When a submarine is at or near the surface it can run the auxiliary diesel engine with the air from the atmosphere and furnish conditioned air for its crew and other fresh air needs. But what happens when a submarine is submerged?
When the submarine is submerged it has to create an artificial atmosphere for often more than 100 people squeezed in a small space which is filled also with heat and off-gassing equipment creating ongoing air contamination. Beside that the HVAC design engineer must deal with the garbage, laundry lint, cooking contaminants, people odours, sewage and chemical leakage.
The factors which are considered when designing the system include heating and cooling loads needed for electronic and electrical equipment, propulsion plant size, crew size and hull size, while also considering the steam leakage load or loss of power. The specifications for temperature and humidity levels and strict control of on-board contaminants require filtration and recirculation using manufacturing oxygen from seawater (or using stored oxygen), scrubbing carbon dioxide from the recirculating filters and absorbing CO by carbon monoxide burner.
The ventilation system circulates cooled, heated and dehumidified air throughout all compartments of a submarine. Electrostatic precipitators remove dust and smoker and other particles. Main induction fans circulate the air (heated or cooled by the ocean).
Source: Air Conditioning in Submarines, ASHRAE Journal, January 2001