9-18 "!PROBLEM 9-18"
"GIVEN"
Q_dot=0.18 "[W]"
"T_infinity=35 [C], parameter to be varied"
L=0.0045 "[m]"
D=0.004 "[m]"
epsilon=0.1
T_surr=T_infinity-10 "[C]"
"PROPERTIES"
Fluid$='air'
k=Conductivity(Fluid$, T=T_film)
Pr=Prandtl(Fluid$, T=T_film)
rho=Density(Fluid$, T=T_film, P=101.3)
mu=Viscosity(Fluid$, T=T_film)
nu=mu/rho
beta=1/(T_film+273)
T_film=1/2*(T_s+T_infinity)
sigma=5.67E-8 "[W/m^2-K^4], Stefan-Boltzmann constant"
g=9.807 "[m/s^2], gravitational acceleration"
"ANALYSIS"
delta=D
Ra=(g*beta*(T_s-T_infinity)*delta^3)/nu^2*Pr
Nusselt=(0.6+(0.387*Ra^(1/6))/(1+(0.559/Pr)^(9/16))^(8/27))^2
h=k/delta*Nusselt
A=pi*D*L+pi*D^2/4
Q_dot=h*A*(T_s-T_infinity)+epsilon*A*sigma*((T_s+273)^4-(T_surr+273)^4)
T∞ [C]
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
Ts [C]
159.9
161.8
163.7
165.6
167.5
169.4
171.3
173.2
175.1
177
178.9
180.7
182.6
184.5
186.4
188.2
190
185
180
T s [C]
175
170
165
160
155
10
15
20
T
25
∞
[C]
30
35
40