• Title/Summary/Keyword: Low Temperature Heat Source

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The World's Thinnest Graphene Light Source (세상에서 가장 얇은 그래핀 발광 소자)

  • Kim, Young Duck
    • Vacuum Magazine
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    • v.4 no.3
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    • pp.16-20
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    • 2017
  • Graphene has emerged as a promising material for optoelectronic applications including as ultrafast and broadband photodetector, optical modulator, and nonlinear photonic devices. Graphene based devices have shown the feasibility of ultrafast signal processing for required for photonic integrated circuits. However, on-chip monolithic nanoscale light source has remained challenges. Graphene's high current density, thermal stability, low heat capacity and non-equilibrium of electron and lattice temperature properties suggest that graphene as promising thermal light source. Early efforts showed infrared thermal radiation from substrate supported graphene device, with temperature limited due to significant cooling to substrate. The recent demonstration of bright visible light emission from suspended graphene achieve temperature up to ~3000 K and increase efficiency by reducing the heat dissipation and electron scattering. The world's thinnest graphene light source provides a promising path for on-chip light source for optical communication and next-generation display module.

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.

Analysis of Efficiency of Solar Hot Water System based on Energy Demand (에너지 수요처의 사용특성에 따른 태양열 급탕시스템의 효율분석)

  • Jun, Yong-Joon;Park, Kyung-Soon
    • Journal of the Korean Solar Energy Society
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    • v.37 no.5
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    • pp.39-47
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    • 2017
  • In a hot water system using solar energy, solar heat is not simply collected by the heat collecting plate, but by heat exchange between the solar collector (flat or vacuum type) and the hot water storage tank. Therefore, the amount of collected solar energy depends on the hot water usage patterns that determine the temperature of the thermal storage tank. Also, if the temperature of the hot water stored in the storage tank exceeds the dangerous temperature during the summer, the heat must be released for safety. If the temperature of the hot water in the storage tank is low, it is necessary to heat by the auxiliary heat source. In this study, three buildings are defined as hotel, swimming pool, and school facilities. And we calculated the released heat energy, auxiliary heat source, and pure storage heat energy based on different hot water usage patterns and installation angle of the solar collectors.

Thermodynamic Performance Analysis of Ammonia-Water Power Generation System Using Low-temperature Heat Source and Liquefied Natural Gas Cold Energy (저온 열원과 LNG 냉열을 이용하는 암모니아-물 동력 사이클의 열역학적 성능 해석)

  • Kim, Kyoung Hoon;Kim, Kyung Chun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.6
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    • pp.483-491
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    • 2014
  • In this study, a thermodynamic analysis was carried out for a combined power generation system using a low-temperature heat source in the form of sensitive energy and liquefied natural gas cold energy. An ammonia-water mixture, which is a zeotropic mixture, was used as the working fluid, and systems with and without a regenerator were comparatively analyzed. The effects of the mass fraction of ammonia and the condensation temperature of the working fluid on the system variables, including the net work production, exergy destruction, and thermal and exergy efficiencies, are analyzed and discussed. The results show that the performance characteristics of the system varied sensitively with the ammonia concentration or condensation temperature of the working fluid. The system without regeneration was found to be better in relation to the net work per unit mass of the source fluid, whereas the system with regeneration was better in relation to the thermal or exergy efficiency.

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

  • Kim, Kyoung-Hoon;Han, Chul-Ho;Kim, Gi-Man
    • Journal of the Korean Solar Energy Society
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    • v.31 no.3
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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 $300^{\circ}C$.

An Experimental Study on Applying Heat Pump System to Facility Horticulture House (히트펌프 시스템의 시설원예 적용에 관한 실험적 연구)

  • Kim, Jae-Dol
    • Journal of Power System Engineering
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    • v.17 no.6
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    • pp.88-94
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    • 2013
  • As the results of analysis that are applying a heat pump using underground water as heat source of facility horticulture house, temperature change in house, growth of cultivated plants and the crop characteristic, the conclusion can be acquired as follows. It was possible to maintain the chamber temperature through operating heat pump with setting goal temperature at $16^{\circ}C$ and temperature variation at ${\pm}3^{\circ}C$. And cooling and heating coefficient of performance in heat pump system are different from setting room temperature and operation condition of equipment, totally in case that the setting temperature in house is low, the coefficient of performance and the in case that temperature departure is low. In case that the house does not heated, the result of the growth characteristic of cucumber planted last 50days is that cucumber grown in house equipped with heat pump is the most favorable growth characteristic due to maintaining a constant room temperature. After 90 days, the quantity and weight cucumber harvested in each house are averagely 9.8%, 13.1% increase and more heavy weight respectively. So it is researched that crop characteristic is superior.

Control of Heat Pump for Low Emission Diesel Engine (저공해 중소형 디젤차량 히트펌프 제어)

  • Park, Byung-Duck;Lee, Won-Suk;Won, Jong-Phil;Kwon, Sun-Ik
    • Journal of the Korean Society of Industry Convergence
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    • v.5 no.4
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    • pp.379-384
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    • 2002
  • As automotive diesel engines adopt the direct injection method for a lower level of the exhaust emission and a higher fuel efficiency, the maximum temperature of engine coolant decreases. Consequently, the total available heat source from the engine coolant decreases over 35%. However, the heating source of air-conditioning system in automobiles depends on the hot engine coolant completely, so that it is nearly impossible to control air conditioning in heating season. Therefore, the present study has been carried out to develop the air conditioning system for the high efficient heat pump type using the HFC-134a. Especially, the air conditioning system of heating has been developed at a beginning stage, when it has low heat source from small and medium sized diesel recreation vehicles. To develop a control logic system for air conditioning system which is a heat pump type with a heat recovery exchanger, its cycle characteristics has been investigated according to the opening of LEV at a bench system.

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A study on the application Heat Pump to Rolling Stock Air conditioner (히트펌프식 냉난방장치의 철도차량 적용에 관한 연구)

  • Kweon, Tae-Kyun;Song, Young-Jeong;Jeong, Gwang-Moo
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.1689-1696
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    • 2008
  • Heat pumps transfer heat by circulating a substance called a refrigerant through a cycle of evaporation and condensation. But Heat pumps system by only using heat-source is not efficient. Because the mean temperature of North Korean winter season is low, economy of air heat-source heat pump descend. This paper is practiced the simulation on evaluation criteria for Heat pump heating and cooling systems to Rolling Stock. Efficiency of the heat pump in order improving from certainly the development of the technique will be able to prevent a freezing actual condition must proceed. As a result, Below $-10^{\circ}C$ used heating and cooling systems of heat pump format even in cold winter season and is serviceable confirmed with heat source supply circle of the Rolling Stock.

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Performance Analysis and Prior-Treatment of Heat Pump System with Low-Temperature Water Heat Source (저온수열원이용 열펌프시스템의 전처리 및 성능분석)

  • Park, Seong-Ryong;Chang, Ki-Chang;Lee, Sang-Nam;Ra, Ho-Sang;Park, Jun-Tack
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.258-263
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    • 2000
  • River water is higher in temperature than the surrounding environment during the winter. It is highly suitable a heat source for heat pump system. Despite its suitability, however, it is not widely used, due to its fouling and corrosive nature in heat exchanger tubes of evaporator. It is designed prior-treatment system which come into direct contact with the river water, such as auto-seamer, ozone generator for bactericidal test and auto-cleaning system. And it is analyzed treatment effects for its operation. It is designed two-stage compression heat pump system using R-134a with heating load 35.16kW, ad analyzed its performance. As a result it is obtained 3.08 COP when mid-point pressure is 1,200kPa, and bypass ratio of flowing refreigerant to high-stage compressor is 25.1%

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Study on the Simulation of Heat Pump Heating and Cooling Systems to Resident Building (숙박업소 건물의 히트펌프 냉난방 시스템 적용을 위한 시뮬레이션 연구)

  • Choi, Young-Don;Han, Seong-Ho;Cho, Sung-Hwan;Kim, Ju-Sung;Um, Chul-Jun
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.915-920
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    • 2006
  • Recently available heat pump system by using air heat-source is not efficient. Because the mean temperature of korean winter season is low, economy of air heat-source heat pump descend, and COP is below 3.0. This paper was practiced the simulation on evaluation criteria for heat pump heating and cooling systems to resident building. As a result, heating and cooling composition heat pump system apply to the building needed to be provided heat source for 24 hours.

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