The most common non-condensable that gets trapped in a refrigeration system is which of the following?

In refrigeration systems, non-condensables are gases that do not condense into a liquid under the operating conditions of the system. The most common non-condensable that gets trapped in such systems is air. Air can enter the refrigeration circuit through leaks, improper charging, or maintenance procedures. When air becomes trapped within the system, it can lead to significant operational issues such as increased pressure, reduced efficiency, and potential overheating of the compressor.

The presence of air in a refrigeration system is detrimental because it does not facilitate heat transfer effectively like the refrigerant does. This can cause the system to work harder, leading to elevated energy consumption and a decrease in cooling performance. Additionally, trapped air can lead to liquid slugging when mixed with the refrigerant, which can damage the compressor.

While carbon dioxide and ammonia can also exist in certain refrigeration applications, they are not the most common non-condensables found in standard refrigeration systems. Water vapor can occur, but it is typically associated with moisture and may lead to other issues such as corrosion and ice formation rather than being classified as a common non-condensable gas. Therefore, in the context of typical refrigeration scenarios, air stands out as the prevalent non-condensable gas present in systems.