Abstract: A radiator comprising a number of parallel cooling medium pipes having fin stacks secured thereto in which a metal strip of the desired width dimensions is zigzag folded to form a stack having successive fin parts and side parts, each fin part being divided into stepwise parallel portions by additional fold areas parallel to the side parts.

Abstract: Apparatus for heat exchange between a fluid and air, having at least one heat exchanger element comprising a plurality of fluid tubes to which are secured heat transfer strips which define between them air passages having length .ltoreq. 25 mm., hydraulic diameter < 2 mm, with each element being at an angle of at most 45.degree. to the relative flow direction of the air before its entrance into the heat exchanger; at the rear of each element the strips are bent to extend in the discharge direction of the air issuing from the heat exchanger.

Abstract: An isothermal heating device comprises an annular tubular body providing a heating chamber for objects. Between the inner wall and the outer wall of this tubular body there is provided a plurality of separate ducts which are situated in a ring-shape about the heating chamber and which extend parallel to the tubular body axis. These ducts contain an evaporable heat transport medium and are in communication with each other preferably at one end of the tubular body. Such interconnection is in turn connected with a gas buffer reservoir containing an inert control gas.