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Code Manual for CONTAIN 2.0 - Federation of American Scientists

Code Manual for CONTAIN 2.0 - Federation of American Scientists

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4.4.3 User-Specified Flow Rates<br />

The user may want simply to specify the flow rate as a fimction <strong>of</strong> time. The mass or volumetric flow<br />

rate can be directly specified as a function <strong>of</strong> time through tables as described in Sections 4.3 and<br />

14.2.4.2. It should be noted that the energy equation <strong>for</strong> user-specified flow rates is taken to be the<br />

same as <strong>for</strong> pressure-driven flow at the same flow rate. This treatment neglects the work done, in<br />

some cases, by the agent required to sustain the flow. If important, such work should be calculated<br />

and added separately.<br />

The flow area need not be specified when the flow rates are specified. However, if the area is not<br />

specified, it is assumed to be infinitesimal, and consequently the velocity in the flow path will be<br />

calculated as extremely high. Choked flow is not considered in the case <strong>of</strong> user-specified flow rates.<br />

However, the specified flow rates are modified when necessary by the inventory factors, ~ij)in Table<br />

4-1.<br />

4.4.4 Critical Flow Model<br />

Critical or choked flow through gas flow paths occurs when the mass flow rate reaches aj?xed value<br />

independent <strong>of</strong> the pressure ratio across the flow path. The flow velocity is limited at the minimum<br />

area <strong>of</strong> the flow streamlines to the speed <strong>of</strong> sound. The critical flow rate <strong>of</strong> gas WC,jjis then given<br />

by<br />

‘.rJj =(eij-eji)Aijvijiupupuqul’2<br />

where eij equals 1 and O<strong>for</strong> ~ij >0 and Wij 0 and &ij<br />

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