Abstract: An aircraft environmental control system (20) comprises a first heat exchanger (24) configured to exchange heat between air provided by a pressurised air source (13) and a working fluid of a closed cycle refrigeration system, and an air turbine (32) configured to receive cooled air from the first heat exchanger (24). The closed cycle refrigeration system comprises a closed cycle refrigeration system compressor (35) driven by the air turbine (32), a closed cycle refrigeration system expander (36), and a second heat exchanger (33) configured to exchange heat between working fluid of the closed cycle refrigeration system and air downstream of the air turbine (32). The air turbine drives a further load (39).

Abstract: An aircraft environmental control system (20) comprises a first heat exchanger (24) configured to exchange heat between air provided by a pressurised air source (13), and a working fluid of a closed cycle waste heat recovery system, and an air turbine (32) configured to receive cooled air from the first heat exchanger (24). The closed cycle waste heat recovery system comprises a waste heat recovery compressor (35), a waste heat recovery turbine (31), and a second heat exchanger (33) configured to exchange heat between working fluid of the closed cycle waste heat recovery system and air downstream of the air turbine (31). The air turbine is configured to drive a load (39), and the waste heat recovery turbine (31) is configured to drive the waste heat recovery compressor (35).