Conduction: Heat-Transfer Rates and Thermal Insulation

All flashcards

Conduction

Transfer of thermal energy through matter by interactions between neighboring particles, without bulk movement of the material.

Conduction-rate equation for a flat slab

$Q/t = kA(T_2-T_1)/d$, where $k$ is conductivity, $A$ is area, and $d$ is thickness.

Thermal conductivity

A measure of how readily a material conducts heat; higher values indicate better conductors.

R factor

The ratio of thickness to thermal conductivity, $R=d/k$; a larger value indicates greater resistance to conductive heat flow.

Heat and phase change

For a phase change, transferred heat is related to mass by $Q=mL$, where $L$ is latent heat.

Quiz questions

1. For a flat slab, what happens to the conductive heat-transfer rate if its thermal conductivity doubles while area, thickness, and temperature difference stay fixed?Answer: The rate doubles.
2. Which unit is equivalent to joules per second for a heat-transfer rate?Answer: Watt
3. Which listed material has the highest representative thermal conductivity?Answer: Silver
4. When a known amount of heat causes a phase change, which relationship can be used to find the mass?Answer: $Q=mL$, where $L$ is the latent heat.
5. Why is conduction alone ineffective for transporting heat rapidly over large distances?Answer: It transfers energy through local particle interactions.