Nonlinear vacuum gas flow through a short tube due to pressure and temperature gradients

Pantazis, Sarantis; Naris, Steryios; Tantos, Christos; Valougeorgis, Dimitris; André, Julien; Millet, F.; Perin, J.P.

doi:10.1016/j.fusengdes.2013.03.011

Cited by 22 publications

(12 citation statements)

References 9 publications

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“…This discretization ensures grid independent results up to several signi¦cant ¦gures. The implemented algorithm has been extensively applied in previous works to solve with considerable success heat transfer con¦gurations [10] and nonlinear §ows through short tubes due to pressure and temperature gradients [3,11].…”

Section: Kinetic Modelingmentioning

confidence: 99%

Parametric study on propulsion performance of microtubes

Tantos

Valougeorgis

2017

Progress in Flight Physics

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The pressure-driven rare¦ed gas §ow of polyatomic gases through short tubes in a wide range of the Knudsen number is numerically investigated. The downstream over the upstream pressure ratio is taken very close to zero. Such §ows are characterized by low Reynolds numbers and high viscous losses and, therefore, short circular microtubes may be used instead of typical micronozzles. The main computed quantities include the §ow rate, the discharge coe©cient, the thrust, and the impulse factor which are provided in terms of the gas rarefaction and the tube dimensionless length. Based on the above, a parametric study on the propulsion characteristics of microtubes is provided. Furthermore, a comparison between corresponding polyatomic and monoatomic results is performed and the e¨ect of the internal degrees of freedom on the results is investigated.

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Section: Kinetic Modelingmentioning

confidence: 99%

Parametric study on propulsion performance of microtubes

Tantos

Valougeorgis

2017

Progress in Flight Physics

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“…22,23,25 The dimensionless solution depends on three parameters, namely, the reference Knudsen number, the ratio of the downstream over the upstream pressure, and the ratio of the length over the radius of the tube. The case of flows driven both by pressure and temperature gradients have also been studied, [39][40][41] and the solution still depends on the same three parameters as before plus the temperature distribution along the tube wall and the ratio of the downstream over the upstream temperature which must be provided.…”

Section: A Flow Through the Tube (Micromodel)mentioning

confidence: 99%

“…As a result, the temperature at each time step in the two chambers will be different, and in addition to the pressure driven flow, there is a temperature driven flow, well known as thermal creep flow. A suitable kinetic solver, as the one described in the paper, 41 must be implemented to accurately estimate at each time step the flow rate W.…”

Section: B Isentropic Expansionmentioning

confidence: 99%

Hybrid modeling of time-dependent rarefied gas expansion

Vargas¹,

Naris²,

Valougeorgis³

et al. 2013

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The time evolution of the flow parameters in a system where gas is expanded from a high pressure chamber through a tube toward a low pressure chamber is investigated. During the process, the pressure in the two chambers is changing in the opposite direction, while the flow rate is reduced until the system reaches its equilibrium state. Rarefied conditions may be present. Based on the observation that the characteristic time in the chambers is several orders of magnitude larger than that in the tube, the evolution of the flow is modeled in a hybrid manner. At each time step, based on kinetic theory, a steady-state flow configuration is solved to estimate the amount of gas passing through the tube (micromodel) and then the pressure of the two vessels is updated by applying the mass conservation principle and the equation of state (macromodel). The pressure and the flow rate variation with respect to time are provided for several time-dependent configurations and the dependency of the results on the initial Knudsen number and pressure ratio as well as on the length of the tube is analyzed. The proposed methodology, which is applicable when the volume of the chambers is significantly larger than the volume of the tube, is valid in the whole range of the Knudsen number and computationally very efficient.

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“…This is produced by a pre-cooling of the temperature of the inlet gas and parts of the pump to liquid nitrogen or liquid helium temperature, which leads to a significant density increase and a corresponding reduction of the thermal velocity of the gas molecules and increase of the pumping speed. Tests and recent simulations have shown that this is valid only if the pump is operated at low intake pressures below 1 Pa [20,21]. This is a disadvantage because the pressure in the sub-divertor region of DEMO is aimed to be large (following detachmnet conditions).…”

Section: ) Turbomolecular Pumpsmentioning

confidence: 99%

Exhaust pumping of DT fusion devices: Current state-of-the-art and a potential roadmap to a fusion power plant

Day

Giegerich

2013

2013 IEEE 25th Symposium on Fusion Engineering (SOFE)

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The main functions of the exhaust pumping system of a DT fusion device are to pump out the helium ash and to control the divertor neutral gas density. This requires the handling of large gas throughputs at high pumping speeds (but at relatively moderate vacua). The pumped exhaust gas is then usually transported to the tritium plant for cleaning, which involves impurity removal and separation of the pure hydrogenic species for re-injection as fuel.In view of a fusion power plant, a systematic technical review of primary and roughing pump technologies is conducted in order to identify potential exhaust pumping concepts which eliminate some of the disadvantages that eventually result from simple scale-up of the ITER solutions that are based on batchwise operating cryogenic pumps. This paper also illustrates the methodology applied to come to unbiased results and describes the final configuration which is based on a vapor diffusion pump as primary pump together with a metal foil pump for hydrogen separation, and a liquid metal ring pump as roughing pump. All pumps are working continuously and do not require cryogenic temperatures.The new concept will reduce the tritium inventories of a power plant, firstly because of the continuous pumping characteristics of the pumps involved, and secondly because the metal foil pump allows for internal recycling of the unburnt fuel species directly from the divertor to the fuelling systems, bypassing the tritium plant.

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Nonlinear vacuum gas flow through a short tube due to pressure and temperature gradients

Cited by 22 publications

References 9 publications

Parametric study on propulsion performance of microtubes

Parametric study on propulsion performance of microtubes

Hybrid modeling of time-dependent rarefied gas expansion

Exhaust pumping of DT fusion devices: Current state-of-the-art and a potential roadmap to a fusion power plant

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