A composite wall of a refrigerator consists of three different materials; A, B, and C. Two of the used materials have known thermal conductivity, kA = 30 W/m. K and kc-45 W/m. K, and known thickness, LA=0.20 m and Lc = 0.15 m. The third material, B, which is sandwiched between materials A and C, is of known thickness, LB = 0.15 m, but unknown thermal conductivity kB. Under steady-state operating conditions, measurements reveal an outer surface temperature of Ts,o= 20°C, an inner surface temperature of Ts,i = 600°C, and a refrigerator air temperature of Too = 800°C. The inside convection coefficient h is known to be 25 W/m².K. (a) First, draw the thermal circuit for this wall. (b) What is the value of thermal conductivity for material B? T₁1 Air To h KA LA K₁ kc Lg Lc -T₂

A composite wall of a refrigerator consists of three different materials; A, B, and C. Two of the used materials have known thermal conductivity, kA = 30 W/m. K and kc-45 W/m. K, and known thickness, LA=0.20 m and Lc = 0.15 m. The third material, B, which is sandwiched between materials A and C, is of known thickness, LB = 0.15 m, but unknown thermal conductivity kB. Under steady-state operating conditions, measurements reveal an outer surface temperature of Ts,o= 20°C, an inner surface temperature of Ts,i = 600°C, and a refrigerator air temperature of Too = 800°C. The inside convection coefficient h is known to be 25 W/m².K. (a) First, draw the thermal circuit for this wall. (b) What is the value of thermal conductivity for material B? T₁1 Air To h KA LA K₁ kc Lg Lc -T₂

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Concept explainers

Conduction and Convection

When energy travels from one object to another it is said to have undergone heat transfer. Heat transfer is nothing but the transfer of thermal energy or internal energy from one thing to another, like e.g., when a vessel with water, kept on top of a burner, heats up because of the flame underneath it.

Question

A composite wall of a refrigerator consists of three different materials; A, B, and C. Two of the used
materials have known thermal conductivity, KA = 30 W/m. K and kc-45 W/m. K, and known thickness,
LA=0.20 m and Lc = 0.15 m. The third material, B, which is sandwiched between materials A and C, is of
known thickness, LB = 0.15 m, but unknown thermal conductivity kB. Under steady-state operating
conditions, measurements reveal an outer surface temperature of Ts,o= 20°C, an inner surface temperature of
Ts,i = 600°C, and a refrigerator air temperature of Too = 800°C. The inside convection coefficient h is known
to be 25 W/m².K. (a) First, draw the thermal circuit for this wall. (b) What is the value of thermal
conductivity for material B?
Tsi
Air
To, h
KA
K₂ kc
Lg Lc
Figure 2: Composite wall configuration described in problem 3.

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