• 한국초전도ㆍ저온공학회논문지
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• 제3권1호
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• pp.64-68
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• 2001

An experimental study on the Joule-Thomson cryocooler with the mixed refrigerant (MR) is described in this paper, J-T refrigeration experiment was performed with a single stage regular air-conditioning compressor The mixed refrigerant in the experiment was composed of 75% mol fraction of $N_2$. 30% moi fraction of CH$_4$. 30% moi fraction of $C_2$H$_{6}$. 10% mot fraction of $C_3$H$_{8}$ and 15% mot fraction of iso-C$_4$H$_{10}$. Oil mist in the MR stream could be eliminated completely by the glass microfiber filter. Since a single stage compressor that had been designed thor R22 is not appropriate for high Pressure ratio of the mixed refrigerant especially during the transient period. two modifications were incorporated to regular J-T refrigeration cycle. First. a Portion of the MR was by-passed at the inlet of the heat exchanger and transferred directly to 7he suction of the compressor in the modified system. Second, a buffer volume was Prepared to change the mass flow rate of refrigerant. The pressure ratio in J-T expansion device was relieved at the beginning of the operation due to the by-Pass scheme. but it gradually decreased during the transient Process as some of the MR component condensed at low temperature. The buffer volume at the suction side was used to increase the MR gas density in the system after the transient cool-down period. Form the experiment with the modified system, the refrigerator could reach the lowest temperature of -152$^{\circ}C$ without cooling load. and about -15$0^{\circ}C$ with 5 W of cooling load . . . .

• 반도체디스플레이기술학회지
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• 제21권2호
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• pp.144-149
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• 2022

A cryogenic Mixed Refrigerant Joule-Thomson refrigeration cycle was designed to be applied to the semiconductor etching process with non-flammable constituents. 3-stage cascade refrigerator, single mixed refrigerant Joule-Thomson refrigerator, and 2-stage cascade type mixed refrigerant Joule-Thomson refrigerator are analyzed to figure out the coefficient of performance. Non-flammable mixture of argon(Ar), tetrafluoromethane(R14), trifluoromethane (R23) and octafluoropropane(R218) were utilized to analyze the refrigeration cycle efficiency. The designed refrigeration cycle was adapted to cool down the coolant of HFE7200(Ethoxy-nonafluorobutane, C₄F₉OC₂H₅) with certain constraints. Maximum coefficient of performance of the refrigeration system is obtained as 0.289 for the cooling temperature lower than -100℃. The detailed result of the coefficient of performance according to the mixture composition is discussed in this study.

• 한국해양공학회지
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• 제38권5호
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• pp.245-256
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• 2024

As the importance of carbon capture and storage (CCS) technology increases for greenhouse gas reduction, CO2 transportation technology is also becoming crucial. Efficiently handling boil-off gas (BOG) generated during voyages is particularly important. This paper proposes a process incorporating two-stage separation and mixed refrigerants to reliquefy CO2 BOG containing nitrogen efficiently. This process was optimized based on specific power consumption (SPC) criteria and compared with the conventional single-stage separation using an ammonia refrigerant. The two-stage separation allows the removal of non-condensable gases, such as nitrogen, before expansion, and the use of mixed refrigerants enables more efficient heat exchange than ammonia refrigerants, improving the reliquefaction rate. As a result, the proposed process reduced SPC by up to 8.8 % with a nitrogen content of 5 mol% and up to 74.7 % with a nitrogen content of 15 mol%. In addition, the proposed process achieved a reliquefaction rate of over 74.2 % across all nitrogen content ranges of 5-15 mol%.

• 대한조선학회논문집
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• 제49권1호
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• pp.33-44
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• 2012

In this study, the optimal operating conditions for the dual mixed refrigerant(DMR) cycle were determined by considering the power efficiency. The DMR cycle consists of compressors, heat exchangers, seawater coolers, valves, phase separators, tees, and common headers, and the operating conditions include the equipment's flow rate, pressure, temperature, and refrigerant composition per flow. First, a mathematical model of the DMR cycle was formulated in this study by referring to the results of a past study that formulated a mathematical model of the single mixed refrigerant(SMR) cycle, which consists of compressors, heat exchangers, seawater coolers, and valves, and by considering as well the tees, phase separators, and common headers. Finally, in this study, the optimal operating conditions from the formulated mathematical model was obtained using a hybrid optimization method that consists of the genetic algorithm(GA) and sequential quadratic programming(SQP). Moreover, the required power at the obtained conditions was decreased by 1.4% compared with the corresponding value from the past relevant study of Venkatarathnam.

• 한국가스학회지
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• 제20권3호
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• pp.46-51
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• 2016

천연가스 액화공정은 극저온에서 운전되며, 에너지 집약적이다. 따라서 에너지 소모량을 최소화하기 위한 최적화 연구가 많이 진행되고 있으나, 천연가스 액화공정의 용량에 따른 비용 최적화는 많이 이루어지지 않고 있다. 본 연구에서는 다양한 천연가스 액화공정 중 SMR (Single Mixed Refrigerant) 공정을 대상으로, 용량별 설치비용과 운전비용을 분석하였다. SMR 공정의 용량은 1 MTPA (million ton per annum)부터 0.5 MTPA 단위로 증가하여 2.5 MTPA까지 설정하였다. 플랜트 용량의 증가에 따라 천연가스와 냉매의 유량만을 증가시켰으며, 온도, 압력, 조성 등 다른 운전조건은 모든 용량에서 동일하게 적용하였다. 비용 분석을 위해 Aspen Economic Evaluator(v8.7)를 사용하였으며, 비용 정보를 얻기 힘든 다중 흐름 열교환기의 경우에는 six tenths factor rule을 적용하여 계산하였다. 또한 용량별 SMR 공정의 비용 연구결과를 2천만 톤, 4천만 톤 및 8천만 톤 규모의 소규모 가스전에 대하여 적용한 결과, 가스전 규모에 따라 최적의 플랜트 용량을 찾을 수 있었다. 이러한 비용 분석을 통해 비용기반 최적화의 발판을 마련하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권4호
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• pp.502-507
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• 2014

본 논문에서는 혼합작동유체를 해양온도차발전에 적용하였을 때에 그에 따른 사이클의 성능특성에 대해 연구를 수행하였다. 다양한 혼합작동유체 중 본 논문에서는 R32/R152a를 해양온도차발전에 적용하였다. 사이클로는 기존의 밀폐형사이클, 암모니아/물 혼합물에 적용하고 있는 칼리나 사이클에 대해 시뮬레이션 해석을 수행하였고, 온열원의 온도는 $26^{\circ}C$, 냉열원의 온도는 $5^{\circ}C$를 적용하였다. R32를 적용한 밀폐사이클의 출력은 22kW, 사이클의 효율은 2.02%를 보였다. 혼합작동유체를 적용하였을 때에 R32/R152a(90%:10%)의 출력은 29.93kW, 사이클 효율은 2.78%로 기존의 단일 냉매보다 36%, 사이클효율은 37%상승함을 확인 하였다. 칼리나 사이클 또한 위와 같은 방법으로 연구를 수행하였다.

• 한국가스학회지
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• 제24권1호
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• pp.1-9
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• 2020

LNG사업에서 액화공정의 운전비용은 큰 비중을 차지하기 때문에 적합한 액화공정을 선정하고 그 운전조건을 결정하는 것은 중요한 일이다. 현재까지 다양한 구성의 액화공정들이 개발되어 왔기 때문에 이들을 최적화하고 비교하여 최적의 액화공정을 선택하는 것은 많은 시간과 노력을 요하는 일이다. 다양한 구조 및 선택 사항을 포함한 초구조 모델을 사용한 초구조 최적화를 수행하면 공정 구성에 대한 선택과 최적의 운전변수를 한 번에 최적화하는 것이 가능하다. 본 연구에서는 SMR 액화공정에 대한 다양한 선택지를 포함하는 초구조 모델을 만들고 이를 최적화하였다. 결과적으로 초구조 모델이 개별적인 액화공정에 준하는 최적 포인트를 도출하는 것을 확인하였다.

• 설비공학논문집
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• 제22권7호
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• pp.442-447
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• 2010

FPSO (Floating Production Strorage and Offloading) method for LNG industry is efficient and facile compared to onshore NG (Natural Gas) treatment facility. Five simple natural gas liquefaction cycles for FPSO are presented and simulated in this paper. SMR (Single Mixed Refrigerant) cycle, SNE (Single Nitrogen Expander) cycle, DNE (Double Nitrogen Expander) cycle, PNE (Precooled Nitrogen Expander) cycle, and PDNE (Precooled Double Nitrogen Expander) cycle are compared. Simple analysis results in this paper show that precooling process and adding an expander in the liquefaction cycle is an effective way to increase liquefaction efficiency.

• 한국해양공학회지
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• 제32권2호
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• pp.95-105
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• 2018

An FLNG (floating liquefied natural gas) or LNG FPSO (floating production, storage and offloading) unit is a notable offshore unit with the increasing demand for LNG. The liquefaction process on an FLNG unit is the most important process because it determines the economic feasibility, but would be a hazard source because of the large quantity of hydrocarbons. While a high efficiency process such as C3MR has been preferred for onshore liquefaction processes, a relatively simple process such as the SMR (single mixed refrigerant) or DMR (dual mixed refrigerant) liquefaction process has been selected for offshore units because they require a more compact size, lighter weight, and higher safety due to their space limitation for facilities and long distance from shore. It is known that an SMR has the advantages of a simple configuration, small footprint, and lower risk. However, with an increased production rate, the inherent safety of SMR needs to be evaluated because of its small train capacity. In this study, the potential explosion risks of the SMR and DMR liquefaction processes were evaluated at the conceptual design stage. The results showed that an SMR has a lower overpressure than a DMR at the same frequency, only with a small production capacity of 0.9 MTPA. With increased capacity, the overpressure of the SMR was higher than that of the DMR. The increased number of trains increased the frequency in spite of the small amount of equipment per train. This showed that the inherent risk of an SMR is not always lower than that of a DMR, and an additional risk management strategy is recommended when an SMR is selected as the concept for an FLNG liquefaction process compared to the DMR liquefaction process.

• 대한기계학회논문집B
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• 제21권12호
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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.