SAChE Source Models (ELA965) Practice Test 2026 - Free SAChE Source Models Questions and Study Guide

P represents the static pressure at a specific location in the flow—the throat of the opening. In gas-flow equations, pressure denotes the force per area exerted by the gas, and it can vary along the path. The throat is a defined point where the cross-sectional area is smallest, so the static pressure at that point is the quantity described by P. It isn’t the density (which would be ρ) or the temperature (which would be T), and it isn’t the overall pressure of the entire process unit. The throat pressure is the relevant, defined value used for analyzing flow through the restriction.