Ql: A composite wall is made of 10 mm and 16 mm layers of materials of thermal conductivity 10 and 20 W/m K. The contact resistance between surfaces is 5 x 10 *m °C/W. The hot side is exposed to fluid at 400°C with h- 75 W/m2K and the cold side is exposed to fluids at 60°C with h- 400 W/m. K. Determine the heat flow, temperature drop of the first layer and overall heat transfer coefficient. Comment on the contribution of contact resistance.

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
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QI: A composite wall is made of 10 mm and 16 mm layers of materials of themal
conductivity 10 and 20 W/m. K. The contact resistance between surfaces is 5 x 10
*m °C/W. The hot side is exposed to fluid at 400°C with h = 75 W/m2K and the
cold side is exposed to fluids at 60°C with h= 400 W/m. K. Determine the heat
flow, temperature drop of the first layer and overall heat transfer coefficient.
Comment on the contribution of contact resistance.
400°C
T,
AT,
T2
AT,
h, = 75 Wim K
h = 400 Wim K
ATs
400°c
T, AT
60°C
60°C
10 mm 16mm
Q2: Calculate the critical radius of insulation for asbestos [k = 0.162 W/m K]
surrounding a pipe and exposed to room air at 25 °C with ho = 2.8 W/m K.
Calculate the heat loss from a 200 °C, 50 mm diameter pipe when covered with
the critical radius of insulation and without insulation.
Transcribed Image Text:QI: A composite wall is made of 10 mm and 16 mm layers of materials of themal conductivity 10 and 20 W/m. K. The contact resistance between surfaces is 5 x 10 *m °C/W. The hot side is exposed to fluid at 400°C with h = 75 W/m2K and the cold side is exposed to fluids at 60°C with h= 400 W/m. K. Determine the heat flow, temperature drop of the first layer and overall heat transfer coefficient. Comment on the contribution of contact resistance. 400°C T, AT, T2 AT, h, = 75 Wim K h = 400 Wim K ATs 400°c T, AT 60°C 60°C 10 mm 16mm Q2: Calculate the critical radius of insulation for asbestos [k = 0.162 W/m K] surrounding a pipe and exposed to room air at 25 °C with ho = 2.8 W/m K. Calculate the heat loss from a 200 °C, 50 mm diameter pipe when covered with the critical radius of insulation and without insulation.
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