What gas should be purged through a refrigerant circuit to prevent the formation of oxides during brazing?

To prevent the formation of oxides during brazing in a refrigerant circuit, dry nitrogen is used as a purging gas. When brazing, it is essential to eliminate oxygen from the environment where the heat is applied, as oxygen can react with the heated metals to form oxides. The presence of oxides can lead to weak joints and can compromise the integrity of the brazed connections.

Dry nitrogen serves as a non-reactive gas that effectively displaces oxygen from the area where brazing occurs. It also helps maintain a protective atmosphere around the joint, preventing oxidation and ensuring a clean surface for the brazed joint. This protective environment forms a barrier between the heated metal and any atmospheric contaminants, supporting the overall quality and strength of the brazing process.

Using other gases, such as carbon dioxide or oxygen, would not achieve the same protective effect, as carbon dioxide has different reactive properties, and oxygen can actually contribute to oxidation. Argon, while an inert gas, is less commonly used in typical refrigerant brazing processes compared to dry nitrogen, which is more practical and effective for this specific application.