Patent ID: 7581593

Claim:
A system for heating a fluid stream in a wellbore, said system comprising: (a) a tubing string disposed in said wellbore, said tubing string comprised of a plurality of tubular members through which fluid can flow; and (b) a heating apparatus, said heating apparatus comprising a mixing section with an inlet and outlet, said outlet in fluid communication with a tubular member; and a heating section disposed adjacent said inlet of said mixing section, said heating section capable of generating heat for transfer to a fluid passing therethrough, (c) wherein said heating section comprises (i) an elongated, equiangular and equilateral polygonal heat transfer tube characterized by at least six flat contiguous sides and a plurality of radially disposed fins extending from said sides, said heat transfer tube having an inner surface and an outer surface and (ii) a tubular shroud surrounding said elongated heat transfer tube, wherein said heat transfer tube is co-axially mounted in said tubular shroud so as to form an annular space between said outer surface of said heat transfer tube and said shroud, thereby defining a first flowpath for said fluid stream, said inner surface of said heat transfer tube defining a second flowpath for said fluid stream; (d) wherein said mixing section comprising a mixing chamber configured to cause said first and second flowpaths to converge, wherein said mixing chamber is surrounded by a tubular shroud co-axially disposed around said mixing chamber.