What is the dew point in a refrigerant blend?

• A. The temperature at which the first refrigerant in a blend turns to liquid.
• B. The temperature at which all refrigerants in the blend boil.
• C. The pressure at which the refrigerant becomes a gas.
• D. The boiling point of the most volatile component.

Answer: (A)

Dew point in a refrigerant blend is the temperature at which the vapor begins to condense into liquid at a given pressure. In a blend, the components have different boiling points, so as you cool the vapor, the component with the highest tendency to stay in vapor (the most volatile) will reach its condensation point first and start forming liquid. That onset of liquid formation marks the dew point. So the dew point is specifically the temperature where the first refrigerant in the blend turns to liquid, not the temperature where every component boils, nor a pressure value, nor the boiling point of the most volatile component in isolation.