Method of making tubular heat exchangers

Claim 1

A method of assembling multiple tubes to longitudinally spaced apart headers to form the core of a tubular heat exchanger, including the steps of: (a) providing multiple tubes and headers to mount said tubes, at least one of said headers being made as a plate-like part out of a heat recoverable metal and having front and back external faces; (b) drilling a multiplicity of closely spaced apart through holes in said one header each to a diameter somewhat less than the outside diameter of a tube to be installed therein, the drilled holes being separated by relatively narrow ligaments of solid plate material; (c) lowering the temperature of said header and at a temperature below a determined transition temperature subjecting the hole walls to a deforming pressure enlarging said holes each to a diameter somewhat greater than the outside diameter of a tube to be installed therein, said deforming pressures being applied individually to said holes to displace deformed material in a longitudinal sense of said header without appreciable transference of stress into said ligaments toward the walls of adjacent holes; (d) assembling the heat exchanger core including the step of installing tube ends in respective enlarged holes in said one header, tube end portions extending substantially through said holes; and (e) raising the temperature of said header to and above said transition temperature whereupon deformed material of said header at each hole location returns or attempts to return to its original configuration independently of and simultaneously with deformed material at other hole locations and in the process grips a respective tube forming a seal and a bond therewith.

Claim 2

A method of assembling multiple tubes to longitudinally spaced apart headers to form the core of a tubular heat exchanger, including the steps of: (a) providing multiple tubes and headers to mount said tubes, at least one of said headers being made as a plate-like part out of a heat recoverable metal and having front and back external faces; (b) drilling a multiplicity of closely spaced apart through holes in said one header each to a diameter somewhat less than the outside diameter of a tube to be installed therein, the drilled holes being separated by relatively narrow ligaments of solid plate material; (c) lowering the temperature of said header and at a temperature below a determined transition temperature subjecting the hole walls to a deforming pressure enlarging said holes each to a diameter somewhat greater than the outside diameter of a tube to be installed therein, said deforming pressures being applied individually to said holes to displace deformed material in a longitudinal sense of said header without appreciable transference of stress into said ligaments toward the walls of adjacent holes; (d) assembling the heat exchanger core including the step of installing tube ends in respective enlarged holes in said one header, tube end portions extending substantially through said holes; and (e) raising the temperature of said header to and above said transition temperature whereupon deformed material of said header at each hole location returns or attempts to return to its original configuration independently of and simultaneously with deformed material at other hole locations and in the process grips a respective tube forming a seal and a bond therewith.

Claim 10

A method of assembling multiple tubes to longitudinally spaced apart headers to form the core of a tubular heat exchanger, including the steps of: (a) providing a tube element and a header element to mount the tube, one thereof being made of a heat recoverable material, the header having a hole to receive the tube and the hole and tube being dimensioned for an interference fit; (b) lowering the temperature of the element made of heat recoverable material and at a temperature below a determined transition temperature subjecting said element to a deforming pressure whereby the tube may be inserted in the header hole with a non-interference fit. (c) Inserting the tube in said header; and (d) raising the temperature of the deformed element to and above a transition temperature at which it reverts to its original pre-deformed configuration and accomplishes an interference fit of the tube in its accommodating hole.

Claim 11

A method of assembling multiple tubes to longitudinally spaced apart headers to form the core of a tubular heat exchanger, including the steps of: (a) providing a tube element and a header element to mount the tube, one thereof being made of a heat recoverable material, the header having a hole to receive the tube and the hole and tube being dimensioned for an interference fit; (b) lowering the temperature of the element made of heat recoverable material and at a temperature below a determined transition temperature subjecting said element to a deforming pressure whereby the tube may be inserted in the header hole with a non-interference fit. (c) Inserting the tube in said header; and (d) raising the temperature of the deformed element to and above a transition temperature at which it reverts to its original pre-deformed configuration and accomplishes an interference fit of the tube in its accommodating hole.