• Journal of the Korean Solar Energy Society
• /
• v.32 no.4
• /
• pp.71-81
• /
• 2012

This study for the understanding of the radiation environment according to the altitude in urban area in the summer observes the long and short wave radiation environment at the 4 urban areas with different height and the 1 suburban area. The results of this study are as follows. (1) When the altitude was high, the more short wave radiation was observed. (2) As the altitude was high, the temperature of atmosphere got lower. And because of that the downward long wave radiation was also lower. This general trend was confirmed through the study. (3) Through the observation of long wave radiation, the upper atmosphere of suburban area had the atmosphere characteristic which the temperature was rising and decreasing faster. Therefore, the difference radiation characteristics between the urban and suburban area were confirmed. (4) The result of the ratio of short wave radiation to long wave radiation(short wave radiation/long wave radiation) according to the altitude and location, the value was increased when the distance was far from the artificiality structure or a heat source, and the urban effect became smaller. Thus, it is expected that the ratio will be an evaluation index for evaluating urbanization effect.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.6
• /
• pp.705-712
• /
• 2004

An inverse boundary analysis of surface radiation in an axisymmetric cylindrical enclosure has been conducted in this study. Net energy exchange method was used to calculate the radiative heat flux on each surface, and a hybrid genetic algorithm was adopted to minimize an objective function, which is expressed by sum of square errors between estimated and measured or desired heat fluxes on the design surface. We have examined the effects of the measurement error as well as the number of measurement points on the estimation accuracy. Furthermore, the effect of a variation in one boundary condition on the other boundary conditions was also investigated to get the same desired heat flux and temperature distribution on the design surface.

• Journal of Food Hygiene and Safety
• /
• v.11 no.3
• /
• pp.197-201
• /
• 1996

D10 values obtained for radiation alone in Bacillus subtilis and Clostridium perfrigenes were 0.35-0.48 kGy in vegetative cells, and 2~2.08 kGy in spores, respectively. Irradiation dose of 24 kGy completely inhibited spores. In the case of heat treatment, D50, 60 values ranged from 10 to 14 minutes in vegetative cells, and D70, 80, 90 values ranged from 10 to 140 minutes in spores. In the case of combined treatment with heat and radiation, D10 values ranged form 1 to 1.25 kGy in vegetative cells, and from 3.42 to 3.61 kGy in spores. Thus, resistance of cells to gamma radiation did not seem to be influences by pre-heating.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.31 no.2
• /
• pp.107-111
• /
• 2018

In this study, we designed the temperature coefficient of resistance (TCR) and heat radiation properties of shunt fixed resistors by adjusting the atomic composition of a metal alloy resistor, and fabricated a resistor that satisfied the designed properties. Resistors with similar atomic composition of copper and nickel showed low TCR and excellent shunt fixed resistor properties such as short-time overload, rated load, humidity load, and high temperature load. Finally, we expect that improved sensor accuracy will be obtained in current-distribution-type shunt fixed resistor for IoT sensors by designing the atomic composition of the metal alloy resistor proposed in this work.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.19 no.1
• /
• pp.83-102
• /
• 2015

The present paper analyses the radiation effects of mass transfer on steady nonlinear MHD boundary layer flow of a viscous incompressible fluid over a nonlinear porous stretching surface in a porous medium in presence of heat generation. The liquid metal is assumed to be gray, emitting, and absorbing but non-scattering medium. Governing nonlinear partial differential equations are transformed to nonlinear ordinary differential equations by utilizing suitable similarity transformation. The resulting nonlinear ordinary differential equations are solved numerically using Runge-Kutta fourth order method along with shooting technique. Comparison with previously published work is obtained and good agreement is found. The effects of various governing parameters on the liquid metal fluid dimensionless velocity, dimensionless temperature, dimensionless concentration, skin-friction coefficient, Nusselt number and Sherwood number are discussed with the aid of graphs.

• Journal of the Korean Ceramic Society
• /
• v.54 no.6
• /
• pp.499-505
• /
• 2017

Flexible silicon carbide fibrous mats were fabricated by a combination of electrospinning and a polymer-derived ceramics route. Polycarbosilane was used as a solute with various solvent mixtures, such as toluene and dimethylformamide. The electrospun PCS fibrous mats were cured under a halogen vapor atmosphere and heat treated at $1300^{\circ}C$. The structure, fiber morphology, thermal behavior, and crystallization of the fabricated SiC fibrous mats were analyzed via scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal imaging. The prepared SiC fibrous mats were composed of randomly distributed fibers approximately $3{\mu}m$ in diameter. The heat radiation of the SiC fiber mats reached $1600^{\circ}C$ under microwave radiation at a frequency of 2.45 GHz.

• Plant Journal
• /
• v.14 no.1
• /
• pp.42-46
• /
• 2018

The flow and heat transfer characteristics inside a solar chimney power plant system are analyzed in this article. 3-D model with the $k-{\varepsilon}$ turbulence closure was developed. In this model, to solve the radiative transfer equation the discrete ordinates radiation model was implemented, using a two-band radiation model. To simulate radiation effects from the sun's rays, the solar ray tracing algorithm was coupled to the calculation via a source term in the energy equation. Simulations were carried out for a system with the geometry parameters of the Manzanares power plant. Based on the numerical results, the velocity and temperature distributions were illustrated and the results were validated by comparing with experimental data of the Manzanares prototype power plant. Moreover, temperature profile of the ground surface of the system was illustrated.

• Journal of Advanced Marine Engineering and Technology
• /
• v.19 no.4
• /
• pp.17-26
• /
• 1995

In general existing air conditioning devices, which are carried out by convection heat transfer, are very popular compared with the radiation type air conditioning devices. But perconal convection tpe air conditioning units are unuseful air conditioning type because it handles amount of surrounded air to meet the temperature and humidity. In this view, this study is intended to develope personal dir conditioning units using a radiation type radiator. Liquid Droplet Radiator(L.P.R.) radiates the energy by means of thermal radiation. Radiative energy from L.P.R. is the infrared rays which heat the objects without lose of energy. It is a desirable heating method for the local area within the large room. In this study, the analysis uses the Monte Carlo methd to predict the temperature distribution in the droplet sheet and the net heat flux from the L.D.R.. And for this study and experiment was carried out to analyse the radiative and convective heat transfer characteristics in the L.D.R.. And the experiment was investigated the effects of inlet temperature, feed rate, optical thickness and droplet diameter on heat transfer characteristics of L.D.R.. The obtained results from the numerical and experimental studies of L.D.R. were as follows ; (1) The heat flux of L.D.R. was effected by extinction coefficient of droplet sheet, optical thickness and droplet temperature, surface area and emissivity of the droplet. And it was increased with the temperature, feed rate and optical thickness, on the other hand decreased with increasing of droplet diameter. (2) The experimental results for heat flux was ecalucted below 20% than that of the numerical solution by Monte Carlo method, but the tendency of the variation shows relatively good agreement.

• Journal of Environmental Science International
• /
• v.15 no.7
• /
• pp.653-657
• /
• 2006

Based on the monthly weather report of Korea Meteorological Administration (KMA) and daily sea surface temperature (SST) data from National Fisheries Research and Development Institute (NFRDI) (1995-2004), mean heat fluxes were estimated at the port of Yeosu. Net heat flux was transported from the air to the sea surface during February to September, and it amounts to $205 Wm^{-2}$ in daily average value in May. During October to January, the transfer of net heat flux was conversed from the sea surface to the air with $-70 Wm^{-2}$ in minimum of daily average value in December. Short wave radiation was ranged from $167 Wm^{-2}$ in December to $300 Wm^{-2}$ in April. Long wave radiation (Sensible heat) was ranged from $27 (-14) Wm^{-2}$ in July to $90 (79) Wm^{-2}$ in December. Latent heat showed $42 Wm^{-2}$ with its minimum in July and $104 Wm^{-2}$ with its maximum in October in daily average value.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.2
• /
• pp.1-10
• /
• 2013

Simulation study of a solar hybrid heat pump using R744 and R22 for residential applications was carried out according to heat pump operating temperature, outdoor temperature and solar radiation. As a result, when the heat pump operating temperature increases from $40^{\circ}C$ to $48^{\circ}C$, the COP of a R744 and R22 heat pump system decrease from 2.15 to 1.7 and from 3.09 to 2.69, respectively. Besides, as the outdoor temperature rises from $3^{\circ}C$ to $11^{\circ}C$, the COP of R744 and R22 heat pump system increase from 1.73 to 2.12 and from 2.73 to 3.02. When the solar radiation increases from 10 to 20 $MJ/m^2$, the collector operating time and collector efficiency of R744 heat pump increase 10.3 times and 50.7%, respectively. The performance of R744 solar hybird heat pump is more sensitive to operation condition compared to that of R22. Besides, the solar heating system is more effective to the R744 heat pump system.