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

## 8.5. Calculating C_{v} for liquids

Introduction

The equation for the flow coefficient (C

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

(8.2)

where:

C

_{v}= Valve sizing coefficientF

_{P}= Piping geometry factorq = Flow rate, gpm

ΔP

_{a}= Allowable pressure drop across the valve for sizing, psiG

_{f}= Specific gravity at flowing temperatureThe 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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