Air conditioning system

An air conditioning system configured to provide air to a cabin of an aircraft, the air conditioning system comprising:

• a pressurized air source configured to provide work air with a pressure higher than 100 kPa while in an operating mode;
• a cooling air source configured to provide cooling air;
• a main heat exchanger with a cold side and a hot side, the hot side comprising an inlet and an outlet, and the cold side comprising an inlet and an outlet, wherein the inlet of the cold side of the main heat exchanger is in fluid communication with the cooling air source and the inlet of the hot side of the main heat exchanger is in fluid communication with the pressurized air source;
• a secondary duct through which flows air bled from the outlet of the cold side of the main heat exchanger or from the inlet of the cold side of the main heat exchanger,
• a first valve configured to allow or restrict passage of air bled to the secondary duct;
• and
• a compressor with an inlet and an outlet, the inlet of the compressor in fluid communication with the outlet of the cold side of the main heat exchanger or the inlet of the cold side of the main heat exchanger;
• a second valve in fluid communication with the outlet of the compressor;
• wherein the outlet of the compressor is in fluid communication with a mixing assembly which in turn is in fluid communication with the cabin;
• a turbine with an inlet and an outlet, wherein the inlet of the turbine is in fluid communication with an outlet of the cabin and the compressor is driven by energy produced in the turbine, and
• a secondary heat exchanger which transfers heat from air flowing through the outlet of the cabin to air in the secondary duct.

An aircraft air conditioning system:

• a work air passage having an inlet coupled to a pressurized air source and an outlet coupled to a cabin in an aircraft;
• a cooling air passage having an inlet coupled to a cooling air source;
• a main heat exchanger including a hot air passage and a cold air passage, wherein the hot air passage is included with the work air passage and the cold air passage is included with the cooling air passage;
• a secondary air flow passage including an inlet in fluid communication with the cooling air passage downstream of the cold air passage and an outlet in fluid communication with the work air passage downstream of the hot air passage, wherein cooling air flows from the cooling air passage, through the secondary air flow passage and mixes with work air flowing through the work air passage towards the cabin, and
• a compressor in the secondary air flow passage, wherein the compressor is configured to compress the cooling air flowing through the secondary air flow passage.