Device for expanding a fluid, wherein the device (1) is provided with an expander element (2) for expanding the fluid, a generator (3) and a transmission (4) between the two, characterized in that the generator (3) is a liquid-cooled generator and the expander element (2) is heated using liquid, wherein the device (1) is further provided with a common liquid circuit (8) for the generator (3) and the expander element (2), wherein the liquid circuit (8) comprises a liquid pump (10) which can pump up liquid from a liquid reservoir (11), wherein the liquid circuit (8) also comprises a liquid line (9) which runs from the liquid reservoir (11) and which incorporates the liquid pump (10), the generator (3) and the expander element (2).