Method for controlling a closed circuit operating according to a Rankine cycle and circuit using such a method

The method involves sweeping a heat exchanger (14) by a heat source (16) to heat working liquid. The hot fluid is expanded by an expansion unit (22). A cooling exchanger (26) is swept by cooling fluid (28) i.e. water, for cooling the working fluid. The working fluid is supplied within a closed circuit (10) in communication with ambient air after detection of vehicle crash situation. A valve unit is controlled with an opening (46) provided on the circuit communicating with the air, and comprises a valve (48) tilted between two extreme positions for closing and releasing the opening. An independent claim is also included for a closed circuit.