_{v}) in non-laminar liquid flow is:

Introduction

The equation for the flow coefficient (C_{v}) in non-laminar liquid flow is:

${C}_{\text{v}}=\frac{q}{{F}_{\text{P}}}\sqrt{\frac{{G}_{\text{f}}}{\Delta {P}_{\text{a}}}}$

(8.2)

where:

C_{v} = Valve sizing coefficient

F_{P} = Piping geometry factor

q = Flow rate, gpm

ΔP_{a} = Allowable pressure drop across the valve for sizing, psi

G_{f} = Specific gravity at flowing temperature

The following steps should be used to compute the correct C_{v}, body size and trim number (Figures 8.3–8.5):

Step 1: Calculate actual pressure drop

The allowable pressure drop, ΔP_{a}, across the valve for calculating C_{v}, is the smaller of the actual ΔP from Eqn 3.2 and choked ΔP_{ch} from Eqn 3.3.

$\Delta P={P}_{1}-{P}_{2}$

(8.3)

Step 2: Check for choked flow, ...

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