Heat treating apparatus for liquids

Apparatus for heat treatment of a liquid at a predetermined temperature, the apparatus comprising at least two members and driving means for rotating at least one of the members relative to the other around a rotational axis, said members forming between them a narrow passage extending around the rotational axis and serving for through-flow of said liquid, said driving means being operable to effect relative movement between the walls defining the narrow passage, whereby liquid flowing through the passage is heated by internal friction in the liquid, said passage, as viewed in a section along the rotation axis, having a liquid inlet spaced from said axis and extending from said inlet, via a point spaced a greater distance from said axis than is said inlet, to a liquid outlet located closer to said axis than is said point, the apparatus being characterized in that one of said members is heat conducting and operable to transfer heat from liquid situated in the passage, and which has passed the passage part farthest from said axis, to liquid also situated in the passage but which is on its way to the passage part farthest from said axis, said members being formed so that most the temperature rise of the liquid flowing through said passage is caused by heat transfer through said heat conducting member, and so that the liquid is heated by internal friction substantially in a small part of the passage located farthest from the rotation axis, thereby providing for a rapid and uniform heat treatment of liquid at high temperature, including heating and subsequent cooling of the liquid.