The objective of this study is to produce our own experimental data of physical properties of domestic concrete used in Korean NPPs, and to study on the thermal behavior of concrete exposed to high ...temperature conditions. The compressive strength and chemical composition of the concrete used in the Yonggwang NPP units 3 and 4 were analyzed. The chemical composition of Korean concrete is similar to that of US basaltic concrete. The thermal properties of the concrete, such as density, conductivity, diffusivity, and specific heat were also measured with a wide temperature range of 20–1100
°C. Most thermo-physical properties of concrete decrease with an increase in temperature except for the specific heat, and particularly the conductivity and the diffusivity are a 50% lower at 900
°C as compared with the values at room temperature. The specific heat increases until 500
°C, decreases from 700 to 900
°C, and then increases again when temperature is above 900
°C. In this work, we also have performed CORCON analysis and MCCI experiments to simulate a transient thermal behavior of concrete exposed to high temperature conditions. The measured maximum downward heat flux to the concrete specimen was estimated to be about 2.1 MW m
−2 and the maximum erosion rate of the concrete to be 175 cm h
−1 with maximum erosion depth of about 2 cm. In the CORCON analysis, it is found that the concrete compositions have an important effect upon concrete erosion.
This paper presents both experimental and theoretical works concerning evaluation of the thermal conductivity, thermal diffusivity and heat capacity of wood composites. Moreover, the aim of this ...study is to show that the transient plane source technique originally used for measuring thermal properties of isotropic materials can be spread worthy of heat capacity, thermal conductivity and thermal diffusivity measurements of highly porous materials. Measurements of the thermal conductivity, thermal diffusivity and heat capacity have been performed at room temperature (20 ± 0.5°C) and normal pressure. An attempt has been made to predict the thermal diffusivity of wood composites from the predicted values of thermal conductivity using a Verma
et al's model based on Ohms law and the calculated values of heat capacity using the enthalpy concept. The predicted values by the proposed model are compared with the values of the thermal diffusivity measured using the TPS method. A comparison shows a good agreement.
A multidimensional, finite difference numerical scheme for the freezing process of biological tissues during cryosurgery is presented, which is a modification of an earlier numerical solution for ...inanimate materials. The tissues are treated as nonideal materials, freezing over a temperature range and possessing temperature-dependent thermophysical properties, blood perfusion, and metabolic heat generation. The numerical scheme is based on the application of an effective specific heat, substituting the intrinsic property, to include the latent heat effect within the phase transition temperature range. Results of the numerical solution were verified against an existing exact solution of a one-dimensional inverse Stefan problem in Cartesian coordinates. Results were further validated against experimental data available from the literature. The utility of the numerical solution for the design and application of cryodevices is demonstrated by parametric studies of the freezing processes around spherical and cylindrical cryoprobes. The parameters studied are the cryoprobe cooling power and the dimensions of the frozen region. Results are calculated for typical thermophysical properties of soft biological tissues, for angioma and for water.
A mathematical model of simultaneous heat and moisture transfer is proposed for the prediction of moisture and temperature distributions during drying in a slab-shaped solid. The model took into ...account the effect of moisture-solid interaction at the drying surface by means of sorption isotherms of food. Non-constant physical and thermal properties were also incorporated in the model. The model was applied to the air drying of potatoes. A finite difference method (Crank-Nicolson) was used in the solution of simultaneous heat and moisture transfer equations at different times during drying. When the experimental results were compared with those obtained from the finite difference method, good agreement was found.
The thermophysical properties (effective thermal conductivity
k, permeability
K, porosity
x and effective specific heat
C) of two types of monolithic activated carbons are investigated with the ...intention of designing a high performance generator for sorption refrigeration systems and heat pumps using ammonia as refrigerant. This paper is mainly focussed on the experimental results. Typical values obtained with one of the samples tested are: thermal conductivity=0.44 W m
−1 K
−1, limiting concentration=0.36 kg NH
3/kg carbon and carbon specific heat=1080 J kg
−1 K
−1 at 100°C. The permeability results are highly anisotropic.
Describes a system for thawing frozen cell suspensions and tissues by electromagnetic absorption. A 25-ml sample is heated in a cylindrical resonant cavity, which is excited in three modes all close ...to 434 MHz. Maximum warming rates are over 10/spl deg/C/s (600 C/min), and a frozen sample may be brought from -65/spl deg/C to room temperature in <30 s, with final spatial differences of <20/spl deg/C. Samples may be frozen externally, or cooled within the cavity at typically 1/spl deg/C/min. The authors have also used the resonant cavity to measure the permittivity and conductivity of the sample at temperatures from -83/spl deg/C to +8/spl deg/C. By measuring the heat capacity of the sample, the authors have calculated the power deposited in it as a function of its temperature. The system is currently being used to investigate the effect of warming rate on cell survival.
Although a number of analyses have been presented on the size effects on transport properties like the thermal conductivity, very few studies have focused on size effects on thermodynamic properties ...like the heat capacity. The present analysis considers the effect of size on thermodynamic properties when the dimension in one, two or all three directions is extremely small, leading to a reduction in the number of phonon wave vectors. The results are presented in a novel non-dimensional form, so that the effect of dimension on the thermal properties of any material can be easily obtained once the bulk properties are known.
The average heat capacity method was successfully implemented for the analysis of conjugate heat transfer during the two-phase solidification process in continuous castings. The finite element ...technique with fixed grid was used for the current research. This method overcomes the limitation of the time increment of the otherwise so-called effective heat capacity method. The investigation included the ranges of mold cooling rate (
Bi
2) , post-mold cooling rate (
Bi
3) , superheat (Θ
o) , and withdrawal speed (
Pe) from 0.025 to 0.075, 0.042 to 0.126, 1.2 to 2.7, and 1.0 to 3.45, respectively. The current study shows that two parameters, namely,
Pe and Θ
o are very important in controlling the microstructure and breakout condition of the cast material.
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