//Example 8-4 Determining the Diameter of an Air Duct
L = 150 //length of pipe[m]
Vdot = 0.35 //air flow rate[m^3 / s]
h_L = 20 //maximum head loss in pipe [m]
//Properties of air at 35C
rho = 1.145 //density [kg / m^3]
mu = 1.895 * 10**-5 //dynamic viscosity [kg / m.s]
nu = 1.655 * 10**-5 //kinematic viscosity [m^2 / s] 
g = 9.81 //gravitational acceleration [m / s^2]