Chapter 7
External Forced Convection
785
A cylindrical oven is to be insulated to reduce heat losses. The optimum thickness of insulation and
the amount of money saved per year are to be determined.
Assumptions
1
Steady operating conditions exist.
2
Heat transfer through the insulation is one
dimensional.
3
Thermal conductivities are constant.
4
The thermal contact resistance at the interface is
negligible.
5
The surface temperature of the furnace and the heat transfer coefficient remain constant.
6
The surfaces of the cylindrical oven can be treated as plain surfaces since its diameter is greater than 1 m.
Properties
The thermal conductivity of insulation is given to be
k
= 0.038 W/m
⋅
°C.
Analysis
We treat the surfaces of this cylindrical furnace as plain surfaces since its diameter is
greater than 1 m, and disregard the curvature effects. The exposed surface area of the furnace is
2
2
2
side
base
m
69
.
70
m)
m)(6
5
.
1
(
2
m)
5
.
1
(
2
2
2
2
=
+
=
+
=
+
=
π
ππ
rL
r
A
A
A
o
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This note was uploaded on 01/22/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.
 Fall '10
 Dr.DanielArenas
 Thermodynamics, Convection, Force, Mass, Heat

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