"ME 462 LESSON 22 example (b)"


"Given info and constants"
g = 9.81 "m/s^2"
r_i = 0.005 "m"
r_o = r_i + t "m"
D_o = 2*r_o "m"
k_insul = 0.2
"h = 10"

T_1 = 450 "K"
T_amb = 300 "K"

"Fluid properties"
T_film = (T_2+T_amb)/2
{T_film = T_amb}
k_fl = conductivity(air,T=T_film)
mu = viscosity(air,T=T_film)
rho = density(air,T=T_film,P=101.325)
nu = mu/rho
beta = volexpcoef(Air,T=T_film)
Pr = Prandtl(Air,T=T_film)

"Conv. coeff."
Ra = ((g*beta*(T_2-T_amb)*D_o^3)/nu^2)*Pr
Nusselt = 0.68 + (0.67*Ra^(1/4))/(1+(0.492/Pr)^(9/16))^(4/9)
Nusselt = (h*D_o)/k_fl

"Heat transfer - resistance analogy"

Q_dot = (T_2-T_amb)/(1/(h*2*pi*r_o))
Q_dot = (T_1-T_2)/( ln(r_o/r_i)/(2*pi*k_insul))