• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2055-2060
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• 2007

Microfin arrays with fin heights of 100 ${\mu}$m and 200 ${\mu}$m and six different spacings from 30 ${\mu}m$to 360 ${\mu}m$ are fabricated using the DRIE process. Natural convective heat transfer around the microfin arrays on both vertical and horizontal surfaces is experimentally examined. It turns out that the orientation effect of microfin arrays is negligible compared with macrofin arrays. The obtained heat transfer coefficients are compared with the existing heat transfer correlation for the macrofin arrays. It is concluded that the existing macrocorrelation is no longer valid for the microfin arrays. Relevant empirical correlations for microfin arrays on the vertical and horizontal surfaces are presented based on the present experimental data.

• 대한설비공학회지:설비저널
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• 제17권3호
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• pp.230-237
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• 1988

An experiment was carried out to study the condensation heat transfer enhancement of horizontal circular cylinders with varying outside surface configurations. The refrigerant used is Freon-22 and the test condensing temperature is 34.1C. Pin-finned tube shows about 2.5-3.5 times higher overall heat transfer coefficient compared to that of smooth surface tube, thus has larger encomic benifit for condenser design. The condensation heat transfer coefficient was shown to increase as the fin-pitch of the pin-finned tube decreases for film Reynolds number larger than 100.

• Journal of Advanced Marine Engineering and Technology
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• 제29권7호
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• pp.779-784
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• 2005

This paper presents the theory of similarity transformations applied to the momentum and energy equations for laminar, forced, external boundary layer flow over a horizontal flat plate which leads to a set of non-linear, ordinary differential equations of phase change material slurry(PCM Slurry). The momentum and energy equation set numerically to obtain the non-dimensional velocity and temperature profiles in a laminar boundary layer are solved. The heat transfer characteristics of PCM slurry was numerically investigated with similar method. It is clarified that the similar solution method of Newtonian fluid can be used reasonably this type of PCM slurry which has low concentration. The data of local wall heat flux and convective heat transfer coefficient of PCM slurry are higher than those of water more than 150$\~$200$\%$, approximately.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.29-34
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• 2006

In general, the vertical vibration problems for .strength of members and serviceability of building structures are not considered in structural design process, but the prediction of the vertical vibration is very important and essential to structural design process. This study aims to investigate the characteristics of vertical vibration in terms of the transfer of horizontal directions on the rahmen building structures. In order to examine the characteristics of vertical vibration, the modal test and the impact (heel-drop and hammer) excitation experiments were conducted several times on three building structures. The results from the experiments are analyzed and compared. with the results. The results of this study suggest that the characteristics of vertical vibration transfer in horizontal way are effected from the fundamental frequency of the slabs and excitation forces.

• Journal of Mechanical Science and Technology
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• 제14권12호
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• pp.1396-1402
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• 2000

Here is investigated the characteristics of double-diffusive convection in thermally-stable stratified horizontal fluid layer. By employing an electrochemical technique, and adopting aqueous CuSO$_4$-H$_2$SO$_4$solution as electrolyte, experiments on ionic mass transfer have been conducted systematically. And, also a new mass transfer correlation in double-diffusive situations has been derived by extending the model of micro-scales of turbulence, which was proposed by Arpaci. The resulting correlation of the Sherwood number as a function of the thermal Rayleigh number was in good agreement with the present experimental results. The present study provides plausible understanding in controlling both mass and heat transfer rates for practical situations including double-diffusive convection.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.565-570
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• 1998

An interfacial condensation heat transfer phenomenon in a steam/water countercurrent stratified flow in a nearly horizontal pipe has been experimentally investigated. The present study has been focused on the measurement of the temperature and velocity distributions within the water layer. In particular, the water layer thickness used in the present work is large enough so that the turbulent mixing is limited and the thermal stratification is established. As a result, the thermal resistance of the water layer to the condensation heat transfer is increased significantly. An empirical correlation of the interfacial condensation heat transfer has been developed. The present correlation agrees with the data within $\pm$15%

• 한국태양에너지학회 논문집
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• 제21권3호
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• pp.43-50
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• 2001

A horizontal mantle heat exchanger for a thermosyphon-driven SDHW(solar domestic hot water) was numerically simulated and fluid flow and heat transfer in the annulus of the mantle heat exchanger were quantitatively investigated. The Reynolds number, the location of the inlet, and the gap of the annulus were selected as the important design variables. The effects of the design variables on the heat transfer characteristics were thoroughly studied. Based on the numerical results, a correlation for predicting the heat transfer coefficient was suggested as the conclusion of this study.

• 설비공학논문집
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• 제15권10호
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• pp.787-794
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• 2003

The effect of inclination angle on natural convection heat transfer has been studied for water layers. The range of the Raleigh number was from the subcritical value to 1.4${\times}$10$^{7}$ , and the range of the inclination angle, $\theta$, measured from the horizontal was 0$\leq$$\theta$$\leq$180$^{\circ}$. For horizontal water layers, present results agreed well with the results of previous investigators and also showed significant departures from the results of air layers in the turbulent regime. Inclined cylindrical water layers showed secondary maxima in heat transfer, whereas rectangular air layers showed continuous decline of Nusselt number.

• 설비공학논문집
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• 제14권1호
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• pp.21-30
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• 2002

The thermal performance of a modular shell and tube-bundle heat exchanger has been analyzed using section-by-section method. Investigated are the effects of air and water inlet conditions on condensation heat transfer of horizontal tubes. It is found that they are significant for the heat transfer of the modular shell and tube-bundle heat exchanger It is shown that the predictions and experimental results are in good agreements.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2200-2205
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• 2007

In order to investigate the variation on a heat transfer coefficient during evaporation of $CO_2$, basic experiment on the evaporation heat transfer characteristics in a horizontal micro-channel tube was performed. Hydraulic diameters of micro-channels were 0.68 and 1.46 mm. The experiment apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiments were conducted for various mass fluxes of 300 to 800 kg/$m^2s$, heat fluxes of 10 to 40 kW/$m^2$ and saturation temperatures of -5 to 5$^{\circ}C$. With the increase heat flux, the evaporation heat transfer coefficient increased. And the significantly change of the heat transfer coefficient was observed at any heat flux and mass flux. As the saturation temperature increased and the hydraulic diameter decreased, the heat transfer coefficient increased.