Thermal conductivity of sodium tetrafluoroborate in the condensed phase

Abstract The presented work is devoted to the study of heat-mass transfer in vapor and liquid, taking into account multi-particle interactions in the condensed phase. An appropriate numerical procedure is proposed to solve the kinetic equation, both in the vapor and in the liquid. Using this approach, the problems of thermal conductivity in liquid argon, as well as the problem of evaporation-condensation, are solved.

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Effects of the Finite Thermal Conductivity of the Condensed Phase on Evaporation and Condensation Flows of Its Vapor: Existence of the Maximum Mass and Energy Flows

ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference, Volume 3 ◽

10.1115/ht2007-32743 ◽

2007 ◽

Author(s):

Yoshimoto Onishi ◽

Takahiro Fuji ◽

Yuuki Mannari ◽

Takeshi Ooshida

Keyword(s):

Thermal Conductivity ◽

Boltzmann Equation ◽

Condensed Phase ◽

Fluid Dynamic ◽

Temperature Fields ◽

Condensed Phases ◽

Evaporation And Condensation ◽

Energy Flows ◽

Internal Structures ◽

Dynamic Formulation

Transient to steady motions of a vapor due to evaporation and condensation processes between the plane condensed phases with temperature fields as their internal structures have been studied in detail based on the new governing system at the ordinary fluid dynamic level, i.e., fluid dynamic formulation, which consists of the compressible Navier-Stokes equations and the boundary conditions appropriate for evaporation and condensation problems derived earlier from the kinetic theory analysis. The previous studies based on the Boltzmann equation of BGK type have shown that the mass and energy flows may take their maximum values at a certain value of the latent heat parameter when the condensed phases have temperature fields as their internal structures; the internal structure is a reflection of the thermal conductivity of the condensed phase being finite compared to that of its vapor. This is a striking feature in contrast to the case in which no internal structures exist in the condensed phases. Particular attention, therefore, is paid to the quantitative aspect of this behavior of the mass and energy flows. Incidentally, the comparison between the present results and the corresponding ones from the Boltzmann equation of BGK type has been made and found to be quite good, indicating that the fluid dynamic formulation works satisfactorily in the present case with temperature fields as the internal structures of the condensed phases.

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A Benchmark Study of Burning Rate of Selected Thermites through an Original Gasless Theoretical Model

Applied Sciences ◽

10.3390/app11146553 ◽

2021 ◽

Vol 11 (14) ◽

pp. 6553

Author(s):

Sarah Brotman ◽

Mehdi Djafari Rouhani ◽

Samuel Charlot ◽

Alain Estève ◽

Carole Rossi

Keyword(s):

Thermal Conductivity ◽

Theoretical Model ◽

Condensed Phase ◽

Oxygen Diffusion ◽

Thermal Conduction ◽

Maximum Density ◽

Benchmark Study ◽

Diffusion Characteristics ◽

The Common ◽

Burn Rate

This paper describes a kinetic model dedicated to thermite nanopowder combustion, in which core equations are based on condensed phase mechanisms only. We explore all combinations of fuels/oxidizers, namely Al, Zr, B/CuO, Fe2O3, WO3, and Pb3O4, with 60 % of the theoretical maximum density packing, at which condensed phase mechanisms govern the reaction. Aluminothermites offer the best performances, with initiation delays in the range of a few tens of microseconds, and faster burn rates (60 cm s−1 for CuO). B and Zr based thermites are primarily limited by diffusion characteristics in their oxides that are more stringent than the common Al2O3 barrier layer. Combination of a poor thermal conductivity and efficient oxygen diffusion towards the fuel allows rapid initiation, while thermal conductivity is essential to increase the burn rate, as evidenced from iron oxide giving the fastest burn rates of all B- and Zr-based thermites (16 and 32 cm·s−1, respectively) despite poor mass transport properties in the condensed phase; almost at the level of Al/CuO (41 versus 61 cm·s−1). Finally, formulations of the effective thermal conduction coefficient are provided, from pure bulk, to nanoparticular structured material, giving light to the effects of the microstructure and its size distribution on thermite performances.

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