Efficiency air cycle environmental control system

Abstract

In a compressed air powered refrigeration system for aircraft containing a refrigeration turbine and associated heat exchangers for supplying cool air to the aircraft cabin, air is recirculated from the cabin by a recirculation means and combined with the turbine discharge air to simultaneously melt ice present in the turbine discharge and provide cooling to the recirculated air. The lack of ice in the turbine discharge allows the use of an ice-free regenerative heat exchanger, in heat exchange relation with the mixture of the turbine discharge air and recirculated cabin air, to condense moisture from the air entering the turbine. The use of heat from the cabin air to melt ice coupled with maximum utilization of the recirculation means supplying the recirculating cabin air enables the turbine to provide air at a temperature below freezing and results in improved cycle efficiency as well as maximum possible ventilation rate to the load.

Having thus described a typical embodiment of my invention, that which I claim as new and desire to secure by Letters Patent of the United States is: 
     
       1. In an air cycle refrigeration system for aircraft receiving pressurized air and supplying refrigerated air to an enclosure; a turbine having an inlet and an outlet, said inlet receiving said pressurized air and said turbine expanding and cooling said air through said outlet;   means for recirculating air at a temperature above freezing from said enclosure to a junction downstream from the outlet of said turbine whereby said recirculated air is mixed with the cool air from said turbine to melt ice present in said turbine outlet and to provide cooling to said recirculated enclosure air;   a regenerative condenser connecting, through heat transfer surfaces within said condenser, the pressurized air upstream of said turbine inlet with the cooled air mixture downstream of said junction, said cooled air mixture absorbing heat from said pressurized air and cooling said pressurized air below its dewpoint so that moisture in said pressurized air condenses on said heat transfer surfaces and is made available for removal;   and means for supplying said cooled air mixture from said regenerative condenser to said enclosure, the quantity of airflow supplied to said enclosure .Iadd.through said regenerative condenser .Iaddend.being equal to the sum of the pressurized air and the recirculated air.   
     
     
       2. An air cycle refrigeration system as in claim 1 and including means for removing said moisture condensed in said regenerative condenser. 
     
     
       3. An air cycle refrigeration system as in claim 1 and including: sensing means located upstream from said regenerative condenser and downstream from said junction;   and means responsive to said sensing means for adding to said air mixture upstream from said sensing means and downstream from said turbine outlet sufficient pressurized air at a temperature higher than said air mixture to prevent formation of ice during operating conditions of said system when the recirculated air from said enclosure has insufficient heat content to prevent icing.   
     
     
       4. An air cycle refrigeration system as in claim 3 in which said sensing means is a temperature sensor. 
     
     
       5. An air cycle refrigeration system as in claim 3 in which said sensing means is a pressure sensor. 
     
     
       6. An air cycle refrigeration system as in claim 1 and including: temperature sensing means located downstream from said regenerative condenser;   and means responsive to said temperature sensing means for adding to said air mixture upstream from said regenerative condenser and downstream from said turbine outlet sufficient pressurized air at a temperature higher than said air mixture to prevent formation of ice during operating conditions of said system when the recirculated air from said enclosure has insufficient heat content to prevent icing.   
     
     
       7. An ice cycle refrigeration system as in claim 1 in which said means for recirculating air from said enclosure includes: duct means connecting said enclosure with said junction; and electric fan means located in said duct means.   
     
     
       8. An air cycle refrigeration system as in claim 1 in which said means for recirculating air from said enclosure includes: duct means connecting said enclosure with said junction;   and ejector means located at said junction where said duct means connects with said junction utilizing pressure energy from the turbine outlet to pump said recirculated air.   
     
     
       9. An air cycle refrigeration system as in claim 1 and including: a source of ambient air;   heat exchange means connecting, through heat transfer surfaces within said heat exchange means, the pressurized air upstream of said regenerative condenser with said ambient air, said ambient air absorbing heat from said pressurized air and cooling said pressurized air;   means for discharging said ambient air from said system;   and means for passing said pressurized air from said heat exchanger means to said regenerative condenser.   
     
     
       10. An air cycle refrigeration system as in claim 9 and including: fan means powered by said turbine and communicating with said ambient air source and said ambient air discharge means for maintaining a continuous flow of ambient air through said heat exchange means.   
     
     
       11. An air cycle refrigeration system as in claim 9 and further including a compressor powered by said turbine, said compressor receiving said pressurized air and feeding said compressed pressurized air to said heat exchange means. 
     
     
       12. An air cycle refrigeration system as in claim 9 in which said heat exchange means includes a primary heat exchanger and a secondary heat exchanger. 
     
     
       13. An air cycle refrigeration system for an aircraft enclosure comprising: a source of pressurized air;   a regenerative condenser receiving said pressurized air and removing moisture from said air, said condenser also being supplied with a coolant fluid in heat exchange relationship with said air;   an expansion turbine receiving the pressurized air from said regenerative condenser and lowering the temperature thereof;   means for recirculating air from said enclosure at a temperature above freezing;   means for mixing said recirculated enclosure air with the cooled air discharged from said turbine to maintain said air mixture at a temperature sufficiently high to prevent the formation of ice;   means for passing said air mixture through said regenerative condenser as said coolant fluid;   and means for supplying said air mixture from said regenerative condenser to said enclosure, the quantity of airflow supplied to said enclosure .Iadd.through said regenerative condenser .Iaddend.being equal to the sum of sid pressurized air and said recirculated air.   
     
     
       14. An air cycle refrigeration system as in claim 13 and including: sensing means located upstream of said regenerative condenser;   and means responsive to a preselected condition of said sensing means for adding warm air to said air mixture upstream of said sensing means to prevent icing.   
     
     
       15. An air cycle refrigeration system as in claim 14 in which said sensing means is a temperature sensor. 
     
     
       16. An air cycle refrigeration system as in claim 14 in which said sensing means is a pressure sensor. 
     
     
       17. An air cycle refrigeration system as in claim 13 and including: temperature sensing means located downstream of said regenerative condenser;   and means responsive to a preselected temperature of said temperature sensing means for adding warm air to the air mixture between said turbine discharge and said regenerative condenser to prevent icing.   
     
     
       18. A method for cooling an aircraft enclosure from a source of pressurized air comprising the steps of: removing moisture from said pressurized air by heat exchange in a regenerative condenser between said pressurized air and a coolant fluid;   expanding said pressurized air, after removal of moisture therefrom, through a turbine to cool said air;   mixing air recirculated from said enclosure with said cooled air at the outlet of said turbine so that the resultant air mixture prevents ice in said turbine and cools said recirculated air;   passing said air mixture through said regenerative condenser as said coolant fluid;   and supplying said air mixture from said regenerative condenser to said enclosure, said air mixture .Iadd.supplied to said enclosure through said regenerative condenser .Iaddend.being equal to the sum of said pressurized air and said recirculated air.   
     
     
       19. The method of claim 18 and further including the steps of: sensing a condition of the air mixture upstream of said regenerative condenser;   and adding to said air mixture at a point downstream of the turbine outlet and upstream of the regenerative condenser a sufficient amount of warm air to prevent icing when the sensed condition of said air mixture is such as to cause icing.   
     
     
       20. The method of claim 18 and further including the steps of: sensing the temperature of the air mixture downstream of said regenerative condenser;   and adding to said air mixture at a point downstream of the turbine outlet and upstream of the regenerative condenser a sufficient amount of warm air to prevent icing therein at preselected temperature of the air mixture downstream of said regenerative condenser.