Vacuum fluid flow

Valves, see pipe, fittings, and valves Vapor cloud explosions, 520 Velocities, fluid flow, 85, 89, 90 Vacuum lines, 133 Velocity head, 71... 

Filters have been designed to reduce the fouling or clogging of solid materials at the surface of the membrane by taking into account fluid flow. Among them are the rotary drum vacuum filter (designed for... 

Filtration. Filtration can include filter presses, rotary drum vacuum filters (RDVF), belt filters, and variations on synthetic membrane filtration equipment, such as filter cartridges, pancake filters, or plate and frame filter presses. These processes typically operate in a batch mode when the filter chamber is filled up or the vacuum drum cake is exhausted, a new batch must be started. This type of filtration is also called dead-end filtration because the only fluid flow is through the membrane itself. Due to the small size of cells and their compressible nature, typical cell cakes have low permeability and filter aids, such as diatomaceous earths, perlite, or other mined materials are added to overcome this limitation. Moreover, the presence of high solids and viscous polymeric fermentation byproducts can limit filtration fluxes without the use of filter aids. 

Solid particles are generally removed from the solution by filtration. The fluid is passed through a filtering medium, namely, a bed of fine particles, cloth, mesh, or sintered plate. The fluid flow is achieved either by forcing the mixture under pressure or by applying a vacuum on the opposite side. 

An important class of fluid flow problems involves free surface flows where only the flow phenomena in a single phase are of importance despite the fact that two or more phases are present in the system. Such situations are encountered, for example, in gas-liquid two-phase flows where, due to the large density difference, from a hydrodynamic point of view the flow can be treated as a liquid flow in a vacuum. The analysis of such free surface flows is rather complex due to the fact that in addition to the fluid flow problem the position of the interface and enforcement of appropriate boundary conditions have to be dealt with. 

Volume lA hird Edition, which covers process planning, scheduling, and flowsheet design, fluid, flow, pumping of liquids, mechanical separations, mixing of liquids, ejector and vacuum systems, and pressure-relieving devices. 

Fredette, L. Tanguy, P.A. Hurez, P. Blouin, D. On the determination of heat transfer coefficient between PVC and steel in vacuum extrusion calibrators. Int. J. Num. Methods Heat Fluid Flow 1996, 6, 3-12. 

High vacuum is not and should not be regarded as a unit operation in itself. Rather, it should be viewed as a very low pressure range in which conventional unit operations such as heat transfer, fluid flow, distillation, and extraction are put to use in the light of physical and chemical equilibria, reaction rates, and transfer rates characteristic of this pressure range. 

Modem adiabatic calorimeters employ a technique whereby the enthalpy of vaporization is measured under conditions in which a measured amount of electrical energy is supplied to a heater immersed in the sample to compensate for the heat absorbed by the substance during the evaporation and hence the temperature is kept constant. The main differences among adiabatic calorimeters are that the vapour flows out of the calorimeter at atmospheric pressure (those of Mathews and Fehlandt [65]), into a vacuum, [67,69-71] into a gas stream [68], or into a closed recirculation system with continuous fluid flow [66]. 

FIGURE 53.13 Microfluidic device integrated into a standard MALDI-TOF target plate. The vacuum of the MALDI-MS vacuum chamber is used as the driving force for inducing fluid flows on the chip (self-activating chip). (Reprinted from Brivio, M., et al.. Anal. Chem., 74, 3972-3976, 2002. Copyright 2002. With permission from American Chemical Society.)... 

These insulation systems are desirable where it is necessary to gain entrance into the vacuum space in order to install, remove, or repair some instrumentation. This is important for missile mock-up tests, where it is necessary to monitor various parameters, enter the inner vessel, and possibly even take photographs to observe the fluid flow of liquid hydrogen or oxygen during test. With superinsulation, it is possible to enter the vacuum space to... 

Vascular endothelial cells under cyclic stretching are one of important factors to study [64]. As shown in Fig. 6C and 6D, upper microfluidic channel layer and bottom groove layer were separated by an elastic membrane that applies cyclic stretching strain to cells. A groove layer was attached under the elastic membrane and is connected to a vacuum pump that applies suction pressure to stretch the elastic membrane. Cells were cultured on top of the membrane and fluid flow is passed through the upper channel layer while vacuum pressure is applied to the stretched cells on the elastic membrane. The cells cultured on the membrane were cyclically stretched and relaxed. 

Syringe pumping and vacuum pumping remain predominant in microfluidic flows. Fluid flows driven by capillarity become more efficient on downscaling due to its favorable scaling behavior. 

Viscosity can also be measured with viscometers where the movement or the developed force is due to gravity, by the fluid s own weight. Such a system is developed when the fluid flows in special glass tubes (capillary tubes). In this case, the kinematic viscosity (qj or v) is measured, and the measurement unit is in square millimetres per second. This unit is also known as centistoke (cSt). However, when the fluid is forced to flow under negative pressure (vacuum), then the dynamic viscosity (Pa-s) is measured. 

A porous carbon fiber carbon composite with a density >0.2 gcm with a significant volume of mesopores (2 50 mn) and macropores (50-100 pm) which allow excellent fluid flow with minimal pressure drop has potential as catalyst support. Fortafll P200 PAN based carbon fiber was slurried in water with a phenolic resin, vacuum molded, dried at 50°C, cured for 3 h at 130°C and carbonized in a flow of N2 at 650°C. In this process, O2, CO2, H2O and CO were trapped inside the micropores during carbonization and gasified the surface of the PAN fibers, resulting in large surface areas (572 m g ) and mesopore volumes (1 cm g ), a possible candidate for a catalyst support [25 27). 

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