Page 67 - Mechanical Engineers' Handbook (Volume 2)

56 Input and Output Characteristics

Figure 16 Flow versus pressure drop characteristics for the valve orifices.

negative otherwise. These data can be picked off and plotted as the Q–P characteristic of
the valve, as shown in Fig. 17.
Figure 17 illustrates that an operating point on an input–output characteristic forces
compatibility and continuity, but as long as those are preserved, a second energy exchange
as at the P Q port of this valve can still be accommodated. This approach can be
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extremely useful in systems such as air-conditioning ducting where the fan characteristic is
known only graphically, and then its output impedance at some point along the ducting must
be determined. Exactly the same procedure is used.

Figure 17 The output characteristic of the valve.