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Performance Characteristics of a Liquid-Metal Heat Pipe for igh-temperature Solar Thermal Devices Depending on the Operating Conditions (고온 태양열기기용 액체금속 히트파이프의 작동조건에 따른 성능 특성)

  • Park, Cheol-Min;Lee, Jung-Ryun;Boo, Joon-Hong;Kang, Yong-Heack
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.247-250
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    • 2009
  • Sodium heat pipe for high-temperature solar thermal application was manufactured and tested for transient and steady-state operations. Total length of the heat pipe was 650 mm and the outer diameter was 12.7 mm. Thermal performance was compared experimentally for two different cooling methods of the forced and the natural convection cooling in the heat pipe condenser. During the experiment, the maximum temperature was about 1300K, and different cooling methods were applied to the condenser region to charge the operating temperature. The effective thermal conductivity and the thermal resistance were investigated as a function of heat flux, heat transport length, and operating temperature.

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An Analysis for Predicting the Thermal Performance of Fin-Tube Heat Exchanger under Frosting Condition (착상시 핀-관 열교환기의 열적 성능 예측을 위한 해석)

  • Lee, T.H.;Lee, K.S.;Kim, W.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.8 no.2
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    • pp.299-306
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    • 1996
  • This work presents an analytical model, so called modified LMTD method, to predict the thermal performance of finned-tube heat exchanger under frosting conditions. In this model, the total heat transfer coefficient and effective thermal conductivity of the frost layer were defined as a function of frost surface temperature. The surface temperature of the frost layer formed on the heat exchanger was calculated through the analysis of the heat and mass transfer process in the air and frost layer. To examine the validity of this analytical model, the computed results from the present model, such as heat transfer rate, frost mass and thickness of frost, were compared with the ones of the expermental work and LMED method.

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A Numerical Analysis of Characteristics of Combined Heat Transfer in Laminar Layer Along Cylinderical Periphery by P-N Method (P-N 근사법을 이용한 원관주위 층류 경계층내 조합 열전달 전달 특성 해석)

  • 이종원;이창수
    • Journal of Advanced Marine Engineering and Technology
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    • v.19 no.2
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    • pp.10-19
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    • 1995
  • Heat trnasfer for absorbing and emitting media in laminar layer along the cylinders has been analyzed. Governing equation are transformed to local nonsimilarity equations by the dimensional analysis. The effects of the Stark number, Prandtl number, Optical radius and wall emissivity are mainly investigated. For the formal solution a numerical integration is performed and the results are compared with those obtained by P-1 and P-3 approximation. The results show that boundary layers consist of conduction-convection-radiation layer near the wall and convection-radiation layer far from the wall. As the Stark number of wall emissivity increases the local radiative heat flux is increased. The Pradtl number or curvature variations do not affect the radiative heat flux from the wall, but The Prandtl number or wall emissivity variations affect the conduction heat flux. Consequently the total heat flux from the wall are affected by the Prandtl number or wall emissivity variation.

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An Experimental Study on the Heat Transfer Characteristics of High-Temperature Cylindrical Heat Pipes (고온 원관형 히트파이프의 열전달 특성에 관한 실험 연구)

  • 박수용;부준홍
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.1
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    • pp.70-76
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    • 2004
  • High-temperature cylindrical sodium/stainless-steel heat pipes were manufactured and tested for transient as well as steady states. Total length of the heat pipe was 1 m and the diameter was 25.4 mm. Screen meshes of 3 different sizes were used to estimate the effect of mesh size on the thermal performance of the heat pipe. The minimum thermal resistance achieved was as low as 0.02$^{\circ}C$/W for the maximum thormal load of 2 ㎾. The average heat transfer coefficient in the evaporator was about 2,000 ㎾/$m^2$K and those in the condenser region were up to 5 times higher.

A Study on the Characteristics of Condensation Heat Transfer of Two-Phase Loop Thermosyphons (루우프형 2상 유동 열사이폰의 응축열전달 특성에 관한 연구)

  • Park, Jong-Un;Cho, Dong-Hyun
    • Journal of Fisheries and Marine Sciences Education
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    • v.26 no.4
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    • pp.894-901
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    • 2014
  • This study concerns the performance of condensation heat transfer in two-phase loop thermosyphons. In the present work, R134a has been used as the working fluid. Liquid fill charge ratio defined by the ratio of working fluid volume to total internal volume of thermosyphon, heat flux and wind speed of condensation have been used as the experimental parameters. The results show that the filling rate of working fluid and heat flux are very important factors for the operation of two-phase loop thermosyphons. The optimum liquid fill charge ratio for the best condensation heat transfer rate was 80%.

Performance Analysis of Heat Pump System for Greenhouse Cooling (온실 냉방을 위한 히트펌프의 성능 분석)

  • 윤용철;서원명;이석건
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.43 no.6
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    • pp.120-126
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    • 2001
  • This experiment was carried out to analyse on the cooling and dehumidifying effects of greenhouse by air-to-water heat pump system employing the air as cooling source. following results were obtained ; 1. The coefficients of performance (COP) of heat pump itself and total heat pump system were approximately 2.71~2.88 and 1.99~2.22, respectively. 2. The night-time cooling load of experimental greenhouse was 64.9 MJ/h, and the heat absorbed (cooling load) from heat pump system was 816.3~1,004.6 MJ/day. 3. The dehumidified moisture amount from experimental greenhouse was 7.0~15.0 kg/h. 4. The night time temperature of experimental greenhouse cooled by heat pump system could be maintained 4~6$^{\circ}C$ lower than that of control greenhouse which was almost equal to outside air temperature.

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A Study on Surface Case Hardening of Blend Heat Treated Mild Steel (복합열처리(複合熱處理)한 연강(軟鋼)의 표면경화(表面硬化)에 관한 연구)

  • Chung, In-Sang;Chon, Hae-Dong;Sin, Soug-Mok
    • Journal of the Korean Society for Heat Treatment
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    • v.5 no.1
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    • pp.23-31
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    • 1992
  • It is investigated that Fe-C-N compound layer, defusion layer, and induction hardened layer produced by nitrocarburizing blend heat treatment in austenitic temperature with high frequency induction heating of mild steel specimen sprayed sursulf salt-bath. As the temperature of blend-heat treatment got increased, the thickness and hardness of compound layer and diffusion layer were increased. Compound layer(max. $35{\mu}m$), diffusion layer (max. 2.5mm) and induction hardened layer were gained in the shortest time 10 sec and in the case of $1000^{\circ}C$ total hardness depth of those was about 3.5mm. When the blend-heat treated specimen was reheated, maximum hardness of compound layer was dropped more than that of the reheated compound layer after sursulf treated, whereas hardness of diffusion layer was increased.

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Heat and Mass Transfer Characteristics and Performance Evaluation of a Double-Tube Condenser for an Alternative Refrigerant (대체냉매의 2중관 응축기 열 및 물질전달과 성능평가)

  • 이상무;박병덕;소산번
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.6
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    • pp.468-476
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    • 2002
  • This paper deals with heat and mass transfer characteristics and performance evaluation of a counter flow double-tube condenser for a multi-component refrigerant mixture. The local heat and mass transfer characteristics of ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a are evaluated for a counter flow double-tube condenser cooled by water. Then, the local values of vapor quality, thermodynamic states at bulk vapor, vapor-liquid interface and bulk liquid, heat flux and condensation mass flux are obtained. The heat exchange performance for ternary zeotropic refrigerant mixtures composed of HFC32/HFC125/HFC134a on the total pressure drop and the heat transfer characteristics are also compared with those for R404A, R410A, R502, R22, R32, Rl23 and R134a.

Characteristics Evaluation of Absorption Cycles using the Waste Heat (배열 이용형 흡수식 사이클 특성평가)

  • Yoon, J.I.;Kwon, O.K.;Moon, C.G.
    • Solar Energy
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    • v.18 no.4
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    • pp.23-32
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    • 1998
  • Fuel cells supply electric power and heat at work, and their exhaust gas is comparatively clear. So they are in the limelight as one of the co-generation systems which behave friendly with the environment. Fuel cells discharge both steam and hot water. Accordingly, if we combine absorption heat pump driven by waste heat with fuel cells, we can construct an advanced energy conserving system. The purpose of this study is the objective for evaluating the possibilities of effectively utilizing waste heat of fuel cells as a heat source for the single and double effect absorption systems. Simulation studies on single and double effect absorption have been performed for water/lithium-bromide pair. The effectiveness of introducing a waste heat source of fuel cells is demonstrated. The result of this study showed that total efficiency was about 85% at rated operation and about 75% at 75% load operation. Absorption cycle moved to more strong concentration when fuel cell operated at 75% load.

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Fire Characteristics of Composites for Interior Panels Using Cone calorimeter (콘칼로리미터를 이용한 내장판용 복합재료의 화재특성)

  • 이철규;정우성;이덕희
    • Journal of the Korean Society for Railway
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    • v.7 no.1
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    • pp.55-59
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    • 2004
  • Composite materials were used widely due to merit of light weight, low maintenance cost and easy installation. But it is the cause of enormous casualties to men and properties because of weak about the fire. Particularly, it is more serious in case of subway train installed composite materials. For this reason, experimental comparison has been done fur measuring heat release rate(H.R.R) and smoke production rate(S.P.R) of interior panels of electric motor car using cone calorimeter. A high radiative heat flux of 50kW/㎡ was used to bum out all materials and to simulate the condition of fully developed fire case in the tests. It was observed that Heat Release Rate and Smoke Production Rate curves were dependent on the kinds of the interior materials. From the heat release rate curves, the sustained ignition time, peak heat release rate and total heat release rate were deduced, These data are useful in classifying the materials by calculating two parameters describing the possibility to flashover.