Abstract: An apparatus for the conversion of mechanical energy or kinetic energy into heat, comprising a hydraulic pump (1) for supplying energy to a hydraulic liquid under pressure build-up, and an energy transformer (3) to which hydraulic liquid is supplied which liquid is heated in the energy transformer, and means (d, b) to recirculate the hydraulic liquid after release of heat to the pump (1). The energy transformer (1) includes a casing (9) having at least one inlet (15) and at least one outlet (17) for the hydraulic liquid and velocity increasing means or friction-generating restrictions (19, 21, 31) arranged between said inlet and outlet, whereby the kinetic or mechanical energy of the hydraulic liquid is converted into heat energy.