This patent is directed to an external air conditioning system connected to a parked airplane. A heat exchanger can be connected in fluid communication with the upstream and downstream ports to receive a flow of coolant liquid that results from a differential pressure between the upstream and downstream ports because of the pressure drop caused by the flow restrictor. The case is attached to the outer shaft, projects toward the same direction as the reaction receiver, is so sized as to be hidden by a contour of the reaction receiver and is so positioned as to be hidden behind the reaction receiver when seen from the forward end side of the engaging portion. The housing further includes a second opening in fluid communication with the tubing system.