A leading manufacturer of household appliances is proposing a self-cleaning oven design that involves use of a composite window separating the oven cavity from the room air (Figure 2a). The composite is to consist of two high-temperature plastics (A and B) of thicknesses LA = 2LB and thermal conductivities ka = 0.15 W/m·K and kB = 0.08 W/m•K. During the self-cleaning process, the oven wall and air temperatures, Tw and Ta, are 400°C, while the room air temperature T, is 25°C. The inside convection and radiation heat transfer coefficients hị and hr, as well as the outside convection coefficient ho, are each approximately 25 W/m².K. What is the minimum window thickness, L = LA + LB, needed to ensure a temperature that is 50°C or less at the outer surface of the window? This temperature must not be exceeded for safety reasons.

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
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Composite
window,
LA = 2LB
Lope
LA
Oven
cavity
Ist
T. 250 °C
T = 400 °C
h, = 25 W/m2-K
Air
B, kg = 0.08 W/m-K
A, kA = 0.15 W/m-K
%3D
11
T = 400 °C
h = 25 W/m2-K
%3D
T = 25 °C
%3D
Air
%3D
h, = 25 W/m2-K
%3D
Figure 2a
Transcribed Image Text:Composite window, LA = 2LB Lope LA Oven cavity Ist T. 250 °C T = 400 °C h, = 25 W/m2-K Air B, kg = 0.08 W/m-K A, kA = 0.15 W/m-K %3D 11 T = 400 °C h = 25 W/m2-K %3D T = 25 °C %3D Air %3D h, = 25 W/m2-K %3D Figure 2a
Q2 a) A leading manufacturer of household appliances is proposing a self-cleaning oven
design that involves use of a composite window separating the oven cavity from the
room air (Figure 2a). The composite is to consist of two high-temperature plastics
(A and B) of thicknesses LA = 2LB and thermal conductivities ka = 0.15 W/m·K and
kB = 0.08 W/m•K. During the self-cleaning process, the oven wall and air
temperatures, Tw and Ta, are 400°C, while the room air temperature To is 25°C. The
inside convection and radiation heat transfer coefficients h; and h,, as well as the
outside convection coefficient ho, are each approximately 25 W/m².K. What is the
minimum window thickness, L = LA + LB, needed to ensure a temperature that is
50°C or less at the outer surface of the window? This temperature must not be
exceeded for safety reasons.
Transcribed Image Text:Q2 a) A leading manufacturer of household appliances is proposing a self-cleaning oven design that involves use of a composite window separating the oven cavity from the room air (Figure 2a). The composite is to consist of two high-temperature plastics (A and B) of thicknesses LA = 2LB and thermal conductivities ka = 0.15 W/m·K and kB = 0.08 W/m•K. During the self-cleaning process, the oven wall and air temperatures, Tw and Ta, are 400°C, while the room air temperature To is 25°C. The inside convection and radiation heat transfer coefficients h; and h,, as well as the outside convection coefficient ho, are each approximately 25 W/m².K. What is the minimum window thickness, L = LA + LB, needed to ensure a temperature that is 50°C or less at the outer surface of the window? This temperature must not be exceeded for safety reasons.
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