A compressor decreases the volume of a gas at constant pressure through a process called adiabatic compression. Adiabatic compression refers to the compression of a gas without any heat exchange with the surroundings. During this process, the compressor does work on the gas, increasing its pressure and reducing its volume.
Here's a simplified explanation of how a compressor achieves this:
Inlet Stage: The gas enters the compressor through an inlet valve. At this point, the gas has a certain volume and pressure.
Compression Stage: The compressor mechanism, typically a piston or a rotating impeller, begins to compress the gas. As the piston or impeller moves, it reduces the volume available to the gas. The compressor applies a force to the gas, causing it to be compressed.
Pressure Increase: As the gas is compressed, its volume decreases while the pressure increases. The work done by the compressor transfers energy to the gas, raising its internal energy and pressure.
Outlet Stage: Once the compression is complete, the gas exits the compressor through an outlet valve. The gas now has a smaller volume and higher pressure compared to when it entered the compressor.
It's important to note that in an ideal adiabatic compression process, there is no heat exchange with the surroundings. However, in real-world scenarios, compressors generate heat due to factors like friction and inefficiencies. This heat needs to be managed to prevent overheating, which is why many compressors incorporate cooling mechanisms to maintain operational efficiency.
In summary, a compressor decreases the volume of a gas at constant pressure by doing work on the gas, transferring energy and increasing its internal pressure.