Solution Found!
Using the Energy BalanceAs shown in Fig. P2.60, the outer
Chapter 2, Problem 60P(choose chapter or problem)
As shown in Fig. P2.60, the outer surface of a transistor is cooled convectively by a fan-induced flow of air at a temperature of \(25^{\circ} \mathrm{C}\) and a pressure of \(1 \mathrm{~atm}\). The transistor's outer surface area is \(5 \times 10^{-4} \mathrm{~m}^2\). At steady state, the electrical power to the transistor is \(3 \mathrm{~W}\). Negligible heat transfer occurs through the base of the transistor. The convective heat transfer coefficient is \(100 \mathrm{~W} / \mathrm{m}^2 \cdot \mathrm{K}\). Determine (a) the rate of heat transfer between the transistor and the air, in W, and (b) the temperature at the transistor's outer surface, in \({ }^{\circ} \mathrm{C}\).
Questions & Answers
QUESTION:
As shown in Fig. P2.60, the outer surface of a transistor is cooled convectively by a fan-induced flow of air at a temperature of \(25^{\circ} \mathrm{C}\) and a pressure of \(1 \mathrm{~atm}\). The transistor's outer surface area is \(5 \times 10^{-4} \mathrm{~m}^2\). At steady state, the electrical power to the transistor is \(3 \mathrm{~W}\). Negligible heat transfer occurs through the base of the transistor. The convective heat transfer coefficient is \(100 \mathrm{~W} / \mathrm{m}^2 \cdot \mathrm{K}\). Determine (a) the rate of heat transfer between the transistor and the air, in W, and (b) the temperature at the transistor's outer surface, in \({ }^{\circ} \mathrm{C}\).
ANSWER:
Step 1 of 2
Part a
We are required to calculate the rate of heat transfer at the steady state.
The electrical power to the transistor is W
From energy balance,
Where, is the rate of heat transfer.
At the steady state,
So, W
This is the rate of heat transfer.