• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.117-123
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• 2018

Automotive headlamps have been continuously developed as one of the most important devices for securing the driver's view, and the LED lamps are getting popular in recent years. However, in case of the LED lamps, because the heat generated by the LED lamps are too high, it shorten the product life and lower the LED efficiency. Therefore, this study was investigated the cooling characteristics of the LED lamp heat sink for automobile by forced convection for LED heat generation control. In order to analyze the cooling characteristics of the heat sink, the temperature distribution results were investigated through the experiment and computational analysis under the increase of the air flow velocity, and the convective heat transfer coefficient was obtained. Also, convective heat transfer coefficient was calculated by the theoretical formula under the same condition and compared with experimental and computational results. From the result of this study, as the air flow velocity around the heat sink fins increased, the convective heat transfer coefficient significantly increased, confirming the improvement in the cooling effect.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.35-43
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• 1996

A vaporization model for single component fuel droplet has been developed for applying to sub- and supercritical conditions. This model can account for transient liquid heat ins and circulation effect inside the droplet, forced and natural convection, Stefan flow effect, real gas effect and ambient gas solubility into the liquid droplet in high-pressure conditions. Thermodynamic and transport properties are calculated as functions of temperature and pressure in both phases. Numerical calculations are carried out for several validation cases with the detailed experimental data. Numerical results confirm that this supercritical vaporization model is applicable to the high-pressure conditions encountered in the combustion processes of diesel engine.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.100-103
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• 2005

This work discusses the numerical analysis, the design and experimental test of the SMA (Shape Memory Alloy) actuator along with its capabilities and limitations. Convection heating and cooling using water actuate the SMA element of the actuator. The fuel such as propane, having a high energy density, is used as the energy source for the SMA actuator in order to increase power and energy density of the system, and thus in order to obviate the need for electrical power supplies such as batteries. The system is composed of a pump, valves, bellows, a heater (burner), control unit and a displacement amplification device. The actuation frequency is compared with the prediction obtained from numerical analysis. For the designed SMA actuator system, the results of numerical analysis were utilized in determining design parameters and operating conditions.

• Journal of the Korean Society of Safety
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• v.24 no.6
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• pp.13-19
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• 2009

The thermoelectric cooling system consisted of the thermoelectric module, a heat sink and a cooling fan, respectively. Also, the piezoelectric actuator was applied to improve the performance of thermoelectric cooling system and investigate the heat transfer phenomenon. The temperature distribution of test section was measured to investigate cooling characteristics of thermoelectric cooling system. The flow phenomenon of test section was visualized using visualization device. When the piezoelectric actuator was applied to the heat transfer process of thermoelectric cooling system, acoustic streaming was occurred in test section. The acoustic streaming was occurred forced convection flow, and was regularly formed the temperature distribution in test section. The results clearly show that the acoustic streaming is one of the prime effects to enhance the convection heat transfer and can enhance the performance of thermoelectric cooling system.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.829-832
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• 2005

Thermal analysis of new designed heat-sink models was carried out according to the natural ana the forced convection using computational fluid dynamics(CFD). Heat resistance of wave type, top vented wave type and plate type of heat sink was compared with each other As the direction of fin and air flow are vertical(z-axis), it is shown that radiant heat performance of all of heat sinks was superior than other experimental conditions. Especially, the heat resistance of top vented wave heat sink was $0.17^{\circ}C/W$(forced convection) and $0.48^{\circ}C/W$(natural convection). The radiant heat performance of heat sink was increased with increasing the height of fin and the width of fin pitch.

• 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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.345-353
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• 1987

An analysis is performed to study flow and heat transfer characteristics of mixed free and forced convection about a sphere. Nonsimilar boundary layer equations which are valid over the entire regime of mixed convection are derived in terms of the mixed convection parameter, Gr/Re$^{2}$, through a dimensional analysis. The transformed conservation equations are solved by a finite difference method for the whole range of mixed convection regime. Numerical results for fluids having the Prandtl number 0.7 and 7 are presented. As the mixed convection parameter increases, the local friction coefficient and local heat transfer coefficient increases as well. For small Prandtl number, the friction coefficient is larger, while for large Prandtl number, the heat transfer coefficient is larger. Natural convection effect on the forced flow is more sensitive for small Prandtl number fluid. Flow separation migrates rearward as an increase in the mixed convection parameter. For small Prandtl number, the buoyancy effect is relatively small so that the flow separation occurs earlier.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.277-284
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• 2004

This paper describes the influence of through-flow on the mixed convection in a parallel plates with the upper part is cooled and the lower part heated. When forced convection is imposed on natural convection, it is found that the flow pattern of mixed convection in the parallel plates can be classified into three patterns which were affected by Reynolds number. In such a mixed convection, the flow pattern plays an important role in the heat transfer process. In this study, thermo-sensitive liquid crystal suspension method is employed, then the visualization image acquired through the above method is processed by the color image processing technique and the two-dimensional velocity vector and temperature configuration are measured simultaneously.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.699-705
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• 1985

Heat transfer characteristics in terms of the tube wall-temperature and the enthalpy have been investigated utilizing ribbed (rifled) tubes in order to enhance heat transfer performance. Considerations were given for the cases of smooth tubes in order to compare with the case of ribbed tubes. The tilt angle of the experimental tubes are from 0.deg. to 90.deg. , in order to simulate the boiler water tubes having 15.deg.-90.deg. inclined angle in boiler nose and studded tubes (burner zones), Natural convection and forced convection (Re=1810) conditions were considered in the experiments. The experimental results for the effect for the tube inclination through a natural convection and forced convection are presented and it is shown that ribbed tubes permit an appreciable increase in heat transfer coefficients and consequently it means substantial reductions in boiler water wall tubes and heat exchanger surface areas.

• The Korean Journal of Food And Nutrition
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• v.25 no.1
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• pp.50-56
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• 2012

This paper examines the effects of various methods of soft steaming(i.e., forced convection-boiler, forced convection-fan, and natural convection) on the quality of potatoes. In particular, the paper investigates the effects of cooking conditions (the steaming method, the treatment time, and the temperature) on the color(L, a, b), moisture content, texture profile, and ascorbic acid of potatoes. The results indicate that not only the cooking method, the treatment time, and the temperature but also the heat transfer mechanism had considerable influence on potato quality. In addition, natural convection steaming was superior to other treatment methods in terms of nutrient retention and texture maintenance. The results of this study should be useful for establishing commercial standards for processing potatoes and improving the quality of thermally processed foods.