A device for evaporating a liquid such as liquid fuel. The device comprises: a shell; means for supplying heat to the shell; a porous wick located in the shell so that there is a gap between an outer surface side of the porous wick and an inner surface of the shell; means for supplying liquid to the porous wick; and an outlet in the shell for vapour produced in the gap by the application of heat from the shell to the liquid in the wick.