• Journal of the Korean housing association
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• v.6 no.2
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• pp.51-55
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• 1995

This study presents a real neutral floor surface temperature in floor panel heating system(Ondol). The Ondol heating system can keep the constant temperature. However, the actual temperature when a person sits on a floor can be different from the surface temparature of a floor it self. The contents of this study are as follows : 1) measuring the spatial distributions of thermal conditions 2) the thermal sensation vote of residents is taken in order to investigate the relation between thermal condition and human thermal sensation in sedentary condition 3) estimating the neutral floor surface temperatures by measuring floor surface temperatures.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.969-974
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• 2002

Thermal characteristics according to the cooling methods are studied for the three type spindles with high frequency motor. For the analysis, three dimensional mode]s are built considering heat transfer characteristics such as natural and force convection coefficients. Unsteady-state temperature distributions and thermal deformations according to the cooling conditions are analyzed by using the finite element method.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.273-276
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• 2007

A natural graphite heat spreader increased the upper operating temperature limit of a CCFL backlit LCD television. A 0-80W heat source was used to simulate additional electronics. Without the heat spreader, internal circuitry shut-down at ${\sim}30;$ no shut-down occurred above 80W with a heat spreader. Additionally, brightness, temperature uniformity, and operating ranges were improved, verified by environmental chamber performance testing at various ambient conditions.

• 연구논문집
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• s.24
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• pp.151-159
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• 1994

The heat transfer and thermal stress analysis was performed on the ceramic core of the matrix-type recuperator. The efficiency was calculated as 34% to 65%. Triple-pass arrangement provided higher preheated air temperatures, lower thermal stresses and the increase of pressure drops. Higher temperature gradients and maximum peak stresses appeared on the corners of the ceramic core. The effect of boundary conditions was significant and the use of spring-load sealing mechanism could release thermal stresses.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.427-432
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• 2005

This study treats the advantage of in situ line source method measuring the heat transfer capacity of a borehole, using mobile equipment, to determine the thermal properties of the entire borehole system such as thermal conductivity, diffusiveity. volumetric heat capacity, and borehole thermal resistance. The results from the response test include not only the thermal properties of the ground and the borehole, but also conditions that are difficult to estimate, e,g. natural convection in the boreholes, asymmetry in the construction, etc. In this study, 1) theoretical in situ methods for assessing working fluid temperature variation in V-type PE tube have been introduced, and 2) TRTE(Thermal Response Test Equipment) has been built based on these kinds of theoretical in situ methods. Basically TRTE consists of a pump, a heater and temperature sensors for measuring the inlet and outlet temperatures of the borehole. In order to make equipment easily transportable it is set up on a small trailer. Since the response test takes above two days to execute, the test was fully automatic in recording measured data using Labview DAS(Data acquisition system) program. The test was demonstrated in the course of intensive research in this field through the one site at Ulsan city in Korea. From this kind of thermal properties test of borehole systems in situ, the design of the borehole system can be optimized regarding the total geological, hydro-geological and technical conditions at the location.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.294-301
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• 2018

In winter, thermal screens are widely used to reduce heat loss from greenhouse to save energy. Unfortunately, not much data are available to the farmer to compare thermal screens while selecting the one that meets their specific requirements. Thus, there is a need to investigate the thermal performance of thermal screens. To address this issue, the Building Energy Simulation (BES) model of a hot box was used to calculate the overall heat transfer coefficient (U-value) of the thermal screens. To validate the model, computed and experimental U-values of single-and double-layered polyethylene (PE) material were compared. This validated model was used to predict the U-values of the selected thermal screens under defined weather conditions. We quantified the U-values of each selected material and significant changes in their U-values were noted in response to different weather conditions. Notably, the thermal properties of the tested screens were taken from the previous literature to calculate U-values using the BES model. The U-values of the thermal screens can help researchers and farmers evaluate their screens and make pre-design decisions that suit their investment capabilities.

• Geophysics and Geophysical Exploration
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• v.21 no.4
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• pp.220-230
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• 2018

When thermal conductivity of rock is measured with PEDB (Portable Electronic Divided Bar) in a laboratory, it can be greatly influenced by the change of room temperature. Therefore, measuring the thermal conductivity in a thermo-hygrostat is necessary, where it can remain in its constant temperature and humidity condition. In this study, a system for thermal conductivity measurement in a thermo-hygrostat has been set up and the thermal conductivities for the 45 samples collected from GH3 and GH4 boreholes in Ulleung Island have been measured both in dry and saturated conditions. Also, the correlations between those thermal conductivities, density, and effective porosity have been discussed. As a result of correlation analysis among the thermal conductivity, density, and effective porosity, it showed higher correlation with dry samples than saturated samples. Especially, thermal conductivity ratio between saturated and dry conditions shows very high correlation ($R^2=0.90$) with effective porosity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1968-1973
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• 2004

Structural degradations are often experienced on the components of nuclear power plants in reactor pressure vessels (RPV) and steam generators (SG) when these components are exposed to high temperature and high pressure for a long period of time. Such conditions result in the change of microstructures and of mechanical properties of materials, which requires an evaluation of the safeguards related to structural integrity. In a primary reactor cooling system (RCS), a dissimilar weld zone exists between cast stainless steel (CF8M) in a pipe and low-alloy steel (SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time under the operating temperature between 290 and 33$0^{\circ}C$. Under the same conditions, it is well known that degradation is not observed in low alloy steel. An investigation of the effect of thermal aging on the various mechanical properties of the dissimilar weld zone is required. The purpose of the present investigation is to find the effect of thermal aging on the dissimilar weld zone. The specimens are prepared by an artificially accelerated aging technique maintained for various times at 43$0^{\circ}C$, respectively. Then, The various mechanical test for the dissimilar welds are performed.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.1-4
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• 2005

A higher order zig-zag shell theory is developed to refine accurately predict deformation and stress of smart shell structures under the mechanical, thermal, and electric loading. The displacement fields through the thickness are constructed by superimposing linear zig-zag field to the smooth globally cubic varying field. Smooth parabolic distribution through the thickness is assumed in the transverse deflection in order to consider transverse normal deformation. The mechanical, thermal, and electric loading is applied in the sinusoidal distribution function in the in-surface direction. Thermal and electric loading is given in the linear variation through the thickness. Especially, in electric loading case, voltage is only applied in piezo-layer. The layer-dependent degrees of freedom of displacement fields are expressed in terms of reference primary degrees of freedom by applying interface continuity conditions as well as bounding surface conditions of transverse shear stresses. In order to obtain accurate transverse shear and normal stresses, integration of equilibrium equation approach is used. The numerical examples of present theory demonstrate the accuracy and efficiency of the proposed theory. The present theory is suitable for the predictions of behaviors of thick smart composite shell under mechanical, thermal, and electric loadings combined.

• Journal of the Korean Society of Combustion
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• v.15 no.4
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• pp.58-64
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• 2010

Spontaneous ignition tests of five different coals with non-iso-thermal and iso-thermal test method based on the standard test procedure of NF T20-036 were carried. These five coals included the 2 low rank coals and 3 bituminous coals. Test results showed that the ignition temperatures of all coals at the iso-thermal conditions were higher than that of non-isothermal condition, and those of low rank SM and BR coal in both nonisothermal and isothermal conditions were lower than bituminous AN and CN coals. The chemical species of coals such as oxygen and hematite also plays an important role in enhancing the ignition rate that the ignition temperature of SM coal was lowered. The heat accumulation tendency of five coals inside outdoor stack pile was monitored with emphasis on the change in the temperature of the coal depth in stack pile. In case of low rank BR coal, its temperature inside coal stack pile due to the rate of high heat accumulation and oxidation was $59^{\circ}C$ compared to $51^{\circ}C$ for other SW bituminous coal. And the heat accumulation rate inside coal stack piles was increased with increased the Cp value which it was defined as the specific heat of coal at constant pressure, whereas other factors such as thermal diffusivity and conductivity of coal relatively had less effect on heat accumulation.