• Journal of the Korean GEO-environmental Society
• /
• v.13 no.3
• /
• pp.21-27
• /
• 2012

Estimating the thermal conductivity of clayey soils is important for enhancing the performance of geoengineering structures in cold regions and clay barriers for nuclear waste repositories, but specimen disturbance, saturation, and heat boundary conditions of the test apparatus hinder reliable measurements of the thermal conductivity of saturated clayey soils. This paper presents the results of an experimental study carried out using modified consolidation tests with the needle probe method to measure thermal conductivity. Experimental consolidation tests with saturated kaolinite were performed to investigate the effect of effective stress and dry density on thermal conductivity for saturated kaolinite. In addition, thermal conductivity of soil particles were thoroughly investigated and experimental results were used to evaluate the accuracy of the models to predict thermal conductivity.

• The Journal of Engineering Geology
• /
• v.21 no.2
• /
• pp.157-162
• /
• 2011

Experimental tests have been performed to measure the thermal conductivity of unsaturated soils, and computational models have been widely used to predict thermal conductivity. However, measured values of the thermal conductivity of unsaturated soils cannot be compared with predicted values because of the gradient in moisture content within unsaturated soils. In this study, experimental consolidation tests on saturated unfrozen kaolinite were performed to investigate the effect of dry density and moisture content on thermal conductivity. The results were used to evaluate the validity of a model employed to calculate thermal conductivity.

• The Journal of Engineering Geology
• /
• v.22 no.3
• /
• pp.275-281
• /
• 2012

Thermal distribution in soils must be considered in engineering designs and constructions, including estimates of frost heave and thaw settlement, infrastructure in cold regions, and geothermal systems. Because thermal conductivity is a key parameter for evaluation of thermal distribution in soils, it must be accurately estimated. The thermal conductivity of fine-grained soils has been widely studied in recent years; however, few studies have reported a reliable method for experimental measurement. The present study presents the results of an experimental investigation of the thermal conductivity of a saturated kaolinite-silica mixture with respect to the variation of dry density. Thermal conductivities were measured in Constant Rate of Strain (CRS) consolidation tests, and the experimental data were analyzed to evaluate the accuracy of the new measurement system. In addition, we present an evaluation method for predicting thermal conductivity in fine-grained soils.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.10
• /
• pp.887-894
• /
• 2013

Effective thermal conductivity of nanofluids has been predicted by using generalized self-consistent model and modified Eshelby model, which have been used for analysis of material properties of composites. A nanolayer between base fluid and nanoparticle, one of key factors for abrupt enhancement of thermal conductivity of nanofluids, is included in the analysis. The effective thermal conductivities of the nanofluid predicted by the present study show good agreement with those by models in the literature for the nanolayer with a constant or linear thermal conductivity. The predicted results by the present approach have been confirmed to be consistent with experiments for representative nanofluids such as base fluids of water or ethyleneglycol and nanoparticles of $Al_2O_3$ or CuO to be validated.

• Composites Research
• /
• v.14 no.3
• /
• pp.57-68
• /
• 2001

This paper predicted the thermal conductivity of spatially reinforced composites(SRC) by applying the volume averaging method and the thermal resistance method. The former method employs existing micro-mechanical theories and conventional transformation rules to obtain the constitutive relations for the unit cells of the composites and the latter one uses the analogy between the diffusion of heat and electrical charge. To verify the theoretical predictions, the thermal conductivity of 4-D(dimensional) SRC was examined experimentally. The comparison of the numerical results with those measured by the experiment showed good agreement.

• Journal of Biosystems Engineering
• /
• v.22 no.1
• /
• pp.59-67
• /
• 1997

An experimental apparatus was developed for the rapid determination of thermal conductivity by transient probe method. The theoretical basis for transient probe method has been investigated. The mathematical model for this method is the Carslaw and Jaeger model which is used perfect line source theory. The small needle probe which is equipped with thermocouple and heating element is constructed. A software that performs data analysis and acquisition is programmed. The influence of the power dissipated per unit length of the probe has been assessed for glycerin. The result showed no significant correlation between thermal conductivity and power input. Determination made with this experimental apparatus were found to agree well with the recommended thermal conductivity data.

• The Korean Journal of Food And Nutrition
• /
• v.17 no.1
• /
• pp.32-40
• /
• 2004

This Study was conducted to predict temperature profile of Jangjorim (boiled beef in soy sauce) food during retorting using the commercial NISA (Numerical Integrated Elements for System Analysis) program. NISA program is a good tool to simulate the temperature profile of a specific material based upon the finite element method. The cold point of Jangjorim food located not at the geometrical center but at 26.9 mm backward in y plane because specific heat of soy sauce was 20% higher than that of boiled beef. The effects of heat transfer coefficients on heat transfer during retorting process of Jangjorim were analyzed by response surface methodology (RSM). Independent variables were thermal conductivity of soy sauce, thermal conductivity of boiled beef, and convection heat transfer coefficient and dependent variables were temperature error and lethality error. Thermal conductivity of soy sauce was the most significant contributor among those (P<0.01).

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.6
• /
• pp.966-975
• /
• 1986

유한한 열전도율과 두께를 갖는 수평동심원관 내의 층류자연대류 문제를 유한차분법을 사용하여 수치적으로 연구하였다. 동심원관 내에는 전도-대류가 복합되어, 전체-유체 경계면에서의 온도분포는 미리 알려져 있지 않다. Prandtl수를 0.7, L/D$_{i}$ = 0.8로 고정하고 각각의 Rayleigh수와 열전도계수의 비, 기하학적변수에 대하여 계산을 수행하였으며, 그 결과를 등온 수평동심원관의 경우와 비교하였다. Rayleigh수와 t/D$_{i}$가 클수록, 열전도계수의 비 K가 작을수록 열저도 효과는 강하게 나타났으며, 국소등가전도계수와 온도분포에 비하여 속도분포는 영향을 덜 받는다는 것이 밝혀졌다.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.23 no.4
• /
• pp.95-103
• /
• 2015

The purpose of this study was performed to quantitatively measure the thermal conductivity of poultry slaughter waste with variation of reaction temperature for optimal design of thermal hydrolysis reactor. We continuously quantified the thermal conductivity of dehydrated sludge related to the reaction temperature. As the reaction temperature increased, the dehydrated sludge is thermally liquefied under high temperature and pressure by the thermal hydrolysis reaction. Therefore, the bond water in the sludge cells comes out as free water, which changes the dehydrated sludge from a solid phase to slurry of a liquid phase. As a result, the thermal conductivity of the its sludge was more than 2.11 times lower than that of the water at $20^{\circ}C$. However, the thermal conductivity of the sludge approached to $0.677W/m{\cdot}^{\circ}C$ of water at $200^{\circ}C$, experimentally substantiating liquefaction of the dehydrated sludge. Therefore, we confirmed that the change in physical properties due to thermal hydrolysis appears to be an important factor for heat transfer efficiency. And the thermal conductivity function related to reaction temperature was derived to give the boundary condition for the optimal design of the thermal hydrolysis reactor. The consistency of the calculated function was 99.69%.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.4
• /
• pp.347-355
• /
• 2014

Thermal problems that are directly related to the lifetime of an electronic device are becoming increasingly important owing to the miniaturization of electronic devices. To solve thermal problems, it is essential to study thermal stability through thermal diffusion and insulation. A honeycomb sandwich plate has anisotropic thermal conductivity. To analyze the thermal deformation and temperature distribution of a system that employs a honeycomb sandwich plate, the thermal and elastic properties need to be determined. In this study, the thermal and elastic properties of a honeycomb sandwich plate, such as thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and shear modulus, are predicted. The properties of a honeycomb sandwich plate vary according to the hexagon size, thickness, and material properties.