• Title/Summary/Keyword: organic Rankine cycles

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Effects of Internal Heat Exchanger on Performance of Organic Rankine Cycles (유기랭킨사이클의 성능에 미치는 내부열교환기의 영향)

  • Kim, Kyoung-Hoon;Jung, Yoong-Guan
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.3
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    • pp.402-408
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    • 2011
  • Organic Rankine cycles (ORC) can be used to produce power from heat at different temperature levels available as geothermal heat, as biogenic heat from biomass, as solar or as waste heat. In ORC working fluids with relatively low critical temperatures and pressures can be compressed directly to their supercritical pressures and heated before expansion so as to obtain a better thermal match with their heat sources. In this work thermal performance of ORC with and without an internal heat exchanger is comparatively investigated in the range of subcritical and transcritical cycles. R134a is considered as working fluid and special attention is paid to the effect of turbine inlet pressure on the characteristics of the system. Results show that operation with supercritical cycles can provide better performance than subcritical cycles and the internal heat exchanger can improve the thermal efficiency when the temperature of heat source becomes higher.

Thermodynamic Performance Analysis of Ammonia-Water Rankine Cycle and Organic Rankine Cycle Using Cold Energy of LNG (LNG 냉열을 이용하는 암모니아-물 랭킨 사이클과 유기 랭킨 사이클의 열역학적 성능 특성 해석)

  • KIM, KYOUNG HOON
    • Transactions of the Korean hydrogen and new energy society
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    • v.31 no.4
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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.

Simulation of HFC organic Rankine cycles for geothermal power generation (지열발전을 위한 HFC 유기랭킨 사이클의 시뮬레이션)

  • Baik, Young-Jin;Kim, Min-sung;Chang, Ki-Chang;Yoon, Hyung-Kee;Lee, Young-Soo;Ra, Ho-Sang
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.569-572
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    • 2009
  • In this study, HFC ORCs (Organic Rankine Cycles) are investigated for a low-temperature geothermal power generation by a simulation method. A steady-state simulation model is developed to analyze and optimize cycle's performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump are modelled by an isentropic efficiency. Simulations were carried out for the given heat source and sink inlet temperatures, and given flow rate that is based on the typical power plant thermal-capacitance-rate ratio. 3 HFC fluids are considered as a candidate for a working fluid of low-temperature ORCs. In this study, all optimized HFC ORCs are shown to yield almost the same performance in terms of power for a low-temperature heat source of about $100^{\circ}C$.

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Performance analysis of an organic Rankine cycle for ocean thermal energy conversion system according to the working fluid and the cycle (작동유체 및 사이클에 따른 해양온도차발전용 유기랭킨사이클의 성능분석)

  • Kim, Jun-Seong;Kim, Do-Yeop;Kim, You-Taek;Kang, Ho-Keun
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.9
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    • pp.881-889
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    • 2015
  • Ocean thermal energy conversion is an organic Rankine cycle that generates power using the temperature difference between surface water and deep water. This study analyzes the thermodynamic efficiency of the cycle, which strongly depends on the working fluid and the cycle configuration. Cycles studied included the classical simple Rankine cycle, Rankine cycles with an open feedwater heater and an integrated regenerator, as well as the Kalina cycle. Nine kinds of simple refrigerants and three kinds of mixed refrigerants were investigated as the working fluids in this study. Pinch-point analysis that set a constant pinch-point temperature difference was applied in the performance analysis of the cycle. Results showed that thermodynamic efficiency was best when RE245fa2 was used as the working fluid with the simple Rankine cycle, the Rankine cycles with an open feedwater heater and an integrated regenerator, and when the mixing ratio of $NH_3/H_2O$ was 0.9:0.1 in the Kalina cycle. If the Rankine cycles with an open feedwater heater, an integrated regenerator, and the Kalina cycle were used for ocean thermal energy conversion, efficiency increases could be expected to be approximately 2.0%, 1.0%, and 10.0%, respectively, compared to the simple Rankine cycle.

Analysis of Design and Part Load Performance of Micro Gas Turbine/Organic Rankine Cycle Combined Systems

  • Lee, Joon-Hee;Kim, Tong-Seop
    • Journal of Mechanical Science and Technology
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    • v.20 no.9
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    • pp.1502-1513
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    • 2006
  • This study analyzes the design and part load performance of a power generation system combining a micro gas turbine (MGT) and an organic Rankine cycle (ORC). Design performances of cycles adopting several different organic fluids are analyzed and compared with performance of the steam based cycle. All of the organic fluids recover greater MGT exhaust heat than the steam cycle (much lower stack temperature), but their bottoming cycle efficiencies are lower. R123 provides higher combined cycle efficiency than steam does. The efficiencies of the combined cycle with organic fluids are maximized when the turbine exhaust heat of the MGT is fully recovered at the MGT recuperator, whereas the efficiency of the combined cycle with steam shows an almost reverse trend. Since organic fluids have much higher density than steam, they allow more compact systems. The efficiency of the combined cycle, based on a MGT with 30 percent efficiency, can reach almost 40 percent. hlso, the part load operation of the combined system is analyzed. Two representative power control methods are considered and their performances are compared. The variable speed control of the MGT exhibits far better combined cycle part load efficiency than the fuel only control despite slightly lower bottoming cycle performance.

Comparative Exergy Analysis of Kalina and Organic Rankine Cycles for Conversion of Low-Grade Heat Source (저등급 열원의 변환을 위한 칼리나 사이클과 유기 랭킨 사이클의 엑서지 성능의 비교 해석)

  • KIM, KYOUNG HOON;JUNG, YOUNG GUAN;KO, HYUNG JONG
    • Transactions of the Korean hydrogen and new energy society
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    • v.31 no.1
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    • pp.105-111
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    • 2020
  • The organic Rankine cycle (ORC) and the Kalina cycle system (KCS) are being considered as the most feasible and promising ways to recover the low-grade finite heat sources. This paper presents a comparative exergetical performance analysis for ORC and Kalina cycle using ammonia-water mixture as the working fluid for the recovery of low-grade heat. Effects of the system parameters such as working fluid selection, turbine inlet pressure, and mass fraction of ammonia on the exergetical performance are parametrically investigated. KCS gives lower lower exergy destruction ratio at evaporator and higher second-law efficiency than ORC. The maximum exergy efficiency of ORC is higher than KCS.

Thermodynamic Performance Characteristics of Transcritical Organic Rankine Cycle Depending on Source Temperature and Working Fluid (열원온도와 작동유체에 따른 초월임계 유기랭킨사이클의 열역학적 성능 특성)

  • Kim, Kyoung Hoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.11
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    • pp.699-707
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    • 2017
  • This study presents a comparative thermodynamic analysis of subcritical and transcritical organic Rankine cycles for the recovery of low-temperature heat sources considering nine substances as the working fluids. The effects of the turbine inlet pressure, source temperature, and working fluid on system performance were all investigated with respect to metrics such as the temperature distribution of the fluids and pinch point in the heat exchanger, mass flow rate, and net power production, as well as the thermal efficiency. Results show that as the turbine inlet pressure increases from the subcritical to the supercritical range, the mismatch between hot and cold streams in the heat exchanger decreases, and the net power production and thermal efficiency increase; however, the turbine size per unit power production decreases.

Thermodynamic Efficiencies of Organic Rankine Cycles with a Feed Liquid Heater or Regenerator (급액가열기, 재생기를 적용한 유기랭킨사이클(ORC)의 열역학적 효율에 관한 해석적 연구)

  • Park, Chang-Yong;Hong, Woong-Ki;Kim, Jung-Min
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.10
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    • pp.662-669
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    • 2011
  • A numerical study was performed for thermodynamic efficiencies of a basic ORC (Organic Rankine Cycle), ORC with a FLH (Feed Liquid Heater), and ORC with a regenerator. The efficiencies of the basic ORC were higher in the order of R113, R123, R245ca, and R245fa for its working fluids. It was confirmed that an optimal FLH pressure existed to maximize efficiency of the ORC with a FLH. A correlation was developed to predict the optimal FLH pressure as a function of evaporation and condensation pressure and its average absolute deviation was 0.505%. The efficiency enhancement of the basic ORC with a FLH was higher than that with a regenerator. It was presented that the basic ORC efficiency could be improved more than 10% by a FLH with $30^{\circ}C$ condensation and over $110^{\circ}C$ evaporation temperatures.

Enhancement of MCFC System Performance by Adding Bottoming Cycles (하부 사이클 추가에 의한 MCFC 시스템의 성능향상)

  • Ji, Seung-Won;Park, Sung-Ku;Kim, Tong-Seop
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.10
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    • pp.907-916
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    • 2010
  • Integration of various bottoming cycles such as the gas turbine (GT) cycle, organic Rankine cycle, and oxy-fuel combustion cycle with an molten carbonate fuel cell (MCFC) power-generation system was analyzed, and the performance of the power-generation system in the three cases were compared. Parametric analysis of the three different integrated systems was carried out under conditions corresponding to the practical use and operation of MCFC, and the optimal design condition for each system was derived. The MCFC/oxy-combustion system exhibited the greatest power upgrade from the MCFC-only system, while the MCFC/GT system showed the greatest efficiency enhancement.

Performance Analysis of Direct Expansion and Organic Rankine Cycle for a LNG Cold Power Generation System (LNG냉열발전시스템에 있어서 직접팽창 및 유기랭킨사이클의 운전성능평가)

  • Cho, Eun-Bi;Jeong, Moon;Hwang, In-Ju;Kang, Choon-Hyoung
    • Transactions of the KSME C: Technology and Education
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    • v.3 no.1
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    • pp.55-62
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    • 2015
  • The liquefaction to produce LNG (liquefied natural gas) is the only practical way for mass transportation of natural gas across oceans, which accompanies considerable energy consumption in LNG plants. Power generation is one of the effective utilization ways of LNG cold energy which evolves during the vaporization process of LNG with sea water. In this work, performance analysis of two cold energy generation processes, direct expansion and organic Rankine cycles, were carried out by using Aspen HYSYS simulation. The results show that the performance of the organic Rankine cycle is superior to the direct expansion.