Method of fabrication of a formed plate, counterflow fluid heat exchanger and apparatus thereof

A heat exchanger of the formed plate type with a stack of relatively thin material, spaced heat transfer plates. The plates of the heat exchanger are arranged to define sets of multiple counterflow fluid passages for two separate fluid media alternating with each other. Passages of one set communicate with opposed manifold ports on opposite sides of the core matrix. Passages of the other set pass through the stack past the manifolds in counterflow arrangement and connect with inlet and outlet portions of an enclosing housing. An assembly of two plates oppositely disposed establishes integral manifolds for one of the fluid media through the ports and the fluid passage defined between the plates. A third plate joined thereto further defines a passage for the second fluid media to flow between the inlet and outlet portions of the housing. The various fluid passages may be provided with flow resistance elements, such as fins, to improve the efficiency of heat transfer between adjacent counterflow fluids. In each set of aligned ports, collars alternately large and small, are formed in nested arrangement so that the ports formed by adjacent plates bridge the inner spaces between the plates. Such construction permits communication with the aligned ports of alternate fluid channels which are closed to the outside between the heat exchanger plates.In fabrication of a core matrix, the parts are formed and cleaned and the braze alloy is deposited thereon along the surfaces to be joined. The parts are then stacked in the natural nesting configuration followed by brazing in a controlled-atmosphere furnace. The brazing is readily carried out by reason of the sealing construction of the described nesting arrangement.