Air conditioning system

Abstract

An air cycle air conditioning system for conditioning recirculating air from an enclosure includes an enclosure air recirculation loop, a first expansion turbine to which hot pressurized working air is provided, a heat exchanger to which a proportion of the hot pressurized working air is provided, from upstream of the first expansion turbine, and in which heat is exchanged to the cooler expanded air from the first expansion turbine. The working air from the heat exchanger expanded by the first expansion turbine and the cooled pressurized working air from the heat exchanger are combined prior to feeding the combined flows to a second expansion turbine. The system including a mixing apparatus in which the recirculating enclosure air from the loop and the cooled combined working air flows from the second expansion turbine are mixed prior to being provided to the enclosure.

1 . An air cycle air conditioning system for conditioning recirculating air from an enclosure, the system including an enclosure air recirculation loop, a first expansion turbine to which hot pressurized working air is provided, a heat exchanger to which a proportion of the hot pressurized working air is provided, from upstream of the first expansion turbine, and in which heat is exchanged to the cooler expanded air from the first expansion turbine, the working air from the heat exchanger expanded by the first expansion turbine and the cooled pressurized working air from the heat exchanger being combined prior to feeding the combined flows to a second expansion turbine, the system including a mixing apparatus in which the recirculating enclosure air from the loop and the cooled combined working air flows from the second expansion turbine are mixed prior to being provided to the enclosure.  
   
   
       2 . A system according to  claim 1  wherein the second expansion turbine drives a compressor of the working air, upstream of the first expansion turbine.  
   
   
       3 . A system according to  claim 1  wherein the system further includes a heat load heat exchanger in which a heat load of the recirculating enclosure air of the recirculation loop is exchanged with cooler working air from the first expansion turbine.  
   
   
       4 . A system according to  claim 3  wherein the heat load heat exchanger is located downstream of the heat exchanger to which the hot pressurized compressed working air is provided.  
   
   
       5 . A system according to  claim 3  wherein the heat load heat exchanger and the heat exchanger to which the hot pressurized air is provided, are provided as a combined apparatus, or separate apparatus.  
   
   
       6 . A system according to  claim 1  wherein the proportion of the hot pressurized air which is fed from upstream of the first expansion turbine to the heat exchanger is controlled by a valve depending on the flow rate and temperature of the recirculating air in the recirculation loop.  
   
   
       7 . A system according to  claim 1  wherein the system includes a second compressor downstream of the first compressor but upstream of the first expansion turbine, further to pressurize the working air.  
   
   
       8 . A system according to  claim 7  wherein the second compressor is driven by energy recovered from the working air by the first expansion turbine.  
   
   
       9 . A system according to  claim 7  wherein the pressurized air from the second compressor is cooled in a secondary heat exchanger prior to providing to the first expansion turbine.  
   
   
       10 . A system according to  claim 1  which is provided in an aircraft.  
   
   
       11 . A system according to  claim 10 , wherein the system includes a second compressor downstream of the first compressor but upstream of the first expansion turbine, further to pressurize the working air, and wherein the pressurized air from the second compressor is cooled in a secondary heat exchanger prior to providing to the first expansion turbine and a cooling air flow for the secondary heat exchanger is ambient air where the aircraft is flying, and fan driven air where the aircraft is on the ground.  
   
   
       12 . A system according to  claim 1  wherein the heat exchanger is a condensing heat exchanger so that condensate resulting from the cooling of the hot pressurized air by the cooler expanded air from the first expansion turbine is removed from the system.  
   
   
       13 . An aircraft having an air cycle air conditioning system for conditioning recirculating air from an enclosure, the system including an enclosure air recirculation loop, a first expansion turbine to which hot pressurized working air is provided, a heat exchanger to which a proportion of the hot pressurized working air is provided, from upstream of the first expansion turbine, and in which heat is exchanged to the cooler expanded air from the first expansion turbine, the working air from the heat exchanger expanded by the first expansion turbine and the cooled pressurized working air from the heat exchanger being combined prior to feeding the combined flows to a second expansion turbine, the system including a mixing apparatus in which the recirculating enclosure air from the loop and the cooled combined working air flows from the second expansion turbine are mixed prior to being provided to the enclosure.