scholarly journals The thermal conductivity of vitreous silica, with a note on crystalline quartz

1926 ◽  
Vol 113 (764) ◽  
pp. 335-351 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Scientific Work ◽  
Vitreous Silica ◽  
Crystalline Quartz ◽  
Temperature Range ◽  
Physical Constants ◽  
Extended Application ◽  
The Mean

Vitreous silica is a material which finds extended application in many branches of scientific work, and considerable attention has been given to some of its physical constants. Little work has, however, been done on the thermal conductivity. Eucken and Barratt appear to be the only workers who have attacked the problem, their results being by no means in agreement, as is shown in Table I. This paper gives an account of a determination of the thermal conductivity of clear transparent vitreous silica over a temperature range of approximately 60° to 240°C. The value obtained for the conductivity at 100°C. is 0.00338, and for the mean change of conductivity per °C. 0.0000018 5 . Thus the figures do not agree with the results of either Eucken or Barratt, except that the latter’s value for the conductivity increment per °C. is of the same order as that found in the present work.

Determination of the thermal conductivity of polypyrrole over the temperature range 280–335 K

1993 ◽  
Vol 28 (18) ◽  
pp. 5092-5098 ◽  
Author(s):  
B. A. Lunn ◽  
J. Unsworth ◽  
N. G. Booth ◽  
P. C. Innis
Keyword(s):  
Thermal Conductivity ◽  
Temperature Range

scholarly journals The thermal conductivity of carbon dioxide

1927 ◽  
Vol 114 (767) ◽  
pp. 354-366 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Free Path ◽  
Critical Pressure ◽  
Mean Free Path ◽  
Double System ◽  
Wire Method ◽  
The Mean ◽  
The Absolute ◽  
The Many

Of the many experimental determinations of the thermal conductivity of Co 2 which have been made, the absolute values given by the various observers vary from 3·07 × 10 -5 cal. sec. -1 cm. -1 deg. -1 (Winkelman, 1), to 3·39 × 10 -5 cal. sec. -1 cm. -1 deg. -1 (Weber, 2), and generally speaking the experiments were modifications of two principal methods, namely, the electrically heated wire of Schleimacher (3) and the cooling thermometer method. In both of these methods convection losses were present to a degree depending on the dimensions and disposition of the apparatus, and on the pressure of the gas; therefore, in the author’s opinion, the discrepancies amongst various observers are due to the practice of attempting to eliminate these convective losses by diminishing the pressure. Such a procedure is justifiable only if the reduction of pressure is not carried beyond the point at which the mean free path of the molecules becomes comparable with the dimensions of the containing vessel. This is a critical point in the determination of the conductivity of a gas, as the authors’ experiments on Co 2 indicate that the convection becomes negligible only at pressures for which the mean Free Path Effect is such that the significance imposed on the conductivity by Fourier’s law loses its meaning, and below this critical pressure the conductivity varies with the pressure in a manner depending on the dimensions of the vessel containing the gas. In the experiments of Gregory and Archer (4), on the thermal conductivities of air and hydrogen, the use of a double system of electrically-heated wires enabled the authors accurately to identify the critical pressure at which convective losses became negligible. This is an extremely important point in all applications of the hot-wire method to the absolute determination of the conductivities of gases, and alone justifies the procedure of lowering the pressure to eliminate convective losses. Above this critical pressure it is necessary to disentangle the conduction and convection losses, and below, the meaning of conduction loses its ordinary significance.

High Temperature Thermal Conductivity Measurements of Quasicrystalline Al70.8Pd20.9Mn8.3

2000 ◽  
Vol 626 ◽  
Author(s):  
Philip S. Davis ◽  
Peter A. Barnes ◽  
Cronin B. Vining ◽  
Amy L. Pope ◽  
Robert Schneidmiller ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Radiative Heat ◽  
Accurate Determination ◽  
Fourth Power ◽  
Radiative Effects ◽  
Radiative Heat Loss ◽  
3Ω Method ◽  
Temperature Range

ABSTRACTWe report measurements of the thermal conductivity on a potential high temperature thermoelectric material, the quasicrystal Al70.8Pd20.9Mn8.3. Thermal conductivity is determined over a temperature range from 30 K to 600 K, using both the steady state gradient method and the 3ω method. Measurements of high temperature thermal conductivity are extremely difficult using standard heat conduction techniques. These difficulties arise from the fact that heat is lost due to radiative effects. The radiative effects are proportional to the temperature of the sample to the fourth power and therefore can lead to large errors in the measured thermal conductivity of the sample, becoming more serious as the temperature increases. For thermoelectric applications in the high temperature regime, the thermal conductivity is an extremely important parameter to determine. The 3ω technique minimizes radiative heat loss terms, which will allow for more accurate determination of the thermal conductivity of Al70.8Pd20.9Mn8.3 at high temperatures. The results obtained using the 3ω method are compared to results from a standard bulk-thermal-conductivity-technique on the same samples over the temperature range, 30 K to 300 K.

Determination of Thermal Conductivity of Biomaterials in the Temperature Range 233–313K Using a Tiny Detector Made of a Self-Heated Thermistor

2002 ◽  
Vol 1 (2) ◽  
pp. 141-147 ◽  
Author(s):  
Haifeng Zhang ◽  
Shuxia Cheng ◽  
Liqun He ◽  
Aili Zhang ◽  
Ying Zheng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Temperature Range

Optical Determination of Thermal Conductivity with a Plane Source Technique

1968 ◽  
Vol 23 (5) ◽  
pp. 682-686 ◽  
Author(s):  
Silas E. Gustafsson ◽  
Nils-Olov Halling ◽  
Rolf A. E. Kjellander
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Temperature Dependence ◽  
Theoretical Approach ◽  
Experimental Results ◽  
Plane Source ◽  
Melting Points ◽  
Temperature Range ◽  
Optical Determination

The thermal conductivity and the thermal diffusivity of the three alkali nitrates LiNO3 , RbNO3 and CsNO3 have been measured over a temperature range between 50° and 100 °C above their melting points. Any temperature dependence of the thermal conductivity cannot be established for any of the investigated liquids but the results indicate that it must be less than 10-3 °C-1. The experimental results are compared with the conductivities which can be calculated with already excisting theories. A somewhat modified theoretical approach is suggested for estimating the thermal conductivity, where no adjustable parameters are being used. The experimental and theoretical values at the melting points agree within about 10 percent.

scholarly journals Measurement of Thermal Conductivity of Sludge and Liquid Materials

2018 ◽  
Vol 168 ◽  
pp. 01001
Author(s):  
Mária Čarnogurská ◽  
Miroslav Příhoda ◽  
Tomáš Brestovič ◽  
Marián Lázár ◽  
Natália Jasminská ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Natural Gas ◽  
Heat Flux Density ◽  
Solid Material ◽  
Experimental Measurements ◽  
Gas Filtration ◽  
The Mean ◽  
Semi Solid

The present article describes two various methods of determination of thermal conductivity of semi-solid and liquid materials. One is based on experimental measurements of heat flux through a layer of semi-solid material while using the Heat Flow Plates, and the second one uses Peltier Elements to determine the heat flux density. The first method was used to determine thermal conductivity of sludge taken from natural gas coolers. Its value, identified by measurements, was 0.746 W·m-1·K-1. The second method was applied to determine thermal conductivity for sludge taken from natural gas filtration units. Values thereof were ranging from 0.608 W·m-1·K-1 (at the mean sludge temperature of 22 °C) to 0.652 W·m-1·K-1 (at the sludge temperature of 43 °C).

scholarly journals Determination of the Radiation Exchange Factor in the Bundle of Steel Round Bars

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5263 ◽  
Author(s):  
Rafał Wyczółkowski ◽  
Marek Gała ◽  
Stanisław Szwaja ◽  
Andrzej Piotrowski
Keyword(s):  
Thermal Conductivity ◽  
Geometric Model ◽  
Initial Point ◽  
Temperature Range ◽  
Exchange Factor ◽  
Radiation Exchange ◽  
The Difference ◽  
Radiative Thermal Conductivity ◽  
Bar Diameter

A method to obtain a radiation exchange factor FR in the bundle of steel round bars is presented. This parameter is required for determination of the radiative thermal conductivity krd, which is one of the basic thermal properties of the bar bundles. In the presented approach, the analyzed parameter is calculated indirectly. The initial point for calculations is the geometric model of the medium defined as a unit cell. Then, for the elements present in this cell, the thermal resistance of both conduction and radiation is determined. The radiation resistance is calculated from the radiosity balance of the surfaces enclosing the analyzed system. On this basis, the radiation thermal conductivity krd is calculated. Next, taking into account the bar diameter, the value of parameter FR is also determined. The analysis is performed at the process temperature range of 200 to 800 °C for three bar diameters: 10, 20 and 30 mm, and for the three porosities of the bundle. Different emissivity of bars in the range of 0.5 to 0.9 was also taken into account. Finally, a relationship that allows calculating the FR factor correlated with the emissivity of the bars and the bundle porosity was established. The krd obtained from the methodology presented and compared with the values calculated directly do not exceed 9%; however, after averaging over the entire temperature range of the process, the difference does not exceed 0.2%.

scholarly journals A Method for Measurement of Terrestrial Heat Flow Density in Water Wells

2018 ◽  
Vol 4 (2) ◽  
pp. 45
Author(s):  
Janilo Santos ◽  
Valiya M. Hamza ◽  
Po-Yu Shen
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Density ◽  
Heat Flow Density ◽  
Terrestrial Heat Flow ◽  
The Mean

ABSTRACT. A simple method for measurement of terrestrial heat flow density in wells drawing groundwater from confined aquifers is presented. It requires laboratory determination of thermal resistance but the field work is simple, being limited to measurement of temperature of water at the well mouth during pumping tests.The aquifer temperature (Ta) is calculated from the measured temperature at the well mouth (Tw), the mass flow rate (M) and the depth to the top of the aquifer (H) using the relation(Tw – To) / (Ta – To) = M'R [1 – exp(–1/M'R)]where To is the mean annual surface temperature, R a dimensionless diffusion parameter and M' = MC/KH is the dimensionless mass flow rate, C being the specific heat of water and K the thermal conductivity of the rock formation penetrated by the well. The heat flow density (q) is then calculated from the relationq = (Ta –To) / ∑ n (i=1) Pi Zjwhere Pi is the thermal resistivity of the jth layer of thickness Zi and n the number of layers. The procedure also allow corrections for the influence of thermal conductivity variations oi the wall rocks.This method was used for the determination of heat flow density values for thirteen sites in the northeastern part of the Paraná basin. The mean value obtained is 62±4 mW/m2 in good agreement with the mean of 59±9 mW/m2 obtained by the conventional method for thirteen sites in the Paraná basin. Though similar in principle to the bottom-hole temperature method used in oil wells, the present technique has some inherent advantages. lt is potentially capable of providing a wider geographic representation of heat flow density (being not limited to petroleum fields) and is relatively free of the sampling problems normally encountered in working with oil companies. 0n the other hand the present method may provide unreliable values in the case of wells drawing water from more than one aquifer. RESUMO. Apresenta-se neste trabalho, um método simples para a determinação do fluxo geotérmico em poços em atividade de bombeamento de água subterrânea. O método requer a determinação em laboratório da resistência térmica total das camadas atravessadas pelo poço mas, o trabalho de campo é simples, limitando-se à medida da temperatura da água na boca do poço durante ensaios de bombeamento.A temperatura do aquífero (Ta) é calculada a partir da temperatura da água (TW), medida na boca do poço da vazão (M) expressa em massa  de água produzida pelo poço por unidade de tempo e, da profundidade do topo do aquífero (H) usando-se a relação(Tw – To) / (Ta – To) = M'R [1 – exp(–1/M'R)]onde TO é a temperatura média anual da superfície, R é um parâmetro adimensional de difusão, M' = M C/K H é a vazão adimensional do poço, C é o calor específico da água e, K é a condutividade térmica da rocha atravessada pelo poço. O fluxo geotérmico (q) é calculado pela relaçãoq = (Ta –To) / ∑ n (i=1) Pi Zjonde Pi é a resistência térmica da i-ésima camada de espessura Zi e, n é o número de camadas.O método permite também a introdução de correções da influência das variações de condutividade térmica das paredes do poço.Este método foi utilizado na determinação do fluxo geotérmico em treze localidades no nordeste da Bacia do Paraná. O valor médio obtido foi de 62±4 mW /m2 concordando com o valor médio de 59±9 mW/m2 obtido pelo método convencional de determinação de fluxo geotérmico em treze localidades da Bacia do Paraná. Apesar de ser um método similar ao das temperaturas de fundo de poço usado em poços de petróleo, esta técnica apresenta algumas vantagens. O método é potencialmente capaz de fornecer uma representação geográfica mais ampla do fluxo geotérmico, não estando limitado a campos de produção de petróleo, e é relativamente livre de problemas de amostragem normalmente encontrados quando se trabalha com companhias de petróleo. Por outro lado, este método pode fornecer valores irreais de fluxo geotérmico no caso em que o poço extraia água de mais de um aquífero. 

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