Subdynamic asymptotic behavior of microfluidic valves

Decreasing the Reynolds number of microfluidic no-moving-part flow control valves considerably below the usual operating range leads to a distinct “subdynamic” regime of viscosity- dominated flow, usually entered through a clearly defined transition. In this regime, the dynamic effects on which the operation of large-scale no-moving-part fluidic valves is based, cease to be useful, but fluid may be driven through the valve (and any connected load) by an applied pressure difference, maintained by an external pressure regulator. Reynolds number ceases to characterize the valve operation, but the driving pressure effect is usefully characterized by a newly introduced dimensionless number and it is this parameter which determines the valve behavior. This summary paper presents information about the subdynamic regime using data (otherwise difficult to access) obtained for several recently developed flow control valves. The purely subdynamic regime is an extreme. Most present-day microfluidic valves are operated at higher Re, but the paper shows that the laws governing subdynamic flows provide relations useful as an asymptotic reference

Fluidic valve for reactor regeneration flow switching

An unusual and in many respects advantageous no-moving-part valve is described,developed for switching fluid flows in a through-flow reactor that requires a periodic regeneration by temporary replacement of the process fluid by another, regeneration fluid. The unusual feature of the valve is that it is axisymmetric, built integrally into the inlet part of the reactor body. The valve operation is based upon a monostable axisymmetric variant of the Coanda effect of jet attachment to a wall. The jet is annular and there are two attachment walls of conical shape. The outer hollow cone is dominant while the auxiliary inner convex cone is small, almost vestigial. Concentrating on the performance in a no-spillover regime, experimental data obtained in cold-air laboratory tests using a full-scale model are compared with numerical flowfield computations, using unusual non-dimensional presentation

SNTP propellant management system

Viewgraphs on the following are presented: (1) space nuclear thermal propulsion (SNTP) propellant management system; (2) SNTP cycle selection; (3) NTP system components unique design constraints; (4) bleed cycle unique design requirement for turbopump; (5) bleed cycle turbopump; (6) SNTP carbon-carbon turbine wheel; and (7) turbine development program

Increasing the Retention of Lipid-Soluble Components in a Curd Matrix

Retention of lipid-soluble components can be increased in a curd matrix by using emulsions rather than the direct addition of fortified oil. The retention of vitamin D_3 was increased in a model system with fortified emulsions (emulsifier: dairy proteins) 96-97% compared to 62-72% control. Retention of fortified emulsions (78%) remained greater than the control (58%) in small-batch Cheddar cheese. Bilayer emulsions were evaluated to increase retention of lipid-soluble components even further. Physicochemical characteristics of the bilayer emulsions were evaluated prior to curd inclusion. Nonfat dry milk (NDM) was used as the primary emulsifier at 1wt% dairy proteins. Polysaccharides (iota-carrageenan, low-methoxyl [LMp] and high-methoxyl pectin) and gelatin were secondary layers. Secondary emulsions formulation was 2.5 wt% oil, 0.5 wt% protein, and 0.2 wt% secondary biopolymer. Emulsions were adjusted to pH 3, 5, and 7 after homogenization. Factors that influence stability are biopolymer concentration, droplet size/distribution/charge (zeta-potential), and viscosity. iota-Carrageenan was the most stable, independent of pH, of all the emulsions. This increased stability was a consequence of the affinity of the protein layer and iota-carrageenan through the additional homogenization step. LMp was also stable at pH 7 due to calcium bridging, which correlates with the increased viscosity. The microstructure of the emulsions was examined using scanning electron microscopy. A strong correlation was found between emulsion instability and the presence of thick webbing, due to excess biopolymer, as seen in the micrographs. Stable emulsions were likely to have distinct droplets without a thick web. The exception was gelatin (pH 3), which still had individual droplets but was unstable due to depletion flocculation. The retention of lipid-soluble substances using secondary emulsion was evaluated in a model curd matrix between primary (50:50 fortified: non-fortified oil) and secondary (100% fortified oil) emulsions. There was no significant difference (α=0.05) in retention of “fortified” oil between primary and secondary emulsions; however, the same fortification level was obtained using secondary emulsions using half the oil. Curd made with 0.01M CaCl_2 had overall lower retention than curd with no additional calcium. Secondary emulsions could be used to fortify various gel matrices (e.g., curd, yogurt, and tofu). Marketing possibilities are endless after preliminary evaluation

Every Day Monuments: A Restoration & Style Guide for Cache Valleyʼs Historic Residential Architecture

Picturesque tree lined streets, and the eclectic mingling of architectural styles from a bygone era are what draw many people to historic districts and vintage suburbs across the nation. As one tours these old neighborhoods, one can find a vast expanse of historic architectural styles ranging from exuberantly decorated Victorians, to Craftsman Bungalows and the emergence of modernism. Great lengths have been put into place to protect architectural landmarks built for historically prominent people, or properties designed by influential architects. But what about the quaint Gothic Revival cottage built for the dress maker, the local bakers foursquare on Center Street, or the Tudor Revival for the town banker? These humble monuments to the working men and women who contributed to our society also deserve careful preservation and restoration. Too often these architecturally rich dwellings fall subject to misguided additions, cheap makeovers, and uninformed design alterations that destroy the original art, beauty, and intent of these structures, obliterating the history, meaning, and architectural significance they have to offer. The residential suburbs of Logan, Utah, are filled with charming period homes that range from immaculately maintained, to neglected and forgotten, and even “remuddled” and mutilated. The purpose of this project is to highlight the architectural styles from the founding of Logan to the 1940’s in the Cache Valley area. Each section begins by highlighting a period style, giving a brief history of the political, economic, and artistic history and inspiration behind that style. Examples of stylistically correct details are contrasted with illustrations of misguided modifications. With clear “do this, not that” instructions, this work will serve as a resource to help the most uninformed home owners and professionals alike update, restore, and even add on to local buildings while still maintaining their original beauty

Flow Visualisation by Condensing Steam – an Unusual Method Applied to Development of a Low Reynolds Number Fluidic Selector Valve

A visualization method so far not mentioned in the literature has been recently developed by the authors as a useful validation supplement to numerical flowfield computations in the design of microfluidic devices. The method is based upon water vapour condensation on device channel walls. It is extremely easy to set up with minimum expense – and yet it is very reliable. As an application example, the paper shows the method used in study of properties of a microfluidic valve intended for switching gaseous sample flows in a microfluidic selector sampling unit. A scaled-up model of the valve was built, as usual, in transparent acrylic material, making possible observation and photo-recording of the deposition and subsequent drying of the condensed droplets. The scaling-up slowed down the time scale enough for investigating the transition processes which takes place as the flow in the valve is switched on and off.

Flow Visualisation by Condensing Steam – an Unusual Method Applied to Development of a Low Reynolds Number Fluidic Selector Valve

A visualization method so far not mentioned in the literature has been recently developed by the authors as a useful validation supplement to numerical flowfield computations in the design of microfluidic devices. The method is based upon water vapour condensation on device channel walls. It is extremely easy to set up with minimum expense – and yet it is very reliable. As an application example, the paper shows the method used in study of properties of a microfluidic valve intended for switching gaseous sample flows in a microfluidic selector sampling unit. A scaled-up model of the valve was built, as usual, in transparent acrylic material, making possible observation and photo-recording of the deposition and subsequent drying of the condensed droplets. The scaling-up slowed down the time scale enough for investigating the transition processes which takes place as the flow in the valve is switched on and off.

Development of a microfluidic unit for sequencing fluid samples for composition analysis

A microfluidic sample-sequencing unit was developed as a part of a high-throughput catalyst screening facility. It may find applications wherever a fluid is to be selected for analysis from any one of several sources, such as microreactors operating in parallel. The novel feature is that the key components are fluidic valves having no moving parts and operating at very low sample flow Reynolds numbers, typically below 100. The inertial effects utilized in conventional no-moving-part fluidics are nearly absent; instead, the flows are pressure-driven. Switching between input channels is by high-Reynolds-number control flows, the jet pumping effect of which simultaneously cleans the downstream cavities to prevent crosscontamination between the samples. In the configuration discussed here, the integrated circuit containing an array of 16 valves is etched into an 84mm diameter stainless steel foil. This is clamped into a massive assembly containing 16 mini-reactors operated at up to 400C and 4 MPa. This paper describes the design basis and experience with prototypes. Results of CFD analysis, with scrutiny of some discrepancies when compared with flow visualization, is included

Computational Fluid Dynamic Studies of Vortex Amplifier Design for the Nuclear Industry—II. Transient Conditions

In this paper computational fluid dynamics (CFD) techniques have been used to investigate the effect of changes to the geometry of a vortex amplifier (VXA) in the context of glovebox operations in the nuclear industry. These investigations were required because of anomalous behavior identified when, for operational reasons, a long-established VXA design was reduced in scale. The study simulates the transient aspects of two effects: back-flow into the glovebox through the VXA supply ports, and the precessing vortex core in the amplifier outlet. A temporal convergence error study indicates that there is little to be gained from reducing the time step duration below 0.1 ms. Based upon this criterion, the results of the simulation show that the percentage imbalance in the domain was well below the required figure of 1, and imbalances for momentum in all three axes were all below measurable values. Furthermore, there was no conclusive evidence of periodicity in the flow perturbations at the glovebox boundary, although good evidence of periodicity in the device itself and in the outlet pipe was seen. Under all conditions the modified geometry performed better than the control geometry with regard to aggregate reversed supply flow. The control geometry exhibited aggregate nonaxisymmetric supply port back-flow for almost all of the simulated period, unlike the alternative geometry for which the flow through the supply ports was positive, although still nonaxisymmetric, for most of the period. The simulations show how transient flow structures in the supply ports can cause flow to be reversed in individual ports, whereas aggregate flow through the device remains positive. Similar to the supply ports, flow through the outlet of the VXA under high swirl conditions is also nonaxisymmetric. A time-dependent reverse flow region was observed in both the outlet and the diffuser. It is possible that small vortices in the outlet, coupled with the larger vortex in the chamber, are responsible for the oscillations, which cause the shift in the axis of the precessing vortex core (and ultimately in the variations of mass flow in the individual supply ports). Field trials show that the modified geometry reduces the back-flow of oxygen into the glovebox by as much as 78. At purge rates of 0.65 m 3h the modified geometry was found to be less effective, the rate of leakage from the VXA increasing by 16-20. Despite this reduced performance, leakage from the modified geometry was still 63 less than the control geometry. © 2012 American Society of Mechanical Engineers

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