Noncondensable gases can contribute to which performance issue?

• A. Low capacity
• B. High capacity
• C. No effect
• D. Faster response time

Answer: (A)

Noncondensable gases in a vapor-compression refrigeration system reduce condenser efficiency. When these gases are present in the condenser, they blanket the condensing surface and create an insulating layer, which makes it harder for heat to be rejected from the refrigerant to the surroundings. To maintain proper condensation, the system has to run at higher pressures and the compressor does more work, while subcooling drops and fewer refrigerant molecules actually condense into liquid. The result is less effective heat transfer and a lower amount of heat removed from the refrigerated space for a given operating condition, which translates to a decrease in cooling capacity. So the performance issue most associated with noncondensable gases is a reduced capacity. The other options don’t fit because noncondensables do not improve capacity or leave it unchanged, and they generally don’t improve response time; they tend to slow or degrade overall performance.