The secondary heat exchanger is a cross-flow, air-to-air heat exchanger. Hot, high-pressure air, discharged from the compressor end of the refrigeration turbine/ compressor assembly, is transported through the core of the heat exchanger where ram air, augmented by water spray, is forced across the core by aircraft forward motion, absorbing heat from the air and reducing the air temperature. During ground and low-speed operation, cooling air is pulled across the heat exchanger core by ejecting hot air into the heat exchanger exit duct. The ejected air is controlled by the secondary ejector valve in response to signals from the ADC.

Secondary Ejector Valve

The secondary ejector valve is a normally open in-line poppet, pneumatically actuated, solenoid-controlled shutoff valve. The valve controls the flow of bleed air to the secondary heat exchanger ejector in the secondary heat exchanger exit duct. The valve is controlled by an electrical signal from the ADC. At airspeeds below 165 knots, this valve operates on the same principle as the primary ejector valve.

Water Spray Nozzle

The water spray nozzle is used to form a mist in the secondary heat exchanger ram air inlet, which aids in cooling the air. Water is extracted from the conditioned air in the water extractor. The water is transported to the water spray nozzle into the secondary heat exchanger ram air inlet. The nozzle directs a jet of water onto a pin, forming a fine sheet of water before breaking up into a mist. The mist is forced across the heat exchanger with the ram airflow.

Reheater Heat Exchanger

The reheater heat exchanger is a single-pass, cross-flow, air-to-air heat exchanger. The reheater heat exchanger cools air from the secondary heat exchanger before moisture removal in the condenser/ vent suit heat exchanger and water extractor and simultaneously reheats the dried air before expansion through the turbine end of the refrigeration turbine/ compressor assembly. The function of the reheater is to decrease the amount of cooling provided by the condenser heat exchanger and increase turbine inlet temperature, which results in increased turbine power.

Condenser/ Vent Suit Heat Exchanger

The condenser/ vent suit heat exchanger is a cross-flow, air-to-air heat exchanger, which uses cold turbine discharge air from the refrigeration turbine/ compressor assembly to cool and condense moisture from the bleed air before circulation through the water extractor. The heat exchanger inlet receives partially cooled air from the hot side of the reheater and directs it across the condenser core where it is cooled until the water vapor is condensed into large size droplets. The air and water droplets are directed to the water extractor. A separate vent suit heat exchanger is in the condenser assembly. The vent suit heat exchanger receives dry air from the water extractor and cools it by heat exchange with turbine exhaust air for use in the vent suit system.

Water Extractor

The water extractor is an in-line, integral duct device that uses a helix and a water shave-off collector. Moisture-laden air from the condenser enters the water extractor and is given a swirling motion by the helix. The heavy water particles are centrifuged to the duct wall and shaved off into the annular section between the duct wall and re-entrant discharge duct. Approximately 3 percent of the total airflow is also shaved off as scavenge air. The scavenge air/ water enters the outer chamber, which is surrounded by a perforated muff. In this chamber the water droplets are separated from the scavenge air. The dry scavenge air flows into an end chamber, through a baffle and out through the scavenge port. The water flows through the perforations into a sump and out through the drain port to the water spray noz-zle where it is used to augment ram air cooling in the secondary heat exchanger.

Refrigeration Turbine/ Compressor Assembly

The refrigeration turbine/ compressor assem-bly is a centrifugal compressor with a turbine wheel mounted at each end of a common shaft. The compressor end receives partially conditioned air from the flow modulating system pressure reg-ulator valve, where it is compressed to approx-imately double its inlet value. The air is transported through the secondary heat ex-changer, reheater heat exchanger, condenser/ vent suit heat exchanger, and water extractor before entering the turbine end of the refrigeration turbine/ compressor assembly. The conditioned, dry air flows through turbine nozzles to the turbine wheel where heat energy is changed to mechanical energy, driving the compressor. The expanded, cold air exhausting from the turbine is transported back through the reheater heat exchanger, into ducting, where it is used for environmental control.

Anti-Ice Add Heat Valve

The anti-ice add heat valves is a normally closed, electrically controlled, pneumatically actuated, modulating valve. The valve is between the windshield anti-ice/ rain removal manifold and the turbine outlet. The valve is controlled by electrical signals from the ACS temperature/ flow controller and differential pressure sensed across the condenser/ suit vent heat exchanger. This valve maintains the turbine outlet temperature as required to prevent icing by adding hot air to the conditioned, cold air.