Patent ID: 7322405

Claim:
A multi-pipe heat exchanger apparatus comprising a body unit and a plurality of heat conductive pipes provided in said body unit, first passages for a first fluid being formed in said heat conductive pipes, second passages for a second fluid being formed between said heat conductive pipes, said body unit comprising flanges provided at opposite ends thereof, an outer wall plate and an inner wall plate, said heat conductive pipes being provided at said flanges at predetermined angular intervals, wherein each of said heat conductive pipes has opposite walls limiting the passage width of said first passage, and said walls are formed along involute curves; each of said second passages is formed by said walls of adjacent heat conductive pipes formed along said involute curves; an outer circumferential surface of each of said heat conductive pipes is joined to said outer wall plate of said body unit, and an inner circumferential surface of each of said heat conductive pipes is joined to said inner wall plate of said body unit.