Question

When air is used as a heat transfer fluid, has a very low heat capacity and:




condenses at high pressures


tends to leak out of collectors, ducts, and dampers


cause corrosion


is compressible resulting in high pressures

Answer 1

Answer: The first option ("condenses at high pressures") is incorrect; the other three are correct.

Brief reasons:
- Condenses at high pressures — False. Ordinary air (N2/O2 mix) does not liquefy at typical operating temperatures just by raising pressure; condensation requires cooling near cryogenic temperatures (below the components' critical temperatures).
- Tends to leak out of collectors, ducts, and dampers — True. Gases leak far more easily than liquids through small gaps, so air systems are more prone to leakage and ingress.
- Can cause corrosion — True. Air contains oxygen (and often moisture), which promotes oxidation/corrosion of metal components unless mitigated (drying, corrosion-resistant materials, coatings).
- Is compressible resulting in high pressures — True (practically important). Air’s compressibility means you need much higher volumetric flow rates and often higher operating pressures/pumping power and you can get significant pressure/temperature changes with compression/expansion.