Heat Transfer Physics Example 3
Follow the full solution, then compare it with the other examples linked below.
Example 3
mediumA thermos flask uses a vacuum between its double walls. Explain why this reduces heat transfer, and which mode(s) of heat transfer it primarily blocks.
Solution
- 1 A vacuum contains no matter, so conduction (which requires molecular contact) is eliminated.
- 2 Convection (which requires fluid circulation) is also eliminated since there is no fluid in a vacuum.
- 3 Radiation can still pass through the vacuum, so thermos flasks use reflective silver coatings to minimize radiative heat transfer.
Answer
The thermos flask demonstrates all three heat transfer mechanisms. The vacuum eliminates conduction and convection, while the silvered surface reflects infrared radiation, minimizing all heat transfer.
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 āMore 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 2 mediumA glass window ([formula], area [formula], thickness [formula]) has [formula] inside and [formula] o
Example 4 hardA copper rod ([formula]) and an iron rod ([formula]) have the same length ([formula]) and cross-sect