Abstract: A closed-loop Brayton cycle rotating machine is provided with a sealed circuit in which a working fluid flows. This circuit comprises a compressor for compressing the working fluid, a hollow cylindrical recovery heat exchanger for preheating the compressed working fluid, a H.T. boiler for heating the preheated compressed working fluid to a high temperature, a turbine for generating mechanical energy by expanding the compressed H.T. working fluid through the turbine, and downstream of and axially aligned with the turbine, an exhaust pipe for the expanded H.T. working fluid. The circuit is configured so that the expanded H.T. working fluid constitutes a heat source of the recovery heat exchanger. The boiler is in the general shape of a hollow cylinder and is interposed coaxially between the axial turbine/exhaust pipe assembly and the recovery heat exchanger.