
Concept explainers
(a)
To Calculate:The thermal resistance of each cube.
(a)

Answer to Problem 36P
Thermal resistance of copper cube is 0.0831 K/W.
Thermal resistance of aluminum cube is 0.141 K/W.
Explanation of Solution
Given: A copper cube and aluminum cube each having3.00cm long edges.
Formula used:
Thermal resistance
Calculation:
Thermal resistance of copper cube is calculated as follows:
Substitute 3 cm for,
Therefore, thermal resistance of copper cube is 0.0831 K/W.
Thermal resistance of aluminum cube is calculated as follows:
Substitute 3 cm for
Therefore, thermal resistance of aluminum cube is 0.141 K/W
Conclusion: Thermal resistance can be calculated by using heat conductivity.
(b)
To Calculate:The thermal resistance of two cube combination.
(b)

Answer to Problem 36P
The thermal resistance of two-cube combination is 0.224 K/W.
Explanation of Solution
Given:
Cubes are connected in series.
A copper cube and aluminum cube each has 3.00cm long edges.
0.0831 K/W for
Calculation:
The cubes are in series, so the resultant thermal resistance is:
Substitute 0.0831 K/W for
Conclusion: Thus, the thermal resistance of two-cube combination is 0.224 K/W.
(c)
To Calculate:The thermal current I.
(c)

Answer to Problem 36P
Thermal current I at the interface between the two cubes is 0.375 kW.
Explanation of Solution
Given: A copper cube and aluminum cube each has 3.00cm long edges.
Calculation:
The expression for the thermal current I is
Here, ΔT is the difference in temperature and Req is the equivalent resistance.
Substitute the values
Conclusion:
Therefore, thermal current I at the interface between the two cubes is 0.375 kW.
(d)
To Calculate:The temperature at the interface of two cubes.
(d)

Answer to Problem 36P
Explanation of Solution
Given:
I = 357 W
Calculation:
The temperature at the interface between the two cubes is
Substitute
Conclusion: Therefore, the temperature at the interface between the two cubes is
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Chapter 20 Solutions
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