Application Engineering Basics

Terminology

Throughout our site, you will find terminology used for air moving selection and product sizing.
Below are a few of the key terms:

Flow

• Volume Rate/Time
• Rotron charts are in SCFM, m3/min, or L/S
• SCFM = Standard Cubic Feet Per Minute (American) where temperature = 68°F, air density = 0.075 lb/cubic foot, and altitude = 0 feet above sea level
• M/min = Cubic Meters Per Minute (Metric)
• L/sec = Liters Per Second (Metric)
• 1 m/min = 35.3 SCFM
• 1 L/sec = 2.119 SCFM
• 1 m/min = 35.3 SCFM
• 1 L/sec = 2.119 SCFM
• See Standard Engineering Conversions for other flows

• Force/Area
• Rotron charts are in IWG, PSIG, MM of Water, IHG, or mbar
• IWG = Inches of Water Gauge (American)
• PSIG = Pounds Per Square Inch Gauge (American)
• MM of Water = Millimeter of Water Gauge (Metric)
• IHG = Inches of Mercury Gauge (American)
• mbar = Millibar Gauge (Metric)
• PSIA = Pounds Per Square Inch Absolute (American)
• 27.7 IWG = 1 PSIG
• 703.58 MM of Water = 1 PSIG
• 2.036 IHG = 1 PSIG
• 0.069 Bars = 69 mbar = 1 PSIG
• Standard Atmosphere = 0 PSIG = 14.7 PSIA
• See Basic Fan Laws Chart for correcting pressure due to speed or density changes

• Weight/Volume
• Standard Air = 0.075 lb/cubic foot
• See Density Chart for other gases
• See Density Correction Chart due to altitude and temperature changes

• Density Ratio Relative to Air
• Standard Air SG = 1.0
• Methane SG = 0.55
• See Specific Gravity Chart for other gases

• Distance/Time or Flow/Area
• FPM = Feet Per Minute (American)
• MPH = Miles Per Hour (American)
• M/min = Meters Per Minute (Metric)
• Km/h = Kilometers Per Hour (Metric)
• 88 FPM = 1 MPH
• 26.82 M/min = 1 MPH
• 1.609 Km/h = 1 MPH
• See Standard Engineering Conversion Chart for other velocities
• See Orifice Flow Calculation Chart for air flow equations

• Friction causes air to slow down and lost energy is measured in pressure drop terms
• Typical pressure drop areas include piping, elbows, accessories and system
• Each fixed system has a fixed system impedance caused by a single or multiple pressure drop points
• Changing the system impedance will cause blowers work point to change
• Changing the blower with fixed system impedance will change the working back pressure
• See Friction Loss Per Foot of Tubing and Fitting Charts