Final answer:
Stubs on compressors and filter driers are more difficult to braze than copper pipe due to the difference in material properties. Aluminum has a higher rate of thermal expansion and lower ductility compared to copper, making it challenging to create secure connections. The oxidation of aluminum also poses conductivity issues that need to be addressed.
Step-by-step explanation:
The reason why stubs on compressors and filter driers are more difficult to braze than copper pipe is due to the difference in material properties. Copper has a higher ductility and tensile strength compared to aluminum, which makes it easier to work with during the brazing process. Aluminum, on the other hand, has a higher rate of thermal expansion and a lower ductility, making it more challenging to create strong and secure connections.
During the brazing process, the stubs on compressors and filter driers are often subjected to high temperatures. The higher rate of thermal expansion of aluminum can lead to loose connections, as the material expands more than copper. This can result in poor brazed joints and even a potential fire hazard.
In addition, the oxidation of aluminum does not conduct electricity well. Special techniques must be used when working with aluminum components to ensure proper electrical conductivity. Copper, on the other hand, has excellent electrical conductivity. This makes it easier to achieve reliable and efficient connections when brazing copper pipes.