In a multistage air compressor, how does the size of the second stage cylinder compare to the first?

In a multistage air compressor, the second stage cylinder is typically smaller than the first. The reason for this is tied to the compression process and the thermodynamic principles involved.

During the first stage of compression, the air is drawn in and compressed to a certain pressure. This first stage cylinder is designed to accommodate the volume of air at atmospheric pressure before being compressed. When this air moves to the second stage, it is already at a higher pressure. As a result, the volume of air that needs to be compressed further in the second stage is significantly reduced compared to the first. Therefore, the second stage cylinder is designed to handle this smaller volume of air at a higher pressure.

This configuration not only optimizes the efficiency of the compression process but also helps in managing the heat generated during compression. A smaller diameter in the second stage can help achieve adequate pressure while minimizing the work done by the compressor.

While the design of the compressor might introduce variations based on specific applications or engineering choices, the general principle remains that the second stage cylinder is smaller because it is compressing air that has already been partially compressed, thereby reducing the volume yet still needing to achieve a higher overall pressure.