A turbine module for a heat engine, wherein the turbine module defines a working fluid flow duct between a turbine module inlet and a turbine module outlet configured to expand a working fluid as the working fluid passes along the working fluid flow duct; and the turbine module comprises: a first heat exchanger and a turbine rotor stage each provided in the working fluid flow duct; the first heat exchanger provided in flow series between the turbine module inlet and the turbine rotor stage; and the turbine stage being provided in flow series between the first heat exchanger and the turbine module outlet; the first heat exchanger defined by a wall having an external surface which is located in the working fluid flow duct; a heat supply unit which defines a portion of the working fluid flow duct in flow series between the turbine rotor stage and turbine module outlet; wherein the first heat exchanger is in heat transfer communication with the heat supply unit, and the first heat exchanger is configured such that it is operable to transfer heat received from the heat supply unit to the working fluid passing the first heat exchanger; the heat supply unit defines a heating medium flow passage for the transfer of a heating medium; and the heat supply unit defines a first inlet to the heating medium flow passage and an outlet from the heating medium flow passage; the first inlet configured to receive the heating medium from a heat source; characterised in that the heat supply unit defines a second inlet to the heating medium flow passage, the first inlet being spaced apart from the second inlet along the length of the heat supply unit, the heater outlet provided between the first inlet and the second inlet along the length of the heat supply unit, such that heating medium entering the inlets (160, 186) is exhausted via the outlet. wherein the turbine module defines a working fluid flow duct between a turbine module inlet and a turbine module outlet configured to expand a working fluid as the working fluid passes along the working fluid flow duct; and the turbine module comprises: a first heat exchanger and a turbine rotor stage each provided in the working fluid flow duct; the first heat exchanger provided in flow series between the turbine module inlet and the turbine rotor stage; and the turbine stage being provided in flow series between the first heat exchanger and the turbine module outlet; the first heat exchanger defined by a wall having an external surface which is located in the working fluid flow duct; a heat supply unit which defines a portion of the working fluid flow duct in flow series between the turbine rotor stage and turbine module outlet; wherein the first heat exchanger is in heat transfer communication with the heat supply unit, and the first heat exchanger is configured such that it is operable to transfer heat received from the heat supply unit to the working fluid passing the first heat exchanger; the heat supply unit defines a heating medium flow passage for the transfer of a heating medium; and the heat supply unit defines a first inlet to the heating medium flow passage and an outlet from the heating medium flow passage; the first inlet configured to receive the heating medium from a heat source; characterised in that the heat supply unit defines a second inlet to the heating medium flow passage, the first inlet being spaced apart from the second inlet along the length of the heat supply unit, the heater outlet provided between the first inlet and the second inlet along the length of the heat supply unit, such that heating medium entering the inlets (160, 186) is exhausted via the outlet. a first heat exchanger and a turbine rotor stage each provided in the working fluid flow duct; the first heat exchanger provided in flow series between the turbine module inlet and the turbine rotor stage; and the turbine stage being provided in flow series between the first heat exchanger and the turbine module outlet; the first heat exchanger defined by a wall having an external surface which is located in the working fluid flow duct; a heat supply unit which defines a portion of the working fluid flow duct in flow series between the turbine rotor stage and turbine module outlet; wherein the first heat exchanger is in heat transfer communication with the heat supply unit, and the first heat exchanger is configured such that it is operable to transfer heat received from the heat supply unit to the working fluid passing the first heat exchanger; the heat supply unit defines a heating medium flow passage for the transfer of a heating medium; and the heat supply unit defines a first inlet to the heating medium flow passage and an outlet from the heating medium flow passage; the first inlet configured to receive the heating medium from a heat source; characterised in that the heat supply unit defines a second inlet to the heating medium flow passage, the first inlet being spaced apart from the second inlet along the length of the heat supply unit, the heater outlet provided between the first inlet and the second inlet along the length of the heat supply unit, such that heating medium entering the inlets (160, 186) is exhausted via the outlet.