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197. Continuous gas mixing by the use of critical flow through small diameter tubes
Classified abstracts 193-352 Classified
abstracts
193-203 on this page
f ditor’s note
The label immediately following the title of each item denotes country or origin of publication, and that at the end of each abstract indicates country of origin of work (where known).
I. General 14. KINETIC
vacuum THEORY
science
and engineering
15 :40 198. Viscosities
OF GASES 14
193. Rarefied gas dynamics.
(USA)
Two new techniques are developed for the analysis of complicated impact pressure probes at various speed ratios and angles of attack. The first technique is based on the analogy of radiant-heat transfer to that of free molecular flow. The second technique uses the Monte Carlo method of selecting random numbers to follow the paths of individual molecules in a system. The calculation of the drag coefficient of a concave hemispherical shell is extended from the limiting case where all incoming flow is perpendicular to the opening plane of the shell to the case where the incoming flow is at some angle to the opening plane of the shell. A modification of the Monte Carlo method is being used in the flow analysis of a cylindrical duct in the transitionflow regime. Thermal accommodation coefficients have been measured only for low-energy collisions and even then the results are questionable. J 0 Ballance, Rep NASA-TM-53620, space Reps, 5 (17), 3047, N67-30572).
1967, 5 pages (Sci Tech Aero14
194. Asymptotic
solutions for the expansion of gas into vacuum.
(USA) When a spherical or cylindrical gas cloud expands into vacuum, the resultant flow becomes asymptotically self-similar and independent of the original cloud diameter. An analytic solution for the asymptotic density profiles is examined and a new solution is proposed which gives better agreement with the numerical computations. Some applications of the asymptotic solutions are discussed. E H Wedemeyer, Rep BRL-1278, AD-465240, April (US Govt Res Develop Reps, 67 (15), 1967, 137).
1967, 27 pages
14 195. Dynamical similarities in rarefied gas flow. (USA) It is shown that the Knudsen number constitutes a part of the criterion with the Navier-Stokes equation. In view of the criterion, flow regimes are proposed to be redefined. It is sugg:sted that th:re is a possibility of revisions of the slip flow theory by which the application of the Navier-Stokes equation becomes more radical in some rarefied gas flow. T Koga, Rep PZBAL-964, AD-478179, Jan 1966, 18 pages (US Govt Res Develop
Reps, 67 (15), 1967, 137). 14
196. Condensation
(Germany) Viscosities (expressed in technical units) of argon and nitrogen in the ground state and for 1 atm pressure are tabulated for the temperature range from 50°K to 10000°K spaced 10°K apart. In the appendix, numerical values are tabulated for the product of mean free path and pressure as a function of the absolute temperature for argon and molecular nitrogen. K Robert, Rep DLR-MITT-67-06, April 1967, 70 pages (in German) (Sri Tech Aerospace Reps, 5 (17), 3048, N67-30792). 16. GASES
AND SOLIDS
16 : 41 199. Ultrahigh vacuum techniques.
(USA)
The permeation, solubility and diffusion constants of hydrogen in tungsten and the replacement of one adsorbed gas by another was determined. Measurements were also made on the nitrogen-tungsten and nitrogen-molybdenum systems. No measurable replacement was observed for the hydrogen-nitrogen system on tungsten in the study of gas replacement. R Frauenfelder et al, Rep WERL-2823-24, Nov 1966, 35 pages (Sci Tech Aerospace
Reps, 3 (16), 2852, N67-29836).
200. Electron emission from tungsten under proton bombardment of nitrogen adsorption. (USA)
(US Govt Res Develop
Reps, 67 (15), 1967, 140).
15. FLUID DYNAMICS 15 gas mixing by the use of critical flow through small
(USA) Small-diameter tubes and hypodermic needles are used to meter the flow rate in a continuous-flow gas mixing device by means of changing the upstream stagnation pressure. The theoretical and experimental aspects of the problem are considered and a computer program is introduced to find the flow rates. M M Kamel and E A Lundstrom, Rep AS-67-3; AFOSR-67-1028; AD-651637; March 1967, 64 pages (Sci Tech Aerospace Reps, 5 (1%
3046, N67-30265).
16 : 18 effect
The yield of electrons emitted from polycrystalline tungsten under bombardment by 100 keV protons is found to depend upon the coverage of the surface by adsorbed nitrogen gas. The tungsten surface was cleaned by the flash-filament method and the yield measured as nitrogen gas adsorbed on the surface to a coverage of about 1.l layers. The yield increased with increasing surface coverage to about one monolayer, out further adsorption causes the yield to decrease. RI Ewing, Rep SC-R-67-1038, Jan 1967, 12pages Reps, 5 (15), 2762, N67-28354).
(Sci Tech Aerospace
16 201. Gas emission in vacuum from MgO surfaces previously exposed to air. (USA)
The residual gases given off by MgO heated in vacuum were analyzed. It is concluded that MgO adsorbs or chemically reacts with H,d and CO, in air, possibly to form hydroxide or carbonate. J Cohen, j Appl Phys, 38 (9), 1967, 3791.
droplet growth in rarefied gases.
(USA) An analysis is made of thermal and diffusion effects on the droplet growth phenomena in a supersaturated vapour and inert carrier gas. The results indicate that the choice of the slip-regime parameters influence the droplet growth only when the ratio of the droplet size to the mean free path is of order one. S-W Kang, Rep ARL-67-0049, AD-653199, March 1967, 43 pages
197. Continuous diameter tubes.
of argon and nitrogen.
16 202. Determination
of the surface areas of selected solids.
(USA) A study was made of methods for the determination of the surface area of solids with the purpose of investigating new adsorbents. After a review of the literature, the dynamic flow methods using the theory of molecular adsorption was selected. The selected values measured ranged from a high of almost 1000 square metres per gram for activated carbon to a low of 0.078 square metres per gram for glass beads. N L Hatfield, Rep MEL-27167, March 1967, 32 pages (Sci Tech Aerospace Reps, 5 (16), 2849, N67-29664). 16 203. Research studies on solid, hydrogen purification membranes. (USA) The permeation rate of hydrogen through tantalum coated with a thin film of palladium was measured over the temperature range 4OGEOO”C and at pressures up to 175 psia. The permeation rate is substantially greater than that through pure palladium membranes of the same thickness under the same conditions. The permeation rate through tantalum decays with time, particularly at temperatures 500°C or higher. It appears that at high temperatures extensive recrystallization of the palladium film takes place. This process probably leads to 95
abstracts
193-203 on this page
f ditor’s note
The label immediately following the title of each item denotes country or origin of publication, and that at the end of each abstract indicates country of origin of work (where known).
I. General 14. KINETIC
vacuum THEORY
science
and engineering
15 :40 198. Viscosities
OF GASES 14
193. Rarefied gas dynamics.
(USA)
Two new techniques are developed for the analysis of complicated impact pressure probes at various speed ratios and angles of attack. The first technique is based on the analogy of radiant-heat transfer to that of free molecular flow. The second technique uses the Monte Carlo method of selecting random numbers to follow the paths of individual molecules in a system. The calculation of the drag coefficient of a concave hemispherical shell is extended from the limiting case where all incoming flow is perpendicular to the opening plane of the shell to the case where the incoming flow is at some angle to the opening plane of the shell. A modification of the Monte Carlo method is being used in the flow analysis of a cylindrical duct in the transitionflow regime. Thermal accommodation coefficients have been measured only for low-energy collisions and even then the results are questionable. J 0 Ballance, Rep NASA-TM-53620, space Reps, 5 (17), 3047, N67-30572).
1967, 5 pages (Sci Tech Aero14
194. Asymptotic
solutions for the expansion of gas into vacuum.
(USA) When a spherical or cylindrical gas cloud expands into vacuum, the resultant flow becomes asymptotically self-similar and independent of the original cloud diameter. An analytic solution for the asymptotic density profiles is examined and a new solution is proposed which gives better agreement with the numerical computations. Some applications of the asymptotic solutions are discussed. E H Wedemeyer, Rep BRL-1278, AD-465240, April (US Govt Res Develop Reps, 67 (15), 1967, 137).
1967, 27 pages
14 195. Dynamical similarities in rarefied gas flow. (USA) It is shown that the Knudsen number constitutes a part of the criterion with the Navier-Stokes equation. In view of the criterion, flow regimes are proposed to be redefined. It is sugg:sted that th:re is a possibility of revisions of the slip flow theory by which the application of the Navier-Stokes equation becomes more radical in some rarefied gas flow. T Koga, Rep PZBAL-964, AD-478179, Jan 1966, 18 pages (US Govt Res Develop
Reps, 67 (15), 1967, 137). 14
196. Condensation
(Germany) Viscosities (expressed in technical units) of argon and nitrogen in the ground state and for 1 atm pressure are tabulated for the temperature range from 50°K to 10000°K spaced 10°K apart. In the appendix, numerical values are tabulated for the product of mean free path and pressure as a function of the absolute temperature for argon and molecular nitrogen. K Robert, Rep DLR-MITT-67-06, April 1967, 70 pages (in German) (Sri Tech Aerospace Reps, 5 (17), 3048, N67-30792). 16. GASES
AND SOLIDS
16 : 41 199. Ultrahigh vacuum techniques.
(USA)
The permeation, solubility and diffusion constants of hydrogen in tungsten and the replacement of one adsorbed gas by another was determined. Measurements were also made on the nitrogen-tungsten and nitrogen-molybdenum systems. No measurable replacement was observed for the hydrogen-nitrogen system on tungsten in the study of gas replacement. R Frauenfelder et al, Rep WERL-2823-24, Nov 1966, 35 pages (Sci Tech Aerospace
Reps, 3 (16), 2852, N67-29836).
200. Electron emission from tungsten under proton bombardment of nitrogen adsorption. (USA)
(US Govt Res Develop
Reps, 67 (15), 1967, 140).
15. FLUID DYNAMICS 15 gas mixing by the use of critical flow through small
(USA) Small-diameter tubes and hypodermic needles are used to meter the flow rate in a continuous-flow gas mixing device by means of changing the upstream stagnation pressure. The theoretical and experimental aspects of the problem are considered and a computer program is introduced to find the flow rates. M M Kamel and E A Lundstrom, Rep AS-67-3; AFOSR-67-1028; AD-651637; March 1967, 64 pages (Sci Tech Aerospace Reps, 5 (1%
3046, N67-30265).
16 : 18 effect
The yield of electrons emitted from polycrystalline tungsten under bombardment by 100 keV protons is found to depend upon the coverage of the surface by adsorbed nitrogen gas. The tungsten surface was cleaned by the flash-filament method and the yield measured as nitrogen gas adsorbed on the surface to a coverage of about 1.l layers. The yield increased with increasing surface coverage to about one monolayer, out further adsorption causes the yield to decrease. RI Ewing, Rep SC-R-67-1038, Jan 1967, 12pages Reps, 5 (15), 2762, N67-28354).
(Sci Tech Aerospace
16 201. Gas emission in vacuum from MgO surfaces previously exposed to air. (USA)
The residual gases given off by MgO heated in vacuum were analyzed. It is concluded that MgO adsorbs or chemically reacts with H,d and CO, in air, possibly to form hydroxide or carbonate. J Cohen, j Appl Phys, 38 (9), 1967, 3791.
droplet growth in rarefied gases.
(USA) An analysis is made of thermal and diffusion effects on the droplet growth phenomena in a supersaturated vapour and inert carrier gas. The results indicate that the choice of the slip-regime parameters influence the droplet growth only when the ratio of the droplet size to the mean free path is of order one. S-W Kang, Rep ARL-67-0049, AD-653199, March 1967, 43 pages
197. Continuous diameter tubes.
of argon and nitrogen.
16 202. Determination
of the surface areas of selected solids.
(USA) A study was made of methods for the determination of the surface area of solids with the purpose of investigating new adsorbents. After a review of the literature, the dynamic flow methods using the theory of molecular adsorption was selected. The selected values measured ranged from a high of almost 1000 square metres per gram for activated carbon to a low of 0.078 square metres per gram for glass beads. N L Hatfield, Rep MEL-27167, March 1967, 32 pages (Sci Tech Aerospace Reps, 5 (16), 2849, N67-29664). 16 203. Research studies on solid, hydrogen purification membranes. (USA) The permeation rate of hydrogen through tantalum coated with a thin film of palladium was measured over the temperature range 4OGEOO”C and at pressures up to 175 psia. The permeation rate is substantially greater than that through pure palladium membranes of the same thickness under the same conditions. The permeation rate through tantalum decays with time, particularly at temperatures 500°C or higher. It appears that at high temperatures extensive recrystallization of the palladium film takes place. This process probably leads to 95