Question

How does cooling occur in direct expansion vapor compression refrigeration systems?

1) When the refrigerant vapor turns into a liquid.
2) When the refrigerant is under maximum pressure.
3) When the liquid refrigerant is vaporized.
4) When the refrigerant gives off heat.

Answer 1

Cooling in direct expansion vapor compression refrigeration systems occurs when the refrigerant releases heat during condensation from a gas to a liquid, and then through expansion after passing through the expansion valve.

Step-by-step explanation:

In direct expansion vapor compression refrigeration systems, cooling occurs during a key phase change process. The refrigerant is compressed by an electrically driven compressor, which raises its temperature and pressure. Heat transfer from the gas to the room occurs as the refrigerant is then forced into the condenser coils, where it is higher in temperature than the inside of the room, resulting in the refrigerant condensing into a liquid. The cooling effect is achieved as the refrigerant releases its heat to the surroundings during condensation.

Afterward, this liquid passes through an expansion (pressure-reducing) valve which causes it to cool as it expands. The now cool expanded refrigerant enters the evaporator coils, where it absorbs heat, vaporizing back into a gas. This absorption of heat from the environment is what provides the cooling effect inside the refrigerated space. Essentially, the refrigeration cycle repeatedly transitions the refrigerant between liquid and gas states, enabling the heat transfer necessary for cooling.