• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.517-522
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• 2013

Small size ice-cream maker has two evaporators having different evaporating temperatures of $4^{\circ}C$ and $-8^{\circ}C$. In such case, ice-cream maker system design becomes complicated because multiple capillary tubes affects one another. In this study, performance analysis was conducted for the soft ice-cream maker having two evaporators operating at different temperatures. The compressor was analyzed using efficiency models, the capillary tube was modeled assuming one-dimensional flow, the condenser and the evaporators were modeld based on UA-LMTD method. The refrigeration cycle simulation program was developed applying the enthalpy, pressure and mass balance on each component. Comparison of the test data with the simulated results for R404A revealed that evaporator temperatures of refrigerator and freezer agreed within $3^{\circ}C$.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2009.11a
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• pp.345-345
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• 2009

전기화학적 환원 기술을 이용한 고온 용융염 전해환원의 결과 생산되는 금속전환체는 다공성 특성에 의해 전해환원의 매질인 용융염을 함유하게 된다. 전해환원과 후속 전기화학 공정인 전해정련의 전해질은 각각 LiCl과 LiCl-KCl 공융염으로 상이하기 때문에 이렇게 금속전환체에 포함된 LiCl 염이 동반되어 전해정련 공정에 도입될 경우 전해정련 공정의 공융염 조성을 어긋나게 한다. 이에 따라 금속전환체의 잔류염은 효과적으로 제거되어야 하며 공정으로 감압 증류에 의한 잔류염 제거 공정이 고려되고 있다. LiCl은 증기압이 비교적 낮기 때문에 감압의 고온 조건이 공정에 필요하다. 그러나 상평형도 분석 결과 전해환원 공정에서 산화물을 담아 음극으로 사용되어 환원된 금속전환체와 함께 도입되는 SUS 재질의 바스켓과 사용후핵연료 금속전환체의 주된 원소인 우라늄과는 공융할 수 있기 때문에 LiCl 증발 온도는 $720^{\circ}C$ 이하로 유지되어야 한다. 이와 같은 조건에서 LiCl 증발 속도를 높이기 위해서는 감압 조건이 필수적이다. 본 연구에서는 감압조건에서 LiCl 휘발 실험을 위해 폐쇄형 및 개방형 반응기를 제작하여 압력 조건 및 Ar 유량 등에 따른 LiCl 휘발율을 측정하였다. 증발된 LiCl은 일정 감압 조건에서 분말형으로 냉각부위에 회수 될 수 있었으나 완전 진공 조건에서는 결정형으로 냉각 부위에 응축되는 것으로 확인 되었으며 일정 진공 조건에서는 Ar 유량에 따라 증발량이 의존하지 않는 것으로 나타났다. 연구 결과 증발염의 취급 빛 이송을 위해 분말형 회수를 목표로 설정할 수 있었으며 공정조건으로 일정 수준의 감압 조건을 제시하였다. 이 후 후속 연구로 장치의 대형화 및 증발 속도 향상을 위한 추가적인 연구가 계획되어 있으며 연구 결과에 기초하여 공학규모 파이로 공정 시설인 PRIDE에 도입될 장치의 기초 설계 자료를 생산할 예정이다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.7
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• pp.681-687
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• 2005

Experimental results for heat transfer characteristic and pressure gradients of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers are presented. The test sections which has one tube diameter of 12.70 m with 0.86 mm wall thickness, another tube diameter of 9.52 mm with 0.76 mm wall thickness are used for this investigation. The local evaporating heat transfer coefficients of hydrocarbon refrigerants were higher than that of R-22. The average evaporating heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than R-22 in 12.7 mm and 9.52 mm. This results form the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air- conditioning systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.5
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• pp.397-407
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• 2004

It is well known that some key parameters, such as evaporating temperature, refrigerant mass flow rate, face velocity and inlet air temperature, have significant influence on the evaporator performance. However performance studies related to a humid environment have been very scarce. It is demonstrated that the refrigerant mass flow rate, heat flux, water condensing rate and air outlet temperature of the evaporator significantly increase with air inlet relative humidity. As the air inlet relative humidity increases, the latent and total heat transfer rates increase, but the sensible heat transfer rate decreases. The purpose of this study is to provide experimental data on the effect of air inlet relative humidity on the air and refrigerant side pressure drop characteristics for a slit fin-tube heat exchanger. Experiments were carried out under the conditions of inlet refrigerant saturation temperature of 7 $^{\circ}C$ and mass flux varied from 150 to 250 kg/$m^2$s. The condition of air was dry bulb temperature of 27$^{\circ}C$, air Velocity Varied from 0.38 to 1.6 m/s. Experiments Showed that air Velocity decreased 8.7% on 50% of relative humidity 40% of that at degree of superheat of 5$^{\circ}C$, which resulted that pressure drop of air and refrigerant was decreased 20.8 and 8.3% for 50% of relative humidity as compared to 40%, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.6
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• pp.530-537
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• 2004

In recent years, carbon dioxide among natural refrigerants has gained consider-able attention as an alternative refrigerant due to its excellent thermophysical properties. However, few investigations have been performed to develop useful correlations of heat trans-fer coefficients and pressure drop during evaporation of carbon dioxide. This study is aiming at providing the characteristics of heat transfer and pressure drop during the evaporation process of carbon dioxide. Heat is provided by a direct heating method to the test section, which was made of a seamless stainless steel tube with an inner diameter of 7.53 mm, and a length of 5.0 m. Experiments were conducted at saturation temperatures of -4 to 2$0^{\circ}C$, heat fluxes of 12 to 20 ㎾/$m^2$ and mass fluxes of 200 to 530 kg/$m^2$s. A comparison of different heat transfer correlations applicable to evaporation of carbon dioxide has been made. Based on the experiments for evaporation heat transfer and pressure drop, new correlations were developed. The newly developed empirical correlations for the heat transfer and pressure drop show average absolute deviations of 15.3% and 16.2%, respectively.

• Journal of Power System Engineering
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• v.12 no.4
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• pp.26-31
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• 2008

The evaporation heat transfer coefficient and pressure drop of R-22 and R-407C in a small diameter copper tube were investigated experimentally. The main components of the refrigerant loop are a receiver, a compressor, a mass flow mete, a condense and a double pipe type evaporate (test section). The test section consists of a smooth copper tube of 4.3 mm inner diameter. The refrigerant mass fluxes were varied from 100 to $300[kg/m^{2}s]$ and the saturation temperature of evaporator were $5[^{\circ}C]$. The evaporation heat transfer coefficients of R-22 and R-407C increase with the Increase in mass flux and vapor quality. The evaporation heat transfer coefficient of R-22 is about $7.3\sim47.1%$ higher than that of R-407C. The evaporation pressure drop of R-22 and R-407C increase with the increase of mass flux. The pressure drop of R-22 is about $8\sim20%$ higher than that of R-407C.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.9
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• pp.855-862
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• 2004

This study reports pressure drops during evaporation for R-l34a, R-407C (a mixture of 23 wt% R-32, 25 wt% R-125, and 52 wt% R-l34A) and R-410A (a mixture of 50 wt% R-32 and 50 wt% R-125) in the oblong shell and Plate heat exchanger. The effects of the mass fluxes, heat fluxes, refrigerant saturation temperatures and vapor quality of refrigerants on the measured data were explored in detail. The present data showed that pressure drops of all refrigerants increase with the vapor quality. At a higher mass flux, pressure drops are higher for the entire range of the vapor quality A rise in the heat flux doesn't show significant effects on the pressure drops. Finally, at a higher saturation temperature the pressure drops are found to be lower. The pressure drops for R-407C were approximately 20% lower than those of R-l34a. R-410A had 33% lower pressure drops than R-l34a. Correlation is also provided for the measured pressure drops in terms of the friction factor.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.63-69
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• 2007

The evaporation pressure drop of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and an evaporator (test section). The test section consists of a smooth, horizontal stainless steel tube of 4.57 mm inner diameter. The experiments were conducted at saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$, and heat flux of 10 to $40kW/m^2$. The test results showed that the evaporation pressure drop of $CO_2$ are highly dependent on the vapor quality, heat flux and saturation temperature. The measured pressure drop during the evaporation process of $CO_2$ increases with increased mass flux, and decreased saturation temperature. The evaporation pressure drop of $CO_2$ is much lower than that of R 22. In comparison with test results and existing correlations, the best fit of the present experimental data is obtained with the previous correlation. But existing correlations failed to predict the evaporation pressure drop of $CO_2$. Therefore, it is necessary to develop reliable and accurate predictions determining the evaporation pressure drop of $CO_2$ in a horizontal tube.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.542-549
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• 2008

The evaporation heat transfer coefficient and pressure drop of R-22 and R-407C in a horizontal copper tube were investigated experimentally. The main components of the refrigerant loop are a receiver, a compressor, a mass flow meter, a condenser and a double pipe type evaporator (test section). The test section consists of a smooth copper tube of 6.4 mm inner diameter. The refrigerant mass fluxes were varied from 100 to $300\;kg/m^2s$ and the saturation temperature of evaporator were $5^{\circ}C$. The evaporation heat transfer coefficients of R-22 and R-407C increase with the increase of mass flux and vapor quality. The evaporation heat transfer coefficients of R-22 is about $5.68{\times}46.6%$ higher than that of R-407C. The evaporation pressure drop of R-22 and R-407C increase with the increase of mass flux. The pressure drop of R-22 is similar to that of R-407C. In comparison with test results and existing correlations, correlations failed to predict the evaporation heat transfer coefficient of R-22 and R-407C. therefore, it is necessary to develope reliable and accurate predictions determining the evaporation heat transfer coefficient of R-22 and R-407C in a horizontal tube.

• Journal of the Korean Institute of Gas
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• v.25 no.1
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• pp.7-13
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• 2021

The re-liquefaction drum is a product that installed spray nozzles at the top to directly spray overcooled LNG into evaporative gas and installed demistors to facilitate gas separation, which was developed to increase the re-liquidity efficiency of small scale re-liquefaction facilities. In the hydrostatic test of the drum, no leakage occurred even at a pressure of 1.5 times the design pressure, but during the BOR(Boil Off Rate) test, the bolt loosening occurred due to contraction and expansion by temperature change. For the continued use of the product, insulation construction on flange connections was developed to enable detachment and attachment, and the comparison of heat load with existing insulation confirmed that it was very small compared to the inlet flow rate in the drum.