A heat exchanger for an ice machine has the form of a cylinder. In some embodiments, the cylinder is made from an extrusion of a metal such as an aluminum alloy. The heat exchanger includes inner and outer cylindrical walls and one or more refrigeration passages positioned between the inner and outer walls. The inner and outer walls are separated from each other by connecting structures defining the refrigeration passages. The heat exchanger can be extruded as a rectangular panel and subsequently formed into a cylindrical form. Alternatively, the heat exchanger can be extruded as a cylinder, or as an arcuate cylindrical segment in which several of such segments are subsequently joined together (as by welding) into a cylinder. Ice machines that feature ice formation on both the inner and outer walls of the cylinder are also disclosed.
