Total Pressure Radial-Blade Centrifugal Tubeaxial Backward-inclined Airfoil Centrifugal Forward-curved Centrifugal Ducted Propeller Airflow Volume
Figure 2: Forward-Curved Centrifugal Fan Rotation Forward Curved Fan Curve Increasing Pressure Increasing Airflow Power Curve Increasing Power
Figure 3: Radial-Blade and Radial-Tip Centrifugal Fans Rotation Rotation Radial-Blade Radial-Tip Fan Curve Increasing Pressure Increasing Airflow Power Curve Increasing Power
Figure 4: Backward-Inclined Centrifugal Fans Rotation Rotation Rotation Backward-Inclined Flat-Blade Backward-Inclined Curved-Blade Backward-Inclined Airfoil-Blade Increasing Pressure Fan Curve Power Curve Increasing Airflow Increasing Power
Figure 5: Comparative Fan Designs at an Equal Power Consumption in. wg 20 kpa 5.0 Radial-Blade Centrifugal 16 4.0 Total Pressure 12 8 4 3.0 2.0 1.0 Tubeaxial Backward-inclined Airfoil Centrifugal Forward-curved Centrifugal Ducted Propeller 3 10 20 30 m /s 20,000 40,000 60,000 CFM Airflow Volume
Figure 7: Propeller Fan Propeller Fan Rotation Airflow Direction Front View Side View Fan Curve Increasing Pressure Power Curve Increasing Airflow Increasing Power
Figure 8: Tubeaxial Fan Tubeaxial Air Flow Front View Side View Fan Curve Increasing Pressure Power Curve Increasing Airflow Increasing Power
. Figure 9: Vaneaxial Fan Vaneaxial Air Flow Front View Side View Increasing Pressure Power Curve Increasing Airflow Fan Curve Increasing Power
Airflow final Airflow initial RPM RPM final initial pressure final pressure initial RPM RPM final initial 2 Power final Power initial RPM RPM final initial 3
Total pressure airflow Total Efficiency bhp 6362 Static pressure airflow Static Efficiency bhp6362
Static Pressure Increasing Figure 10: Fan Curve with Instability Zone Region of Instability In this region, the slopes of the fan curve and the system curve are near parallel. Instability results when the fan curve intersects the system curve at more than one point, causing the fan to hunt. System Curves Slope Lines Fan Curve Air Flow Increasing
Figure 12: Effect of Arc-of-Contact on V-Belt Horsepower Rating Correction Factor for horsepower rating of V-Belts Degrees of Contact Correction Factor 180 1.00 170 0.98 160 0.95 150 0.92 140 0.89 130 0.86 120 0.83 110 0.79 100 0.74 90 0.69 Arc of Contact
Fan Power Increasing Figure 13: Flow Control by Speed Regulation Static Pressure Increasing Pressure (Full Speed) A = Full Speed B = 75% Full Speed C = 50% Full Speed Pressure (75% FS) Power (Full Speed) A System Curve Design Working Point Power (75% FS) Pressure (50% FS) B Power (50% FS) C Air Flow Increasing
Figure 15: A Fan within a System Balance or Control Damper Air Inlet F i l t e r H e a t e r Fan Fan Outlet Diffuser Air Delivery to Ventilated Space Ducting, Bends, etc.
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Figure 16: System Effect for a Typical Fan and System Static Pressure (in. WG) 22 18 14 10 6 2 Fan Curve System Curve (with system effect) Actual Performance B 2,000 6,000 10,000 14,000 18,000 Flow Rate (CFM) System Curve (as calculated) A Expected Performance
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Figure 18: Use of Fan Curve to Determine Power Consumption Static Pressure (in. WG) 22 18 14 10 6 2 Fan Curve Power Curve 60 50 40 30 20 10 Fan Power (BHP) 2,000 6,000 10,000 14,000 18,000 Flow Rate (CFM)
Figure 19: Alternative Methods of Measuring Fan Pressure Ducted Inlet & Outlet Air Flow Ducted Inlet - Free Outlet Air Flow Static Pressure Total Pressure Free Inlet - Ducted Outlet Air Flow Static Pressure Total Pressure
Figure 20: Low Duct Pressure with Fans Operating in Series Two Fans in Series Fan System Resistance Airflow Fan System Resistance Pressure Peak Pressure Average Pressure Single Fan Fan Distance Along Duct System Resistance Airflow Peak Pressure Pressure Average Pressure Distance Along Duct
Figure 21: Instability Region with Identical Fans in Parallel Operation Static Pressure (in. WG) 22 18 14 10 6 2 Region of Instability Flow Rate (CFM) Pt 1 Single Fan Curve Combined Fan Curve 2,000 6,000 10,000 14,000 18,000
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FAN AUDIT DATA SHEET Audit Date: System Information System or Location: Annual Hours of Operation: hrs System Description: Fan Information Fan Manufacturer: Fan Age: yrs Fan Model: Rated Input power: hp or kw Rated Speed: RPM (circle one) Actual Flow: CFM Actual Pressure: inches WG (if available) (if available) Max. (rated) Flow: CFM Max. (rated) Pressure: inches WG Impeller Type: (Circle one) Forward-curved Radial Backward-Curved Other: (specify) Air-Foil Fan Drive and Controls Inlet Damper: % open control Auto Manual Fixed or Outlet Damper: % open Auto Manual Fixed adjustment: Inlet Guide Vanes: % open (circle) Auto Manual Fixed Variable Speed Drive: No Yes if yes, Type: (circle one) (circle one) ASD Eddy- Current Hydraulic coupling Wound Rotor % speed Motor-Fan Coupling: (circle one) Direct Drive Belt Drive pulley ratio Adjustable sheaves? Yes No Gear Reducer gear ratio Motor Information Motor Manufacturer: Motor Age: yrs Motor Model: Nameplate Data: hp RPM NEMA % Efficiency Volts FLA Load Factor and Energy Cost Average Cost of power $ / kwh Formula: Three-phase power (kw) = 1.732 x Amps x Volts x Power Factor/1000 Load Duty Cycle Operating Flow Point (% or CFM) 1 2 3 4 5 Annual Totals Average Annual Operating Cost ($) = Average power (kw) x Annual Operating hours x Average Cost of Power ($/kwh) Hours per year - Motor Amps Motor Volts Damper Setting Fan Speed (RPM) Power Factor* Input Power (kw) Average Cost ($) - - - - - - * Tip: Power factor (PF) varies with motor load; estimate the PF at the operating point from manufacturer's data sheets or use typical values
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