A numerical and experimental analysis of the methodology of thermal conductivity measurements in fluids by concentric cylinders

A study of thermal conductivity measurements of fluids, using the technique of steady-state heat transfer in concentric cylinders, is presented. In order to evaluate the effect of convective flow on the measured value of conductivity, numerical results, which were obtained using computational fluid...

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Bibliographic Details
Published in:Heat and mass transfer 2019-03, Vol.55 (3), p.669-683
Main Authors: Costa, Henrique C. B., Silva, Danylo O., Vieira, Luiz Gustavo M.
Format: Article
Language:English
Subjects:
Computational fluid dynamics
Computer simulation
Concentric cylinders
Conductivity
Convection
Convective flow
Design of experiments
Dimensionless numbers
Empirical equations
Engineering
Engineering Thermodynamics
Heat and Mass Transfer
Heat conductivity
Heat transfer
Industrial Chemistry/Chemical Engineering
Original
Temperature profiles
Thermal conductivity
Thermodynamics
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Summary:A study of thermal conductivity measurements of fluids, using the technique of steady-state heat transfer in concentric cylinders, is presented. In order to evaluate the effect of convective flow on the measured value of conductivity, numerical results, which were obtained using computational fluid dynamics (CFD) in three dimensions, are compared with experimental data and analytical results of temperature profiles. This latter was obtained considering the hypothesis of heat transfer mechanism being entirely diffusive and solely in the radial direction. An experimental design was proposed aiming to analyze the effects of glycerol mass fraction (0%, 50 and 100%), annuli size (2.525, 4.525 and 6.525 mm) and heat rate (5, 10 and 15 W) in the formation of convective streamlines. The ratio between effective and absolute conductivities ( k ef /k ) was used as a response to evaluate the convection intensity. The results were compared with empirical equations that correlate the ratio k ef /k with the dimensionless numbers of Prandtl and Rayleigh, which are in the rate 4.37 ≤  Pr  ≤ 3.8 × 10 3 and 9.0 ≤  Ra  ≤ 4.4 × 10 4 . An evaluation of the accuracy in measuring k ef is showed based on the simulated data of temperature profiles in the axial, radial and angular directions.
ISSN:0947-7411
1432-1181
DOI:10.1007/s00231-018-2448-6