A heating arrangement for heating a fluid, the arrangement comprising an elongate housing having a main axis. An inner chamber (21) for a first fluid surrounds the axis. A plurality of axially extending fins (22) project into the inner chamber. An exhaust gas inlet which receives exhaust gas, for example, from a Stirling engine, is provided at one end of the inner chamber. A supplementary burner (20) at the opposite end of the chamber is arranged to fire radially outwardly on to the fins. An outer chamber (30) for a second fluid surrounds the inner chamber.