Containerless Thermal Diffusivity Determination of High-Temperature Levitated Spherical Specimen by Extended Flash Methods: Theory and Experimental Validation

1997 ◽  
Vol 119 (2) ◽  
pp. 210-219 ◽  
Author(s):  
F. Shen ◽  
J. M. Khodadadi ◽  
M. C. Woods ◽  
J. K. R. Weber ◽  
B. Q. Li
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Transfer Problem ◽  
Single Step ◽  
Temperature History ◽  
Step Method ◽  
Measured Time ◽  
Analytic Expressions

In order to determine the thermal diffusivity of materials, especially solids and liquids at high temperatures, two extended containerless flash techniques that are applicable to levitated spherical specimen are proposed. The extended flash methods are modeled as an axisymmetric transient conduction heat transfer problem within the sphere. For the “single-step” method, analytic expressions for the temperature history on the surface of the sphere are obtained that are independent of the incident energy and the absorption layer thickness. It is shown that by knowing the sample diameter and recording the temperature transient history at least at two different points on the surface simultaneously, the thermal diffusivity can be determined. A detailed discussion of the effects of the various parameters is presented. For the “two-step” analysis the problem of nonlinearity of the radiative heat transfer boundary condition is overcome by replacing it with the measured time-dependent surface temperature data. Upon obtaining the temperature field the determination of the thermal diffusivity turns into a minimization problem. In performing the proposed two-step procedure there is a need to undertake a cool-down experiment. Results of an experimental study directed at determining the thermal diffusivity of high-temperature solid samples of pure Nickel and Inconel 718 superalloy near their melting temperatures using the single-step method are discussed. Based on close agreement with reliable data available in the literature, it is concluded that the proposed techniques can provide reliable thermal diffusivity data for high-temperature materials.

Thermal Diffusivity Determination of High-Temperature Levitated Oblate Spheroidal Specimen by a Flash Method

1998 ◽  
Vol 120 (3) ◽  
pp. 777-781 ◽  
Author(s):  
F. Shen ◽  
J. M. Khodadadi
Keyword(s):  
Thermal Diffusivity ◽  
Transfer Problem ◽  
Oblate Spheroid ◽  
Single Step ◽  
Flash Method ◽  
Conduction Heat Transfer ◽  
Oblate Spheroidal ◽  
Flash Technique ◽  
Transient Conduction

In extending the range of applicability of a recently developed method, a single-step containerless flash technique for determining the thermal diffusivity of levitated oblate spheroidal oblate spheroidal samples is proposed. The flash method is modeled as an axisymmetric transient conduction heat transfer problem within the oblate spheroid. It is shown that by knowing the sample geometric parameters and recording the temperature rise history at least at two different points on the surface simultaneously, the thermal diffusivity can be determined without knowing needed for determining the thermal diffusivity of oblate spheroidal samples are provided.

Experimental investigation of wall heat transfer due to spray combustion in a high-pressure/high-temperature vessel

2021 ◽  
pp. 146808742110072
Author(s):  
Karri Keskinen ◽  
Walter Vera-Tudela ◽  
Yuri M Wright ◽  
Konstantinos Boulouchos
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
High Temperature ◽  
High Speed ◽  
Transfer Problem ◽  
Wall Heat Transfer ◽  
Gas Temperature ◽  
Reference Case ◽  
High Pressure High Temperature

Combustion chamber wall heat transfer is a major contributor to efficiency losses in diesel engines. In this context, thermal swing materials (adapting to the surrounding gas temperature) have been pinpointed as a promising mitigative solution. In this study, experiments are carried out in a high-pressure/high-temperature vessel to (a) characterise the wall heat transfer process ensuing from wall impingement of a combusting fuel spray, and (b) evaluate insulative improvements provided by a coating that promotes thermal swing. The baseline experimental condition resembles that of Spray A from the Engine Combustion Network, while additional variations are generated by modifying the ambient temperature as well as the injection pressure and duration. Wall heat transfer and wall temperature measurements are time-resolved and accompanied by concurrent high-speed imaging of natural luminosity. An investigation with an uncoated wall is carried out with several sensor locations around the stagnation point, elucidating sensor-to-sensor variability and setup symmetry. Surface heat flux follows three phases: (i) an initial peak, (ii) a slightly lower plateau dependent on the injection duration, and (iii) a slow decline. In addition to the uncoated reference case, the investigation involves a coating made of porous zirconia, an established thermal swing material. With a coated setup, the projection of surface quantities (heat flux and temperature) from the immersed measurement location requires additional numerical analysis of conjugate heat transfer. Starting from the traces measured beneath the coating, the surface quantities are obtained by solving a one-dimensional inverse heat transfer problem. The present measurements are complemented by CFD simulations supplemented with recent rough-wall models. The surface roughness of the coated specimen is indicated to have a significant impact on the wall heat flux, offsetting the expected benefit from the thermal swing material.

Single step method for the accurate concentration determination of polysorbate 80

1997 ◽  
Vol 786 (1) ◽  
pp. 99-106 ◽  
Author(s):  
Travis H. Tani ◽  
Jamie M. Moore ◽  
Thomas W. Patapoff
Keyword(s):  
Single Step ◽  
Polysorbate 80 ◽  
Step Method ◽  
Concentration Determination

scholarly journals Determination of Thermal Diffusivity and Its Temperature Dependence of Fe1−xO Scale at High Temperature by Electrical-Optical Hybrid Pulse-Heating Method

2021 ◽  
Vol 61 (1) ◽  
pp. 26-32
Author(s):  
Yuanru Yang ◽  
Hiromichi Watanabe ◽  
Megumi Akoshima ◽  
Miyuki Hayashi ◽  
Masahiro Susa ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Diffusivity ◽  
Temperature Dependence ◽  
Pulse Heating ◽  
Heating Method

Determination of Time-Resolved Heat Transfer Coefficient and Adiabatic Effectiveness Waveforms With Unsteady Film Cooling

2012 ◽  
Author(s):  
James L. Rutledge ◽  
Jonathan F. McCall
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Random Noise ◽  
Temperature History ◽  
Flow Conditions ◽  
Adiabatic Effectiveness

Traditional hot gas path film cooling characterization involves the use of wind tunnel models to measure the spatial adiabatic effectiveness (η) and heat transfer coefficient (h) distributions. Periodic unsteadiness in the flow, however, causes fluctuations in both η and h. In this paper we present a novel inverse heat transfer methodology that may be used to approximate the η(t) and h(t) waveforms. The technique is a modification of the traditional transient heat transfer technique that, with steady flow conditions only, allows the determination of η and h from a single experiment by measuring the surface temperature history as the material changes temperature after sudden immersion in the flow. However, unlike the traditional transient technique, this new algorithm contains no assumption of steadiness in the formulation of the governing differential equations for heat transfer into a semi-infinite slab. The technique was tested by devising arbitrary waveforms for η and h at a point on a film cooled surface and running a computational simulation of an actual experimental model experiencing those flow conditions. The surface temperature history was corrupted with random noise to simulate actual surface temperature measurements and then fed into an algorithm developed here that successfully and consistently approximated the η(t) and h(t) waveforms.

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