Frequently Used Notations

From Chemepedia

This is an ongoing list of the frequently used notations and their units. Please feel free to add variables that you find yourself always looking for.

Symbol Description English Units SI Units
Cp Specific Heat with constant pressure Btu/(lbm°F) kJ/kg·K
Cv Specific Heat with constant volume Btu/(lbm°F) kJ/kg·K
DAB Molecular diffusivity of substance A through substance B ft2/s m2/s
E** Activation Energy cal/g·mol J/kg·mol
F Frictional Loss ft·lbf/lbm J/kg
F Force lbf N
g Gravity ft/s2 m/s2
h Head ft·lbf/lbm J/kg
h Heat Transfer Coefficient btu/h·ft2·°F W/m2·K
H Enthalpy btu/lbm J/kg
jA Mass Flux of A kg·s/m2
JA Molar Flux of A kg·mol/s·m2
k Thermal Conductivity btu/hr·ft·°F W·m/K
L Length ft m
m Mass Flow Rate kg/s lbm/s
MWA Molecular Weight of A lbm/lb·mol kg/kg·mol
NPSH Net Positive Suction Head ft m
P Pressure lbf/ft2, atm, psia N/m2, Pa
pv Vapor Pressure lbf/ft2, atm, psia N/m2, Pa
q, Q, V̇ Volumetric Flow Rate ft3/s m3/s
r radius ft m
Sp Particle Surface Area ft2 m2
ν Velocity ft/s m/s
ρ Density lbm/ft3 kg/m3
τ Shear Stress lbf/ft2 N/m2
λ Latent Heat btu/lbm J/kg
μ Viscosity P(Poise) Pa*s or kg/m*s
U Internal Energy btu/lbm J/kg
Example Example Example Example


  • Geankoplis, Christie John. Transport Processes and Separation Process Principles. Pearson Education Inc, 2015. Book.
  • Engineering ToolBox, (2003).

Catherine Lintner (talk)