What does the term "flash gas" refer to in refrigeration?

The term "flash gas" refers to the vapor that forms when refrigerant experiences a pressure drop. In refrigeration cycles, refrigerants can change state from liquid to vapor when they undergo a decrease in pressure, which occurs in expansion devices such as expansion valves or during evaporator operation.

When a refrigerant is in a high-pressure liquid state and passes through an expansion valve, the sudden drop in pressure allows some of the refrigerant to evaporate or "flash" into vapor. This process is crucial for the refrigeration cycle to absorb heat from the surroundings. As a result, flash gas plays a significant role in the efficiency of the system, helping to cool the evaporator and facilitating the heat transfer process.

Other options do not accurately describe the concept of flash gas. The vapor produced during compression is essential to the refrigeration cycle but occurs at a different stage. The gas that is released during system shutdown may refer to various scenarios but does not specifically define flash gas. Likewise, the gas used to restore system pressure may involve refrigerant management but does not pertain to the flash gas concept.