Feasibility Study of Noninvasive Measurement of Thermal Conductivity and Thermal Diffusivity for Biological Materials

2007 ◽  
Author(s):  
Keisuke Yoshida ◽  
Satoru Uchida ◽  
Hiroshi Takamatsu ◽  
Motoo Fujii
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Laser Irradiation ◽  
Temperature Fluctuation ◽  
Irradiation Time ◽  
Temperature Response ◽  
Biological Materials ◽  
Material Surface ◽  
Accuracy Of Measurement

A noninvasive technique was developed to measure the thermophysical properties of biological materials. In this technique the temperature response of a material surface heated by CO2 laser irradiation is measured with an infrared thermometry and compared with the theoretical response. The thermal conductivity and the thermal diffusivity are determined as the both values which yield the smallest deviation between the measured and analyzed temperature responses. The objective of the present study is to establish this technique by investigating the uncertainty of the method. An appropriate model of heat transfer is discussed first by taking into account of the effect of the laser absorption within the material and a heat loss from the material surface to the ambient. Then the accuracy of measurement is examined by using virtual experimental data with temperature fluctuation expected in an actual experiment. The virtual experimental data are generated by adding artificial fluctuation to a theoretical temperature response. The accuracy of measurement is estimated as a function of the standard deviation (S.D.) of the temperature fluctuation and the laser irradiation time. The effect of uncertainty in the absorption coefficient of the target material is also examined.

Thermal Properties of Electro Insulating Paper

2019 ◽  
Vol 955 ◽  
pp. 25-30
Author(s):  
Lucie Marackova ◽  
Veronika Melcova ◽  
Josef Samek ◽  
Oldrich Zmeskal
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Temperature Response ◽  
Differential Method ◽  
Thermal Parameters ◽  
Insulating Paper ◽  
Steady State Temperature

This paper is focused on the determination of thermal parameters (thermal conductivity, thermal diffusivity, and specific heat capacity) of electrical insulating paper from various producers. The transient step-wise method was used to determine all thermal parameters simultaneously. Evaluation was carried out using the differential method. Thermal conductivity was determined from the steady-state temperature response on thickness (corresponding to the number of paper layers), while thermal diffusivity and specific heat capacity was obtained from the dependence of derivative maximum and the corresponding temperature on thickness. Four electro insulating papers differing by composition and thickness: materials NKN (Nomex-Kapton-Nomex), DMD (Dacron-Mylar-Dacron), TFT (TufQUIN TFT 50) and TVAR (ThermaVolt AR) were studied. As a result, the highest value of thermal conductivity (0.17 W/m/K) was determined for the DMD. Remaining three materials possessed thermal conductivity about 0.12 W/m/K. However, differences in specific heat capacity and thermal diffusivity were found to be significantly higher. The lowest specific heat capacity was found for the DMD sample (1200 J/kg/K), while the highest specific heat capacity was found for TVAR sample (4000 J/kg/K).

Laser Flash Measurement of Samples With a Transparent Reference Layer

2009 ◽  
Author(s):  
Heng Ban ◽  
Zilong Hua
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Temperature Response ◽  
Front Surface ◽  
Laser Flash ◽  
Laser Flash Method ◽  
Flash Method ◽  
Thermal Diffusivity Measurement ◽  
Reference Layer

The laser flash method is a standard method for thermal diffusivity measurement. This paper reports the development of a method and theory that extends the standard laser flash method to measure thermal conductivity and thermal diffusivity simultaneously. By attaching a transparent reference layer with known thermal properties on the back of a sample, the thermal conductivity and thermal diffusivity of the sample can be extracted from the temperature response of the interface between the sample and the reference layer to a heating pulse on the front surface. The theory can be applied for sample and reference layer with different thermal properties and thickness, and the original analysis of the laser flash method becomes a limiting case of the current theory with an infinitely small thickness of the reference layer. The uncertainty analysis was performed and results indicated that the laser flash method can be used to extract the thermal conductivity and diffusivity of the sample. The results can be applied to, for instance, opaque liquid in a quartz dish with silicon infrared detector measuring the temperature of liquid-quartz interface through the quartz.

Thermophysical Characterization of Genipap Pulp

2010 ◽  
Vol 6 (3) ◽  
Author(s):  
Normane Mirele Chaves da Silva ◽  
Renata Cristina Ferreira Bonomo ◽  
Luciano Brito Rodrigues ◽  
Modesto Antonio Chaves ◽  
Rafael da Costa Ihéu Fontan ◽  
...  
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Water Content ◽  
Thermophysical Properties ◽  
Empirical Models ◽  
Influence Of Temperature ◽  
Thermophysical Characterization

The influence of temperature and water content on thermophysical properties (density, thermal diffusivity, thermal conductivity and specific heat) of genipap (Genipa americana, L) pulp at medium maturity were studied. The thermophysical properties were determined at concentrations between 6.0% m/m and 24.0% m/m of water content and temperatures range of 5 to 80°C. The density decreased with increase in temperature and water content, while the thermal diffusivity and conductivity increased as temperature and water content increased. The specific heat decreased with the moisture content. Empirical models were fitted to the experimental data for each property and the accuracy of those models was checked.

PENENTUAN SIFAT TERMOFISIK MAHKOTA DEWA (THERMAL PROPERTIES OF Phaleria macrocarpha)

2013 ◽  
Vol 13 (3) ◽  
Author(s):  
Lamhot P. Manalu
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Temperature Change ◽  
Measurement Method ◽  
Indirect Methods

of information on their thermal properties. Although a lot of experimental data can be found, the variety of products and the differences in measurement method make limitation on the value of the available data, especially for Indonesia’s products. These data are needed to get information about temperature change when a product was processed by heating or cooling. The data are important for optimizing the efficiency of energy used in the process. The objective of this study is to determine thermal diffusivity and conductivity of mahkota dewa or crown of god (Phaleria macrocarpha). The values were determined numerically with indirect methods. The result shows that thermal conductivity of mahkota dewa is 0.1359 W/moC, while its thermal diffusivity is 4.11x10-8 m2/s.

Method for Obtaining Thermal Conductivity From Modified Laser Flash Measurement

2005 ◽  
Author(s):  
Bochuan Lin ◽  
Heng Ban ◽  
Chao Li ◽  
Rosalia N. Scripa ◽  
Ching-Hua Su ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Rear Surface ◽  
Temperature Response ◽  
Laser Flash ◽  
Fused Silica ◽  
Laser Flash Method ◽  
Flash Method ◽  
Silica Cell

Laser flash method is commonly used to measure the thermal diffusivity of solids. In the original thermal analysis, adiabatic boundary conditions were used and the time for sample rear surface temperature to reach 50% of maximum value was used to calculate the thermal diffusivity. Later other boundary conditions were included in the analysis to compensate for the heat loss. The laser flash method can be modified to determine the thermal conductivity by comparing the temperature rise of the sample with a standard sample, both of which are coated to ensure identical surface emissivity. In our previous studies of applying the laser flash method to semiconductor melts, we have shown that it is possible to obtain thermal conductivity, specific heat capacity and thermal diffusivity from the experimental data. In these studies, the melt sample was sealed in a specially-designed fused silica cell. The heat transfer between melt sample and the fused silica cell allows the thermal conductivity to be included in the analysis. Therefore, the temperature response of the melt sample was controlled not only by the thermal diffusivity and conductivity of sample, but also by the thermal properties of fused silica cell. Using a computational fitting process, we obtained both thermal diffusivity and thermal conductivity of the sample. In this paper, an analytic solution for the transient heat transfer inside the sample and fused silica cell was developed. The influence of fused silica cell was included and the heat transfer to fused silica cell had a significant effect on the time-temperature response of the sample. Therefore, the rear surface temperature of the sample, described by an analytical solution, could be used to obtain both thermal diffusivity and thermal conductivity of the sample with known properties of the fused silica cell. The results indicated that this method was applicable for a wide range of sample and cell properties. The original solution for laser flash method became an extreme case in the current theory

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