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A double-glazed window has two panes of glass separated by an air space, Fig. 14–20
Chapter 14, Problem 43P(choose chapter or problem)
Problem 43P
A double-glazed window has two panes of glass separated by an air space, Fig. 14–20. (a)Show that the rate of heat flow through such a window by conduction is given by
where k1, k2, and k3 are the thermal conductivities for glass, air, and glass, respectively. (b) Generalize this expression for any number of materials placed next to one another.
Figure 14–20
Questions & Answers
QUESTION:
Problem 43P
A double-glazed window has two panes of glass separated by an air space, Fig. 14–20. (a)Show that the rate of heat flow through such a window by conduction is given by
where k1, k2, and k3 are the thermal conductivities for glass, air, and glass, respectively. (b) Generalize this expression for any number of materials placed next to one another.
Figure 14–20
ANSWER:
Solution 43P
Step 1 of 2
Part a
We are required to prove the given rate of heat flow equation.
Let the temperature of the left air-glass boundary is .
Let the temperature of the right air-glass boundary is .
Let the thermal conductivities of the glass on left, air and the glass on right be ,
and
.
Now, the rate of heat flow is,
From here,
Adding all three expressions,
This is the required equation of rate of heat flow.