Patent ID: 7594326

Claim:
A method of making a heat exchanger, comprising: a) cutting two portions out of a flat piece of metal to form two notches, the notches being cut on opposite sides of said flat piece, and folding the piece of metal back and forth upon itself to form a monolith so that each notch defines an opening which provides access to an interior region of the monolith when the piece of metal has been folded, b) inserting a comb having teeth into folds of the monolith adjacent a first end of the monolith, the comb having a spine which extends in a direction opposite the teeth and which defines a sidewall of a duct, c) providing a second piece of metal in a vicinity of said spine, but spaced apart from said spine and forming a second sidewall of said duct, and d) inserting a duct box onto said first end of the monolith, wherein the duct box, together with the second piece of metal and the spine of the comb, defines the duct connected to the monolith.