• 제목/요약/키워드: Amount of Heat

검색결과 2,361건 처리시간 0.032초

SrTiO3GBL Capacitor의 유전성에 대한 2차 열처리 조건의 효과 (Effect of the Second Heat Treatment Condition on the Dielectric Properties of SrTiO3GBL Capacitor)

  • 윤기현;안일석;이남양;오명환
    • 한국세라믹학회지
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    • 제26권3호
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    • pp.297-304
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    • 1989
  • The dielectric properties of SrTiO3 GBL Capacitor have been investigaetd as a function of the second heat treatment time and the amount of Ta. The grain size of semiconductive SrTiO3 after sintering at 1,46$0^{\circ}C$ for 4 hours in N2/H2 atmosphere increased as the amount of Ta increased, and then decreased as the amount of Ta exceed 0.01 mole. Also, the dielectric constant after the second heat treatment showed the same tendency. When the semiconductive SrTiO2 was second heat treated at 1,10$0^{\circ}C$ in air with varying time, the dielectric constant increased as the second heat treatment time increased up to 60 minutes, and then decreased as the time became longer than 60 minutes.

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가습연소 폐열회수 보일러의 물분사 설계모델 구축에 관한 연구 (Establishing the Models for Optimized Design of Water Injection in Boilers with Waste-heat-recovery System)

  • 신재훈;문석수
    • 한국분무공학회지
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    • 제26권2호
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    • pp.96-103
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    • 2021
  • In order to improve the overall efficiency and meet the emission regulations of boiler systems, the heat exchanging methods between inlet air and exhaust gas have been used in boiler systems, named as the waste-heat-recovery condensing boiler. Recently, to further improve the overall efficiency and to reduce the NOx emission simultaneously, the concept of the water injection into the inlet air is introduced. This study suggests the models for the optimized design parameters of water injection for waste-heat-recovery condensing boilers and performs the analysis regarding the water injection amount and droplet sizes for the optimized water injection. At first, the required amount of the water injection was estimated based on the 1st law of thermodynamics under the assumption of complete evaporation of the injected water. The result showed that the higher the inlet air and exhaust gas temperature into the heat exchanger, the larger the amount of injected water is needed. Then two droplet evaporation models were proposed to analyze the required droplet size of water injection for full evaporation of injected water: one is the evaporation model of droplet in the inlet air and the other is that on the wall of heat exchanger. Based on the results of two models, the maximum allowable droplet sizes of water injection were estimated in various boiler operating conditions with respect to the residence time of the inlet air in the heat exchanger.

중온 태양열 축열조용 히트파이프의 작동액체 충전량이 열성능에 미치는 영향 (The Effect of Working Fluid Charge on the Performance of a Heat Pipe for Medium-temperature Solar Thermal Storage System)

  • 박민규;부준홍
    • 한국태양에너지학회:학술대회논문집
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    • 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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    • pp.68-73
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    • 2011
  • An experimental study was conducted to investigate the thermal performance of a medium-temperature heat pipe against the charge amount of working fluid. The container and the wick of the heat pipe were made of stainless steel and the working fluid was Dowtherm-A for medium-temperature applications around $250^{\circ}C$. The diameter and length of the heat pipe were 25.4 mm and 1 m, respectively. The maximum thermal load was 1 kW and the working fluid charge ratio varied from 372% to 420%. The results showed that the thermal resistance ranged from 0.12 to $250^{\circ}C/W$ and the effective thermal conductance ranged from 7,703 to $8,898 W/m{\cdot}K$. Dry-out occurred for the heat pipe with 372% fill-charge at the heat load of 950 W, while the other heat pipes with higher charge amount did not encounter dry-out up to 1060 W.

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막비등 영역에서 액적-벽면 충돌 시 충돌각도가 열전달에 미치는 영향에 관한 실험적 연구 (Experimental Study of Collision Angle Effects on Heat Transfer During Droplet-wall Collision in Film Boiling Regime)

  • 박준석;김형대
    • 한국분무공학회지
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    • 제22권3호
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    • pp.129-136
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    • 2017
  • Effects of collision angle on heat transfer characteristics of a liquid droplet impinging on a heated wall above the Leidenfrost point temperature were experimentally investigated. The heated wall and droplet temperatures were $506^{\circ}C$ and $100^{\circ}C$, respectively, and the impact angle varied from $20^{\circ}$ to $90^{\circ}$ while the normal collision velocity was constant at 0.27 m/s. The droplet collision behaviors and the surface temperature distribution were measured using synchronized high-speed video and infrared cameras. The major physical parameters influencing upon droplet-wall collision heat transfer, such as residence time, wall heat flux, effective heat transfer area, heat transfer amount, were analyzed. It was found at the constant normal collision velocity that the residence time, wall heat flux and effective heat transfer area were hardly not changed, resulting in the almost constant heat transfer amount.

Sensitivity Studies on Thermal Margin of Reactor Vessel Lower Head During a Core Melt Accident

  • Kim, Chan-Soo;Kune Y. Suh
    • Nuclear Engineering and Technology
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    • 제32권4호
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    • pp.379-394
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    • 2000
  • As an in-vessel retention (IVR) design concept in coping with a severe accident in the nuclear power plant during which time a considerable amount of core material may melt, external cooling of the reactor vessel has been suggested to protect the lower head from overheating due to relocated material from the core. The efficiency of the ex-vessel management may be estimated by the thermal margin defined as the ratio of the critical heat flux (CHF)to the actual heat flux from the reactor vessel. Principal factors affecting the thermal margin calculation are the amount of heat to be transferred downward from the molten pool, variation of heat flux with the angular position, and the amount of removable heat by external cooling In this paper a thorough literature survey is made and relevant models and correlations are critically reviewed and applied in terms of their capabilities and uncertainties in estimating the thermal margin to potential failure of the vessel on account of the CHF Results of the thermal margin calculation are statistically treated and the associated uncertainties are quantitatively evaluated to shed light on the issues requiring further attention and study in the near term. Our results indicated a higher thermal margin at the bottom than at the top of the vessel accounting for the natural convection within the hemispherical molten debris pool in the lower plenum. The information obtained from this study will serve as the backbone in identifying the maximum heat removal capability and limitations of the IVR technology called the Cerium Attack Syndrome Immunization Structures (COASISO) being developed for next generation reactors.

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An Experimental Study on the Defrosting Behavior of a Fin-Tube Heat Exchanger

  • Lee, Kwan-Soo;Jhee, Sung
    • International Journal of Air-Conditioning and Refrigeration
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    • 제7권
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    • pp.101-111
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    • 1999
  • The effect of various conditions of frosting and defrosting on the defrosting behavior of a fin-tube heat exchanger has been examined experimentally. An electric heater is used for defrosting in a fin-tube heat exchanger. There are several local maxima in the water draining rate. The amount of residual water on the heat exchanger after completion of defrosting is kept constant due to surface tension on the heat exchanger. Without considering degradation of the thermal performance due to the frosting, the defrosting efficiency is improved with increasing amount of frost irrespective of the frosting condition. The defrosting behavior is affected by frosting density as well as frost accumulation, both of which vary with the experimental operating conditions. The heat loss to the surrounding air decreases, and melting and defrosting efficiencies show high values with decreasing heat input.

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열원이 부착된 수평 평판에서 복합 열전달에 관한 연구 (A Study on the Conjugate Heat Transfer from Horizontal Plate with Protruding Heat Source)

  • 김병철;주동인
    • 설비공학논문집
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    • 제14권6호
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    • pp.512-518
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    • 2002
  • The real chip and similarity model were used to investigate the thermal behavior and velocity distribution of air from the heat source with the location and the amount of heat experimentally and numerically, and compared. The heat generated in the block is not cooled by convection and show the high temperature by the stagnation of heat flow. After maintaining the high temperature of block by the natural convection, the sudden drop of temperature with the air flow was shown in the channel but the decreasing rate was small with the time. The inward block was effected by infinitesimal air flow generated between block and channel and outward block was effected by the entry condition.

중간기 열원수 온도에 따른 만액식 해수냉각시스템의 성능 특성 (Performance Characteristics of Flooded Type Evaporator for Seawater Cooling System with Heat Source Temperature of Mid-year)

  • 윤정인;손창효;이정목;강인호
    • 동력기계공학회지
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    • 제21권2호
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    • pp.64-69
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    • 2017
  • The purpose of this study is to investigate the performance characteristics of seawater cooling system for a fishing vessel. The circulation amount of refrigerant, condensation capacity, evaporation capacity, compression work and coefficient of performance(COP) were analyzed as the heat source temperature changed. The experimental setup consisted of an open-type compressor, a shell&tube type condenser, an evaporator and an expansion valve. The heat source was controlled by a constant temperature chamber. The main results of this study are summarized as follows. The condensation capacity increased with increasing heat source temperature, and it was confirmed that the effect of circulating amount of refrigerant was dominant. The amount of heat for vaporization was almost constant even though the temperature of the heat source increased. On the other hand, the compression power was increased. This is because the compression ratio increases as the condensation pressure, the enthalpy difference between inlet and outlet, the amount of circulating refrigerant increases. The performance coefficient of this system showed a tendency decreasing with increasing heat source temperature. Therefore, the basic data of the seawater cooling system for the maintenance of the catch line of the shore fishing boats was acquired through this study, and it is considered that it will be sufficient for the actual design.

요철형상의 CFD 해석을 통한 대용량 로타형 폐열회수열교환기 성능에 관한 연구 (Research on Performance of Large Rotor-type Heat Recovery Exchanger using CFD Analysis on Surface Corrugation)

  • 김동규;하병용;김근오;금종수;정석권
    • 설비공학논문집
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    • 제24권12호
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    • pp.875-880
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    • 2012
  • The field of the large volume heat exchanger for wasted heat recovery ventilation system is being expanded enormously seeing as the fact that the quantity of reducing energies are huge due to the large volume heat exchanger for wasted heat recovery system at large buildings and factories, which consume large amount of energies while it has been arising huge amount of losses in Korea because of the lack of technology. To develop large volume waste heat recovery heat exchanger, rotor type heat exchanger was simulated for the surface corrugation. Based on the simulation results produced $30,000m^3/h$ grade waste heat recovery, heat exchanger was performed for the actual experiment. In addition, performance tests exceed the capacity of a large waste heat recovery heat exchanger performance test methods proposed.

물분사 폐열회수 보일러의 효용성에 대한 실험적 검증 (Experimental Validation on Performance of Waste-heat-recovery Boiler with Water Injection)

  • 신재훈;박태준;조현석;유준상;문석수;이창언
    • 한국분무공학회지
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    • 제28권1호
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    • pp.43-48
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    • 2023
  • The waste-heat-recovery boiler with water spray (HR-B/WS) applies the heat exchange between the inlet air and exhaust gas with the water spray into the inlet air. The evaporation of water in the inlet air promotes heat recovery from the exhaust gas so that thermal efficiency can be improved by the enhanced condensing effect. The NOx emission can also be reduced by lowering the flame temperature due to the dilution effect of the water. In this study, the validity of this concept is examined by the practical boiler test performed with a 24 kW condensing boiler under the full load condition according to the water injection amount. The theoretical amount of water injection is calculated under the assumption of full evaporation of the sprayed water, which is calculated as 50 g/min. Since the injected water cannot evaporate fully in the actual system, the maximum water spray amount is set as 100 g/min. The results showed that the water injection can increase the thermal efficiency up to 95.59% and reduce NOx and CO emissions simultaneously to 8.9 ppm and 35 ppm at 0% of O2. Although the heat energy loss increased due to the unevaporated water, the increase in water injection amount caused higher thermal efficiency due to the increased amount of the evaporated water.