# Calculation Methods - Venturi tube

The calculation method used is based on the correlations and charts found in Pipe Flow - A Practical & Comprehensive Guide - AIChE [24], p 158. The terms used in the equations below are set out illustrated in Figure 1. Figure 1: Venturi Tube. The loss coefficient for a venturi tube is determined from the following equation: KT = fi (1 - β4) / 8 sin (α1/2) + fT (l T/d T) + 8.3 [tan αD/2]1.75 (1 - β2)2 + fD (1 - β4) / 8 sin (α1/2). where: β is the diameter ratio. fi is the friction factor of the venturi inlet cone. fT is the friction factor of the throat. fD is the friction factor of the diffuser section of the venturi. α1 is the included angle of the venturi inlet cone (typically 21o). αD is the included angle of the venturi diffuser/outlet cone (the recommended included angle of the outlet cone is 7-8o; however, it may be as large as 15o). l T is the throat length. d T is the throat diameter.