Structure of heat exchanger core without header plate

A heat exchanger core without a header plate, comprising:

• a plurality of like flat tubes,
• wherein each of the flat tubes is comprised of a pair of like rectangular plates, each of the plates having a bottom part which is predominantly planar, each of the plates having a pair of side walls only at each of a first pair of mutually opposed edges of the bottom part, the side walls extending along the first pair of edges, orthogonally to a plane of the bottom part, each of the plates having bulging parts contiguous with each of a second pair of mutually opposed edges of the bottom part, a direction of bulging of the bulging parts being opposite a direction in which the side walls extend along the first pair of edges, the pair of rectangular plates being joined together at longitudinal edges of the side walls to form a respective one of the flat tubes in which the side walls of the plates constitute side walls of the flat tube;
• wherein the plurality of flat tubes is arranged as a stack of the plates with the first pairs and second pairs of mutually opposed edges of the bottom parts in alignment;
• a casing in which the stack of flat tubes is arranged,
• wherein the casing is comprised of casing side walls overlying the side walls of the flat tubes and casing upper and lower walls overlying, respectively, an upper wall of the uppermost flat tube and a lower wall of the lowermost flat tube in the stack;
• a pair of like frames each received over an outer periphery of a respective edge portion of the stack comprised of exposed edges of the bulging parts,
• wherein each of the frames comprises:
• a peripheral flange portion having an inner periphery configured to match and be received over the outer periphery of said respective edge portion of the stack;
• and
• a peripheral packing holding portion formed at an inner edge of the flange portion and extending away from the flange portion orthogonally to said respective face of the stack;
• and
• wherein, at each of open ends of the casing an annular groove configured to receive a packing to provide a seal is formed between the packing holding portion of the frame and edges of the casing at the open end of the casing.