• Title, Summary, Keyword: Heat Transfer Coefficient

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Heat Transfer Characteristics of Small Slush Maker (소형 슬러시 제조기의 전열현상에 관한 연구)

  • Kim, Do-Young;Kim, Nae-Hyun;Oh, Wang-Kyu;Choi, Yong-Min;Byun, Ho-Won
    • Proceedings of the SAREK Conference
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    • pp.346-350
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    • 2008
  • Tests were conducted to obtain heat transfer coefficients during slush formation from 10% sucrose solution. The slush was made by scraping the ice formed on the cylinder. Cold brine was supplied inside of the cylinder to cool the outer surface. Below a certain brine temperature, which was $5^{\circ}C$ in this study, the solution was supercooled, and suddenly turned into ice. The super-cooling increases as the brine temperature increased. During slush formation, the heat transfer coefficient oscillated significantly, due to periodic removal of ice chunk form the surface. The average heat transfer coefficient during slush formation was approximately twice of that obtained during single phase cooling. The heat transfer coefficient was also affected by the brine temperature with increasing heat transfer coefficient at lower brine temperature.

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Heat Transfer Characteristics of Plastic Particle Slurry in a Circular tube Flow (관내 유동 플라스틱 슬러리의 열전달 특성)

  • 김명환;김명준
    • Journal of the Korean Society of Marine Engineering
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    • v.28 no.3
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    • pp.451-456
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    • 2004
  • This present experimental study has dealt with the heat transfer characteristics of plastic particle slurry which flows in a circular tube. This type of slurry is suggested for heat transfer enhancement effect cause by random and vortex effect of plastic particle dispersed in water. As a result, the thermal boundary layer becomes thin so the heat transfer coefficient on the tube wall more increase compare to pure water flow. This experimental test section was composed with stainless pipe which has the length of 2000mm, inner pipe diameter of 14mm and outer pipe diameter of 60mm. The most effective and important parameter of this experiment is plastic packing factor(PPF). The focuses of these results are pressure drop and heat transfer coefficient. As results, the friction factor of plastic particle slurry becomes higher at laminar flow region than pure water because of buoyancy effect of plastic particle but the local heat transfer coefficient becomes higher.

Numerical Analysis and 2-D Experiment of Heat Transfer Coefficient on the Pintle of a Controllable Thruster Nozzle (고온 고압 환경에서 가변추력기용 핀틀의 열전달 계수에 대한 수치적 연구 및 2D 실험)

  • Park, Soon Sang;Moon, Young gi;Kawk, Jae Su
    • Journal of Aerospace System Engineering
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    • v.6 no.4
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    • pp.24-28
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    • 2012
  • In this paper, 2-D experiment and steady-state computational fluid analysis were conducted for measuring the hear transfer coefficient of pintle type controllable thruster in high pressure and temperature. In case of 2-D experiment, transient liquid crystal technique was used for measuring heat transfer coefficient for the 2-D pintle model. The experimental result was used to validate the CFD result. The CFD results well predicted the heat transfer coefficient on the pintle surface except the nozzle downstream region, where the results by CFD was higher than experimental results. The CFD results were also compared with the result by Bartz equation and the it was shown that the Bartz equation overestimated the heat transfer coefficient on the nozzle throat as much as 80%.

A Study on Prediction Model of Flow and Heat Transfer in the Circulating Fluidized Bed Heat Exchanger with Multiple Vertical Tubes (다관형 순환유동층 열교환기의 유동 및 전열성능 예측모델 연구)

  • Park, Sang-Il
    • Proceedings of the SAREK Conference
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    • pp.1199-1204
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    • 2006
  • The pressure drop and heat transfer coefficient were measured at room temperature in CFB heat exchanger with multiple vertical tubes. Also the circulation rate of solid particles was measured. The theoretical model for predicting heat transfer coefficient using the solid flowrate was developed in this study. The model predictions were compared with the measured heat transfer coefficient to show relatively good agreement.

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Study on Film Boiling Heat Transfer of Spray Cooling in Dilute Spray Region (희박 분무영역에서의 분무냉각 막비등 열전달에 관한 연구)

  • Kim, Yeung-Chan
    • Proceedings of the KSME Conference
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    • pp.1481-1486
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    • 2004
  • This report presents experimental results on the heat transfer coefficients in the boiling region of spray cooling for actual metallurgical process. In this study, the heat flux distribution of a two dimensional dilute spray impinging on hot plate was experimentally investigated. Based on the experimental results, they classified the heat transfer area into the stagnation region and wall-flow region. In the stagnation region, the local heat transfer coefficient relates mainly to the droplet-flow-rate supplied from spray nozzle directly, so the local heat transfer coefficients is good agreement with the predicted values from correlation for spray cooling proposed by former report However, the local heat transfer coefficient in wall-flow region is larger than predicted values, and it is found that the rebounding droplets-flow-rate must be accurately evaluated to predict the local heat transfer coefficient in this region.

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Computer Analysis of Heat Transfer in Squeeze Casting (용탕단조에 있어서의 열전달 해석)

  • Yoo, Seung-Mok;Han, Yo-Sub;Lee, Ho-In;Hong, Chun-Pyo
    • Journal of Korea Foundry Society
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    • v.10 no.6
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    • pp.495-502
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    • 1990
  • A basic heat flow model has been developed to estimate the heat transfer coefficient at the casting/mold interface during squeeze casting. Based on the measured temperature profiles in squeeze casting of Al-4.5%Si alloy, heat transfer coefficients which vary with time were calculated by numerical method. The influences of the load and the amount of fraction solid on the heat transfer coefficient have also been studied. Using the calculated heat transfer coefficient two dimensional solidification analysis in the squeeze casting process was carried out by the finite difference method, and the results were in good agreement with the experiments. It may be concluded that heat flow analysis in the squeeze casting process with accurate heat transfer coefficient at the casting /mold interface is important for a proper design of cooling in die and finally for improving productivity and die life as well.

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Study on Evaporating Heat Transfer of HCs Refrigerants by Changing of Tube Diameter (관경별 탄화수소계 냉매의 증발 열전달에 관한 특성평가)

  • Lee, Kwang-Bae;Lee, Ho-Saeng;Moon, Choon-Geun;Kim, Jae-Dol;Yoon, Jung-In
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.41-42
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    • 2005
  • The experimental apparatus has been set-up as a conventional vapor compression type heat pump system. The test section is a horizontal double pipe heat exchanger. A tube diameter of 12.70 mm, 9.52 mm, 6.35 mm with 1.78 mm,1.52 mm,1.4 mm wall thickness each is used for this investigation. The local evaporating heat transfer coefficients of hydrocarbon refrigerants were superior to that of R-22. and the maximum increasing rate of heat transfer coefficient was found in R-1270. The average evaporating heat transfer coefficient increased with the increase of the mass velocity and it showed the higher values in hydrocarbon refrigerants than R-22. The highest evaporating heat transfer coefficient of all refrigerants was shown in a tube diameter of 6.35 mm with same mass flux.

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Measurement of Transient Heat Transfer Coefficient of In-cylinder Gas in the Hydrogen Fueled Engine with Dual Injection System (이중분사식 수소기관 연소실내 가스의 순간열전달계수의 측정)

  • Wei, Shin-Whan;Kim, Yun-Young;Lee, Jong-Tai
    • Transactions of the Korean hydrogen and new energy society
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    • v.12 no.4
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    • pp.267-275
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    • 2001
  • To clear the differences of heat transfer coefficient of in-cylinder gas with fuel properties, the transient heat transfer coefficient of hydrogen gas is investigated by using the hydrogen fueled engine. The measured results were also compared with those of gasoline engine and several empirical equations. Transient heat transfer coefficients were determined by measurements of unsteady heat flux and instantaneous wall temperature in the cylinder head. As the main results, it is shown that transient heat transfer coefficients have remarkable differences according to fuel properties, and it's value for hydrogen engine is twice higher than that of gasoline engine. It means that equation of heat transfer coefficient that the effect of fuel properties is considered sufficiently, is needed to analyze or simulate the gas engine performance.

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Condensation Heat Transfer of R22, R407C, and R410A in Slit Fin-and-Tube Heat Exchanger

  • Jeon, Chang-Duk;Lee, Jin-Ho
    • International Journal of Air-Conditioning and Refrigeration
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    • v.11 no.4
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    • pp.188-198
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    • 2003
  • R410A and R407C are considered to be alternative refrigerants of R22 for the air-conditioners. An experimental study is carried out to investigate the effect of the change of mass flow rate on the characteristics of heat transfer and pressure drop in three row slit finned-tube heat exchanger for R407C, R410A and R22. R407C, a non-azeotropic refrigerant mixture, exhibited a quite different condensation phenomenon from those of R22 and R410A and its condensation heat transfer coefficient was much lower than that of R22 and R410A. On the other hand, the condensation heat transfer coefficient of R410A, near-azeotropic refrigerant mixture, was a little higher than that of R22. R410A also showed the lowest condensation pressure drop across the test section. For all refrigerants, the condensation heat transfer coefficient and pressure drop increase as the mass flux increases. The condensation heat transfer coefficient correlation proposed by Kedzierski shows the best agreement with the experimental data within $\pm$20%.

Boiling Heat Transfer Characteristics of $CO_2$ in Horizontal Smooth Microchannel (수평 microchannel의 $CO_2$ 비등열전달)

  • Choi, Kwang-Il;Ardiyansyah, Ardiyansyah;Oh, Jong-Taek
    • Proceedings of the SAREK Conference
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    • pp.241-246
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    • 2007
  • The present paper dealt with an experimental study of boiling heat transfer characteristics of $CO_2$. Heat transfer coefficients of the refrigerant flow inside horizontal smooth microchannel were obtained with inner tube diameter of 0.3mm and length of 300mm. The direct electric heating method was applied for supplying the heat uniformly to the refrigerant. The experiments were conducted with $CO_2$ purity of 99.99%, at saturation temperature of $10^{\circ}C$, mass flux ranges of $300{\sim}900\;kg/m^2s$, and heat flux ranges of $15{\sim}45\;kW/m^2$. While heat transfer coefficient increased with the increase of heat flux in the low quality region, the heat transfer coefficient decreased with the increase of quality in the high quality region. The heat transfer coefficients were compared with seven existing correlations with the Gungor-Winterton's(1986) correlation gave the best prediction. A new corelation to predict the two-phase flow heat transfer coefficient was developed based on the Chen(1966) correlation. The new correlation predicted the experimental data well with a mean deviation of 9.69% and average deviation of -3.03%.

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