What does "flash gas" refer to in refrigeration terminology?

"Flash gas" specifically refers to the vapor that is formed when liquid refrigerant experiences a reduction in pressure. This phenomenon occurs when the liquid refrigerant is introduced into a lower pressure environment, such as at the expansion valve or in the evaporator. The drop in pressure causes some of the liquid refrigerant to instantly vaporize, creating flash gas. This process is critical in refrigeration systems as it enables the cooling effect necessary for the refrigerator to function properly.

In contrast, the other options describe different scenarios in refrigeration. The vapor formed when a liquid refrigerant is heated excessively relates to a different phase change that typically does not occur simply due to pressure reduction. The vapor formed during the condensation process refers to a different stage of the refrigeration cycle, where vapor is converted back into a liquid under pressure and is not considered "flash gas." Lastly, while gas released during compressor operation is integral to the cycle of a refrigeration system, it does not relate specifically to the concept of flash gas, which is tied to the immediate phase change due to pressure drop.