An environmental control system, comprising: a refrigerant circuit with a pump segment and an evaporator segment; an evaporator arranged along the evaporator segment and in fluid communication with of the refrigerant circuit; and a coolant circuit extending through the evaporator and thermally coupled to the refrigerant circuit by the evaporator, wherein the coolant circuit has a first segment and a second segment arranged in parallel to transfer a first heat flow from a first zone to a first liquid coolant portion traversing the first segment and transfer a second heat flow from a second zone to a second liquid coolant portion traversing the second segment of the coolant circuit; wherein: a liquid coolant is disposed within the coolant circuit; and a refrigerant is disposed within the refrigerant circuit, wherein the refrigerant is fluidly separated from the liquid coolant and in thermal communication with the liquid coolant through the evaporator; characterised in that the system comprises an ejector fluidly coupling the pump segment of the refrigerant circuit with the evaporator segment of the refrigerant circuit, wherein the ejector comprises: a duct having a converging portion with a primary fluid inlet a diverging portion with an outlet, the converging and diverging portions connected via a throat; a secondary fluid inlet that fluidly couples the refrigerant evaporator segment to the converging portion; a nozzle supported within the converging portion of the duct with a nozzle outlet located within the converging portion, the nozzle fluidly coupling the primary fluid inlet to the ejector, wherein the outlet fluidly couples the converging portion of the duct to the evaporator segment and the pump segment of the refrigeration circuit via a condenser; and the system further comprises an overboard air duct in fluid communication with the condenser and in thermal communication therethrough with refrigerant traversing the condenser. a refrigerant circuit with a pump segment and an evaporator segment; an evaporator arranged along the evaporator segment and in fluid communication with of the refrigerant circuit; and a coolant circuit extending through the evaporator and thermally coupled to the refrigerant circuit by the evaporator, wherein the coolant circuit has a first segment and a second segment arranged in parallel to transfer a first heat flow from a first zone to a first liquid coolant portion traversing the first segment and transfer a second heat flow from a second zone to a second liquid coolant portion traversing the second segment of the coolant circuit; wherein: a liquid coolant is disposed within the coolant circuit; and a refrigerant is disposed within the refrigerant circuit, wherein the refrigerant is fluidly separated from the liquid coolant and in thermal communication with the liquid coolant through the evaporator; characterised in that the system comprises an ejector fluidly coupling the pump segment of the refrigerant circuit with the evaporator segment of the refrigerant circuit, wherein the ejector comprises: a duct having a converging portion with a primary fluid inlet a diverging portion with an outlet, the converging and diverging portions connected via a throat; a secondary fluid inlet that fluidly couples the refrigerant evaporator segment to the converging portion; a nozzle supported within the converging portion of the duct with a nozzle outlet located within the converging portion, the nozzle fluidly coupling the primary fluid inlet to the ejector, a duct having a converging portion with a primary fluid inlet a diverging portion with an outlet, the converging and diverging portions connected via a throat; a secondary fluid inlet that fluidly couples the refrigerant evaporator segment to the converging portion; a nozzle supported within the converging portion of the duct with a nozzle outlet located within the converging portion, the nozzle fluidly coupling the primary fluid inlet to the ejector, wherein the outlet fluidly couples the converging portion of the duct to the evaporator segment and the pump segment of the refrigeration circuit via a condenser; and the system further comprises an overboard air duct in fluid communication with the condenser and in thermal communication therethrough with refrigerant traversing the condenser.