Reference Guide

5-30 Equation Reference
Convection (6, 4)
Equations:
q h A T∆⋅ ⋅= q h A Th Tc–( )⋅ ⋅=
Example:
Given: Tc= 300_K, A=200_m^2, h=0.005_W/(m^2 ∗ K), q=10_W.
Solution: ∆T=10_°C, Th=36.8500_°C.
Conduction + Convection (6, 5)
If you have fewer than three layers, give the extra layers a zero thickness and any nonzero conductivity. The two
temperatures are fluid temperatures – if instead you know a surface temperature, set the corresponding convective
coefficient to 10
499
.
Equations:
q
A T
∆
⋅
1
h1
------
L1
k1
-------
L2
k2
-------
L3
k3
-------
1
h3
------
+ + + +
------------------------------------------------------------
=
q
A Th Tc–
(
)
⋅
1
h1
------
L1
k1
-------
L2
k2
-------
L3
k3
-------
1
h3
------
+ + + +
------------------------------------------------------------
=
U
q
A T∆⋅
----------------
=
U
q
A Th Tc–( )⋅
---------------------------------
=
Example:
Given: ∆T=35_°C, Th=55_°C, A=10_m^2, h1=0.05_W/(m^2 ∗ K) , h3=0.05_W/(m^2 ∗ K), L1=3_cm,
L2=5_cm, L3=3_cm, k1=0.1_W/ (m ∗ K), k2=.5_W/ (m ∗ K), k3=0.1_W/ (m ∗ K).
Solution: Tc=20_°C, U=0.0246_W/ (m^2 ∗ K), q=8.5995_W.