Flow calculation with known cv and pressure drop

I am using simulink to calculate flow from known cv and pressure drop.

Cv=1.9

Pr.drop= 1.74 psi

Flow obtained from Simulink results to be 11.65 lpm

Working tempwerature to be 60 deg F

But flow from calculation using below formulae results with 10.46 lpm

Kindly suggest for the reson for variation.