A thermodynamic apparatus (10) comprising a compressor module (100), a turbine module (200), and a regenerative heat exchanger (300) centred on a central axis (12). The compressor module (100), turbine module (200) and regenerative heat exchanger (300) are arranged in series along the central axis (12) such that the regenerative heat exchanger (300) is provided between the compressor module (100) and the turbine module (200).