Cirrus SR22 Pilot Operating Handbook page 254

Section 7 Cirrus Design
Airplane Description SR22
Distribution
Ventilation and cooling is provided by ducting fresh air from a NACA
inlet on the RH cowl to the mixing chamber located on the lower RH
portion of the firewall. Depending on operating mode and temperature
selection, the air in the mixing chamber is ducted directly into the
distribution system or, if in Air Conditioning mode (optional), is further
cooled as it passes through the evaporator assembly located under
the front passenger seat.
Heating is accomplished by mixing ventilation air from the fresh air
inlet with heated air provided by the heat exchanger in the mixing
chamber on the firewall. From the mixing chamber - which also
controls airflow into the cabin compartment - the conditioned air is
forced by ram air pressure or by blower fan into a distribution manifold
mounted to the center, aft side of the firewall. The distribution manifold
uses butterfly valves to control airflow to the floor and defrost vents.
Airflow is ducted directly to all panel air vents.
Crew panel air vents are located inboard on the RH and LH bolster
panels and on the outboard section of the instrument panel. The crew
floor air vents are mounted to the bottom of each kick plate. The
passenger panel air vents are chest high outlets mounted in the
armrests integral to the LH and RH cabin wall trim panels. The
passenger floor air vents are mounted to the bottom portion of the LH
and RH cabin wall trim panels. The windshield diffuser, located in the
glareshield assembly, directs conditioned air to the base of the
windshield.
Heating
Ram air from the NACA inlet flows through the upper cowl and is
ducted to the heat exchanger. The heated air is then routed to the hot
air valve, mounted to the forward side of the firewall, which controls
entry of hot air into the cabin distribution system. When the valve is
open, the air flows into the cabin mixing chamber. When the valve is
closed, the heated air exits into the engine compartment and is
exhausted overboard with the engine cooling airflow. Cabin heat is
regulated by controlling the volume of hot air admitted into the
distribution system's air mixing chamber. The proportion of heated air
to fresh air is accomplished using the temperature selector mounted
on the RH instrument panel.
7-80 P/N 13772-001
Revision A10