Thermal-wave resonant-cavity measurements of the thermal diffusivity of air: A comparison between cavity-length and modulation-frequency scans

1996 ◽  
Vol 17 (6) ◽  
pp. 1241-1254 ◽  
Author(s):  
J. Shen ◽  
A. Mandelis ◽  
B. D. Aloysius
Keyword(s):  
Thermal Diffusivity ◽  
Thermal Wave ◽  
Cavity Length ◽  
Modulation Frequency ◽  
Resonant Cavity

Optical device for thermal diffusivity determination in liquids by reflection of a thermal wave

2017 ◽  
Vol 88 (8) ◽  
pp. 084901
Author(s):  
C. Sánchez-Pérez ◽  
A. De León-Hernández ◽  
C. García-Cadena
Keyword(s):  
Thermal Diffusivity ◽  
Thermal Wave ◽  
Optical Device

scholarly journals THERMAL DIFFUSIVITY MEASUREMENT OF SOLID USING PYROELECTRIC SENSOR

2017 ◽  
Vol 19 (1) ◽  
pp. 91-95
Author(s):  
B. Z. Azmi ◽  
Y. T. Ling ◽  
M. Hashim ◽  
W. M. M. Yunus ◽  
M. M. Moksin
Keyword(s):  
Thermal Diffusivity ◽  
Thermal Wave ◽  
Spectroscopic Technique ◽  
Thermal Diffusivity Measurement ◽  
Pyroelectric Sensor ◽  
Diffusivity Measurement ◽  
Sensor Position ◽  
Aluminium Copper ◽  
Lateral Distance ◽  
Good Agreement

The recently developed pyroelectric spectroscopic technique has been used to measure the thermal diffusivity of solids. The method has been applied to conductors and insulator where by the thermal wave is measured at various lateral distances on the sample between laser illuminated line and pyroelectric sensor position. The thermal diffusivity is obtained from the gradient of the plot of thermal wave signal versus the lateral distance. A good agreement to the previously reported thermal diffusivity value has been obtained for aluminium, copper and spray paint that is 0.809 cm2s-1, 1.128 3cm2s-1 and 1.547 x 10-3 cm2s-1 respectively.

Thermal-diffusivity measurements by the converging-thermal-wave technique

1986 ◽  
Vol 64 (9) ◽  
pp. 1172-1177 ◽  
Author(s):  
P. Cielo ◽  
L. A. Utracki ◽  
M. Lamontagne
Keyword(s):  
Thermal Diffusivity ◽  
Thermal Wave ◽  
Infrared Detector ◽  
Thermal Flux ◽  
Thin Sheet ◽  
High Amplitude ◽  
Practical Implementation ◽  
Noise Sources ◽  
Wave Technique ◽  
Effect Of Surface

A converging-thermal-wave technique is described for the measurement of thermal diffusivity in bulk or thin-sheet materials. An annular-shaped area is heated by a pulsed laser beam focused on the material's surface through a combination of spherical and conical lenses, and the surface temperature is monitored by an infrared detector focused on the center of the annulus. The converging action of the thermal flux results in a high amplitude of the detected signal with little overheating of the irradiated material. An analysis of such a technique is presented, as well as some experimental results obtained on heterogeneous materials. Several aspects relevant to the practical implementation of such a technique in an industrial environment, such as the effect of surface losses and different noise sources, are discussed.

Measurement of the thermal diffusivity of human epidermis by studying thermal wave propagation

1992 ◽  
Vol 37 (1) ◽  
pp. 21-35 ◽  
Author(s):  
U Werner ◽  
K Giese ◽  
B Sennhenn ◽  
K Plamann ◽  
K Kolmel
Keyword(s):  
Wave Propagation ◽  
Thermal Diffusivity ◽  
Thermal Wave ◽  
Human Epidermis

Absorption losses and thermal diffusivity of optical fibers investigated by photothermal methods: theory and experiments

1983 ◽  
Vol 61 (9) ◽  
pp. 1334-1346 ◽  
Author(s):  
Dominique Chardon ◽  
Serge J. Huard
Keyword(s):  
Thermal Diffusivity ◽  
Absorption Coefficient ◽  
Optical Fibers ◽  
Rayleigh Scattering ◽  
Modulation Frequency ◽  
Threshold Value ◽  
Phase Delay ◽  
Algebraic Expression ◽  
Photothermal Methods ◽  
Scattering Losses

Both the absorption coefficient and the thermal diffusivity of an optical fiber have been measured using photothermal methods: photoacoustics (P.A.) and photothermal deflection (P.D.). The amplitude of the photothermal signal is proportional to the heat density generated in the fiber core. This in turn is proportional to the light absorption coefficient β. Thus, these techniques allow one to separate the absorption and Rayleigh scattering losses. The results obtained by the two methods are in agreement. A threshold value of 10 dB km−1 mW has been determined experimentally. In both cases, the device is calibrated by replacing the fiber with a heated electric wire. Moreover, the heat must diffuse from the core to the gas so that when the light is modulated, a phase delay appears. A study of phase delay versus modulation frequency gives the thermal diffusivity of the fiber. This is required in order to improve fiber sensors.Theoretically, the cylindrical geometry of the sample permits simple calculations. The thermoelastic equations in solids and coupled thermodynamic ones in the gas have been solved without neglecting viscosity effects. Noting that silica is almost unexpansible, an algebraic expression of the signal has been obtained without any assumptions on the gas transformation processes. Finally, the P.A. and P.D. techniques are compared and some extensions are presented.

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