An environmental control system of an aircraft comprising: a ram air circuit including a ram air shell having at least one heat exchanger positioned therein; at least one dehumidification system arranged in fluid communication with the ram air circuit; a compressing device comprising a compressor , a turbine , and a power turbine operably coupled to each other via a shaft , the compressing device being arranged in fluid communication with the ram air circuit and the dehumidification system and an expansion device comprising a turbine and a fan operably coupled via a shaft , the expansion device being separate from the compressing device and arranged in fluid communication with the ram air circuit and the at least one dehumidification system; wherein the at least one heat exchanger includes a first heat exchanger , a second heat exchanger , and a third heat exchanger , characterized by the third heat exchanger being arranged in fluid communication with the first heat exchanger, such that during at least one mode of operation of the environmental control system, a first medium passes from the first heat exchanger to the third heat exchanger; and wherein: the first medium is provided to the compressing device, and simultaneously a second medium is provided to the compressing device and then passes sequentially through the second heat exchanger and the expansion device, and, in the at least one mode of operation, both the first medium and the second medium are configured to be provided to a cabin of the aircraft. a ram air circuit including a ram air shell having at least one heat exchanger positioned therein; at least one dehumidification system arranged in fluid communication with the ram air circuit; a compressing device comprising a compressor , a turbine , and a power turbine operably coupled to each other via a shaft , the compressing device being arranged in fluid communication with the ram air circuit and the dehumidification system and an expansion device comprising a turbine and a fan operably coupled via a shaft , the expansion device being separate from the compressing device and arranged in fluid communication with the ram air circuit and the at least one dehumidification system; wherein the at least one heat exchanger includes a first heat exchanger , a second heat exchanger , and a third heat exchanger , characterized by the third heat exchanger being arranged in fluid communication with the first heat exchanger, such that during at least one mode of operation of the environmental control system, a first medium passes from the first heat exchanger to the third heat exchanger; and wherein: the first medium is provided to the compressing device, and simultaneously a second medium is provided to the compressing device and then passes sequentially through the second heat exchanger and the expansion device, and, in the at least one mode of operation, both the first medium and the second medium are configured to be provided to a cabin of the aircraft. the first medium is provided to the compressing device, and simultaneously a second medium is provided to the compressing device and then passes sequentially through the second heat exchanger and the expansion device, and, in the at least one mode of operation, both the first medium and the second medium are configured to be provided to a cabin of the aircraft. <EOS>