Heat Transfer Physics Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

medium
A glass window (k=0.8 W/(m\cdotpK)k = 0.8 \text{ W/(m·K)}, area 2 m22 \text{ m}^2, thickness 0.005 m0.005 \text{ m}) has 20°C20°\text{C} inside and 5°C5°\text{C} outside. What is the rate of heat loss through the window?

Solution

  1. 1
    Use the conduction formula: Qt=kAΔTd\frac{Q}{t} = \frac{kA\Delta T}{d}.
  2. 2
    Qt=0.8×2×(20−5)0.005=0.8×2×150.005\frac{Q}{t} = \frac{0.8 \times 2 \times (20 - 5)}{0.005} = \frac{0.8 \times 2 \times 15}{0.005}
  3. 3
    Qt=240.005=4800 W\frac{Q}{t} = \frac{24}{0.005} = 4800 \text{ W}

Answer

Qt=4800 W\frac{Q}{t} = 4800 \text{ W}
Heat conduction through a material depends on its thermal conductivity, the area, the temperature difference, and the thickness. Thicker windows and double glazing reduce heat loss significantly.

About Heat Transfer

The spontaneous flow of thermal energy from a hotter object to a cooler one until they reach thermal equilibrium (the same temperature).

Learn more about Heat Transfer →

More Heat Transfer Examples

Example 1 easy

Identify the primary mode of heat transfer in each case: (a) a metal spoon in hot soup, (b) warmth f

Example 3 medium

A thermos flask uses a vacuum between its double walls. Explain why this reduces heat transfer, and

Example 4 hard

A copper rod ([formula]) and an iron rod ([formula]) have the same length ([formula]) and cross-sect

← All Heat Transfer Examples Heat Transfer Concept