• Coupled systems mechanics
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• v.10 no.2
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• pp.103-121
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• 2021

The present research deals with the investigation of the effect of hall current in an orthotropic magneto-thermoelastic medium with two temperature in the context of multi-phase-lag heat transfer due to thermomechanical sources. The bounding surface is subjected to linearly distributed and concentrated loads(mechanical and thermal source).Laplace and Fourier transform techniques are used to solve the problem. The expressions for displacement components,stress components and conductive temperature are derived in transformed domain and furtherin physical domain with the help of numerical inversion techniques. The effect ofrotation and hall parameter hasshown with the help of graphs.

• Structural Engineering and Mechanics
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• v.81 no.4
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• pp.503-511
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• 2022

In this article, we have examined the effect of fractional order parameter in a two-dimensional orthotropic magneto-thermoelastic solid in generalized thermoelasticity without energy dissipation with fractional order heat transfer in the context of hall current, rotation and two-temperature due to normal force. Laplace and Fourier transform techniques are used to obtain the solution of the problem. The expressions for displacement components, stress components, current density components and conductive temperature are obtained in transformed domain and then in physical domain by using numerical inversion method. The effect of fractional parameter on all the components has been depicted through graphs. Some special cases are also discussed in the present investigation.

• Journal of the Korean Solar Energy Society
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• v.21 no.1
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• pp.33-42
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• 2001

The paper discusses the modelling of the thermal storage roof with the air circulation system. In this system, the fully glazed absorber plate is put on the top of the conventional pitch roof made of massive concrete and acts as a solar air heater. Solar radiation collected into absorber is stored in the roof structure by radiation and convection so that it reduces the nighttime heating load through the roof. Another part of the energy is also transmitted to internal air drawn into the channel and is then introduced Into the room. To analysis the system, the energy balance equations are developed and are solved using a finite difference method. The calculation results show a good agreement with the measured ones obtained from our experiments. From the results, it is seen that the thermal storage roof with the air circulation system reduces significantly the conductive heat loss compared with that for the conventional roof and has the instantaneous solar collection efficiency of about 30%.

• Journal of Hydrogen and New Energy
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• v.30 no.6
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• pp.540-548
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• 2019

This study was conducted to develop insulation for solid oxide fuel cell (SOFC). The developed insulation is based on the lamination technology and the radiation shielding technology of the satellite insulation. The insulation material is consisting of insulation material for conduction resistance, spacer, and radiation shielding material. The experimental apparatus consisting vacuum bell jar, pump, heater and temperature recording device has developed to verify the performance of the insulation. The experimental values were used as reference data for the modeling development. In this paper, heat transfer is assumed to be one- dimensional phenomena for the prediction of insulation performance and internal temperature distribution in high temperature region of SOFC. The developed model was used to compare the performance difference of insulation types according to composition materials. The analysis result shows that the insulation including spacer and radiation shielding has better heat insulation performance than other cases. In this study, the thickness reduction effect of about 20% was shown compared to the insulation including only conductive material. It is noted that the radiant shielding material should be carefully selected for durability, because SOFC insulation should be used for a long time at high temperature.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.531-538
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• 2012

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and $TiO_2$ for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the $TiO_2$ is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of $TiO_2$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.122-129
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• 2019

Predicting heat transfer from the inner wall of the combustion chamber of the liquid rocket is a very difficult task. Several complex processes, such as convection, radiation and conduction must be taken into consideration. Usually commercial programs are used for the analysis of this processes. However, commercial programs are not a perfect solution, because of the long calculation times and a burdening data-input work. In this study, we developed and implemented one - dimensional thermal analysis. This technique can be easily used on the initial stage. The design of the combustion chamber's cooling channel of the steam generator designed using developed technique. In order to compare experimental and theoretical data, the combustion test was performed. Obtained experimental data for the coolant temperature differ from the theoretical prediction by only 8.5%.

• Korean Journal of Food Science and Technology
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• v.15 no.3
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• pp.282-286
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• 1983

In order to obtain practical information for efficient energy usage in sterilization, energy consumption was monitored for various processing variables, i.e. heat transfer type (conduction and convection), can size (No. 202-2, No. 301-3, No. 301-7, and No. 603-2), retorting temperature $(110^{\circ}C-121^{\circ}C\;and\;130^{\circ}C)$, and sterilization method (steam, and hot water sterilization). Less energy was consumed for smaller can size and higher temperature, and this trend was more distinguished in conductive food than convective food. Hot water sterilization could lower energy consumption in conductive food, but not in convective food. Energy consumption data of this work was reasonable when compared with energy consumption of sterilization in canneries, and therefore thought to be able to be used for estimation, design and optimization of energy consumption in sterilization.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1844-1851
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• 2017

As the capacity of the wireless power transmission increases, a higher supply current which may induce current in nearby conductive parts requires. Induced current may affect electric shock to the human body and malfunction of the electrical equipment. In order to prevent such induced phenomena as a risk factor, shielding is required between the source of the wireless power transmission and the conductive parts. The resonance frequency for the large capacity wireless power transmission has the wavelength of several hundred meters, so most environments are included in the near-field area. By wave impedance, the electric field has higher density in the near-field area and needs to be analyze for protecting. For this purpose, it is necessary to select a substance having a larger electric conductivity and optimized shielding structure. In this paper, an aluminum base shielding structure was presented to conduct experiments on thickness, position, and heat dissipation. In the 35 kW, 60 kHz environments, the optimized 5T Al base shielding structure attenuates the induced current to 43 %.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.181-188
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• 2001

The present research is an experimental study of subcooled flow boiling behavior using flat, microporousenhanced square heater surfaces in pure FC-72. Two $1-cm^{2}$ copper surfaces, one highly polished (plain) and one microporous coated, were flush-mounted into a 12.7 mm square, horizontal flow channel. Testing was performed for fluid velocities ranging from 0.5 to 4 m/s (Reynolds numbers from 18,700 to 174,500) and pure subcooling levels from 4 to 20 K. Results showed both surfaces' nucleate flow boiling curves collapsed to one line showing insensitivity to fluid velocity and subcooling. The log-log slope of the microporous surface nucleate boiling curves was lower than the plain surface due to the conductive thermal resistance of the microporous coating layer. Both, increased fluid velocity and subcooling, increase the CHF values for both surfaces, however, the already enhanced boiling characteristics of the microporous coating appear dominant and require higher fluid velocities to provide additional enhancement of CHF to the microporous surface.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.73-80
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• 2016

The preliminary test for the dual mode plasma torch system was carried out to explore the operation properties in advance. The dual mode plasma torch system that is able to operate in transferred, non-transferred, or dual mode is very adequate for melting the mixed wastes including nonconductive materials such as concrete, asbestos, etc. since it exploits both the high efficiency of heat transfer to the melt in transferred mode and stable operation in non-transferred mode. Also, system operation including restarting is reliable and very easy. A stationary melter with a refractory structure was designed and manufactured considering the melting behavior of slags to minimize the refractory erosion. The power supply for the dual mode plasma torch system built with high power insulated gate bipolar transistor (IGBT) modules has functions for both current control and voltage control and is sufficient to suppress the harmonics during the operation of the plasma torch. The power supply provides two different voltages for transferred operation and non-transferred. It is confirmed that the operation voltage in transferred is always higher than non-transferred. The dual mode plasma torch system was successfully developed and is under operation for a melting experiment to optimize operation data.