5. Thermal and Statistical Physics

Heat Transfer — Quiz

Test your understanding of heat transfer with 5 practice questions.

Practice Questions

Question 1

A composite wall consists of two layers, A and B, with thermal conductivities $k_A$ and $k_B$ and thicknesses $L_A$ and $L_B$ respectively. If the heat transfer is one-dimensional and steady-state, what is the total thermal resistance of the composite wall?

Question 2

In a counter-flow heat exchanger, how does the Log Mean Temperature Difference (LMTD) compare to that of a parallel-flow heat exchanger under the same inlet and outlet temperatures?

Question 3

A blackbody at an absolute temperature $T$ emits radiation with a total emissive power $E$. According to the Stefan-Boltzmann Law, if the temperature of the blackbody is doubled to $2T$, by what factor does the total emissive power increase?

Question 4

Consider a heat sink with a thermal resistance of $R_{sa} = 0.8 \text{ \textdegree C/W}$ (sink to ambient) and a CPU with a thermal resistance of $R_{jc} = 0.2 \text{ \textdegree C/W}$ (junction to case). If the CPU dissipates $75 \text{ W}$ of power and the ambient temperature is $25 \text{ \textdegree C}$, what is the junction temperature of the CPU, assuming an ideal thermal interface between the CPU case and the heat sink?

Question 5

Which of the following dimensionless numbers is most relevant for characterizing forced convection heat transfer in fluids?