What effect do noncondensable gases have on system performance?

What effect do noncondensable gases have on system performance?

• A. They cause an increase in head pressure and a decrease in capacity.
• B. They cause a decrease in head pressure and an increase in capacity.
• C. They have no effect on head pressure or capacity.
• D. They improve overall efficiency.

Answer: (B)

Noncondensable gases in a refrigeration system hinder heat transfer in the condenser. When gases like air are present, they collect at the refrigerant–condenser surface and form an insulating layer, reducing the heat transfer coefficient. To condense properly, the refrigerant must reach a higher temperature and pressure, so the condenser pressure (head pressure) rises. This poorer heat rejection means the system can’t remove heat as effectively, leading to a drop in overall capacity and efficiency. So the correct effect is an increase in head pressure and a decrease in capacity. These gases don’t improve performance; they impede it by degrading condenser heat transfer.

Noncondensable gases in a refrigeration system hinder heat transfer in the condenser. When gases like air are present, they collect at the refrigerant–condenser surface and form an insulating layer, reducing the heat transfer coefficient. To condense properly, the refrigerant must reach a higher temperature and pressure, so the condenser pressure (head pressure) rises. This poorer heat rejection means the system can’t remove heat as effectively, leading to a drop in overall capacity and efficiency. So the correct effect is an increase in head pressure and a decrease in capacity. These gases don’t improve performance; they impede it by degrading condenser heat transfer.