What characterizes superheated vapour in refrigeration systems?

• A. Vapour that has not undergone evaporation
• B. Vapour that remains at temperatures below 100°C
• C. Vapour that has been heated beyond 100°C after evaporation
• D. Vapour that is at maximum pressure

Answer: (C)

Superheated vapour in refrigeration systems is characterized as vapour that has been heated beyond its saturation temperature after the phase transition from liquid to vapour has occurred. When the refrigerant evaporates, it absorbs heat and transforms into vapour. If this vapour is then further heated, causing it to exceed the temperature at which it condenses back into a liquid, it becomes superheated. The significance of superheated vapour lies in its ability to carry more energy than saturated vapour, leading to increased efficiency in refrigeration cycles.

The other choices do not accurately describe superheated vapour. The first option suggests that the vapour has not undergone evaporation, which is incorrect as superheated vapour must be fully evaporated. The second option states that it remains at temperatures below 100°C, which does not hold true, as superheated vapours can exist at much higher temperatures. The fourth option describes vapour at maximum pressure, which does not consider the temperature aspect necessary for defining superheated vapour.