• 제목/요약/키워드: Low-temperature energy source

검색결과 283건 처리시간 0.028초

저온 열원으로부터 최대 동력을 생산하기 위한 유기랭킨사이클(ORC)에 관한 연구 (Study on Organic Rankine Cycle (ORC) for Maximum Power Extraction from Low-Temperature Energy Source)

  • 김경훈;한철호;김기만
    • 한국태양에너지학회 논문집
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    • 제31권3호
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    • pp.73-79
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    • 2011
  • ORC(organic Rankine cycle) has potential of reducing consumption of fossil fuels and has many favorable characteristics to exploit low-temperature heat sources. This work analyzes performance of ORC with superheating using low-temperature energy sources in the form of sensible energy. Maximum mass flow rate of a working fluid relative to that of a source fluid is considerd to extract maximum power from the sources. Working fluids of R134a, $iC_4H_{10}$ and $C_6C_6$, and source temperatures of $120^{\circ}C$, $200^{\circ}C$ and $300^{\circ}C$ are considered in this work. Results show that for a fixed source temperature thermal efficiency increases with evaporating temperaure, however net work per unit mass of source fluid has a maximum with respect to the evaporating temperature in the range of low source temperature. Results also show that the maximum power extraction is possible with R134a for the source temperature of $120^{\circ}C$, with $iC_4H_{10}$ for $200^{\circ}C$, and with $C_6C_6$ for $300^{\circ}C$.

저온 열원 활용을 위한 암모니아-물 혼합물을 작동유체로 하는 칼리나 사이클의 성능 해석 (Performance Analysis of Kalina Cycle using Ammonia-Water Mixture as Working Fluid for Use of Low-Temperature Energy Source)

  • 김경훈;고형종;김세웅
    • 한국수소및신에너지학회논문집
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    • 제22권1호
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    • pp.109-117
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    • 2011
  • Since the thermal performance of cycles for use of low-temperature source is low if a pure working fluid is used, the cycles using ammonia-water binary mixture as a working fluid has attracted much attention over past two decades. Recently, several commercial power plants using Kalina cycles have been built and being operated successfully. In this work thermodynamic performance of Kalina cycles using ammonia-water mixture as a working fluid is investigated for the purpose of extracting maximum power from low-temperature energy source. Special attention is paid to the effect of system parameters such as concentration of ammonia and turbine inlet pressure on the characteristics of the system. Results show that the system performance is influenced sensitively by the ammonia concentration, and the role of the performance of heat exchangers is crucial.

저온 열원 활용을 위한 암모니아-물 재생 랭킨 사이클의 성능 해석 (Performance Analysis of Ammonia-Water Regenerative Rankine Cycles for Use of Low-Temperature Energy Source)

  • 김경훈;한철호
    • 한국태양에너지학회 논문집
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    • 제31권1호
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    • pp.15-22
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    • 2011
  • It is a great interest to convert more energy in the heat source into the power and to improve the efficiency of power generating processes. Since the efficiency of power generating processes becomes poorer as the temperature of the source decreases, to use an ammonia-water mixture instead of water as working fluid is a possible way to improve the efficiency of the system. In this work performance of ammonia-water regenerative Rankine cycle is investigated for the purpose of extracting maximum power from low-temperature waste heat in the form of sensible energy. Special attention is paid to the effect of system parameters such as mass fraction of ammonia and turbine inlet pressure on the characteristics of system. Results show that the power output increases with the mass fraction of ammonia in the mixture, however workable range of the mass fraction becomes narrower as turbine inlet pressure increases and is able to reach 16.5kW per unit mass flow rate of source air at $180^{\circ}C$.

저온열원 활용을 위한 암모니아-물 재생 랭킨사이클의 엑서지 해석 (Exergy Analysis of Regenerative Ammonia-Water Rankine Cycle for Use of Low-Temperature Heat Source)

  • 김경훈;고형종;김세웅
    • 한국수소및신에너지학회논문집
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    • 제23권1호
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    • pp.65-72
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    • 2012
  • Rankine cycle using ammonia-water mixture as a working fluid has attracted much attention, since it may be a very useful device to extract power from low-temperature heat source. In this work, the thermodynamic performance of regenerative ammonia-water Rankine cycle is thoroughly investigated based on the second law of thermodynamics and exergy analysis, when the energy source is low-temperature heat source in the form of sensible energy. In analyzing the power cycle, several key system parameters such as ammonia mass concentration in the mixture and turbine inlet pressure are studied to examine their effects on the system performance including exergy destructions or anergies of system components, efficiencies based on the first and second laws of thermodynamics. The results show that as the ammonia concentration increases, exergy exhaust increases but exergy destruction at the heat exchanger increases. The second-law efficiency has an optimum value with respect to the ammonia concentration.

캐스케이드 열펌프시스템의 운전 특성에 관한 연구 (A Study on the Operating Performance of a Cascade Heat Pump)

  • 장기창;백영진;나호상;김지영;이재훈
    • 한국지열·수열에너지학회논문집
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    • 제5권1호
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    • pp.7-11
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    • 2009
  • The purpose of this study is to investigate the performance of a water heat source cascade heat pump system R717(Ammonia) is used for a low-stage working fluid while R134a is for a high-stage. In order to gain a high temperature supply water in winter season, the system is designed to perform a cascade cycle. In this study, two experiments were carried out. One is a system starting test from the low load temperature of $10^{\circ}C$. The other is a system performance investigation over the R717 compressor capacity changes. Experimental results show that when it starts from the low load temperature, the suction temperature of the low-stage compressor is higher than that of a high-stage. The system performance increases when a water source temperature or a low-stage compressor rotational frequency goes higher.

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다수의 히트펌프로 구성된 냉난방시스템에서 하절기 히트펌프의 최적운전에 관한 연구 (A Study on Optimal Operation of Summer Season Cooling System with Numbers of Heat Pumps)

  • 신관우
    • 전기학회논문지P
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    • 제55권1호
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    • pp.35-40
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    • 2006
  • Heat-pump system has a special feature that provides heating operation in winter season and cooling operation in summer season with a single system. It also has a merit that absorbs and makes use of wastewater heat, terrestrial heat, and heat energy from the air. Because heat-pump system uses midnight electric power, it decreases power peak load and is very economical as a result. By using the property that energy source is converted to low temperature when losing the heat, high temperature energy source is used to provide heating water and low temperature energy source is used to provide cooling water simultaneously in summer season. This study made up a heat-pump system with 4 air heat sources and a water heat source and implemented the optimal operation algorithm that works with numbers of heat pumps to operate them efficiently. With the heat-pump system, we applied it to cooling and heating operation in summer season operation mode in a real building.

작동유체에 따른 유기랭킨사이클(ORC)의 열역학적 성능에 관한 연구 (Study of Working Fluids on Thermodynamic Performance of Organic Rankine Cycle (ORC))

  • 김경훈
    • 한국수소및신에너지학회논문집
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    • 제22권2호
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    • pp.223-231
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    • 2011
  • The thermal efficiency of energy-to-power conversion becomes uneconomically low when the temperature of heat source drops below $370^{\circ}C$. ORC (Organic Rankine Cycle) has attracted much attention in last few years due to its potential in reducing consumption of fossil fuels and relaxing environmental problems, and its favorable characteristics to exploit low-temperature heat sources. In this work thermodynamic performance of ORC using nine working fluids is comparatively assessed. Special attention is paid to the effect of system parameters such as turbine inlet temperature and pressure on the characteristics of the system such as volumetric flow rate and quality at turbine exit, latent heat, net work as well as thermal efficiency. Results show that in selection of working fluid it is required to consider various criteria of performance characteristics as well as the thermal efficiency. Results also show that the system efficiencies become same irrespective of kind of working fluid when the temperature of heat source decreases to low range.

저온 열원 및 LNG 냉열을 이용하는 복합 발전 사이클의 성능 해석 (Performance Analysis of a Combined Power Cycle Utilizing Low-Temperature Heat Source and LNG Cold Energy)

  • 김경훈;오재형;고형종
    • 한국수소및신에너지학회논문집
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    • 제23권4호
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    • pp.382-389
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    • 2012
  • Power generation cycle using ammonia-water mixture as working fluid has attracted much attention because of its ability to efficiently convert low-temperature heat source into useful work. If an ammonia-water power cycle is combined with a power cycle using liquefied natural gas (LNG), the conversion efficiency could be further improved owing to the cold energy of LNG at $-162^{\circ}C$. In this work parametric study is carried out on the thermodynamic performance of a power cycle consisted of an ammonia-water Rankine cycle as an upper cycle and a LNG cycle as a bottom cycle. As a driving energy the combined cycle utilizes a low-temperature heat source in the form of sensible heat. The effects on the system performance of the system parameters such as ammonia concentration ($x_b$), turbine 1 inlet pressure ($P_{H_1}$) and temperature ($T_{H_1}$), and condenser outlet temperature ($T_{L_1}$) are extensively investigated. Calculation results show that thermal efficiency increases with the increase of $P_{H_1}$, $T_{H_1}$ and the decrease of $T_{L_1}$, while its dependence on $x_b$ has a downward convex shape. The changes of net work generation with respect to $P_{H_1}$, $T_{H_1}$, $T_{L_1}$, and $x_b$ are roughly linear.

중온형 원통다관형 수증기 개질기의 부분단열 및 반경방향 분배 구조의 영향 (Partial Insulation and Heating Tubes Configuration of Shell and Tube Steam Reformer at Medium Temperature)

  • 박다인;유상석
    • 한국수소및신에너지학회논문집
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    • 제28권6호
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    • pp.618-626
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    • 2017
  • Conventional high temperature reformers are not suitable for hybrid fuel cell systems that use waste heat as a heat source. So, development of a low temperature type reformer is needed. However, the analysis was conducted in two ways to increase the thermal efficiency, because of low reforming rate due to the low heat source. First, it is a way to ger thermal gain from the outside through partial insulation. In the case of one heat source tube and several heat source tubes, we analyzed the effect of partial heat insulation in some cases. Second, we found the most efficient arrangement of the heat source tubes by changing the location of the heat source tubes. The interpretation was carred out using the COMSOL Mutiphysics program.

LNG 냉열을 이용하는 암모니아-물 복합 재생 동력 사이클의 성능 특성 (Performance Characteristics of a Combined Regenerative Ammonia-Water Based Power Generation Cycle Using LNG Cold Energy)

  • 김경훈;오재형;정영관
    • 한국수소및신에너지학회논문집
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    • 제24권6호
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    • pp.510-517
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    • 2013
  • The ammonia-water based power generation cycle utilizing liquefied natural gas (LNG) as its heat sink has attracted much attention, since the ammonia-water cycle has many thermodynamic advantages in conversion of low-grade heat source in the form of sensible energy and LNG has a great cold energy. In this paper, we carry out thermodynamic performance analysis of a combined power generation cycle which is consisted of an ammonia-water regenerative Rankine cycle and LNG power generation cycle. LNG is able to condense the ammonia-water mixture at a very low condensing temperature in a heat exchanger, which leads to an increased power output. Based on the thermodynamic models, the effects of the key parameters such as source temperature, ammonia concentration and turbine inlet pressure on the characteristics of system are throughly investigated. The results show that the thermodynamic performance of the ammonia-water power generation cycle can be improved by the LNG cold energy and there exist an optimum ammonia concentration to reach the maximum system net work production.