Abstract: Heat exchanger, particularly for use as a rack evaporator in refrigerators or freezers, and process for manufacturing it. The heat exchanger is composed of a plurality of stacked shelves and comprises, for each shelf, at least one coil constituted by a tubular body extending along a path in which bends alternate with straight and substantially mutually co-planar portions, and a supporting and/or heat-exchange enhancing structure. In the heat exchanger according to the invention, the coils of two contiguous shelves are mutually connected by a tubular portion arranged transversely with respect to the direction along which the various shelves are stacked, starting from one corner of the overlying shelf down to one of the corners contiguous to the corresponding corner of the underlying shelf. The supporting and/or heat-exchange enhancing structure is disconnected from the branches of the coils joined to the tubular portion that mutually connects two coils in two different shelves.