<i>Scientific Foundations of Vacuum Technique</i>

Dushman, Saul; Pierce, J. R.

doi:10.1063/1.3066573

Cited by 269 publications

(271 citation statements)

References 0 publications

Supporting

Mentioning

261

Contrasting

Unclassified

Order By: Relevance

“…For most materials, in the range of vapor pressures below 1 Torr (1.315 10 ±5 atm), it has been observed experimentally [34] that the vapor pressure is indeed related to the temperature in the form of Eq. 13.…”

Section: Evaporation Of a Pure Metalmentioning

confidence: 99%

See 1 more Smart Citation

Physical Aspects of Process Control in Selective Laser Sintering of Metals

Das¹

2003

Adv Eng Mater

392

225

View full text Add to dashboard Cite

Direct selective laser sintering (SLS) is a layered manufacturing technique that can produce fully dense, functional components in high performance metals. In this review paper, a first step is taken towards identifying and understanding some of the important physical mechanisms in direct SLS. This study not only provides an insight into phenomena observed during direct SLS processing of a variety of metallic materials but also helps in selecting those materials that are most amenable to direct SLS processing. The physical mechanisms discussed include oxidation, non‐equilibrium wetting, epitaxial solidification, metal vaporization, and oxide purification. Understanding these mechanisms is crucial for the design of direct SLS machines, process development, and process control.

show abstract

Section: Evaporation Of a Pure Metalmentioning

confidence: 99%

“…14 and 15 have been used by Dushman [34] to tabulate data for a wide variety of elements. The vapour pressure data for selected elements of relevance to SLS are shown in Table 1.…”

Section: Vaporization Characteristics Of Elements Relevant To Slsmentioning

confidence: 99%

Physical Aspects of Process Control in Selective Laser Sintering of Metals

Das¹

2003

Adv Eng Mater

392

225

View full text Add to dashboard Cite

show abstract

“…1). For this case, the expression for the flow of free oxygen Q O 2 (t) outside the fuel element at time t follows from well-known relations for the conductivity of long tubes and channels in the molecular flow regime [9] and has the form where r 1 , l 1 , and T 1 are, respectively, the radius, length, and temperature of the surface of the central channel on the top end of the reflector (see Fig. 1), which is the main gas-dynamic resistance in the path of the flow of molecules leaving the fuel element; m O 2 is the mass of an oxygen molecule; and P O 2 is the oxygen pressure at the entrance into the reflector, calculated using relation (3).…”

mentioning

confidence: 98%

Uranium dioxide mass transfer in the central channel of the fuel kernel of a fuel element of a single-element energy-generating channel

Gontar

Sotnikov

2009

At Energy

View full text Add to dashboard Cite

The methods and computer program for calculating, as well as the computational results obtained, the remaining-life changes occurring in the profile of the central channel of the kernel of a fuel element in a single-element electricity generating channel because of uranium dioxide mass transfer, taking account of the redistribution of the fuel components and the effect of the spacers, are presented. It is shown that the measured and a priori computed profiles of the central channel are close after prolonged testing. It is shown that the superstoichiometric composition of the initial uranium dioxide with oxygen coefficient close to 2.003-2.005 shifts in time to the stoichiometric composition. This is due to the removal of oxygen outside the bounds of the fuel kernel. The calculations show that when uranium dioxide with substoichiometric composition is used or a perforated screen is introduced into the central channel the rate of the axial mass transfer of uranium dioxide is decreased by almost a factor of 2.The radial mass transfer of uranium dioxide in the gap between the kernel and cladding of a ventilated fuel element of a single-element electricity generating channel (EGC) results in elimination of this gap or makes the real contact close to an ideal thermal contact ( Fig. 1) [1]. Previous computational-experimental studies have shown that radial mass transfer in the entire range of the realizable working temperatures of the cladding and the thermal power of the fuel element occurs in a freemolecular regime and is completed in a short time (tens-hundreds of hours) as compared with the service life [2]. Thus, direct loading on the cladding by a swelling kernel occurs irrespective of the initial construction of the fuel element.Longitudinal mass transfer in the central channel of the kernel changes the configuration of the fuel arrangement with the possibility of uranium dioxide condensate blocking the channel. As a response, local constrictions which appear in the initial channel increase the deformation rate of the cladding; the formation of a closed vacuum-sealed cavity results in unacceptable loads on the cladding by gaseous fission products leaving the fuel. Because of small axial temperature gradients, longitudinal mass transfer is a slow process, comparable in duration to the service life, and therefore requires detailed studies taking account of the following concomitant factors: cyclic participation of oxygen in transfer with superstoichiometric composition of the uranium dioxide, change of the oxygen coefficient of uranium dioxide as a result of oxygen outflow from the system into the gas phase and inflow of additional oxygen from the dioxide with uranium burnup, local leaks of heat from the kernel through the system of spacers, as well as a change of the fuel temperature during radial mass transfer.Since strengthened emitter cladding is used in a single-element EGC, effectively redistributing the volume change, during swelling of the uranium dioxide, in the direction of the central channel of the kern...

show abstract

“…[2][3][4]). If the mean free path of the air molecules is smaller than the spacing between the bodies, the heat transfer takes place almost entirely by conduction through air.…”

Section: Introductionmentioning

confidence: 99%

Radiative Heat Loss Correction for 3-Body Graphite Calorimeters

Ionita¹,

Radu

Astefanoaei

2010

Acta Phys. Pol. A

View full text Add to dashboard Cite

For a 3-body Domen-type absorbed-dose graphite calorimeter a refined ordinary differential equation model is developed taking into account the heat loss through radiation from the surface of all three bodies. The new reduced heat transfer coefficients, K * i , i = 1, 2, 3 were defined and the associated calculated heat loss correction factors F * C and F * C+J were determined. The total energy lost by radiation from the core surface was evaluated for both heating and post heating periods as being 31.35% from the total core heat loss (and up to 1.1% from the total energy delivered to the core during the heating time). A new correction factor for heat loss through radiation from the calorimeter bodies' surfaces was introduced and calculated as being k SB ≈ 0.9996.

show abstract

Scientific Foundations of Vacuum Technique

Cited by 269 publications

References 0 publications

Physical Aspects of Process Control in Selective Laser Sintering of Metals

Physical Aspects of Process Control in Selective Laser Sintering of Metals

Uranium dioxide mass transfer in the central channel of the fuel kernel of a fuel element of a single-element energy-generating channel

Radiative Heat Loss Correction for 3-Body Graphite Calorimeters

Contact Info

Product

Resources

About