The Knudsen Compressor As an Energy Efficient Micro-Scale Vacuum Pump

2001 ◽  
Author(s):  
M. Young ◽  
S. Vargo ◽  
G. Shiflett ◽  
E. P. Muntz ◽  
Amanda Green
Keyword(s):  
Energy Efficient ◽  
Gas Flow ◽  
Flow Model ◽  
Low Pressure ◽  
Transitional Flow ◽  
Primary Concern ◽  
Pressure Limit ◽  
Pumping Efficiency ◽  
Continuum Flow ◽  
Knudsen Compressors

Abstract The low-pressure pumping limit of the MEMS Knudsen Compressor, a thermal transpiration pump, is identified and discussed. The practical low-pressure limit is due to a requirement for an approach to continuum flow in the connector section, it is roughly 10mTorr. A previously developed transitional flow model was used to size several Knudsen Compressor cascades that operate down to the low-pressure limit. Designs based on previous experimental Knudsen Compressors do not provide the necessary pumping efficiency. A design, employing carefully sized capillaries etched in aerogel transpiration membranes, is shown to result in a viable device. A cascade incorporating this design provides a gas flow rate of 3E16 mol/sec, while pumping from a pressure of 10mTorr to 1 atm. It requires a volume of 73 cm3 and 2.0 W. Design considerations are outlined for MEMS Knudsen Compressors operating at their lower pressure limit. A primary concern, efficiently transitioning from the capillary section to the connector at constant temperature is discussed.

scholarly journals Venturi Wet Gas Flow Modeling Based on Homogeneous and Separated Flow Theory

2008 ◽  
Vol 2008 ◽  
pp. 1-25 ◽  
Author(s):  
Fang Lide ◽  
Zhang Tao ◽  
Xu Ying
Keyword(s):  
High Pressure ◽  
Pressure Drop ◽  
Gas Flow ◽  
Flow Model ◽  
Separated Flow ◽  
Flow Theory ◽  
Low Pressure ◽  
New Correlation ◽  
Wet Gas ◽  
Low Pressures

When Venturi meters are used in wet gas, the measured differential pressure is higher than it would be in gas phases flowing alone. This phenomenon is called over-reading. Eight famous over-reading correlations have been studied by many researchers under low- and high-pressure conditions, the conclusion is separated flow model and homogeneous flow model performing well both under high and low pressures. In this study, a new metering method is presented based on homogeneous and separated flow theory; the acceleration pressure drop and the friction pressure drop of Venturi under two-phase flow conditions are considered in new correlation, and its validity is verified through experiment. For low pressure, a new test program has been implemented in Tianjin University’s low-pressure wet gas loop. For high pressure, the National Engineering Laboratory offered their reports on the web, so the coefficients of the new proposed correlation are fitted with all independent data both under high and low pressures. Finally, the applicability and errors of new correlation are analyzed.

A CFD and Experimental Investigation of Unsteady Wake Effects on a Highly Loaded Low Pressure Turbine Blade at Low Reynolds Number

2010 ◽  
Author(s):  
Darius D. Sanders ◽  
Chase A. Nessler ◽  
Rolf Sondergaard ◽  
Marc D. Polanka ◽  
Christopher Marks ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Turbine Blade ◽  
Flow Model ◽  
Low Pressure ◽  
Transitional Flow ◽  
Blade Design ◽  
Low Pressure Turbine ◽  
Low Reynolds ◽  
Turbine Blade Design ◽  
Lp Turbine

The flowfield of the L1A low pressure (LP) turbine blade subjected to traversing upstream wakes was experimentally and computationally investigated at an inlet Reynolds number of 25,000. The L1A profile is a high-lift aft-loaded low pressure turbine blade design. The profile was designed to separate at low Reynolds numbers making it an ideal airfoil for use in flow separation control studies. This study applied a new two-dimensional CFD model to the L1A LP turbine blade design using a three-equation eddy-viscosity type transitional flow model developed by Walters and Leylek. Velocity field measurements were obtained by two-dimensional planer particle image velocimetry, and comparisons were made to the CFD predictions using the Walters and Leylek [13] k-kL-ω transitional flow model and the Menter’s [24] k-ω(SST) model. Hotwire measurements and pressure coefficient distributions were also used to compare each model’s ability to predict the wake produced from the wake generator, and the loading on the L1A LP turbine blade profile with unsteady wakes. These comparisons were used to determine which RANS CFD model could better predict the unsteady L1A blade flowfield at low inlet Reynolds number. This research also provided further characterization of the Walters and Leylek transitional flow model for low Reynolds number aerodynamic flow prediction in low pressure turbine blades.

Study on the Deposition Profile Characteristics in the Micron-Scale Trench Using Direct Simulation Monte Carlo Method

1998 ◽  
Vol 120 (2) ◽  
pp. 296-302 ◽  
Author(s):  
Masato Ikegawa ◽  
Jun’ichi Kobayashi ◽  
Morihisa Maruko
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Boundary Conditions ◽  
Gas Flow ◽  
Direct Simulation Monte Carlo ◽  
Low Pressure ◽  
Sputter Deposition ◽  
Direct Simulation ◽  
Simulation Monte Carlo ◽  
Profile Characteristics

As integrated circuits are advancing toward smaller device features, step-coverage in submicron trenches and holes in thin film deposition are becoming of concern. Deposition consists of gas flow in the vapor phase and film growth in the solid phase. A deposition profile simulator using the direct simulation Monte Carlo method has been developed to investigate deposition profile characteristics on small trenches which have nearly the same dimension as the mean free path of molecules. This simulator can be applied to several deposition processes such as sputter deposition, and atmospheric- or low-pressure chemical vapor deposition. In the case of low-pressure processes such as sputter deposition, upstream boundary conditions of the trenches can be calculated by means of rarefied gas flow analysis in the reactor. The effects of upstream boundary conditions, molecular collisions, sticking coefficients, and surface migration on deposition profiles in the trenches were clarified.

Energy-efficient crosslinking with low-pressure lamps

2013 ◽  
Vol 10 (3) ◽  
pp. 26-31
Author(s):  
Benno Blickenstorfer ◽  
Wolfgang Aufmuth
Keyword(s):  
Energy Efficient ◽  
Low Pressure

Behavior of Radial Incompressible Flow in Pneumatic Dimensional Control Systems

2003 ◽  
Vol 125 (5) ◽  
pp. 843-850 ◽  
Author(s):  
G. Roy ◽  
D. Vo-Ngoc ◽  
D. N. Nguyen ◽  
P. Florent
Keyword(s):  
Gas Flow ◽  
Flow Behavior ◽  
Pressure Gauge ◽  
Axisymmetric Flow ◽  
Low Pressure ◽  
Industrial Applications ◽  
Nozzle Geometry ◽  
Machined Surface ◽  
Flow Area ◽  
Simpler Algorithm

The application of pneumatic metrology to control dimensional accuracy on machined parts is based on the measurement of gas flow resistance through a restricted section formed by a jet orifice placed at a small distance away from a machined surface. The backpressure, which is sensed and indicated by a pressure gauge, is calibrated to measure dimensional variations. It has been found that in some typical industrial applications, the nozzles are subject to fouling, e.g., dirt and oil deposits accumulate on their frontal areas, thus requiring more frequent calibration of the apparatus for reliable service. In this paper, a numerical and experimental analysis of the flow behavior in the region between an injection nozzle and a flat surface is presented. The analysis is based on the steady-state axisymmetric flow of an incompressible fluid. The governing equations, coupled with the appropriate boundary conditions, are solved using the SIMPLER algorithm. Results have shown that for the standard nozzle geometry used in industrial applications, an annular low-pressure separated flow area was found to exist near the frontal surface of the nozzle. The existence of this area is believed to be the cause of the nozzle fouling problem. A study of various alternate nozzle geometries has shown that this low-pressure recirculation area can be eliminated quite readily. Well-designed chamfered, rounded, and reduced frontal area nozzles have all reduced or eliminated the separated recirculation flow area. It has been noted, however, that rounded nozzles may adversely cause a reduction in apparatus sensitivity.

scholarly journals Development of the Burden Distribution and Gas Flow Model in the Blast Furnace Shaft

2011 ◽  
Vol 51 (10) ◽  
pp. 1617-1623 ◽  
Author(s):  
Jong-In Park ◽  
Ui-Hyun Baek ◽  
Kyoung-Soo Jang ◽  
Han-Sang Oh ◽  
Jeong-Whan Han
Keyword(s):  
Blast Furnace ◽  
Gas Flow ◽  
Flow Model ◽  
Burden Distribution ◽  
Furnace Shaft

scholarly journals NMR Analysis Method of Gas Flow Pattern in the Process of Shale Gas Depletion Development

Geofluids ◽  
2022 ◽  
Vol 2022 ◽  
pp. 1-7
Author(s):  
Rui Shen ◽  
Zhiming Hu ◽  
Xianggang Duan ◽  
Wei Sun ◽  
Wei Xiong ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Pore Pressure ◽  
Shale Gas ◽  
Gas Flow ◽  
Continuous Medium ◽  
Slip Flow ◽  
Flow Patterns ◽  
Transitional Flow ◽  
Analysis Method ◽  
Adsorbed Gas

Shale gas reservoirs have pores of various sizes, in which gas flows in different patterns. The coexistence of multiple gas flow patterns is common. In order to quantitatively characterize the flow pattern in the process of shale gas depletion development, a physical simulation experiment of shale gas depletion development was designed, and a high-pressure on-line NMR analysis method of gas flow pattern in this process was proposed. The signal amplitudes of methane in pores of various sizes at different pressure levels were calculated according to the conversion relationship between the NMR T 2 relaxation time and pore radius, and then, the flow patterns of methane in pores of various sizes under different pore pressure conditions were analyzed as per the flow pattern determination criteria. It is found that there are three flow patterns in the process of shale gas depletion development, i.e., continuous medium flow, slip flow, and transitional flow, which account for 73.5%, 25.8%, and 0.7% of total gas flow, respectively. When the pore pressure is high, the continuous medium flow is dominant. With the gas production in shale reservoir, the pore pressure decreases, the Knudsen number increases, and the pore size range of slip flow zone and transitional flow zone expands. When the reservoir pressure is higher than the critical desorption pressure, the adsorbed gas is not desorbed intensively, and the produced gas is mainly free gas. When the reservoir pressure is lower than the critical desorption pressure, the adsorbed gas is gradually desorbed, and the proportion of desorbed gas in the produced gas gradually increases.

scholarly journals Diagnostics of low-pressure capacitively coupled RF discharge argon plasma

2019 ◽  
Vol 13 (27) ◽  
pp. 76-82
Author(s):  
Kadhim A. Aadim
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Langmuir Probe ◽  
Gas Flow ◽  
Low Pressure ◽  
Gas Pressure ◽  
Rf Discharge ◽  
Electrode Gap ◽  
Probe Characteristic ◽  
Capacitively Coupled

Low-pressure capacitively coupled RF discharge Ar plasma has been studied using Langmuir probe. The electron temperature, electron density and Debay length were calculated under different pressures and electrode gap. In this work the RF Langmuir probe is designed using 4MHz filter as compensation circuit and I-V probe characteristic have been investigated. The pressure varied from 0.07 mbar to 0.1 mbar while electrode gap varied from 2-5 cm. The plasma was generated using power supply at 4MHz frequency with power 300 W. The flowmeter is used to control Argon gas flow in the range of 600 standard cubic centimeters per minute (sccm). The electron temperature drops slowly with pressure and it's gradually decreased when expanding the electrode gap. As the gas pressure increases, the plasma density rises slightly at low gas pressure while it drops little at higher gas pressure. The electron density decreases rapidly with expand distances between electrodes.

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