This portion of the air flow enters the high pressure water seperator
loop and in its first component, the reheater, it is cooled by the ACM
tubine inlet air.
This cooling can bring the air temperature to below its dew point. Thus
water condensation can start on the outlet side of the reheater and is
then accelerated in the next component, the condenser, of the high
pressure water seperator loop.
In the condenser, the air is cooled further by the ACM tubine-outlet air.
The air, which comes from the ACM turbine outlet, has a subzero
temperature. This subzero temperature air cools the air in the condenser
down to a sea level dew point of approximately 0 DEG.C (32.00 DEG.F).
This makes sure that the dew point of the air, which is supplied to the
mixer-unit, is lower than +10 DEG.C (+50.00 DEG.F).
The +10 DEG.C (+50.00 DEG.F) dew point will allow a maximum cabin air
humdity without condensation in the mix manifold or cabin supply air
ducting.
The condensed moisture is collected in the water extractor and sprayed on
the ram inlet air side of the main heat exchanger to increase its cooling
efficiency.
After the water extractor, the air passes through the reheater again
where it increases in temperature and then enters the ACM turbine inlet.
In the ACM turbine, the high pressure air expends its kinetic energy. The
temperature and the pressure decresase. This will cause additional
condensation during ground operation and low altitude flight operation.
This condensation will occur as snow.
The condenser is a tubular heat exchanger with a tube to tube distance,
which is large enough, to prevent the snow from clogging the condenser.
The final pack temperature regulation takes place by mixing the ACM
by-passed air with the turbine outlet air.
R **ON A/C 004-049, 055-099, 101-149, 151-199, 201-299, 301-399, 401-499,
B. Operation of the Pack Temperature Control The pack temperature control system operates from a source of pressurized air which is supplied from the engines, the APU or from a ground source. The air is metered in the flow control valve to provide a constant volumetric flow regardless of the cabin altitude. The nominal flow can be increased or decreased by cockpit command. The metered flow is cooled in the primary heat exchanger using ambient ram air as a heat sink.
The flow of the ram air is regulated by the movable ram air inlet doors to minimize the ram air flow while at the same time assuring an efficient heat transfer and thrust recovery.
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In flight, ambient ram air pressure helps the fan to supply satisfactory
flow.
For ground operation, the Air-Cycle Machine (ACM) fan provides the
required ram air flow.
During take-off and landing, the ram air inlet is closed to avoid dirt
ingestion and contamination of the heat exchangers.
After passing through the primary heat exchanger, a part of the bleed air
flow is compressed by the ACM compressor where its pressure and
temperature are raised and then cooled in the main heat exchanger using
ram air as a heat sink.
This portion of the air flow enters the high pressure water seperator
loop and in its first component, the reheater, it is cooled by the ACM
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