Fan Curves Manufacturer provides fan curve Predicts the

Fan Curves • Manufacturer provides fan curve • Predicts the pressure-flow rate performance of each fan • Choose fan according to volumetric flow rate for your system pressure drop • Choose fan with peak efficiency at or near your operating point • Sometimes manufacturers use tables instead (Greenheck Handout) BAE 2023 Dr. C. L. Jones Biosystems and Ag. Engineering 2

Fan Curves • Fans follow the affinity laws (ASHRAE) BAE 2023 Dr. C. L. Jones Biosystems and Ag. Engineering 3

Fan Law Example • Fan speed N changes from 600 to 650 rpm for a fan of a given size BAE 2023 Dr. C. L. Jones Biosystems and Ag. Engineering 4

Fan Curves • If we know static pressure and outlet area, we can find total pressure: • Total pressure includes static and velocity pressure • If we know power, static efficiency, or total efficiency, the others can be calculated: BAE 2023 Dr. C. L. Jones Biosystems and Ag. Engineering 5

Sound Power Levels • Energy transfer • In d. B: Sound • W 0 = 1 x 10 -12 Watts • W = power (W) • For additional units, see eqtn. 5. 6 (H/P) • Sones: One sone represents the loudness of a 1 k. Hz tone at 40 d. B SPL. BAE 2023 Dr. C. L. Jones Biosystems and Ag. Engineering 6

More Fans… • Fans in parallel: moves curve to the right… pressure stays the same, flow rate is the sum • Fans in series: moves curve up… flow rate stays the same, pressure is the sum BAE 2023 Dr. C. L. Jones Biosystems and Ag. Engineering 7