Abstract
Equations are derived to model installed exhaust ventilation systems using measured diameters, flows, and pressures. The system of equations does not require knowledge of system components or their loss coefficients except for those components that will be replaced. The approach also allows detection of physical changes in existing systems. Measurement errors limit the accuracy of predictions. The nonquadratic relationship between flow and friction loss limits the accuracy of predictions when there are extreme changes in duct velocities. The modeling procedure is demonstrated for an example problem in which “observed” values are created for “initial” and “final” conditions from velocity pressure loss coefficients.