In which type of compressor are both the motor and compressor enclosed within a welded housing?

The correct answer is hermetic. A hermetic compressor is designed with both the motor and the compressor unit enclosed in a sealed, welded housing. This design prevents any refrigerant loss and protects the internal components from external contaminants, which enhances the efficiency and longevity of the compressor. The hermetic seal allows the compressor to operate without the risk of environmental leakage that can lead to system inefficiency or failure.

In contrast, open type compressors have a separate motor and compressor unit that is not sealed, which can expose them to environmental factors. Rotary compressors may also not have the same level of sealing as hermetic types, as they can come in both hermetic and open variations. Screw compressors typically consist of two helical rotors and are usually designed for larger applications but also do not feature the enclosed design characteristic of hermetic compressors. Thus, the hermetic compressor is the only type that ensures complete enclosure of both components, making it the ideal choice for applications requiring efficiency and reliability.