The vapor that is produced by the pressure drop by a capillary tube is known as _______?

The vapor produced by the pressure drop in a capillary tube is known as flash gas. When the refrigerant passes through the capillary tube, it undergoes a drop in pressure, which causes a portion of the refrigerant to change state from liquid to vapor. This transition occurs because the reduced pressure decreases the boiling point of the refrigerant, leading to the rapid formation of gas. This flash gas is crucial for the functioning of refrigeration systems, as it helps in absorbing heat in the evaporator section of the cycle.

Understanding this concept is vital because the behavior and efficiency of refrigerants in HVAC systems rely heavily on the principles of phase changes and pressure drops. Unlike superheat, which refers to the additional heat added to a refrigerant vapor above its boiling point at a given pressure, or sub-cooling, which refers to a liquid refrigerant being cooled below its condensing temperature, flash gas specifically pertains to the gas produced from pressure drops. Flooding gas is not an appropriate term in this context, as it typically refers to a condition in refrigeration where liquid refrigerant is not adequately evaporated or removed from the evaporator coil. Thus, recognizing flash gas highlights important operational mechanics within HVAC systems.