Numerous instances of the word "efficiency" in fan system evaluation contribute to unclear application of efficiencies in simulations and for power estimation. Ventilation simulations using "fixed flows" and software default fan efficiency values to specify fan duties may result in omission of fan system component losses and under-estimation of required fan pressure and absorbed power. Numerous factors contribute to the overall efficiency of a given fan system, considering aerodynamic and motor/drive components along with factors such as the inlet and diffuser components, silencers, dampers, duct transitions, and/or unfavorable velocity distribution (incompletely developed flow profiles) at the fan inlet or outlet. In this study, the authors review measured operating points of 84 unique main and booster fan installations to determine typical fan system efficiencies.
