Single phase line pressure drop calculation

For single phase liquid line with flow Q (gpm), its line pressure drop can be calculated by following equation  

For vapor line, with high pressure drop (Pl/P2 ), line pressure drop should be corrected using the acceleration factor (AC), see Hq. (4a). For liquid line, AC equals zero, no correction is required. 

DP is uncorrected vapor line pressure drop, in psi DPx is corrected vapor line pressure drop, in psi AC is acceleration factor, dimensionless G is mass flux, in lb/sec- 12 v is line velocity, in fl/sec A is line inside cross sectional area, in fl2 w is vapor weight flow, in Ib/sec PI is line inlet pressure, in p a F2 is line outlet pressure, in psia Pavg is average line pressure, see Eq. (4d), in psia. 

Friction factor (f) is a function of Reynolds number. It can be calculated by following equations Re=10000D v p/(6,72p) (5) 

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Per Eq. (15b) and Eq. (15c), the two phase mixture s density and viscosity are volume averages. Once they are known, we can calculate line pressure drop using the method outlined for single phase flow in section III. 1.2. 

Because flashing steam-condensate lines represent two-phase flow, with the quantity of liquid phase depending on die system conditions, these can be designed following the previously described two-phase flow methods. An alternate by Ruskin [28] uses the concept but assumes a single homogeneous phase of fine liquid droplets dispersed in the flashed vapor. Pressure drop was calculated by the Darcy equation ... 

The design of such systems is conplicated by several factors. The devices are designed to operate under unsteady conditions. Therefore, a dynamic simulation is required. Also, the flow through the relief system may be single-phase or two-phase flow. For two-phase flow, not only are the calculations more difficult, but also more factors affect the pressure drop, such as whether the line is horizontal or vertical. 

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