• Transactions of the Korean hydrogen and new energy society
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• v.28 no.6
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• pp.618-626
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• 2017

Conventional high temperature reformers are not suitable for hybrid fuel cell systems that use waste heat as a heat source. So, development of a low temperature type reformer is needed. However, the analysis was conducted in two ways to increase the thermal efficiency, because of low reforming rate due to the low heat source. First, it is a way to ger thermal gain from the outside through partial insulation. In the case of one heat source tube and several heat source tubes, we analyzed the effect of partial heat insulation in some cases. Second, we found the most efficient arrangement of the heat source tubes by changing the location of the heat source tubes. The interpretation was carred out using the COMSOL Mutiphysics program.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.2
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• pp.205-214
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• 1999

The objective of this paper is to investigate the thermal properties of TMA clathrate compound applicable to cold storage system for building air-conditioning. Especially, the test tube experiments are performed by comparing and analyzing the temperature of phase change, specific heat and subcooling characteristic according to the variation of density, temperature of heat source and charging quantity in TMA clathrate compound. The results are summarized as follows:1) $-15^{\circ}C$ is not proper as the temperature of heat source because the temperature of subcooling is above $8.3^{\circ}C$ 2) temperature of phase change is dropped as the temperature of heat source is lower, 3) the effect of subcooling suppression with about 8$^{\circ}C$ is confirmed when the temperature of heat source is $-10^{\circ}C$ in case of 26, 27, and 30wt%, while the temperature of subcooling is about $0^{\circ}C$ when the temperature of heat source is $-15^{\circ}C$ in case of 25, 26 and 30wt%. Thus, the effect of subcooling suppression is greater as the temperature of heat source is lower. Additionally, the concentrative study is needed on mass concentration causing the phase change without subcooling phenomenon when the temperature of heat source is $-15^{\circ}C$. Thus, it is concluded that TMA clathrate compound has enough thermal properties as the cold storage medium for building air-conditioning.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.8
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• pp.725-734
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• 2000

The objective of this paper is to investigate the thermal properties of TMA clathrate applicable to cold storage system for building air-conditioning. Especially, the test tube experiments are peformed by comparing and analyzing the temperature of phase change, specific heat and subcooling characteristic according to the variation of concentrations and temperature of heat source in TMA clathrate. The results are summarized as follows; 1) temperature of phase change is dropped as the temperature of heat source is lower, 2) the effect of subcooling suppression with about $9.3^{\circ}C$ is confirmed when the temperature of heat source is $-10^{\circ}C$ in case of 30wt%, while the temperature of subcooling is about $0^{\circ}C$ when the temperature of heat source is $-15^{\circ}C$ in case of 25, 29wt% and 30wt% . Thus, the effect of subcooling suppression is greater as the temperature of heat source is lower. Additionally, the concentrative study is needed on mass concentration causing the phase change without subcooling phenomenon when the temperature of heat source is $-15^{\circ}C$ Thus, it is concluded that TMA clathrate has proper properties as the cold storage medium for building air-conditioning.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.162-169
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• 1999

Fourier heat conduction law becomes invalid for the situations involving extremely short time heating, very low temperatures and fast moving heat source(or crack), since the wave nature of heat propagation becomes dominant. For these conditions, the modified heat conduction equation with the finite propagation speed of heat in the medium could be applied to predict heat flux and temperature distributions. In this study, temperature distributions at the vicinity of a very fast moving heat source are investigated numerically. Thermal fields are characterized by thermal Mach numbers(M) defined as the ratio of moving heat source speed to heat propagation speed in the solid. In the transonic and supersonic ranges($M{\ge}1$), thermal shocks are shown, which separate the heat affected zone from the thermally undisturbed zone.

• Structural Engineering and Mechanics
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• v.56 no.3
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• pp.341-354
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• 2015

The dual-phase lag heat transfer model is employed to study the problem of isotropic generalized thermoelastic medium with internal heat source. The normal mode analysis is used to obtain the exact expressions for displacement components, force stress and temperature distribution. The variations of the considered variables through the horizontal distance are illustrated graphically. The results are discussed and depicted graphically.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.8
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• pp.634-640
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• 2002

The purpose of this study is to investigate the propriety of TMA clathrate as a cold storage medium. Particularly, this is to examine the extent of subcooling improvement when the additives is added to the TMA clathrate, because water used for cold storage ma terial has low phase change temperature and subcooling. This study has been analyzed and compared pure water with TMA 30 wt% clathrate how phase change temperature, subcooling and specific heat in the various concentrations are changed. This results prove low phase change temperature and subcooling control effect when the ethanol is added to the TMA 30 wt% clathrate than the TMA 30 wt% clathrate. In addition, it results low specific heat when there is added to the TMA 30 wt% clathrate over 0.5 wt% ethanol in the cold heat source temperature under $-7^{\circ}C$. The other side, it results high specific heat when the ethanol is added in it at the cold heat source temperature under $-5^{\circ}C$. Therefore, it is found that the additive must be controlled by available solution limit and study for new additive must be lasted to know its effect.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.21 no.4
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• pp.245-275
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• 2017

The present investigation deals, Dufour and heat source effects on radiative MHD slip flow of a viscous fluid in a parallel porous plate channel in presence of chemical reaction. The non-linear coupled partial differential equations are solved by using two term perturbation technique subject to physically appropriate boundary conditions. The numerical values of the fluid velocity, temperature and concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. By increasing the slip parameter at the cold wall the velocity increases whereas the effect is totally reversed in the case of shear stress at the cold wall. It is observed that the effect of Dufour and heat source parameters decreases the velocity and temperature profiles.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.11
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• pp.923-930
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• 2002

Cooling characteristics of a parallel channel with protruding heat sources using convection and conduction heat transfer are studied numerically. A two-dimensional model has been developed for numerical prediction of transient, compressible, viscous, laminar flow, and conjugate heat transfer between parallel plates with uniform block heat sources. The finite volume method is used to solve the problem. The assembly consists of two channels formed by two covers and one printed circuit board which has three uniform heat source blocks. Six different cooling methods are considered to find out the most efficient cooling method in a given geometry and heat sources. The velocity and temperature fields of cooling medium, the temperature distribution along the block surface, and the maximum temperature in each block are obtained. The results are compared to examine the cooling characteristics of the different cooling methods.

• Structural Engineering and Mechanics
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• v.68 no.2
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• pp.215-226
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• 2018

In this article, the theory of fractional order two temperature generalized thermoelasticity is employed to study the wave propagation in a fiber reinforced anisotropic thermoelastic half space in the presence of moving internal heat source. The whole space is assumed to be under the influence of gravity. The surface of the half-space is subjected to an inclined load. Laplace and Fourier transform techniques are employed to solve the problem. Expressions for different field variables in the physical domain are derived by the application of numerical inversion technique. Physical fields are presented graphically to study the effects of gravity and heat source. Effects of time, reinforcement, fractional parameter and inclination of load have also been reported. Results of some earlier workers have been deduced from the present analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.854-861
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• 2008

Heat transfer characteristics of protruding electronic components in a horizontal channel are studied numerically. The system consists of two horizontal channels formed by two covers and one printed circuit board which has three uniform protruding heat source blocks. A two-dimensional numerical model has been developed to predict the conjugate heat transfer. and the finite volume method is used to solve the problem. Five different cooling methods are considered to examine the heat transfer characteristics of electronic components according to the different cooling methods. The velocity and temperature of cooling medium and the temperature of the heat source blocks are obtained. The results of the five different cooling methods are compared to find out the most efficient cooling method in a given geometry and heat sources.