The cooling is often obtained through a refrigeration cycle, but from time to time evaporation or absolutely free cooling is employed. Air conditioning devices may also be designed depending on desiccants (chemical compounds which eliminate humidity with the air). Some AC systems reject or shop warmth in subterranean pipes.[two] The https://docs.google.com/spreadsheets/d/14Zqd0FEGkdjJlcohp4SFWeSZ9M4AIBFQpIDlHrjqztI