• 한국전산유체공학회지
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• 제15권1호
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• pp.24-30
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• 2010

A preliminary thermal analysis is performed for the optical payload system of a geostationary satellite. The optical payload considered in this paper is GOCI(Geostationary Ocean Color Imager) of COMS of Korea. The radiative and conductive thermal models are employed in order to predict thermal responses of the GOCI on the geostationary orbit. The results of this analysis are as follows: 1) the GOCI instrument thermal control is satisfactory to provide the temperatures for the GOCI performances, 2) the thermal control is defined and interfaces are validated, and 3) the entrance baffle temperature and shutter wheel motor gradient are found slightly out their specification, therefore further detailed analyses should be continued on these elements.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.8-12
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• 2009

The Knowledge of the solar radiation components are essential for modeling many solar energy systems. This is particularly the case for applications that concentrate the incident energy to attain high thermodynamic efficiency achievable only at the higher temperatures. In order to estimate the performance of concentrating thermal systems, it is necessary to know the intensity of the beam radiation, as only this component can be concentrated. The Korea Institute of Energy Research(KIER) has began collecting solar radiation component data since August, 2002. KIER's component data will be extensively used by concentrating system users or designers as well as by research institutes. The Result of analysis shows that the annual-average daily diffuse radiation on the horizontal surface is $1,458cal/m^2$ and daily direct radiation on the horizontal surface is $1,632cal/m^2$ for all over the 16 areas in Korea.

• 한국안전학회지
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• 제18권4호
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• pp.64-70
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• 2003

The thermal properties of chloroprene rubber (CR) with $^{60}Co\;{\gamma}$-ray irradiation has been investigated. The prepared CR was irradiated up to 1000kGy radiation dose by $^{60}Co\;{\gamma}$-ray and the radiation degradation of CR was investigated by thermogravimetric analysis and differential acanning calorimetry. Dynamic mechanical properties measurement and FT-IR observation are carried out as well. From these analyses results, the glass transition temperature($T_g$), decomposition onset temperature(DOT), oxidative induction time(OIT), the peak temperature of loss modulus and mechanical tan ${\delta}$ values were compared for the radiation degradation level of CR. The tendency between $T_g$ and peak temperature of loss modulus and mechanical tan ${\delta}$ agreed well with radiation doses. Decomposition temperature, OIT and DOT showed the same tendencies as increasing radiation doses. It was verified that these analyses are available to estimate the degradation level of CR.

• 한국포장학회지
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• 제12권1호
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• pp.45-53
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• 2006

Thermal insulation is used in a variety of applications to protect temperature sensitive products from thermal damage. Several factors affect the performance of insulation packages. Among these factors, the thermal resistance of the insulating wall is the most important factor to determine the performance of the insulating package. In many cases, insulating wall consists of multi-layered structure and the heat transfer through this structure is a very complex process. In this study, an one-dimensional mathematical model, which includes all of the heat transfer principles covering conduction, convection and radiation in multi-layered structure, were developed. Based on this model, several heat transfer phenomena occurred in the air space between the layer of the insulating wall were investigated. From the simulation results, it was observed that the heat transfer through the air space between the layer were dominated by conduction and radiation and the low emissivity of the surface of each solid layer of the wall can dramatically increase the thermal resistance of the wall. For practical use, an equation was derived for the calculation of the thermal resistance of a multi-layered wall.

• 한국표면공학회지
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• 제49권2호
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• pp.218-224
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• 2016

Thermal radiation pastes were prepared by dispersing carbon materials as fillers with a content of 1 weight percent in an acrylic resin. The kind of fillers was as follows; $25{\mu}m$ graphite, $45{\mu}m$ graphite, $15{\mu}m$ carbon nanotube(CNT), a 1:1 mixture of $25{\mu}m$ graphite and $15{\mu}m$ CNT, and a 1:1 mixture of $45{\mu}m$ graphite and $15{\mu}m$ CNT. Thermal emissivity was measured as 0.890 for the samples with graphite only, 0.893 for that with CNT only, and 0.892 for those containing both. After coating prepared pastes on a side of 0.4 mm thick aluminium plate and placing the plate over an opening of a box maintained at $92^{\circ}C$ with the coated side out, the temperatures on the uncoated side of the plates were measured. The samples containing graphite and CNT showed the lowest temperatures. The paste with mixed fillers was coated on the back side of the PCB of an LED module and thermal analysis was carried out using Thermal Transient Tester (T3ster) in a still air box. The thermal resistance of the module with coated PCB was measured as 14.34 K/W whereas that with uncoated PCB was 15.02 K/W. The structure function analysis of T3ster data revealed that the difference between junction and ambient temperatures was $13.8^{\circ}C$ for the coated case and $18.0^{\circ}C$ for the uncoated. From the infrared images of heated LED modules, the hottest-spot temperature of the module with coated PCB was lower than that of the uncoated one for a given period of LED operation.

• Journal of Computational Design and Engineering
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• 제3권4호
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• pp.349-362
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• 2016

The numerical solutions of unsteady hydromagnetic natural convection Couette flow of a viscous, incompressible and electrically conducting fluid between the two vertical parallel plates in the presence of thermal radiation, thermal diffusion and diffusion thermo are obtained here. The fundamental dimensionless governing coupled linear partial differential equations for impulsive movement and uniformly accelerated movement of the plate were solved by an efficient Finite Element Method. Computations were performed for a wide range of the governing flow parameters, viz., Thermal diffusion (Soret) and Diffusion thermo (Dufour) parameters, Magnetic field parameter, Prandtl number, Thermal radiation and Schmidt number. The effects of these flow parameters on the velocity (u), temperature (${\theta}$) and Concentration (${\phi}$) are shown graphically. Also the effects of these pertinent parameters on the skin-friction, the rate of heat and mass transfer are obtained and discussed numerically through tabular forms. These are in good agreement with earlier reported studies. Analysis indicates that the fluid velocity is an increasing function of Grashof numbers for heat and mass transfer, Soret and Dufour numbers whereas the Magnetic parameter, Thermal radiation parameter, Prandtl number and Schmidt number lead to reduction of the velocity profiles. Also, it is noticed that the rate of heat transfer coefficient and temperature profiles increase with decrease in the thermal radiation parameter and Prandtl number, whereas the reverse effect is observed with increase of Dufour number. Further, the concentration profiles increase with increase in the Soret number whereas reverse effect is seen by increasing the values of the Schmidt number.

• 한국태양에너지학회 논문집
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• 제28권3호
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• pp.35-44
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• 2008

In this study, the experiment of the measuring of four different types of flooring materials' thermal characteristics was conducted and examined during the summer. The experimental materials were arranged on the existing slab of the roof, and then its thermal characteristics were examined from the point of view of thermal radiation analysis. The aim of this study is ultimately to draw the fundamental data for improvements in a building's thermal function and reduce the urban heat island phenomena through optimizing the thermal characteristics of the surface covering materials of a building. The results from this study are as follows; 1) Each experimental material's albedo was calculated as 0.83 on the aluminum panel, 0.40 on the rock block, 0.37 on the wood deck and 0.21 on the concrete. It shows that the concrete material, which has the lowest short wave reflective rate, absorbed the most radiation energy and the aluminium panel has absorbed the lowest radiation energy. 2) From the each experimental object's value of the long wave radiation, the concrete material measured the highest, at $628W/m^2$, and the aluminium panel measured the lowest at $412W/m^2$. Therefore, it verifies that the experimental objects' own radiation rate determines the amount of the long wave radiation. 3) The degree of energy absorbency of a building's surface covering materials is greatly influenced by its own albedo and radiation rate, Therefore, it needs to be considered for the improvements in a building's thermal function and reducing the urban heat island phenomena. 4) According to the evaluation result of the each experimental object's overall heat transmission screening function on the roof of a building, the wooden deck is proven to be an excellent material for excluding the outside temperature differences effectively with its characteristic of low heat capacity and conduction. Also its surface temperature on the roof slab and the temperature difference during the day were both measured at low.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권3호
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• pp.257-268
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• 2014

The objective of the present study is to investigate thermal diffusion and radiation effects on unsteady MHD flow past a linearly accelerated vertical porous plate with variable temperature and also with variable mass diffusion in presence of heat source or sink under the influence of applied transverse magnetic field. The fluid considered here is a gray, absorbing/emitting radiation but a non-scattering medium. At time t > 0, the plate is linearly accelerated with a velocity $u=u_0t$ in its own plane. And at the same time, plate temperature and concentration levels near the plate raised linearly with time t. The dimensionless governing equations involved in the present analysis are solved using the closed analytical method. The velocity, temperature, concentration, skin-friction, the rate or heat transfer and the rate of mass transfer are studied through graphs in terms of different physical parameters like magnetic field parameter (M), radiation parameter (R), Schmidt parameter (Sc), Soret number (So), Heat source parameter (S), Prandtl number (Pr), thermal Grashof number (Gr), mass Grashof number (Gm) and time (t).

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.137-146
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• 2007

This study is about the passive cooling effects of three outdoor solar shading facilities as trees, pergola with wistaria vine and membrane shading structure, which are expected to provide cool spots in the summer. Field observations of measuring thermal environment of selected facilities is executed. Thermal environment measuring was categorized as short wave radiation, long wave radiation, net radiation, globe temperature, surface temperature measured by infrared camera. Heat transfer mechanism is analyzed with overall data from field measurement. Results from this study are as below; 1) Radiation balance measured on shaded surface under membrane shading structure was 17%($86W/m^2$) of the unshaded surface radiation balance($511W/m^2$). 2) Surface temperature comparison between vegetation and membrane of the shading structure is performed at 3 o'clock in the afternoon. Surface temperature of vegetation was same as air temperature and that of membrane was $5^{\circ}C$ higher than air temperature. Vegetation transpiration is considered as the causing factor which make those differences. 3) Results from this study could be used as fundamental data for reducing heat island phenomena and continuos research on this subject would be needed.

• 설비공학논문집
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• 제6권2호
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• pp.78-92
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• 1994

Thermal performance of pipe network of continuous heating system controlled by thermostat and flow control valve was simulated in consideration of radiation heat transfer and solved by linear analysis method. Thermal performance of real apartment building with radiant floor heating system was simulated by equivalence heat resistance-capacity method. This method enables to simulate the unsteady variation of temperature or each element of building. Heat transfer characteristics of each element were also investigated.