# Reynolds Number for Gas

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

## Reynolds Number for Gas Formula

 $$\large{ Re = 20,100 \; \frac{ SG \; Q }{ d \; \eta } }$$

### Where:

 Units English Metric $$\large{ Re }$$ = Reynolds number $$\large{ dimensionless }$$ $$\large{ Q }$$ = flow rate of gas $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$\large{ SG }$$ = gas specific gravity relative to water (water = 1) $$\large{ dimensionless }$$ $$\large{ d }$$ = inside diameter of pipe $$\large{ in}$$ $$\large{ mm }$$ $$\large{ \eta }$$  (Greek symbol eta)  = viscosity of gas $$\large{\frac{lbf - sec}{ft^2}}$$ $$\large{Pa-s}$$