scholarly journals Influence of temperature difference on thermal conductivity of lightweight mortars with waste aggregate

2019 ◽  
Author(s):  
Danuta Barnat-Hunek ◽  
Małgorzata Grzegorczyk ◽  
Grzegorz Łagód
Keyword(s):  
Thermal Conductivity ◽  
Temperature Difference ◽  
Influence Of Temperature

Influence of Temperature and Tempering Conditions on Thermal Conductivity of Hot Work Tool Steels for Hot Stamping Applications

2015 ◽  
Vol 86 (12) ◽  
pp. 1628-1635 ◽  
Author(s):  
Stephan Hafenstein ◽  
Ewald Werner ◽  
Jens Wilzer ◽  
Werner Theisen ◽  
Sebastian Weber ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Hot Stamping ◽  
Tool Steels ◽  
Influence Of Temperature ◽  
Hot Work Tool Steels

Reliability of Thermal Conductivity Measured by Harman Method

1998 ◽  
Vol 545 ◽  
Author(s):  
Y. Shinohara ◽  
Y. Imai ◽  
Y. Isoda ◽  
I. A. Nishida
Keyword(s):  
Thermal Conductivity ◽  
Temperature Difference ◽  
Electron Concentration ◽  
Thermoelectric Materials ◽  
Comparative Method ◽  
Sintered Compact ◽  
Heat Temperature ◽  
Harman Method ◽  
Highly Sensitive ◽  
Standard Value

AbstractThe Harman method was applied to measure thermal conductivity κ of thermoelectric materials, and the reliability of the measured κ was investigated. The quantitative κ requires a highly sensitive technique to measure minute Peltier heat. Temperature difference by Peltier heat pumping was successfully measured by developing the DC method of resistance measurement. κ of n-type Bi2Te3 sintered compact and n-type PbTe boules was measured at 295K by the Harman method. Static comparative method was also applied to obtain the standard value of κ. In the case of Bi2Te3, the κ by the Harman method agreed well with the standard value. In the case of PbTe in the electron concentration ne range <5 × 1024/m3, the κ almost agreed with the standard value. However, PbTe in the ne range ≥1 × 1025/m3 showed a larger κ than the standard value. The Harman method has an error to give the larger κ for the material with a large carrier component κ, of κ This error is due to the fast conduction of Peltier heat by the carrier. The reliable κ can be measured for the material with a small κ,.

scholarly journals The numerical simulation of enhanced heat transfer on a Linear Fresnel molten salt-type receiver tube filled with porous media

2019 ◽  
Vol 118 ◽  
pp. 01041
Author(s):  
Chenggang Yang ◽  
Yuning Zhang ◽  
Fenghe Yan ◽  
Wenguang Zhang ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Porous Media ◽  
Molten Salt ◽  
Temperature Difference ◽  
Wall Temperature ◽  
Three Dimensional ◽  
Heat Transfer Fluid ◽  
Filling Rate

In this paper, three-dimensional numerical simulation was taken on a Linear Fresnel solar receiver tube using molten salt as heat transfer fluid (HTF), in which the porous media was filled to enhance the heat transfer efficiency. The simulation was to analyze the influence of the different conditions (filling rate, porosity and thermal conductivity) on heat transfer effect and wall temperature difference. The results revealed that the Nu (Nusselt number) increased firstly and then decreased with the increasing filling rate in both center filling and annular filling types. The optimal thermal performance were obtained when filling rate were 0.8 and 0.2 in center filling and annular filling, respectively. The Nu were about 1.7 and 1.5 times as the clear receiver. The circumferential temperature difference decreased firstly and then increased with filling rate increasing in both center filling and annular filling types. The lowest circumferential temperature differences were achieved at the filling rate 0.8 and 0.4 in center filling and annular filling types, and temperature difference decreased 15.88°C and 22°C compared with clear receiver, respectively. The Nu and PEC both decreased with porosity increasing. However, the thermal conductivity of porous media had little influence to the Nu and circumferential wall temperature.

A thermal method for the determination of tissue blood flow

1975 ◽  
Vol 39 (1) ◽  
pp. 170-173 ◽  
Author(s):  
T. V. McCaffrey ◽  
R. D. McCook
Keyword(s):  
Thermal Conductivity ◽  
Blood Flow ◽  
Integrated Circuits ◽  
Myocardial Blood Flow ◽  
Temperature Difference ◽  
Tissue Blood Flow ◽  
Thermal Method ◽  
Fixed Temperature ◽  
Voltage Output

An isothermal flowmeter for the determination of local tissue blood flow is described. Flow is determined by the measurement of the thermal conductivity of the tissue in the vicinity of a heated thermistor maintained at a fixed temperature difference above a reference thermistor. Direct heating of the thermistor is utilized to eliminate the need for specially constructed indirectly heated thermistors. This design results in a device with a voltage output directly proportional to tissue thermal conductivity and to tissue blood flow. The device is shown to be adequate for the qualitative measurement of myocardial blood flow under various situations. Construction is simplified and the size of the circuit reduced by the use of readily available integrated circuits.

The Effect of Sintering Temperature to the Properties of Zinc Oxide

2013 ◽  
Vol 795 ◽  
pp. 419-423 ◽  
Author(s):  
J.H. Lim ◽  
C.K. Yeoh ◽  
Pei Leng Teh ◽  
W.M. Arif ◽  
A. Chik
Keyword(s):  
Thermal Conductivity ◽  
Zinc Oxide ◽  
Thermal Properties ◽  
Solid State ◽  
Sintering Temperature ◽  
Solid State Method ◽  
Influence Of Temperature ◽  
Temperature Range ◽  
Influence Of Temperature On ◽  
State Method

In this paper, different sintering temperature used to study the influence of temperature on the structural and thermal properties of zinc oxide (ZnO). On this research, the sample was prepared by solid-state method for zinc oxide (ZnO) at different sintering temperature which was 700°C, 800°C and 900°C. It was observed that the density of bulk ZnO that sintering at 900°C had the higher value of density 5.03 g/cm3. The microhardness of the bulk ZnO had a higher measurement 397.3 Hv after sintered at 900°C. ZnO that sintering at 900°C had been observed that had thermal conductivity 1.1611W/cm-K in the sintering temperature range 700°C to 900°C.

The effect of imposed temperature difference on thermal conductivity in armchair single-walled carbon nanotube

2015 ◽  
Vol 26 (09) ◽  
pp. 1550105 ◽  
Author(s):  
Ali Mehri ◽  
Maryam Jamaati ◽  
Moslem Moradi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Heat Transport ◽  
Temperature Difference ◽  
Nonequilibrium Molecular Dynamics ◽  
Tube Length ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon ◽  
Brenner Potential ◽  
Umklapp Scattering

Thermal conductivity of carbon nanotubes depends on various factors. The simulation of heat transport in armchair single-walled carbon nanotube by direct nonequilibrium molecular dynamics (NEMD) method employing Tersoff–Brenner potential indicates that, thermal conductivity decreases with increase in temperature difference between two ends of the tube. Increasing the imposed temperature differential along the tube axis, leads to domination of Umklapp scattering and impacts the heat transport. The applied temperature difference does not influence the behavior of thermal conductivity vs. tube length, diameter and temperature, but changes its value.

scholarly journals Investigation of the Precision in Geodetic Reference-Point Positioning Because of Temperature-Induced Pillar Deflections

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3489 ◽  
Author(s):  
Robert Močnik ◽  
Božo Koler ◽  
Dejan Zupan ◽  
Tomaž Ambrožič
Keyword(s):  
Reinforced Concrete ◽  
Temperature Variation ◽  
Temperature Difference ◽  
Reference Point ◽  
Horizontal Displacement ◽  
Research Paper ◽  
Reference Points ◽  
Control Points ◽  
Temperature Changes ◽  
Influence Of Temperature

To perform geodetic measurements of displacements of the ground and manmade constructions, stabilised reference points are needed from which control points on the object or its surroundings could be measured. Reference points are most commonly stabilised with reinforced concrete pillars; however, they are not always constructed in an appropriate manner. The influence of temperature variation within a pillar on the position of the fixed screw for forced centring is not negligible and should be considered when performing precise measurements. In this research paper, the displacement of a pillar was calculated as a result of the temperature changes in the pillar, and then an experiment was performed in which the pillar was heated from one side, and the horizontal displacement of the fixed screw for forced centring was measured. Both, calculations and measurements, show that at a temperature difference of 16.2 °C, the fixed screw on a 1.5 m high pillar moves by approximately 1 mm, which is a displacement that should be taken into account in precise measurements.

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