Convection (6, 4); Conduction + Convection (6, 5) - HP 48gII Advanced User's Reference Manual

Convection (6, 4)

Equations:
q = h A
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
Equations:
A T
----------------------------------------------------------- -
q =
1 L1 L2 L3 1
----- - + ------ - + ------ - + ------ - + ----- -
h1 k1 k2 k3 h3
q
--------------- -
U =
A T
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.
5-30 Equation Reference
T q = h A Th Tc –
499
.
A Th Tc –
----------------------------------------------------------- -
q =
1 L1 L2
----- - + ------ - + ------ - +
h1 k1 k2
q
U = -------------------------------- -
A Th Tc –
L3 1
------ - + ----- -
k3 h3