• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.7-13
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• 2019

This study is about distributions of heat transfer in air conditioning duct used for marine and oil drilling ship. As the convective heat transfer coefficient increased, heat transfer was conducted dynamically to inside as it exited to the outlet of duct. So, it was checked that the amount of heat transfer generated at duct increased as the convective heat transfer coefficient increased. In case the convective heat transfer coefficient was low, the temperature of duct showed the relatively high temperature distribution due to the temperature influence of internal fluid as the heat transfer between the outside and inside of the duct. In case of temperature distribution generated the volume of the duct along the change of the convective heat transfer coefficient, it was found out that the temperature descended as heat transfer was promoted and the convective heat transfer coefficient increased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.39-44
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• 2008

In this paper, heat transfer coefficients were measured in a channel with one side dimpled surface. The sphere type dimples were fabricated and the diameter and depth of dimple was 16mm and 4mm, respectively. Two channel heights of about 0.6 and 1.2 time of the dimple diameter, two dimple configuration were tested. The Reynolds numbers based on the channel hydraulic diameter was varied from 30000 to 50000. The improved hue detection based transient liquid crystal technique was used in the heat transfer measurement. Heat transfer measurement results showed that high heat transfer was induced downstream of dimples due to flow reattachment. Due to the flow recirculation on the upstream side in the dimple, the heat transfer coefficient was very low. As the Reynolds increased, the overall heat transfer coefficients also increased. With same dimple arrangement, the heat transfer coefficients and the thermal performance factor were higher for the lower channel height. As the distance between dimples became smaller, the overall heat transfer coefficient and the thermal performance factor were increased.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.1
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• pp.74-85
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• 2018

This study has analyzed the convective heat transfer on the deck exposed to the high-temperature impingement exhausting from a VTOL vehicle. The heat flow of the impingement on the deck is modeled by the convection heat transfer. The convective heat flux generated by the hot impinging jet is investigated by using both convective heat transfer formulation and conjugate heat transfer formulation. Computational fluid dynamics(CFD) code was used to compute the heat flux distribution. The RANS equation and the k-e turbulence model were used to analyze the thermal flow of the impinging jet. The heat flux distribution near the stagnation zone obtained by the conjugate heat transfer analysis shows more reasonable than the convective heat transfer analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.1
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• pp.73-85
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• 2003

Four different methods of reducing the heat transfer coefficients from experimental data under dehumidifying conditions are compared. The four methods consist of two different heat and mass transfer models and two different fin efficiency models. Data are obtained from two heat exchanger samples having plain fins or wave fins. Comparison of the data with the reduction methods revealed that the single potential heat and mass transfer model yielded the humidity independent heat transfer coefficients. Two different fin efficiency models - enthalpy model and humidity model - yielded approximately the same fin efficiencies and accordingly approximately the same heat transfer coefficients. The heat transfer coefficients under wet conditions were approximately the same as those of the dry conditions for the plain fin configuration. For the wave fin configuration, however, wet surface heat transfer coefficients were approximately 12% higher. The pressure drops of the wet surface were 10% to 45% larger than those of the dry surface.

• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1159-1167
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• 2000

Particles in liquid-solid suspension flow might enhance or suppress the rate of heat transfer and turbulence depending on their size and concentration. The heat transfer characteristics of liquid-solid suspension in turbulent flow are not well understood due to the complexibility of interaction between solid particles and turbulence of the carrier fluid. In this study, the heat transfer coefficients of liquid-solid mixtures are investigated using a double pipe heat exchanger with suspension flows in the inner pipe. Experiments are carried out using spherical fly ash particles with mass median diameter ranging from 4 to $78{\mu}m$. The volume concentration of solids in the slurry ranged from 0 to 50% and Reynolds number ranged from 4,000 to 11,000. The heat transfer coefficient of liquid-solid suspension to water flow is found to increase with decreasing particle diameter. The heat transfer coefficient increases with particle volume concentration exhibiting the highest heat transfer enhancement at the 3% solid volume concentration and then gradually decreases. A correlation for heat transfer to liquid-solid flows in a horizontal pipe is presented.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.7-13
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• 2007

Numerical analysis is carried out for combined heat transfer in an indirected NIR(Near Infrared Ray) heating chamber. Reynolds number and shapes of absorbed cylinder are known as important parameters on the combined heat transfer effects. Reynolds number based on the outer diameter of the cylinder is varied from $10^3$ to $3{\times}10^5$. Four difference heat transfer regimes are observed: forced convection and radiative heat transfer on the outer surface of the cylinder, pure conduction in the cylinder body, pure natural convection and radiation between lamp surface and inner surface of the cylinder, and radiation from the lamp. Flow and temperature characteristics are presented with iso-contour lines for the absorbed circular and elliptic cylinders to compare their differences. The convective and radiative heat transfer fluxes are also compared with different Reynolds numbers. As usual, Reynolds number is an important factor to estimate increasing convective heat transfer as it increases. The shape of absorbed cylinder results overall heat transfer rates remain unchanged.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.220-225
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• 2001

The plate heat exchanger is characterized. by low pressure drop and high heat transfer coefficient. The experimental study has been performed on the condensation heat transfer and pressure drop characteristics of the plate heat exchangers in this study. In the present study, a brazed type plate heat exchanger was investigated at a chevron angle of $45^{\circ},\;55^{\circ},\;and\;70^{\circ}$ with R410A. Condensation temperatures were varied from $20^{\circ}C\;and\;30^{\circ}C$, and mass flux was ranged from $13{\sim}34\;kg/m^{2}s$ with constant heat flux ($=5\;kw/m^{2}$). The heat transfer coefficient and pressure drop increased with the chevron angle. Average condensation heat transfer coefficients and pressure drops are decreased with increasing condensation tempeature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.4
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• pp.351-359
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• 1992

In order to improve the performance of heat exchanger, fluidized bed is often employed. The experiments are carried out in fluidized double pipe parallel flow heat exchanger in which finned tube is vertically immersed. And the heat transfer coefficients between the heated tube and fluidized bed of alumina beads(dp=0.41, 0.54, 0.65, 0.77mm) are calculated as a function of air fluidized velocity and pumping power. The effects of particle size, static bed height and pumping power on the heat transfer coefficients are investigated. And the heat transfer coefficients are compared with that of single phase forced convection heat exchanger. In particular, the heat transfer performance of each type heat exchanger is evaluated in relation to the pumping power.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.238-244
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• 2003

An experimental study was performed to examine the heat transfer performance of individual rows of fin-tube heat exchangers. The heat transfer performance was measured using air-enthalpy type calorimeter. The examined heat exchangers consists of $7{\Phi}$ tube and fin patterns of them are slit and louver types. Equivalent fin spacing are 18 FPI for all samples, and the number of tube rows were 2. In order to confirm that thermal boundary condition on fins of each row are the same, physically separated between two rows as well as connected heat exchangers were used. The frontal air velocity varied from 0.7 to 2.5 m/s. Heat transfer performance for each row are measured. It was observed that the heat transfer coefficient of the 2nd row were smaller than that of the 1st row at low Reynolds number while larger at high Reynolds number.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.280-286
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• 2004

An experimental study is peformed to examine the heat transfer performance of individual rows of fin-tube heat exchangers. The heat transfer performance is measured using an air-enthalpy type calorimeter. The examined heat exchangers consist of 7mm tube and fin patterns of them are slit and louver types. Equivalent fin spacings are 18 fins per inch(fpi) for all samples, and the number of tube rows are two. In order to confirm that thermal boundary condition on fins of each row are the same, physically separated between two rows as well as connected heat exchangers are used. The frontal air velocity is varied from 0.7 to 2.5㎧. Heat transfer performance for each row is measured. It is observed that the heat transfer coefficient of the second row is smaller than that of the first row at low Reynolds number while larger at high Reynolds number.