Abstract: A plate heat exchanger condenser-evaporator with a heat-exchanger block having a number of heat-exchanger plates with fluid-conducting structures. The heat-exchanger block includes first and second outer surface opposite each other, and third and fourth outer surface opposite each other. The fluid-conducting structures of first heat-exchanger plates have first and second openings not covered by fluid feed or fluid-collecting lines. The fluid-conducting structures of second heat-exchanger plates run between a fluid feed line and a fluid-collecting line each arranged on the heat-exchanger block. The fluid feed line may be on the first outer surface with first openings of the fluid-conducting structures of the first heat-exchanger plates in a region of the first outer surface not covered by the fluid feed line or in a first region of the third outer surface and fourth outer surface. A process for low-temperature air separation is also described.