• 한국유체기계학회 논문집
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• 제18권5호
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• pp.33-41
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• 2015

Organic Rankine cycle (ORC) has been used to generate electrical or mechanical power from low-grade thermal energy. Usually, this thermal energy is not supplied continuously at the constant thermal energy level. In order to optimally utilize fluctuating thermal energy, an axial-type turbine was applied to the expander of ORC and two supersonic nozzle were used to control the mass flow rate. Experiment was conducted with various turbine inlet temperatures (TIT) with the partial admission rate of 16.7 %. The tip diameter of rotor was to be 80 mm. In the cycle analysis, the output power of ORC was predicted with considering the load dissipating the output power produced from the ORC as well as the turbine efficiency. The predicted results showed the same trend as the experimental results, and the experimental results showed that the system efficiency of 2 % was obtained at the TIT of $100^{\circ}C$.

• 신재생에너지
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• 제10권4호
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• pp.36-46
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• 2014

Low-grade heats are wasted even though an amount of their energy is huge. In the small and medium industrial complex sites, large amount of low-grade thermal energy generated during the manufacturing process is wasted if it is not used directly for building heating or air-conditioning. In order to utilize this waste thermal energy more efficiently, organic Rankine cycle (ORC) was adopted. The range of operating temperature of ORC was set to $60^{\circ}C$ from $30^{\circ}C$ applicable low-temperature waste heat. A study was conducted to select an appropriate organic working fluid based on these operating conditions. More than 60 working fluids were screened. Eleven working fluids were selected based on the requirements as working fluid for ORC such as environmentally friendly, safety, and good operation on the expander. Finally, six working fluids were selected by considering the operating temperature ranges. Then, a cycle analysis was conducted with these six working fluids. As a results, R-245fa and R-134a appeared as appropriate working fluids for ORC operating at low-temperature condition based on the system efficiency and the turbine output power.

• 한국수소및신에너지학회논문집
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• 제25권2호
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• pp.200-208
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• 2014

This paper presents thermodynamic performance analysis of organic Rankine cycle (ORC) using low temperature heat source in the form of sensible energy and using liquefied natural gas (LNG) as heat sink to recover the cryogenic energy of LNG. LNG is able to condense the working fluid at a very low condensing temperature in a heat exchanger, which leads to an increased power output. Based on the mathematical model, a parametric analysis is conducted to examine the effects of eight different working fluids, the turbine inlet pressure and the condensation temperature on the system performance. The results indicate that the thermodynamic performance of ORC such as net work production or thermal efficiency can be significantly improved by the LNG cold energy.

• 한국기계가공학회지
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• 제18권4호
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• pp.26-33
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• 2019

This study is a thermal and flow analysis of Organic Rankine Cycle (ORC) pipe line for 250 kW grade waste gas heat recovery. We attempted to obtain the boundary condition data through the process design of the ORC, which can produce an electric power of 250 kW through the recovery of waste heat. Then, we conducted a simulation by using STAR-CCM+ to verify the model for the pipe line stream of the 250 kW class waste heat recovery system. Based on the results of the thermal and flow analyses of each pipe line applied to the ORC system, we gained the following conclusion. The pressure was relatively increased at the pipe outside the refracted part due to the pipe shape. Moreover, the heat transfer amount of the refrigerant gas line is relatively higher than that of the liquid line.

• 분석과학
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• 제19권3호
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• pp.203-210
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• 2006

Octopole reaction cell inductively coupled plasma mass spectrometer (ORC-ICP-MS)를 이용하여 우유 분말시료 중 극미량의 셀레늄(Se)을 정량하였다. 반응가스로 $H_2$를 사용함으로써 극미량 측정에서 발생되는 다원자 이온 종들과 공존 원소에 의해 발생되는 분자들의 방해를 현저하게 제거하였다. Normal mode에 비해서 $H_2$ cell gas mode는 정확성과 정밀성을 크게 향상시켰으며, 우유 표준시료의 보증 값에 비해 정량한 결과는 평균 102.7%로 약간 높게 나타났고, 5회 정량한 값에 대한 상대표준편차는 7.6%이었다.

• 대한기계학회논문집B
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• 제39권4호
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• pp.317-324
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• 2015

본 연구에서는 아파트단지에 적용되는 태양열 급탕 시스템의 에너지 활용도를 높이기 위해 유기랭킨사이클을 적용하여 해석적 연구를 수행하였다. 시스템 해석은 Aspen $Plus^{(R)}$을 활용하였으며 태양열집열기는 급탕 온도와 유기랭킨 사이클의 운전 조건을 고려하여 진공관형 집열기를 적용하였다. R134a, R141a, R245fa 등의 냉매를 작동유체로 선정하였으며, 시스템 성능해석을 통하여 R245fa 냉매가 적용가능성이 가장 높게 나타났다. 비가역성 해석과 민감도 해석을 통해 유기랭킨 사이클 시스템의 효율 및 성능 확보를 위해서는 증발기와 터빈에 대한 기술 개발이 매우 중요하다는 것을 밝혀냈으며, 순수 급탕으로만 활용하는 시스템에 전기 생산 설비를 추가하게 되면 약 50%의 추가적인 경제성이 확보됨을 확인하였다.

• 해양환경안전학회지
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• 제27권6호
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• pp.839-845
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• 2021

본 연구에서는 CO₂ 가스 배출 저감 및 선박 폐열 회수 증대를 목적으로 선박 배기로 버려지는 폐열을 전기로 변환하는 ORC(Organic Rankine Cycle) 발전에 대해 시뮬레이션을 통한 냉매별 효율을 보여주고 있다. 상대적으로 고온인 배기가스의 폐열과 상대적으로 저온인 냉각해수를 이용하여 Aspen HYSYS 11을 이용하여 시뮬레이션을 수행하였다. 해수냉각 ORC 발전시스템의 시뮬레이션 결과, 작동유체 효율은 R717 냉매가 2.86 %로 가장 높았고, 다음 순으로 R152a, R134a, R143a, R125a로 나타났다.

• 대한화학회지
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• 제60권5호
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• pp.310-316
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• 2016

Oxidation-reduction cycling (ORC) procedures are widely used for cleaning nanoparticle surfaces when investigating their electrocatalytic activities. In this work, the effect of ORC on the surface structures and electrocatalytic oxygen reduction activity of Au electrodes is analyzed. Different structural changes and variations in electrocatalysis are observed depending on the initial structure of the Au electrodes, such as flat bulk, nanoporous, nanoplate, or dendritic Au. In particular, dendritic Au structures lost their sharp-edge morphology during the ORC process, resulting in a significant decrease in its electrocatalytic oxygen reduction activity. The results shown in this paper provide an insight into the pretreatment of nanoparticle-based electrodes during investigation of their electrocatalytic activities.

• 한국수소및신에너지학회논문집
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• 제31권4호
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• pp.363-371
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• 2020

Recently, the technologies to utilize the cold energy of liquefied natural gas (LNG) have attracted significant attention. In this paper, thermodynamic performance analysis of combined cycles consisting of ammonia Rankine cycle (AWR) and organic Rankine cycle (ORC) with LNG Rankine cycle to recover low-grade heat source and the cold energy of LNG. The mathematical models are developed and the effects of the important system parameters such as turbine inlet pressure, ammonia mass fraction, working fluid on the system performance are systematically investigated. The results show that the thermal efficiency of AWR-LNG cycle is higher but the total power production of ORC-LNG cycle is higher.

• 한국수소및신에너지학회논문집
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• 제26권4호
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• pp.377-385
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• 2015

This paper presents a thermodynamic performance analysis of regenerative organic Rankine cycle (ORC) using turbine bleeding to utilize low-grade finite thermal energy. Refrigerant R245fa was selected as the working fluid. Special attention is paid to the effects of the turbine bleeding pressure and the turbine bleed fraction on the thermodynamic performance of the system such as net power production and thermal efficiency. Results show that the thermal efficiency has an optimum value with respect to the turbine bleeding pressure and the net power production is lower than the basic ORC while the thermal efficiency is higher.