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Difficulty: HardThermodynamics and Heat

A double-walled cryogenic storage container is engineered to maintain liquid nitrogen at extremely low temperatures by minimizing heat gain from the surrounding environment. Which of the following correctly pairs a structural feature of the container with the primary heat transfer mechanism it is designed to inhibit?

  1. A
    The evacuated vacuum space between the double walls primarily minimizes heat gain caused by infrared radiation.
  2. B
    The narrow, low-conductivity structural neck suspending the inner chamber primarily minimizes heat gain caused by fluid convection.
  3. The silvered, mirror-like surface lining the walls primarily minimizes heat gain caused by thermal radiation.Answer
  4. D
    The sealed, airtight exterior lid primarily minimizes heat gain caused by direct solid conduction through open air.

Answer

The silvered, mirror-like surface lining the walls primarily minimizes heat gain caused by thermal radiation.
Thermal radiation transfers energy through electromagnetic infrared waves and does not require particles or a material medium. Highly polished, silvered surfaces reflect these electromagnetic waves away from the inner chamber, significantly reducing radiative heat gain.

Step-by-Step Solution

1
Analyze the physical requirements of the three fundamental heat transfer mechanisms.
Conduction transfers kinetic energy through direct contact of particles in solids, convection transfers heat through the bulk movement of fluids (liquids or gases), and radiation transfers energy via electromagnetic waves without requiring any physical medium.
Understanding whether each transfer mechanism depends on matter is necessary to evaluate the function of each insulating barrier.
2
Examine how each specific component of the cryogenic container operates.
The evacuated space between the walls eliminates particles, blocking conduction and convection; the narrow composite neck reduces cross-sectional contact area, reducing solid conduction; the reflective silver lining reflects infrared electromagnetic waves.
Matching structural components to their physical principles reveals which pairing is scientifically valid.
3
Evaluate the pairing of the reflective lining with thermal radiation.
Because thermal radiation travels across the vacuum gap as electromagnetic waves, highly polished reflective surfaces are required to reflect these waves away from the cold storage chamber.
This confirms that the silvered surface specifically targets and mitigates radiative heat transfer.

Key Concept

Thermal Heat Transfer Mechanisms (Conduction, Convection, and Radiation)
Estimated Time:1m 15s
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Topics

Thermodynamics and Heat

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