Convection (6, 4)

Equations:

q = h ⋅ A ⋅ ΔT

q = h ⋅ A ⋅ (Th – Tc)

Example:

Given: Tc= 300_K, A=200_m^2, h=0.005_W/(m^2K), 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 10499.

Equations:

q = ------------------------------------------------------------1

 

A ⋅ ΔT

 

 

 

 

q = ------------------------------------------------------------1

A ⋅ (Th – Tc)

 

 

L1

+

L2

+

L3

+

1

 

L1

+

L2

+

L3

+

1

-----

------k1

------k2

------k3

h3-----

 

-----

------k1

------k2

------k3

h3-----

h1

 

 

 

 

 

h1

 

 

 

 

 

 

 

 

 

q

 

 

 

q

 

 

 

 

 

 

 

 

 

 

U = A--------------- ΔT

 

U =

A-------------------------------- (Th – Tc)

 

 

 

 

 

Example:

Given: T =35_°C, Th=55_°C, A=10_m^2, h1=0.05_W/(m^2K), h3=0.05_W/(m^2K), L1=3_cm, L2=5_cm, L3=3_cm, k1=0.1_W/ (mK), k2=.5_W/ (mK), k3=0.1_W/ (mK).

Solution: Tc=20_°C, U=0.0246_W/ (m^2K), q=8.5995_W.

530 Equation Reference

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HP 50g Graphing, 48gII Graphing manual Conduction + Convection 6