerants instead of using vapor recompression refrigeration cycle. Normal butane, R134a, NH3, R22, propane and propylene refrigerants were selected for the modeling of refrigeration cycle. It was concluded that LNG cold heat price was inversely proportional to the refrigerant supply temperature, even though LNG supply flow rate is not varied according to the refrigerant supply temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.9
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• pp.1207-1217
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• 1997

The present work experimentally investigated the effects of mass flux, heat flux, inlet quality on the heat transfer performance inside the U-bend of smooth and microfin tube using R-22 and R-407C refrigerants. The parameters were 200 and 400 kg/m$^{2}$ s for mass flux, 6 and 12 kw/m$^{2}$ for heat flux, 0.1 and 0.2 for inlet quality under the pressure of 0.65 MPa. The apparatus consisted of the test section of four straight sections and three U-bends, preheater, condenser, refrigerant pump, mass flow meter etc. The average heat transfer coefficient at the downstream straight section after U-bend was affected by U-bend due to the centrifugal force and mixing of two-phase flow in the U-bend. The average heat transfer coefficient at the U-bend was 4 ~ 33 % higher than that at the straight section. The average heat transfer coefficients were affected in the order of mass flux, heat flux and inlet quality. The average heat transfer coefficients in the microfin tube were lager by 19 ~ 49% and 33 ~ 69% than that in the smooth tube at the straight section and at the U-bend separately. The average heat transfer coefficients for R-407C were larger by 33 ~ 41% and 17 ~ 29% than that for R-22 in the smooth tube and the microfin tube separately.

• Journal of Power System Engineering
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• v.18 no.5
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• pp.42-47
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• 2014

In this paper, the cycle performance analysis for the COP of supercritical heat pump using various refrigerants is presented to offer the basic design data for the operating parameters of the system. The working fluids are R134a, R22, R32, R290, R600, R600a, R1270 and R744. The operating parameters considered in this study include superheating degree of evaporator, temperature of gas cooler inlet and outlet, compressor efficiency and evaporating temperature in the supercritical heat pump system. The main results were summarized as follows : Superheating degree, temperature of gas cooler inlet and outlet, compressor efficiency and evaporating temperature of supercritical heat pump system have an effect on the COP of this system. With a thorough grasp of these effect, it is necessary to design the supercritical heat pump using R134a. And, in comparison of COP of supercritical heat pump using various refrigerants, R32 and R600 is the highest, and R744 is the lowest among other refrigerants. From these results, it is confirmed that the COP of supercritical heat pump using R744 is higher than that using freon refrigerants such as R32 and R134a.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.3
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• pp.167-175
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• 2009

In this study, condensation heat transfer coefficients(HTCs) of R22, R123, R134a and R245fa are measured on both 26fpi low fin and Turbo-C tubes. All data are taken at the vapor temperature of $39^{\circ}C$ with a wall subcooling of $3{\sim}8^{\circ}C$. Test results show that HTCs of the newly developed low vapor pressure alternative refrigerant, R245fa, are $7.8{\sim}9.2%$ and $10.3{\sim}18.6%$ higher than those of R123 for 26fpi low fin tube and Turbo-C tube respectively. For all refrigerants tested, HTCs of Turbo-C enhanced tube are higher than those of 26fpi low fin tube. For the low fin tube, Beatty and Katz's prediction equation yielded 20% deviation for all fluids. The heat transfer enhancement ratio of R245fa on the Turbo-C tube is $5.9{\sim}6.4$ while that of R123 is $5.7{\sim}5.9$. From the view point of environmental safety and condensation heat transfer, R245fa is a long term candidate to replace R123 currently used in centrifugal chillers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.3
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• pp.208-215
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• 2011

In this work, pool boiling heat transfer coefficients(HTCs) of R22, R123, R134a, and R245fa are measured on both horizontal plain and 26 fpi low fin tubes. The pool boiling temperature is maintained at $7^{\circ}C$ and heat flux is varied from 80 $kW/m^2$ to 10 $kW/m^2$ with an interval of 10 $kW/m^2$. Wall temperatures are measured directly by thermocouples inserted through holes of 0.5 mm diameter. Test results show that HTCs of high vapor pressure refrigerants are usually higher than those of low pressure fluids in both plain and low fin tubes. On a plain tube, HTCs of R245fa are 23.3% higher than those of R123 while on a 26 fpi low fin tube, HTCs of R245fa are 46.3% higher than those of R123. The fin effect is more prominent with low vapor pressure refrigerants than with high vapor pressure ones due to a sweeping effect.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.2
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• pp.301-306
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• 2013

In this paper, cycle performance analysis of two-stage compression and two-stage expansion refrigeration system using alternative freon refrigerants is presented to offer the basic design data for the operating parameters of the system. Alternative freon refrigerant for freon refrigerant R22 were used as working fluids in this study. The operating parameters considered in this study included evaporation temperature, condensation temperature, subcooling degree, superheating degree, and mass flow rate ratio of inter-cooler. The main results were summarized as follows : The COP of two-stage compression and two-stage expansion refrigeration system increases with the increasing subcooling degree and mass flow rate ratio of inter-cooler, but decreases with the increasing evaporating temperature, condensing temperature and superheating degree. Therefore, subcooling degree, mass flow rate ratio of inter-cooler of two-stage compression and two-stage expansion refrigeration system using alternative freon refrigerants have an effect on COP of this system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.938-944
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• 2000

Recently, micro fin tube is widely used to heat exchanger for high performance. And, as the alternative refrigerants for R-22, hydrocarbons such as R-290, R-600 and R-600a are very promising because of their low GWP and ODP. Thus, R-290 was used as working fluid in this study. Most design of heat exchanger had been based on heat transfer characteristics of pure refrigerant although refrigerant oil exists in the refrigeration cycles. So, the influence of oil on heat transfer characteristics have to be considered for investigating exact evaporation heat transfer characteristics. But, this is an unresolved problem of refrigeration heat transfer. Therefore the influence of the refrigeration oil to the evaporation heat transfer characteristics of R-290 were conducted in a horizontal micro tin tube. The mineral oil was used as refrigeration oil. The experimental apparatus consisted of a basic refrigeration cycle and a system for oil concentration measurement. Test conditions are as the follows; evaporation temperature $5^{\circ}C$, mass velocity 100 $kg/m^2s$, heat flux 10 $kW/m^2$, oil concentration 0, 1.3, 3.3, 5.7 wt.%, and quality $0.07{\sim}1.0$. When refrigeration oil was entered, oil foaming was observed at the low quality region. And, very small bubbles were observed as quality was increased. Pressure drop and heat transfer coefficient increased as the concentration of refrigeration oil increased to 5 wt.%.. The performance index of heat exchanger was the highest near 3.3 wt.%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1307-1312
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• 2007

The flow characteristics of R-134a in a small diameter tube was investigated experimentally. An experimental apparatus was consisted of a magnetic gear pump, an evaporator, a sight-glass, a condenser and a measurement instruments. The sight-glass for flow pattern observations was located at the inlet and outlet of the evaporator. The experiment was carried out to show the flow characteristics of R-134a in a small diameter tube. Mass flux of refrigerants was ranged from 100 to 1000 $kg/m^2s$, the saturation temperature was $30^{\circ}C$. In the flow patterns during evaporation, the annular flow in a 2 mm inner diameter tube occurred at a relatively lower quality and mass velocity, compared to that in a 8 mm inner diameter tube. The evaporation flow pattern in a small diameter tube has been shown major deviations with the Baker, Mandhane and Taitel-Dutler's flow pattern maps but it was similar to the Dobson's flow pattern map.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.292-297
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• 2008

Various types of refrigerators become popular in the market such as a common refrigerator, kimchi refrigerator and wine cellar. It is required to develop a multi function refrigerator which has different purposes in each evaporator. In this study, the performance of a multi type refrigerator system, which consists of one machine room and three evaporators, was measured in a bench type multi refrigerator. The multi type refrigerator system was tested by varying the number of refrigerator cabinet, refrigerant charge amount, temperature condition. Based on experimental data, the multi type refrigerator showed better performance than the conventional refrigerator(single type) At the same external load condition, the COP of the multi type refrigerator was $1.22{\sim}1.29$, but the COP of the single type refrigerator was 1.0.