• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.286-291
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• 2008

Insulation of refrigerator with gasket material near door becomes the technical point at the aspect of heat loss and energy efficiency. Heat loss of refrigerator through the gasket is nearly 30%. In this paper, quantitative evaluation method of heat loss through gasket in established suggest the method for the improvement of heat loss. To analyze the heat transfer, we have used the common software Fluent that is used to CFD. Because of using the convection coefficient of heat transfer, we have solved only the equation of energy for heat transfer. As a result, we have known that heat loss flows through the heat flux vector and that the heat gathered out of the outside iron plate is transferred inner part through the gasket and ABS, etc. Through the result of the numerical simulation that use sub-gasket, we have known that we are able to reduce the heat loss about $20{\sim}40%$. when we applied that sub-gasket on a real refrigerator, the power consumption had reduced about 4.76%. In addition, when we applied a more improved sub-gasket on a real refrigerator and measured the power of the refrigerator the power consumption does reduce about 3% and we will try to apply the improved sub-gasket on a new models of refrigerator.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2C
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• pp.69-77
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• 2012

In general, geothermal energy pile and horizontal ground heat exchangers are installed in shallower depths than conventional vertical ground coupled heat pumps. Consequently their heat exchange performance is strongly governed by thermal conductivity of soil layer. Previous studies have shown that the thermal conductivity of soil above ground water table significantly affects the heat exchange rate because of partially saturated condition in soil and consequent variation of soil thermal conductivity. This paper presents a study result on the prediction of thermal conductivity of weathered granite soils. For weathered granite soils sampled from 5 locations, thermal conductivity tests were conducted with varying porosity and degree of saturation. The existing thermal conductivity models in literatures appeared inappropriate to the weathered granite soils. Hence, an empirical equation was proposed in this paper and its validity was examined by applying it to thermal conductivity test results obtained for weathered granite soils in this study and from literatures.

• Fire Science and Engineering
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• v.18 no.3
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• pp.45-50
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• 2004

Thermal degradation of PVC which used for insulator of 600V vinyl insulated wire has been studied by thermo gravimetry analysis and accelerated thermal aging test. The activation energy using thermo gravimetry analysis was determined by the kinetic methods, such as Kissinger and Flynn-Wall-Ozawa. The activation energy was determined to from 89.29 kJ/mol to 111.39 kJ/mol in 600V PVC insulated wire and from 97.80 kJ/mol to 119.25 kJ/mol in 600v heat-resistant PVC insulated wire. And also, the activation energy through a long-term thermal aging test was calculated by using Arrhenius equation In the low temperature of 8$0^{\circ}C$, 9$0^{\circ}C$, 10$0^{\circ}C$. The results showed that 600V PVC insulated wire was 92.16 kJ/mol, and 600v heat-resistant PVC insulated wire was 97.52 kJ/mol. Consequently, the activation energy of 600V heat-resistant PVC insulated wire is larger than 600V PVC insulated wire. Therefore, it can be predicted that 600V heat-resistant PVC insulated wire has a long-term stability relatively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.577-582
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• 2015

This paper is the fundamental study for the application of cold storage system to the transportation equipment by sea and land. This numerical study presents the solid-liquid phase change phenomenon of calcium chloride solution of 30wt %. The governing equations are 1-dimensional unsteady state heat transfer equations of $1^{st}$ order partial differential equations. This type of latent heat storage material is often usable in fishery vessel for controlling the temperature of container with constant condition. The governing equation was discretized with finite difference method and the program was composed with Mathcad program. The main parameters of this solution were the initial temperature of heat storage material, ambient temperature of cold air and the velocity of cold air. The data of boundary layer thickness becomes thin with the increasing of cold air flowing velocity and also the heat storage completion time become shorten.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2384-2389
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• 2007

The 2nd order response surface method (RSM) has been carried out to get optimum thermal design for enhanced heat transfer on square channel with bleed holes. The RSM was used as an optimization technique with Reynolds-averaged navier-stokes equation. Turbulence model for heat transfer analysis used RNG k-epsilon model. The wall function used enhanced wall function. Numerical local heat transfer coefficients were similar to the experimental tendency. Two design variables such as attack angle of rib (${\alpha}$), rib pitch-to-rib height ratio (p/e) were chosen. Operation condition considered bleeding ratio per bleed hole ($BR_{hole}$). A response surface were constructed by the design variables and operation condition. As a result, adjusted $R^2$ was more than 0.9. Optimization results of various objective function were similar to heat transfer in channel with and without bleed flow. But friction factor was lower than channel without bleed flow.

• International Journal of Highway Engineering
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• v.17 no.4
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• pp.33-40
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• 2015

PURPOSES: Evaluation of the wind speed effect on the temperature drop of an asphalt mixture during construction, by using the transient heat transfer theory and dominant convective heat transfer coefficient model. METHODS: Finite difference method (FDM) is used to solve the transient heat transfer difference equation numerically for various wind speeds and initial temperature conditions. The Blasius convective heat transfer coefficient model is adapted to account for the effect of wind speed in the temperature predictions of the asphalt mixture, and the Beaufort number is used to select a reasonable wind speed for the analysis. As a function of time and depth, the temperature of the pavement structure is predicted and analyzed for the given initial conditions. RESULTS : The effect of wind speed on the temperature drop of asphalt mixture is found to be significant. It seems that wind speed is another parameter to be accounted for in the construction specifications for obtaining a better quality of the asphalt mixture. CONCLUSIONS: It is concluded that wind speed has a significant effect on the temperature drop of the asphalt layer. Although additional field observations have to be made to reflect the effect of wind speed on the construction specifications, it appears that wind speed is a dominant variable to be considered, in addition to the atmospheric temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.431-438
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• 2000

The major irreversibilities in absorption chillers are associated with the transfer of heat into and out from the machine and irreversible process inside the machine. By modeling only external irreversibilities(endo-reversible), a model was formulated to predict the ideal performance of a single-effect absorption chiller. Its actual performance including both external and internal irreversibilities was calculated with a in-house simulation program. The optimization of heat transfer area distribution was performed for both endo-reversible cycle and actual cycle. The equation of endo-reversible modeling was found to give about 2times higher cooling capacity than the simulation program. At optimal distribution, it was found that heat transfer area of the evaporator was about 30% of total area, that of the generator was 20%, and the rest 50% was for the absorber and condenser. The system COP for endo-reversible cycle was slightly higher than that for actual cycle. In the case of LiBr-water single-effect absorption chiller, the maximum cooling capacity was obtained near the condition that LMTD is same at all heat exchangers.

• Journal of Mechanical Science and Technology
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• v.14 no.3
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• pp.350-357
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• 2000

Experiments were performed by using PF-5060 and water to investigate the influence of an aspect ratio of a horizontal rectangular channel on the cooling characteristics from an in-line $6{\times}1$ array of discrete heat sources which were flush mounted on the top wall of the channel. The experimental parameters were aspect ratio of rectangular channel, heat flux of simulated VLSI chip, and channel Reynolds number. The chip surface temperatures decreased with the aspect ratio at the first and sixth rows, and decreased more rapidly at a high heat flux than at a low heat flux. The measured friction factors at each aspect ratio for both water and PF-5060 gave a good agreement with the values predicted by the modified Blasius equation within ${\pm}7%$. The Nusselt number increased as the aspect ratio decreased, but the increasing rate of Nusselt number reduced as the aspect ratio decreased. A 5:1 rectangular channel yields the most efficient cooling performance when the heat transfer and pressure drop in the test section were considered simultaneously.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.1
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• pp.69-81
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• 2015

The present paper deals with the determination of temperature, displacement and thermal stresses in a semi-infinite hollow circular disk due to internal heat generation within it. Initially the disk is kept at arbitrary temperature F(r, z). For times t > 0 heat is generated within the circular disk at a rate of g(r, z, t) $Btu/hr.ft^3$. The heat flux is applied on the inner circular boundary (r = a) and the outer circular boundary (r = b). Also, the lower surface (z = 0) is kept at temperature $Q_3(r,t)$ and the upper surface ($Z={\infty}$) is kept at zero temperature. Hollow circular disk extends in the z-direction from z = 0 to infinity. The governing heat conduction equation has been solved by using finite Hankel transform and the generalized finite Fourier transform. As a special case mathematical model is constructed for different metallic disk have been considered. The results are obtained in series form in terms of Bessel's functions. These have been computed numerically and illustrated graphically.

• Communications of the Korean Mathematical Society
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• v.33 no.3
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• pp.1025-1037
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• 2018

We consider an ill-posed problem for the heat equation $u_{xx}=u_t$ in the quarter plane {x > 0, t > 0}. We propose a new method to compute the heat flux $h(t)=u_x(1,t)$ from the boundary temperature g(t) = u(1, t). The operator $g{\mapsto}h=Hg$ is unbounded in $L^2({\mathbb{R}})$, so we approximate h(t) by $h_{\delta}(t)=u_x(1+{\delta},\;t)$, ${\delta}{\rightarrow}0$. When noise is present, the data is $g_{\epsilon}$ leading to a corresponding heat $h_{{\delta},{\epsilon}}$. We obtain an estimate of the error ${\parallel}h-h_{{\delta},{\epsilon}}{\parallel}$, as well as the error when $h_{{\delta},{\epsilon}}$ is approximated by the trapezoidal rule. With an a priori choice rule ${\delta}={\delta}({\epsilon})$ and ${\tau}={\tau}({\epsilon})$, the step size of the trapezoidal rule, the main theorem gives the error of the heat flux as a function of noise level ${\epsilon}$. Numerical examples show that the proposed method is effective and stable.