
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN: 9781305387102
Author: Kreith, Frank; Manglik, Raj M.
Publisher: Cengage Learning
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Transcribed Image Text:Passage of an electric current through a long conducting rod of radius r; and thermal conductivity kr,
results in uniform volumetric heating at a rate of q. The conduction rod is wrapped in an electrically
non-conducting cladding material of radius ro and thermal conductivity ke and convection cooling is
provided by an adjoining fluid.
For steady-state conditions,
a) Determine an expression for the heat transfer per unit
length q', passing through the cladding in terms of
à, and ri.
b) Determine an expression for T, the temperature of the
cladding at ri and also for To at ro.
c)
Calculate these cladding temperatures in °C when ri
and ro are 3 mm and 5 mm, q, = 200 kW/m³,
kc = 0.15 W/m/K, T = 20°C and h= 20 W/m²/K.
Conducting
rod, å, k,
Cladding, k
d) Calculate the critical radius. To decrease the internal cladding temperature would it be
necessary to increase or decrease ro; or should it remain unchanged? Explain.
To, h
201
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