• Title/Summary/Keyword: Maximum rate of heat output

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Maximum Power Output Cycle of Heat Engines (열기관의 최대출력 사이클)

  • 김수연;정평석;노승탁;김효경
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.3
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    • pp.694-701
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    • 1990
  • The cycle of heat engine which produces the maximum power output is constructed when heat sources are finitely constant, and the maximum power as a thermodynamic limit of the engine, is obtained. The characteristics of the maximum power cycle are as follows, which represent the operation conditions and design conditions of the heat engine to produce the maximum power output. In heat exchangers, the temperature profiles of the heat source and the working fluid have the same functional formula and the ratio of the working fluid temperature to the heat source temperature is constant. When heat capacity flow rates(product of the specific heat and the mass flow rate) of the working fluid as well as the heat source are constant, the values of those of working fluid exist between those of two heat sources. The relation of the temperature and the heat capacity flow rate is established without the states of the heat sources and the capacities of heat exchangers, which is ( $T_{h}$/ $T_{H}$)( $C_{h}$/ $C_{H}$)=( $T_{1}$/ $T_{L}$)( $c_{1}$/ $c_{L}$)=1. The capacity of the heat exchanger of hot side is equal to that of cold side regardless of the states of the heat sources and the total capacities of heat exchangers.hangers.ers.

A Suggestion of Penalty Cost Appropriation Methodology for Performance Acceptance Test of CGAM Cogeneration - Part II (CGAM 열병합발전의 인수성능에 대한 페널티 비용 책정 방법론 제안 - Part II)

  • Kim, Deok-Jin
    • Plant Journal
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    • v.12 no.4
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    • pp.32-36
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    • 2016
  • In this study, a penalty cost appropriation methodology for CGAM performance acceptance test was suggested. As the result of CGAM performance test, there were 0.31% decreases in electricity output, 0.39% decreases in heat rate on electricity output, 0.31% increases in heat output, and 0.23% increases in heat rate on heat output. As the result of penalty cost appropriation for above performance, the penalty cost was calculated as -$20,837 in electricity output, -$25,930 in heat rate on electricity output, +$10,340 in heat output, and +$7,715 in heat rate on heat output. Each penalty is appropriated as above fore kinds, however the total penalty should be determined as how to combine above fore kinds of penalty. In our calculation, the minimum total penalty was -$18,215 and the maximum total penalty was -$46,767. The methodology of total penalty appropriation should be determined in the contract between ordering organization and construction firm, and we can understand that it is very important.

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Performance Measurements of A Stirling Engine for Household Micro Combined Heat and Power with Heat Source Temperatures and Cooling Flow Rates (가정용 열병합 발전을 위한 스털링 엔진의 열원 온도 및 냉각수 유량에 따른 성능 실험)

  • Sim, Kyuho;Kim, Mingi;Lee, Yoon-Pyo;Jang, Seon-Jun
    • The KSFM Journal of Fluid Machinery
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    • v.18 no.1
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    • pp.37-43
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    • 2015
  • A Beta-type Stirling engine is developed and tested on the operation stability and cycle performance. The flow rate for cooling water ranges from 300 to 1500 ml/min, while the temperature of heat source changes from 300 to $500^{\circ}C$. The internal pressure, working temperatures, and operation speed are measured and the engine performance is estimated from them. In the experiment, the rise in the temperature of heat source reduces internal pressure but increases operation speed, and overall, enhances the power output. The faster coolant flow rate contributes to the high temperature limit for stable operation, the cycle efficiency due to the alleviated thermal expansion of power piston, and the heat input to the engine, respectively. The experimental Stirling engine showed the maximum power output of 12.1 W and the cycle efficiency of 3.0 % when the cooling flow is 900 ml/min and the heat source temperature is $500^{\circ}C$.

A Study for the Output Increament of the Hydrogen Gas Turbine with Water Injection (물분사 수소 가스터빈의 출력 향상을 위한 연구)

  • Jung, K.S.;Oh, B.S.
    • Transactions of the Korean hydrogen and new energy society
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    • v.9 no.1
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    • pp.1-7
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    • 1998
  • Most of today's energy supply is obtained from fossil fuels. Despite of high energy density, higher store efficiency and long mileage, fossil fuels cause environmental pollution and their reserves are limited. In this study pure hydrogen gas and oxygen gas are burned without the emission of pollution. A gas turbine is used to obtain power. Water is injected into a combustor, which prevents overheating and recovers cooling heat. Excessively supplied water is recirculated. With variation of mass flow rate and equivalence ratio, the affection of water injection rate and the temperature of injected water on efficiency and power are experimented. Injected water gets cooling heat, is expanded from liquid to vapor and raises the thermal efficiency. It is enable to determine the rate of water injection, which makes the maximum power. The increase of temperature of water injection raises the efficiency of the system.

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An Experimental Study on the Characteristics of Moxa Combustion in the Moxa Cone size - On the Pattern of Combustion temperature - (애주(艾炷)의 형태별(形態別) 연소(燃燒) 특성(特性)에 대한 연구(?究) - 연소온도(燃燒溫度)의 유형(類型)을 중심(中心)으로 -)

  • Park, Young-Bae;Kang, Sung-Keel;Kim, Chang-Hwan;Koh, Hyung-Kyun;Oh, Hwan-Sup;Huh, Wung
    • The Journal of Korean Medicine
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    • v.16 no.1 s.29
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    • pp.370-378
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    • 1995
  • In order to consider the clinical efficacy of moxa combustion, understand the quality and quantity of heat stimulation and get the basic data for the development of electric moxibustion apparatus, the pattern of combustion temperature was measured by size of moxa(small, medium, large and maximum size). The results were as follows. 1. The pattern of combustion temperature by moxa burning was classified into input period, consisting of preheating and heating periods, and output period, consisting of heat retaining and cooling periods, in all experimental groups. But it was difficult to observe the preheating period in small sized moxa. 2. It was inclined that the more moxa size was large, the more the heating and heat retaining periods were long and the maximum temperature was high. The characteristics of moxa combustion is primarily by the rate of combustion temperature, gradient temperature and duration of combustion, and their correlation among these factors and their clinical effects in practice.

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

  • Kim, Kyoung-Hoon;Han, Chul-Ho
    • Journal of the Korean Solar Energy Society
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    • v.31 no.1
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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 $180^{\circ}C$.

Mechanical Load Performance Measurements of a Low Temperature Differential Stirling Engine with Water-Sprayed Heat Transfer according to Supply Water Flow Rates and Temperatures (스프레이 열전달을 이용한 저온도차 스털링 엔진의 고온수 공급 유량 및 온도에 따른 기계 부하성능 실험)

  • Sim, Kyuho;Jeong, Min-Seong;Lee, Yoon-Pyo;Jang, Seon-Jun
    • The KSFM Journal of Fluid Machinery
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    • v.18 no.1
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    • pp.29-36
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    • 2015
  • Recently, Stirling engines are emerging as a key device for power conversion of renewable energy or waste energy. This study develops a LTDSE(Low Temperature Differential Stirling Engine) using a water spray for higher heat transfer and performs load performance tests for various flow rates and temperatures of hot water spray for variable engine loads emulated by a mechanical friction device. Internal temperature and pressure, working frequency and inlet and outlet temperature of the supply water are measured. As a result, the increases in flow rate and temperature of hot water respectively enhance the power output, efficiency and the working frequency, while the increasing engine load leads to decreases in working frequency but increases in the pressure amplitude. Eventually, it is revealed there exists a maximum shaft power of the test engine.

Pulsed-laser-diode Intermittently Pumped 2-㎛ Acousto-optic Q-switched Tm:LuAG Laser

  • Wen, Ya;Jiang, Yan;Zheng, Hao;Zhang, Hongliang;Wang, Chao;Wu, Chunting;Jin, Guangyong
    • Current Optics and Photonics
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    • v.4 no.3
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    • pp.238-246
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    • 2020
  • The heat distribution in crystals in a 2-㎛ acousto-optic Q-switched Tm:LuAG laser pumped by pulsed-laser-diode (pulsed-LD) intermittent-pumping technology was analyzed using COMSOL software. The thermal lensing effect of the Tm:LuAG crystal can be mitigated by pulsed-LD intermittent-pumping techniques. An experimental setup using this kind of approach achieved maximum output energy of 8.31 mJ, minimum pulse width of 101.9 ns, and highest peak power of 81.55 kW, reached at a Q-switched repetition rate of 200 Hz. It offers significant improvement of performance of the output laser beam, compared to pulsed-LD double-ended pumping technology at the same repetition rate.

Simulation of an Absorption Power Cycle for Maximizing the Power Output of Low-Temperature Geothermal Power Generation (저온 지열발전의 출력 극대화를 위한 흡수식 동력 사이클의 시뮬레이션)

  • Baik, Young-Jin;Kim, Min-Sung;Chang, Ki-Chang;Lee, Young-Soo;Yoon, Hyung-Kee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.2
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    • pp.145-151
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    • 2010
  • In this study, an absorption power cycle, which can be used for a low-temperature heat source driven power cycle such as geothermal power generation, was investigated and optimized in terms of power by the simulation method. A steady-state simulation model was adopted to analyze and optimize its performance. Simulations were carried out for the given heat source and sink inlet temperatures, and the given flow rates were based on the typical power plant thermal-capacitance-rate ratio. The cycle performance was evaluated for two independent variables: the ammonia fraction at the separator inlet and the maximum cycle pressure. Results showed that the absorption power cycle can generate electricity up to about 14 kW per 1 kg/s of heat source when the heat source temperature, heat sink temperature, and thermal-capacitance-rate ratio are $100^{\circ}C$, $20^{\circ}C$, and 5, respectively.

THERMAL ANALYSIS OF THE DUAL CURED RESIN CEMENTS ACCORDING TO CURING CONDITION (중합조건에 따른 dual cured resin cement의 열분석적 연구)

  • Lee, In-Bog;Chung, Kwan-Hee;Um, Chung-Moon
    • Restorative Dentistry and Endodontics
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    • v.24 no.2
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    • pp.265-285
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    • 1999
  • The purposes of this investigation were to observe the reaction kinetics of five commercial dual cured resin cements (Bistite, Dual, Scotchbond, Duolink and Duo) when cured under varying thicknesses of porcelain inlays by chemical or light activation and to evaluate the effect of the porcelain disc on the rate of polymerization of dual cured resin cement during light exposure by using thermal analysis. Thermogravimetric analysis(TGA) was used to evaluate the weight change as a function of temperature during a thermal program from $25{\sim}800^{\circ}C$ at rate of $10^{\circ}C$/min and to measure inorganic filler weight %. Differential scanning calorimetry(DSC) was used to evaluate the heat of cure(${\Delta}H$), maximum rate of heat output and peak heat flow time in dual cured resin cement systems when the polymerization reaction occured by chemical cure only or by light exposure through 0mm, 1mm, 2mm and 4mm thickness of porcelain discs. In 4mm thickness of porcelain disc, the exposure time was varied from 40s to 60s to investigate the effect of the exposure time on polymerization reaction. To investigate the effect on the setting of dual cured resin cements of absorption of polymerizing light by porcelain materials used as inlays and onlays, the change of the intensity of the light attenuated by 1mm, 2mm and 4mm thickness of porcelain discs was measured using curing radiometer. The results were as follows 1. The heat of cure of resin cements was 34~60J/gm and significant differences were observed between brands (P<0.001). Inverse relationship was present between the heat of reaction and filler weight % the heat of cure decreased with increasing filler content (R=-0.967). The heat of reaction by light cure was greater than by chemical cure in Bistite, Scotchbond and Duolink(P<0.05), but there was no statistically significant difference in Dual and Duo(P>0.05). 2. The polymerization rate of chemical cure and light cure of five commercially available dual cured resin cements was found to vary greatly with brand. Setting time based on peak heat flow time was shortest in Duo during chemical cure, and shortest in Dual during light cure. Cure speed by light exposure was 5~20 times faster than by chemical cure in dual cured resin cements. The dual cured resin cements differed markedly in the ratio of light and chemical activated catalysts. 3. The peak heat flow time increased by 1.51, 1.87, and 3.24 times as light cure was done through 1mm, 2mm and 4mm thick porcelain discs. Exposure times recommended by the manufacturers were insufficient to compensate for the attenuation of light by the 4mm thick porcelain disc. 4. A strong inverse relationship was observed between peak heat flow and peak time in chemical cure(R=0.951), and a strong positive correlations hip was observed between peak heat flow and the heat of cure in light cure(R=0.928). There was no correlationship present between filler weight % or heat of cure and peak time. 5. The thermal decomposition of resin cements occured primarily between $300^{\circ}C$ and $480^{\circ}C$ with maximum decomposition rates at $335^{\circ}C$ and $440^{\circ}C$.

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