What is defined as flash gas?

Flash gas refers to the vapor that forms when liquid refrigerant passes through the expansion device. This process occurs when high-pressure liquid refrigerant enters the lower pressure area of the evaporator after going through the expansion valve. Because of the drop in pressure, a portion of the refrigerant rapidly vaporizes, creating a mixture of liquid and vapor known as flash gas. This vapor is essential for the refrigeration cycle as it absorbs heat in the evaporator and facilitates the cooling process by changing the state of the refrigerant from liquid to vapor.

Understanding this concept is crucial because it highlights the importance of the expansion device's role in managing the refrigerant's phase change, ensuring that maximum cooling efficiency is achieved within the system.