• Title/Summary/Keyword: Heat Transfer Experiment

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VERIFICATION OF FIN EFFICIENCY THEORY FOR THE CIRCULAR FINNED-TUBE HEAT EXCHANGER BY NUMERICAL EXPERIMENT (원형휜-원형관 열교환기의 휜효율 이론에 관한 수치적 검증)

  • Kang, H.C.;Lim, B.B.;Lee, J.H.
    • Journal of computational fluids engineering
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    • v.14 no.4
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    • pp.7-12
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    • 2009
  • The purpose of the present study is to investigate the convective heat transfer characteristics and the validity of fin efficiency of the circular finned-tube heat exchanger by using commercial CFD code. The heat transfer coefficient obtained by using the laminar model was 22% overestimated to the experimental data. The fin surface temperature compared with the experimental data measured by the liquid crystal method. The fin efficiency by the present numerical experiment, defined as normalized and averaged fin surface temperature, was greater than the theoretical fin efficiency and the difference is increased at high value of the factor $mr{\phi}$.

Heat transfer analysis on the heat exchanger of a stirling cycle machine (스터링 사이클 기기 열교환기의 열전달 해석)

  • Lee, Dae-Yeong;Jo, Gwan-Sik;No, Seung-Tak;Kim, Byeong-Ha
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.4
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    • pp.1385-1394
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    • 1996
  • A theoretical analysis was performed on the heat transfer by laminar oscillating flow in a simplified heat exchanger of a Stirling cycle machine and the results were compared with the experiment of Hwang. In the analysis the general solution to the temperature field obtained by Lee et. al was applied and extended to a more realistic situation. The results show that the heat transfer is influenced by the ratio of the swept distance of the fluid to the length of the heat exchanger as well as the oscillation frequency. This is well consistent with the result of Hwang's experiment. It is also revealed that there exist three distinct regimes having different heat transfer mechanisms. Through the scale analysis the main parameters governing the heat transfer in each regime are reduced and the dependency of the heat transfer on the parameters are examined.

A Study on the Development of Solar Heat Proof Hat for Summer Field Work (하절기 방서용 농작업모 개발에 관한 연구)

  • Choi Jeong Wha;Jeong Young Ok
    • Journal of the Korean Society of Clothing and Textiles
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    • v.14 no.4 s.36
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    • pp.281-291
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    • 1990
  • Experiment I and II had done to develop the solar heat proof hat for field work in the summer. In the experiment I physical characteristics of several fabrics was tested to determine which one Is proper to make the solar heat proof hat. On the base of above results in the experiment II three improved solar heat proof hat was deviced and tested solar heat proof effect and compared the existing summer working hat by wearing trials in the environmental chamber. The results obtained were as follows. 1. In the view of the physical characteristics of six fabrics (Blue T/C, White poplin, Vapor transfer silver coating nylon taffeta, No vapor trans(or silver coating nylon taffeta, Aluminum coating T/C, Microporous fabric), the light color T/C and no vapor transfer silver coating nylon ta(feta is proper to make improved solar heat proof working hat. 2. Three improved hats that are made of white T/C, grey T/C and no vapor transfer silver coating nylon taffeta have more solar heat proof effect than the existing summer working hat. 3. Among the three improved hats, the improved hat that is made of no vapor transfer silver coating nylon taffeta is most effective to proof the solar heat.

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Study on the Experiment and Numerical Computation of Forced Convection Heat Transfer around Circular Cylinder in a Rectangular Duct (사각덕트 내에서 원형 실린더 주위의 강제대류 열전달에 대한 실험과 수치계산에 관한 연구)

  • 윤영환;김경환
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.5
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    • pp.490-498
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    • 2004
  • This paper measures the forced convective heat transfer from heated cylinder to air flow in a rectangular duct at Re$_{D}$ =2,337, 4,589, 6,621 and 7,944 through experiments. And the heat transfer is computed by 3-D numerical computation in which various turbulent models are applied. It is shown through the comparison of experimental and computed data that numerical computation with standard k-$\varepsilon$ model predicts the experimental data most accurately. Furthermore, the correlation from the computed heat transfer is almost similar to that from the experiment when Re$_{D}$ is greater than 4,589. In addition, the correlation of McAdams is the closest to that from experimental data among various correlations from literature in the range of Reynolds number.ber.

Experiment on condensation heat transfer and pressure drop characteristics in the multi-channel flat tube (다채널 편평관의 응축 열전달 및 압력강하특성에 관한 실험)

  • Jeon, C.D.;Chung, J.W.;Lee, J.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.9 no.3
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    • pp.376-388
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    • 1997
  • In this study, an experiment was performed to investigate the characteristics of pressure drop and heat transfer of multi-channel tubes for automotive condenser using HFC-134a as an alternative refrigerant. The mass flux and inlet saturation pressure of the refrigerant were controlled, respectively, in the range of 200 to $500kg/m^2s$ and 1.0 to 1.6MPa. Pressure drop and heat transfer coefficient were compared with the previously proposed correlations and new correlations based on Traviss' correlation were suggested. Prediction of pressure drop and heat transfer coefficient based on the new correlations agrees with experimental results within ${\pm}9%$ and -18~+11%, respectively.

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Optimal design of a micro evaporator to maximize heat transfer coefficient (열전달 계수 최대화를 위한 마이크로 증발기의 최적 설계)

  • Sung, Tai-Jong;Oh, Dae-Sik;Seo, Tae-Won;Kim, Jong-Won
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2097-2101
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    • 2007
  • This paper presents an optimal design of a micro evaporator which maximizes the heat transfer coefficient. Number of gaps, spanwise distance and streamwise distance are selected as the geometric design parameters. Mass flow rate of the refrigerant is selected as the non-geometric design parameter. Temperature at the surface of the heater is measured to valuate the heat transfer coefficient. Nine experiments are conducted using $L_9(3^4)$ orthogonal array. Maximum heat transfer coefficient is 640 W/$m^2K$ at the parameters of 2 gaps, 0.2 mm spanwise distance, 1.0 mm streamwise distance and 0.72 g/s mass flow rate. Among the 3 geometric parameters, the spanwise distance is the most sensitive parameter influencing the heat transfer coefficient. We conduct a second stage of experiment to increase the heat transfer coefficient by reselecting the mass flow rate. We concluded that 0.87 g/s is the optimized flow rate for an active micro cooler resulting in a heat transfer coefficient of 651 W/$m^2K$.

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Characteristics of Insulation of Core Wall for Traditional Rural House (Earthen House) (전통 농촌주택(흙집) 심벽의 단열 특성)

  • 리신호
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.45 no.5
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    • pp.126-132
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    • 2003
  • The insulation characteristics of earthen core wall were studied in this paper. The overall heat transfer coefficients(U) were obtained through experiment in accordance with Korea Industrial standards. The result of the experiment are compared with the Regional Overall Heat Transfer Coefficient(U) of Building. This results inform that core wall with soil can be used as building walls because the insulation characteristics agree to the rule of building standards.

Heat and Mass Transfer between Hot Waste Gas and Cold Water in a Direct Contact Heat Exchanger (직접접촉식 열교환기내에서 물과 배기가스의 직접접촉에 의한 열 및 물질전달)

  • 이금배
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.6
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    • pp.1171-1178
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    • 1992
  • An experiment was performed to describe the heat and mass transfer occurring between hot waste gas and cold water through direct contact in a direct contact heat exchanger. This model was then used to obtain an equation of overall heat transfer coefficent based on heat exchanger volume. The diffusion heat transfer rate is 2-3 times larger than the convection heat transfer rate as results of condensation of the water vapor contained in the waste gas. The boiler efficiency increases over 10%.

Experimental Study on Effects of PAG Oil for $CO_2$ Evaporation Heat Transfer (PAG 오일이 $CO_2$ 증발열전달에 미치는 영향에 관한 실험적 연구)

  • Lee, Sang-Jae;Kim, Dae-Hoon;Choi, Jun-Young;Lee, Jae-Heon;Kwon, Young-Chul
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.5
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    • pp.357-363
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    • 2008
  • In order to investigate $CO_2$ heat transfer coefficient and pressure drop by PAG oil concentration during $CO_2$ evaporation, the experiment on evaporation heat transfer characteristics in a horizontal micro-fin tube was performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes($400{\sim}1200\;kg/m^2s$), heat fluxes($10{\sim}30\;kW/m^2$) and saturation temperatures ($-5{\sim}5^{\circ}C$), and PAG oil concentration($0{\sim}5\;wt%$). The variation of the heat transfer coefficient was different in accordance with the oil concentration. With the increase of the oil concentration, the evaporation heat transfer coefficient decreased and the delay of dryout by oil addition was found. Pressure drop increased with the increase of the oil concentration and heat flux, and the decrease of saturation temperature.

Heat transfer coefficients for single-Phase flow in a micro-fin tube (마이크로휜 관내의 단상유동 열전달계수)

  • 권정태;김무환
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.4
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    • pp.423-430
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    • 1998
  • Single phase heat transfer coefficients were measured for turbulent water flow in a micro-fin tube by using Wilson plot technique. An experiment for counterflow heat exchange between the micro-fin tube and its outer annulus passage was performed. The annulus side heat transfer resistance was varied and the overall heat transfer coefficients were measured. The single-phase heat transfer coefficients in a micro-fin tube were obtained by Wilson plot technique. Nusselt numbers based on the real heat transfer area and the nominal area were about 35% and 50% larger than those for smooth tube respectively Also, single-phase heat transfer correlations based on real heat transfer area and nominal area have been proposed for a micro-fin tube.

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