Abstract: The invention relates to a unit and a plant with such a unit as part thereof, based on the use of eddy currents for turning mechanical energy into heat energy for heating a fluid. The unit has a driver with at least one permanent magnet and is mechanically driven and takes effect on a rotor placed on the other side of a separating wall. The rotor is fitted with at least one permanent magnet and is turned by the magnetic attraction. The magnetic field, turning in relation to the separating wall, is at the same time responsible for causing eddy currents in the wall and for this reason for the production of heat which is given up to the fluid. In a preferred form of the invention, the rotor side of the unit is completely encapsuled and only one side of the separating wall is acted upon by the fluid so that even fluids that are strong or unstable chemicals may be heated.