Abstract: A heat generating unit for heating a liquid comprising a housing, at least one wedge, generally circularly shaped rotor, and means for rotating the rotor. The housing has a rotor cavity formed in a portion thereof with an inlet opening being formed through a portion of the housing intersecting the rotor cavity, and an outlet opening being formed in the housing intersecting the rotor cavity. Each wedge member is generally triangularly shaped in one cross section and includes a wedge base and a forward wedge wall. The rotor has an outer peripheral surface and is rotatingly disposed in the rotor cavity. The rotor has a forward face and a rearward face. Each wedge member is disposed generally between the forward face of the rotor in the forward end wall in the housing and each wedge member is positioned on the forward end wall so the wedge forward wall generally faces one direction of rotation of the rotor, the outlet in the housing is disposed generally near a central portion of the rotor.