Investigation of the Sensitivity and Stability of Transfer Characteristic of Electromechanical Measuring Transducer of Small Values of Velocity Head of Rarefied Gas

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage. Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.

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On the viscosity of rarefied gas suspensions containing nanoparticles

Doklady Physics ◽

10.1134/1.1623543 ◽

2003 ◽

Vol 48 (10) ◽

pp. 583-586 ◽

Cited By ~ 10

Author(s):

V. Ya. Rudyak ◽

S. L. Krasnolutskii

Keyword(s):

Rarefied Gas ◽

Gas Suspensions

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Investigation of the Squeeze Film Dynamics Underneath a Microstructure With Large Oscillation Amplitudes and Inertia Effects

Journal of Tribology ◽

10.1115/1.4032951 ◽

2016 ◽

Vol 138 (3) ◽

Cited By ~ 1

Author(s):

Nadim A. Diab ◽

Issam A. Lakkis

Keyword(s):

Rarefied Gas ◽

Direct Simulation Monte Carlo ◽

Squeeze Film ◽

Dsmc Method ◽

Inertia Effects ◽

Flow Parameters ◽

Fluid Behavior ◽

Dimensionless Groups ◽

Simulation Monte Carlo ◽

The Impact

This paper presents direct simulation Monte Carlo (DSMC) numerical investigation of the dynamic behavior of a gas film in a microbeam. The microbeam undergoes large amplitude harmonic motion between its equilibrium position and the fixed substrate underneath. Unlike previous work in literature, the beam undergoes large displacements throughout the film gap thickness and the behavior of the gas film along with its impact on the moving microstructure (force exerted by gas on the beam's front and back faces) is discussed. Since the gas film thickness is of the order of few microns (i.e., 0.01 < Kn < 1), the rarefied gas exists in the noncontinuum regime and, as such, the DSMC method is used to simulate the fluid behavior. The impact of the squeeze film on the beam is investigated over a range of frequencies and velocity amplitudes, corresponding to ranges of dimensionless flow parameters such as the Reynolds, Strouhal, and Mach numbers on the gas film behavior. Moreover, the behavior of compressibility pressure waves as a function of these dimensionless groups is discussed for different simulation case studies.

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