Characterization of a Radiantly Driven Multistage Knudsen Compressor

Knudsen Compressors are meso/micro scale gas compressors/pumps based on thermal transpiration or thermal creep. The design of radiantly driven Knudsen Compressors is discussed, along with a model that was developed to understand their performance. Experimental pumping performances for Knudsen Compressors with one, two, five, and fifteen stage, radiantly driven cascades are also discussed. Temperature measurements across the transpiration membranes, for various pressures of Nitrogen, were obtained and compared to those predicted by the performance model. The results agree with the model to within 15% consistently under predicting the measured hot side temperature of the transpiration membrane. The pump-down curves, steady-state maximum pressure differences, and maximum flow rates produced by a single stage Knudsen Compressor were obtained. A variety of configurations were studied at pressures from 500 mTorr to atmospheric pressure. The experimental results agreed with the performance model’s predictions to within 20%.

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Directional Pumping Performance of an Electrostatic Checkerboard Microvalve

Microelectromechanical Systems ◽

10.1115/imece2006-16211 ◽

2006 ◽

Cited By ~ 2

Author(s):

Hanseup Kim ◽

Aaron A. Astle ◽

Luis P. Bernal ◽

Khalil Najafi ◽

Peter D. Washabaugh

Keyword(s):

Flow Rate ◽

Gas Flow ◽

Maximum Flow ◽

Pressure Differential ◽

Oscillatory Motion ◽

Sinusoidal Signal ◽

Maximum Pressure ◽

Experimental Characterization ◽

Gas Pumping

This paper reports experimental characterization of directional gas pumping generated by MEMS-fabricated checkerboard-type electrostatic microvalves. It is found that the oscillatory motion of the checkerboard microvalve membrane provides both the pumping and valve functions of a pump, namely: 1) to cause the volume displacement and, thus, compression and transfer of gas, and 2) to direct gas flow in one direction by closing and opening air paths in the proper sequence. Here, we describe the microvalve-only design, and report the pumping performance producing a maximum flow rate of 1.8 sccm and a maximum pressure differential of 3.0 kPa for five microvalves driven simultaneously with a sinusoidal signal of ± 100V amplitude at 5.5 kHz.

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Performance Model for Optically Driven Micropumps With Carbon Opacified Aerogel Membranes

Volume 10: Micro- and Nano-Systems Engineering and Packaging ◽

10.1115/imece2013-62197 ◽

2013 ◽

Author(s):

Yen-Lin Han

Keyword(s):

Rarefied Gas ◽

Carbon Aerogel ◽

Performance Model ◽

Operating Conditions ◽

Thermal Creep ◽

Maximum Pressure ◽

Membrane Thickness ◽

Carbon Particles ◽

Knudsen Compressors ◽

Highly Porous

Aerogel, a highly porous material with less than several percent of solids, has been utilized in applications requiring high precision thermal managements due to its extremely low thermal conductivity. Combining the advantages of high porosities and low thermal conductivities, aerogels were used as thermal creep membranes in Knudsen Compressors, micro/meso-scale pumps/compressors with no moving parts. Heating one side of the thermal creep membrane to create a temperature gradient, a Knudsen Compressor is operated based on the rarefied gas phenomenon of thermal creep to create flows and to induce a pressure gradient from the cold side to the hot side of the membrane. Adding carbon particles in silica aerogels creates an optically thick, opacified carbon aerogel that can absorb radiation energies to heat up one side of the aerogel membrane in a Knudsen Compressor to create thermal creep flows. An analytical model was developed to predict the temperature profile inside of the carbon opacified aerogel thermal creep membrane for the Knudsen Compressor. Applying this temperature model, pressure ratios achieved by the optically heated Knudsen Compressors for given operating conditions were also studied and correlations between the membrane thickness and the maximum pressure increase were determined.

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Maximum Flow Rates Achievable Through Peripherally Inserted Central Catheters Using Standard Hospital Infusion Pumps

Journal of the Association for Vascular Access ◽

10.1016/j.java.2012.05.005 ◽

2012 ◽

Vol 17 (2) ◽

pp. 78-83

Author(s):

Timothy Royer

Keyword(s):

Pressure Sensor ◽

Infusion Pump ◽

Maximum Flow ◽

Maximum Pressure ◽

Infusion Pumps ◽

Peripherally Inserted Central Catheters ◽

Flow Rates ◽

Type Size ◽

Central Catheters

Abstract Purpose: To determine maximum flow rates through peripherally inserted central catheters (PICCs) using a standard hospital infusion pump. Background: Two questions asked with the use of PICCs and flow rates are (1) can a PICC be used to give nonemergent fluid boluses, and (2) can standard hospital infusion pumps develop enough pressure to rupture a catheter? Methods: New PICCs of different brands and gauges were gathered. Six standard hospital infusion pumps and tubing of the same brand and model were used. The pressure sensor was set at 600 mm Hg. The pumps were connected through the access ports of each intravenous tube in a series fashion. The PICC end was submerged under 5 cm of water. All equipment and fluids were at 70° F. PICCs were trimmed to 45 cm. Fluids were run starting with the first pump at 999 mL/hour and then additional pumps were added until the pump's 600 mm Hg limit stopped the infusion or catheter rupture. Tests with the same PICC were repeated and recorded. Results: Flow rates varied with the type, size, gauge, and brand of PICC catheter. Flows were achieved from 2,100 mL/hour to >6,000 mL/hour. None of the PICCs ruptured. Conclusions: Maximum flow rates through PICCs were limited by the maximum pressure allowed by the standard hospital infusion pump. A standard hospital infusion pump cannot generate enough pressure to rupture a new-out-of-the-package catheter. Implication for Practice: Nonemergent fluid boluses can be given through PICCs and standard infusion pumps will not rupture a PICC.

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A Comprehensive Performance Characterization of a Nanofluid-Powered Dual-Fluid PV/T System under Outdoor Steady State Conditions

Sustainability ◽

10.3390/su132313134 ◽

2021 ◽

Vol 13 (23) ◽

pp. 13134

Author(s):

Muhammad Imtiaz Hussain ◽

Gwi-Hyun Lee ◽

Jun-Tae Kim

Keyword(s):

Steady State ◽

Energy Requirement ◽

Experimental Studies ◽

Energy Output ◽

Performance Characterization ◽

Flow Rates ◽

Comprehensive Performance ◽

T System ◽

Indoor And Outdoor

This paper discusses the effectiveness of simultaneous use of CuO nanofluid and air as a dual-fluid coolant for the thermal management of a photovoltaic/thermal (PV/T) system. Outdoor experimental studies were performed to calculate the discrepancies between indoor and outdoor test findings. The thermal efficiency and the electrical characteristics of the dual-fluid PV/T system were investigated under steady-state test conditions following ISO standards. It was found that the divergence in electrical efficiency between indoor and outdoor-based PVT testing was significantly higher, while the difference in thermal efficiencies was marginal. It was observed that nanofluid/air, even at the lowest flow rates, outclassed the water/air coolant at higher flow rates in terms of PV/T energy output, which also ultimately helps in reducing the energy requirement for pumping. Unlike conventional solar air heaters, the proposed dual-fluid PV/T system produces a high air temperature when operated with only air at stagnant nanofluid. The maximum PV/T efficiency of approximately 85% was recorded when the nanofluid and air flows were kept at 0.02 kg/s and 0.04 kg/s, respectively. It is concluded that outdoor steady state testing provides comprehensive performance characterization of the nanofluid powered dual-fluid coolant for the PV/T system.

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Theoretical and Experimental Performance of a High Frequency Micropump

Microelectromechanical Systems ◽

10.1115/imece2005-81626 ◽

2005 ◽

Cited By ~ 2

Author(s):

Aaron Astle ◽

Luis P. Bernal ◽

Hanseup Kim ◽

Khalil Najafi ◽

Peter D. Washabaugh

Keyword(s):

High Frequency ◽

Maximum Flow ◽

Maximum Pressure ◽

Experimental Characterization ◽

Chemical Monitoring ◽

Multi Stage ◽

Micro Systems ◽

The University ◽

Theoretical Analyses

This paper details theoretical analyses and experimental characterization of high-frequency multi-stage micro pumps. The MEMS-fabricated micro pumps have been developed for use in a highly-integrated chemical monitoring system under development at the University of Michigan’s Wireless Integrated Micro-Systems center. Tests are reported on a 20x meso-scale 2-stage pump developed to validate the theoretical analyses. Detailed comparisons of the pump performance and unsteady pressure traces show that the theoretical analyses capture the main features of the flow in the pump. A MEMS-fabricated device has been developed and tested. The use of theoretical analyses for the design of the pump is described. This device produces A maximum flow of 1.1 ccm and a maximum pressure of 879 Pa.

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Constant-flow ventilation in pigs

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.6.2238 ◽

1986 ◽

Vol 61 (6) ◽

pp. 2238-2242 ◽

Cited By ~ 7

Author(s):

P. Webster ◽

A. S. Menon ◽

A. S. Slutsky

Keyword(s):

Steady State ◽

Gas Exchange ◽

Gas Flow ◽

Blood Gases ◽

Maximum Flow ◽

Constant Flow ◽

Catheter Position ◽

Flow Rates ◽

Co2 Partial Pressure ◽

Flow Through

Constant-flow ventilation (CFV) is a ventilatory technique in which physiological blood gases can be maintained in dogs by a constant flow of fresh gas introduced via two catheters placed in the main-stem bronchi (J. Appl. Physiol. 53: 483–489, 1982). High-velocity gas exiting from the catheters can create uneven pressure differences in adjacent lung segments, and these pressure differences could lead to gas flow through collateral channels. To examine this hypothesis, we studied CFV in pigs, animals known to have a high resistance to collateral ventilation. In three pigs we examined steady-state gas exchange, and in six others we studied unsteady gas exchange at three flow rates (20, 35, and 50 l/min) and three catheter positions (0.5, 1.5, and 2.5 cm distal to the tracheal carina). During steady-state runs we were unable to attain normocapnia; the arterial CO2 partial pressure (PaCO2) was approximately 300 Torr at all flow rates and all catheter positions, compared with 20–50 Torr at similar flows and positions in dogs studied previously. The initial unsteady gas-exchange experiments indicated no consistent effect of catheter position or flow rate on the rate of rise of PaCO2. In three other pigs, the rates of rise of PaCO2 were compared with the rates observed with apneic oxygenation (AO). At the maximum flow and deepest position, the rate of rise of PaCO2 was lower during CFV than during AO. These data suggest that flow through collateral channels might be important in producing adequate gas transport during CFV; however, other factors such as airway morphometry and the effects of cardiogenic oscillations may explain the differences between the results in pigs and dogs.

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Electron microscope characterization of MOCVD-grown gap layers on Si

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144991 ◽

1986 ◽

Vol 44 ◽

pp. 724-725

Author(s):

K.M. Jones ◽

M.M. Al-Jassim ◽

J.M. Olson

Keyword(s):

Atmospheric Pressure ◽

Vapour Deposition ◽

Chemical Vapour ◽

Organic Chemical ◽

Lattice Match ◽

Si Substrates ◽

Metal Organic ◽

Good Lattice ◽

Antiphase Domains

The epitaxial growth of III-V semiconductors on Si for integrated optoelectronic applications is currently of great interest. GaP, with a lattice constant close to that of Si, is an attractive buffer between Si and, for example, GaAsP. In spite of the good lattice match, the growth of device quality GaP on Si is not without difficulty. The formation of antiphase domains, the difficulty in cleaning the Si substrates prior to growth, and the poor layer morphology are some of the problems encountered. In this work, the structural perfection of GaP layers was investigated as a function of several process variables including growth rate and temperature, and Si substrate orientation. The GaP layers were grown in an atmospheric pressure metal organic chemical vapour deposition (MOCVD) system using trimethylgallium and phosphine in H2. The Si substrates orientations used were (100), 2° off (100) towards (110), (111) and (211).

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Holdup and holdup profiles in the reciprocating plate extractor VPE

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19902648 ◽

1990 ◽

Vol 55 (11) ◽

pp. 2648-2661 ◽

Cited By ~ 1

Author(s):

Helena Sovová ◽

Vladislav Bízek ◽

Jaroslav Procházka

Keyword(s):

Steady State ◽

Experimental Results ◽

Model Parameters ◽

Dispersed Phase ◽

Pulse Form ◽

Sieve Plates

In this work measurements of mean holdup of dispersed phase, of axial holdup profiles and of flooding points in a reciprocating plate contactor with both the VPE-type plates and the sieve plates were carried out. The experimental results were compared with a monodisperse model of steady-state column hydrodynamics and the model parameters were evaluated. Important differences in the behaviour of the two plate types could be identified. Comparison was also made between two reciprocating drives of different pulse form.

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