Flow-through-screen pressure drop

In 1-g or imder significant vehicle acceleration, the dominant pressure drop in Equation (3.2) is hydrostatics. In the low Bond number conditions of space however, the dominant pressure loss will be the FTS pressure drop, since the hydrostatic pressure is generally negligible. For a given fluid, each screen has a specific FTS pressure drop associated with its specific geometry and manufacturing. Therefore the second primary influential factor governing LAD screen selection is the FTS pressure drop. 

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Table 3.4 Fitting Parameters for Flow-Through-Screen Pressure Drop Model...

FIGURE 9.15 Normalized Flow-through-Screen Pressure Drop at Three Different Nominal Temperatures. 

FIGURE 12.5 Normalized Flow-through-Screen Pressure Drop along the Channel for Four Different Dutch Twill Screens for (a) flee = 10 (b) fiee = 10 (c) fiee= 10 , and (d) fiee=10. The solution evaluates C am and Cturb fot a 325 X 2300 Dutch Twill Screen for Liquid Oxygen. 

Table 12.1 Flow-Through-Screen Pressure Drop Coefficients for Different Screens...

FIGURE 12.6 Maximum Analytical Model Flow-through-Screen Pressure Drop Divided by the One Dimensional Model Flow-through-Screen Pressure Drop as a Function of Outlet Reynolds Number. 

FIGURE 13.2 Model Predicted Liquid Hydrogen Flow-through-Screen Pressure Drop Over the Anticipated Operating Range of a Cryogenic Fuel Depot for (a) Five Finest Dutch Twill, (b) Coarse Dutch Twill and Plain Dutch, and (c) Twilled and Plain Square Mesh Screens. All curves evaluate a,p at liquid hydrogen temperatures. 

Darr, S.R., Hartwig, J.W., 2015. Validation of the flow through screen pressure drop model for screen channel liquid acquisition devices. 26th Space Cryogenics Workshop, Phoenix, AZ, June 24-26. 

The purpose of the flow-through-screen (FTS) tests was to measure the FTS pressure loss associated with liquid flow through a LAD screen in LH2. While the FTS pressure drop is second order in 1-g, it becomes the dominate pressure loss in flight, in LEO where hydrostatics are minimal. Therefore, experiments are required to determine the magnitude of this contribution as well as validate the FTS model from Chapter 3. 

FIGURE 9.31 One Dimensional Pressure Drop Model Simulations versus Data for Exposed Screen Height at Channel Breakdown Assuming 100% Available Flow-through-Screen Flow Area. 

Provided that the catalyst is active enough, there will be sufficient conversion of the pollutant gases through the pellet bed and the screen bed. The Sherwood number of CO is almost equal to the Nusselt number, and 2.6% of the inlet CO will not be converted in the monolith. The diffusion coefficient of benzene is somewhat smaller, and 10% of the inlet benzene is not converted in the monolith, no matter how active is the catalyst. This mass transfer limitation can be easily avoided by forcing the streams to change flow direction at the cost of some increased pressure drop. These calculations are comparable with the data in Fig. 22, taken from Carlson 112). 

Through circulation dryers employ perforated or open screen bottom tray construction and have baffles that force the air through the bed. Superficial velocities of 150 ft/min are usual, with pressure drops of 1 in. or so of water. If it is not naturally granular, the material may be preformed by extrusion, pelleting, or briquetting so that it can be dried in this way. Drying rates are greater than in cross flow. Rates of 0.2-2 lb/(hr)(sqft tray area) and thermal efficiencies of 50% are realized. Table 9.7(d) has performance data. 

It is important to be able to predict at just what level of t in the inlet cone the slurry begins to consolidate into an ice bed with brine flowing through it. If the zone at which consolidation begins is well below the level of the screens, packed ice may back up and fill the inlet pipe. The pressure drop through the ice packed in the inlet cone is important for specification of the pumping head required. 

The pressure drop for flow through the gas passages resulting from momentum transfer from the flowing gas to the stationary screen-enclosed catalyst slabs follows from the general Fanning equation... 

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