Stacked plate heat exchangers

Claim 1

A HEAT EXCHANGER COMPRISING A STACK OF SHEET METAL PLATES, EACH OF SAID PLATES BEING CORRUGATED TO FORM TWO SETS OF U-SHAPED RIDGES, SAID TWO SETS DEFINING OPEN ENDED GROOVES ON OPPOSITE SIDES OF THE GIVEN PLATE, THE OPEN ENDS OF THE GROOVES OF SAID TWO SETS BEING OPPOSITELY DIRECTED, THE RIDGES OF EACH OF SAID PLATES BEING IN CONTACT WITH THE RIDGES OF AN ADJACENT PLATE, MANFOLDING SURROUNDING SAID HEAT EXCHANGER, BAFFLES IN SAID MANIFOLDING COOPERATING WITH THE LATTER IN DEFINING FOUR SEPARATE CHAMBERS OUTSIDE SAID STACK AND EXTENDING THE LENGTH OF THE LATTER, TWO OF SAID CHAMBERS BEING IN COMMUNICATION WITH OPPOSITE OPEN ENDS OF SAID GROOVES AS DEFINED BY ALTERNATE PLATES AND ADAPTED TO CONDUIT ONE FLUID, THE OTHER TWO OF SAID FOUR CHAMBERS BEING IN COMMUNICATION WITH OPPOSITE OPEN ENDS OF THOSE GROOVES DEFINED BY THE PLATES SEPARATED BY SAID ALTERNATE PLATES AND ADAPTED TO CONDUCT A SECOND FLUID, SAID MANIFOLDING DEFINING FOUR PORTS, EACH OF SAID FOUR PORTS COMMUNICATING WITH ONE OF SAID FOUR SEPARATE CHAMBERS, AND THE ARRANGEMENT BEING SUCH THAT EACH OF SAID FLUIDS WILL FLOW THROUGH ONE OF SAID PORTS, INTO ONE OF SAID CHAMBERS, THROUGH SAID STACK BETWEEN ADJACENT PLATES, INTO ANOTHER OF SAID CHAMBERS AND OUT FROM ANOTHER OF SAID PORTS.