Photopyroelectric (PPE) determination of thermal diffusivity of Bi2Te2.85Se0.15 sintered thermoelectric semiconductors

1991 ◽  
Vol 6 (8) ◽  
pp. 1711-1714 ◽  
Author(s):  
Hideo Wada ◽  
Masahito Watanabe ◽  
Jun Morimoto ◽  
Toru Miyakawa
Keyword(s):  
Thermal Diffusivity ◽  
Flow Direction ◽  
Modulation Frequency ◽  
Strong Dependence ◽  
Signal Amplitude ◽  
Orientation Factor ◽  
Hot Press ◽  
Ppe Method ◽  
Thermal Diffusivities

Thermal diffusivity of the sintered semiconductors was measured by the photopyroelectric (PPE) method. The measurement based on the phase-modulation frequency characteristics was shown to give superior results, eliminating errors expected in the conventional signal amplitude-distance characteristics measurements. Thermal diffusivities of the melt-grown and hot-pressed samples were found to be αmelt(c⊥) = 0.014 cm2/s, αmelt(c//) = 0.011 cm2/s, αhot(c⊥) = 0.012 cm2/s, and αhot(c//) = 0.008 cm2/s, depending on the relation between the c-axis direction of grain and thermal flow direction. The thermal diffusivity of the hot-pressed samples shows a strong dependence on the hot-press pressure through the orientation factor.

Development of a Device for the Nondestructive Thermal Diffusivity Determination of Combustion Chamber Deposits and Thin Coatings

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Mark A. Hoffman ◽  
Benjamin J. Lawler ◽  
Zoran S. Filipi ◽  
Orgun A. Güralp ◽  
Paul M. Najt
Keyword(s):  
Heat Flux ◽  
Thermal Diffusivity ◽  
Combustion Chamber ◽  
Temperature Response ◽  
Rotating Disk ◽  
Inert Atmosphere ◽  
Thermal Diffusivities ◽  
Economy Benefit ◽  
The Impact

An experimental radiation chamber has been developed to nondestructively measure the thermal diffusivity of a combustion chamber deposit (CCD) layer. The accumulation of CCD shifts the operability range of homogeneous charge compression ignition (HCCI) to lower loads where the fuel economy benefit of HCCI over a traditional spark ignition strategy is at a maximum. The formation and burn-off of CCD introduce operational variability, which increases the control system burden of a practical HCCI engine. To fully characterize the impact of CCD on HCCI combustion and develop strategies which limit the CCD imposed variability, the thermal and physical properties of HCCI CCD must be determined without destroying the morphology of the CCD layer. The radiation chamber device provides a controlled, inert atmosphere absent of cyclical pressure oscillations and fuel/air interactions found within an engine. The device exposes temperature probes coated with CCD to controlled heat flux pulses generated by a graphite emitter and a rotating disk. CCD layer thermal diffusivity is then calculated based on the phase delay of the sub-CCD temperature response relative to the response of the temperature probe when clean. This work validates the accuracy of the radiation chamber's diffusivity determination methodology by testing materials of known properties. Wafers of three different materials, whose thermal diffusivities span two orders of magnitude centered on predicted CCD diffusivity values, are installed over the temperature probes to act as CCD surrogates. Multiple thicknesses of each material are tested over a range of heat flux pulse durations. Diffusivity values determined from radiation chamber testing are independent of sample thickness with each of the three calibration materials. The radiation chamber diffusivity values exhibit a slight, but consistent underprediction for all wafers due to residual contact resistance at the wafer–probe interface. Overall, the validation studies establish the radiation chamber as an effective device for the nondestructive thermal diffusivity determination of thin insulative coatings. The similarity of expected CCD diffusivity values to those of the validation specimens instills confidence that the methodology and device presented herein can be successfully utilized in the characterization of HCCI CCD layers.

scholarly journals Investigations of Thermal Diffusivity of Material of Compressor Blade of Turbine Jet Engine Using Modified Temperature Oscillation Metho

2018 ◽  
Vol 9 (1) ◽  
pp. 79-92
Author(s):  
Łukasz OMEN ◽  
Andrzej PANAS
Keyword(s):  
Thermal Diffusivity ◽  
Heat Conduction Problem ◽  
Exact Analytical Solution ◽  
Signal Amplitude ◽  
Harmonic Excitation ◽  
Temperature Oscillation ◽  
Turbine Engine ◽  
Iterative Procedures

The modified temperature oscillation method was applied for investigation of thermal diffusivity of the aviation turbine engine’s part. The studies resulted in characterization of the applied method and experimental procedures performance. They were motivated by a need of determination of thermophysical data of the investigated material. The acquired thermal diffusivity data enabled identification of the material’s type and will be applied as input data for numerical analyses on thermo-mechanical loads of the structure. The investigated specimen was a sample of material from the first stage compressor’s blade of the AŁ-21F3 turbine engine. The measurements were conducted within the range of 5°C to 95°C. The thermal diffusivity was calculated from both the amplitude and phase responses to the harmonic excitation from exact analytical solution of the appropriate heat conduction problem. The appropriate transcendental equations describing the response signal amplitude attenuation and phase shift were solved applying iterative procedures. The analysis confirmed the effectiveness of the research methods and enabled to identify the material as titanium alloy.

Developing an Accurate Heat Transfer Simulation Model of Alaska Pollock Surimi Paste by Estimating the Thermal Diffusivities at Various Moisture and Salt Contents

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Hyeon W. Park ◽  
Myeong G. Lee ◽  
Jae W. Park ◽  
Won B. Yoon
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Simulation Model ◽  
Strong Dependence ◽  
Salt Content ◽  
Salt Dependence ◽  
Heat Penetration ◽  
Heat Transfer Simulation ◽  
Thermal Diffusivities

AbstractAlaska pollock (AP) surimi paste was prepared (0–3% salt and 76–84% moisture). The density, specific heat, and thermal conductivity were measured and modelled in temperatures between 25 and 90 °C (R2 > 0.92). The thermal diffusivity (α) function showed a strong dependence on the moisture content and a unique salt dependence at 84% of the moisture content and applied to the heat transfer simulation of surimi paste. The simulation model coupled with the empirical thermal properties accurately predicted the heat penetration curves during heating with RMSE values ranging from 0.43 to 1.22 °C. The salt dependence on thermal diffusivity was identified and modeled only at 84% moisture content. With a model for 84% moisture content, the RMSE value of 3% salt content decreased from 1.11 °C to 0.56 °C. This study demonstrated that an accurate prediction of the heat transfer of the surimi paste needs to be coupled with the nonlinear thermal diffusivity functions.

scholarly journals Numerical and experimental determination of the minimum and maximum measuring times for the hot wire parallel technique

Cerâmica ◽  
2003 ◽  
Vol 49 (309) ◽  
pp. 29-35 ◽  
Author(s):  
W. N. dos Santos ◽  
R. Gregório
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Ceramic Materials ◽  
Time Interval ◽  
Hot Wire ◽  
High Thermal Diffusivity ◽  
Different Dimensions ◽  
Thermal Diffusivities ◽  
Parallel Technique

The hot wire technique is considered to be an effective and accurate means of determining the thermal conductivity of ceramic materials. However, specifically for materials of high thermal diffusivity, the appropriate time interval to be considered in calculations is a decisive factor for getting accurate and consistent results. In this work, a numerical simulation model is proposed with the aim of determining the minimum and maximum measuring time for the hot wire parallel technique. The temperature profile generated by this model is in excellent agreement with that one experimentally obtained by this technique, where thermal conductivity, thermal diffusivity and specific heat are simultaneously determined from the same experimental temperature transient. Eighteen different specimens of refractory materials and polymers, with thermal diffusivities ranging from 1x10-7 to 70x10-7 m²/s, in shape of rectangular parallelepipeds, and with different dimensions were employed in the experimental programme. An empirical equation relating minimum and maximum measuring times and the thermal diffusivity of the sample is also obtained.

scholarly journals Investigation of sintering kinetics of NiO using photo acoustic spectroscopy

2004 ◽  
Vol 36 (3) ◽  
pp. 165-170
Author(s):  
M.V. Nikolic ◽  
D. Lukovic ◽  
S. Savic ◽  
V. Blagojevic ◽  
Pantelija Nikolic
Keyword(s):  
Thermal Diffusivity ◽  
Nickel Oxide ◽  
Modulation Frequency ◽  
Acoustic Properties ◽  
Sintering Kinetics ◽  
Acoustic Spectroscopy ◽  
Sample Density ◽  
Kinetics Of ◽  
Photo Acoustic Spectroscopy

Sintering kinetics of NiO was investigated using photo acoustic spectroscopy This method was used to follow the change of phase and amplitude of the photo acoustic signal of nickel-oxide samples sintered at 1373 K for 15-240 min. as a function of modulation frequency of the laser beam. Fitting of experimental data enabled determination of photo acoustic properties including thermal diffusivity of sintered nickel-oxide. Analysis of the change of sample density during sintering showed that the sintering process of this material can be observed from the viewpoint of activated volume and the change of thermal diffusivity can be correlated with the change of density of this material.

Study of thin smectic A samples by a photoacoustic technique

1986 ◽  
Vol 64 (9) ◽  
pp. 1230-1233 ◽  
Author(s):  
G. Louis ◽  
P. Peretti ◽  
J. Billard ◽  
B. Mangeot
Keyword(s):  
Phase Transitions ◽  
Liquid Crystal ◽  
Thermal Diffusivity ◽  
Modulation Frequency ◽  
Rear Surface ◽  
Photoacoustic Signal ◽  
Sample Thickness ◽  
Photoacoustic Technique ◽  
Smectic A

First we recall some experimental results about phase transitions in a thermotropic liquid crystal investigated by means of a photoacoustic technique. Then this paper examines the photoacoustic signal as a function of the sample thickness and the modulation frequency for rear-surface illumination of the smectic A sample. The results are consistent with the McDonald and Wetsel model and lead to the determination of thermal diffusivity.

scholarly journals Through-Plane and In-Plane Thermal Diffusivity Determination of Graphene Nanoplatelets by Photothermal Beam Deflection Spectrometry

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7273
Author(s):  
Humberto Cabrera ◽  
Dorota Korte ◽  
Hanna Budasheva ◽  
Behnaz Abbasgholi-NA ◽  
Stefano Bellucci
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Thermal Parameter ◽  
Heat Propagation ◽  
Graphene Nanoplatelets ◽  
Beam Deflection ◽  
Significant Difference ◽  
Photothermal Beam Deflection Spectrometry ◽  
Thermal Diffusivities

In this work, in-plane and through-plane thermal diffusivities and conductivities of a freestanding sheet of graphene nanoplatelets are determined using photothermal beam deflection spectrometry. Two experimental methods were employed in order to observe the effect of load pressures on the thermal diffusivity and conductivity of the materials. The in-plane thermal diffusivity was determined by the use of a slope method supported by a new theoretical model, whereas the through-plane thermal diffusivity was determined by a frequency scan method in which the obtained data were processed with a specifically developed least-squares data processing algorithm. On the basis of the determined values, the in-plane and through-plane thermal conductivities and their dependences on the values of thermal diffusivity were found. The results show a significant difference in the character of thermal parameter dependence between the two methods. In the case of the in-plane configuration of the experimental setup, the thermal conductivity decreases with the increase in thermal diffusivity, whereas with the through-plane variant, the thermal conductivity increases with an increase in thermal diffusivity for the whole range of the loading pressure used. This behavior is due to the dependence of heat propagation on changes introduced in the graphene nano-platelets structure by compression.

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