The refrigerant that immediately vaporizes as it passes through the metering device is referred to as what?

The term used to describe refrigerant that immediately vaporizes as it passes through the metering device is "flash gas." When refrigerant flows through the metering device, such as an expansion valve, it experiences a drop in pressure. This pressure drop causes the refrigerant to expand, leading to a portion of it vaporizing immediately. This phenomenon is essential for the cooling cycle in refrigeration and air conditioning systems, as the vaporization absorbs heat from the surrounding environment and cools the refrigerant effectively.

In contrast, superheated vapor refers to vapor that has been heated beyond its boiling point without changing phase, while subcooled liquid describes liquid refrigerant that is cooled below its saturation point without vaporizing. Heat transfer fluid is a broader term that includes fluids used in various heating and cooling applications, but it does not specifically refer to the behavior of refrigerant in this context.