Method for recovering heat losses of an internal combustion engine

A method for recovering heat dissipated by an internal combustion engine (2) in a recovery circuit including a pump unit (3), a heat exchanger (4), an expansion device (5), a condenser (6) and a first control unit (7) for controlling the pump unit (3) and first temperature and pressure sensors (7.1, 7.2) connected to the first control unit (7) for sensing the temperature and pressure of the working fluid leaving the heat exchanger (4) and a second control unit (8) for controlling a lower process pressure (pu) as well as a second pressure sensor (8.1) for sensing the lower process pressure, said method comprising the following steps:

• compressing a liquid working medium (A) from a the lower process pressure (pu) and a first temperature (T1) to an upper process pressure (po) and a second temperature (T2) in the pump unit (3);
• vaporizing the working medium (A) in the heat exchanger (4) by transferring heat from a hot medium containing heat dissipated by the internal combustion engine (2) to the working medium (A), whereby the working medium (A) is heated to a third temperature (T3) while being vaporized during passage through the wet vapor area (NG) of a vapor pressure-enthalpy diagram to a superheat area (TG);
• expanding the working medium (A) approximately to the lower process pressure (pu), which is adjustable depending on engine operating conditions so that the working fluid is expanded and its temperature is reduced to a point which is close to a fourth temperature (T4) in the expansion device (5), while generating mechanical energy;
• condensing the working medium (A) in the condenser (6) and
• transferring the working medium (A) to the pump unit (3),
• adjusting the upper process pressure (po) by the first control unit (7) in an operating region of the internal combustion engine (2) to such a value that the working medium (A) is expanded in the expansion device (5) approximately to a point close to the saturated vapor limit (S) and
• adjusting the lower process pressure (pu) by the second control unit in an operating range of the internal combustion engine within a pre-settable pressure range by controlling the load on the expansion device (5).