Air volumetric and mass flowrateDefinition, Calculation and Conversions 

Pneumatic
Transport
Types of pneumatic transport Conveying phases Dilute Phase transport Dense Phase transport Air mover Roots Blower After Cooler Airlock Rotary Valve Product inlet / Injector Piping Pickup
velocity
Conveying speed / velocity Air volumetric and mass flowrate Pipe Equivalent Length Solids velocity in pipe Bends Solids Breakage Pressure drop Pipe Diameter or Bore
Design methods
Pipe Blockage
Powder Buildup
Selecting dilute or dense
phase
Horizontal Conveying
Vertical Conveying

1. DefinitionThe air flow is a fundamental data in pneumatic conveying systems. From the air flow, the air speed, solids loading ratio, pressure drop... can be calculated. It must however be noted that the air flow is usually given in normal conditions (Nm^{3}/h) not necessary representative of the conditions in the conveying line as the air is compressible. The objective of this page is to show how to calculate the air volumetric flowrate at different conditions and calculate as well the mass flowrate. 2. CalculationFrom the volumetric air flowrate given in conditions 1 (often the normal conditions, 101325 Pa and 20°c), the volumetric flow can be calculated in conditions 2. Conditions 2 should be either the beginning of the line or the end of the line. The pressure in conveying line is not very high, few bar abs at maximum, thus the perfect gas law applies well. Throughout the line, the number of moles of air / h is conserved, so the following equality can be written : Equation 1 : calculation of the air volumetric
flowrate at different conditions With :  Q_{1} = air volumetric flow rate in (known) conditions (m3/h) Q_{2} = air volumetric flow rate to be determined in conditions 2 (m3/h)  P1 = pressure in conditions 1 (Pa)  P2 = pressure in conditions 2 (Pa)  T1 = temperature in conditions 1 (K)  T2 = temperature in conditions 1 (K) To calculate the air mass flowrate, it is necessary to calculate the air volumetric mass at the conditions studied. It can also be defined thanks to the perfect gas law. Equation 2 : calculation
of the volumetric mass of air in conditions P and T
With : ρ_{air} = volumetric mass of the air at the conditions considered (kg/m^{3})  P = pressure at the conditions considered (Pa)  T = temperature at the conditions considered (K)  M_{air} = the molecular weight of air 0.029 kg/mol The volumetric mass can thus be multiplied by the volumetric flowrate to get the air mass flowrate in the pneumatic conveying pipe : Equation 3 : calculation
of the air mass flowrate
With :  m_{air} = air mass flowrate (kg/h)  Q_{air} = air volumetric flowrate at the conditions for which the volumetric mass has been calculated m^{3}/h ρair = volumetric mass of the air at the conditions considered (kg/m^{3}) 3. UsageThe following data can be calculated from the air volumetric flowrate and air mass flowrate  Air conveying velocity at any point of the line  Air solids ratio  Pressure drop in pipes Examples of calculation and conversions can be see on the page dedicated to the shortcut design method for calculation of dilute phase pneumatic conveying lines. 
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