Downfired boiler having vertical heat transfer tubes

Claim 1

A water heating boiler comprising: upper and lower tube sheets, each of said tube sheets, being oriented in a horizontal plane; a vertically oriented circular combustion tube having upper and lower end portions thereof extending through said tube sheets; a burner located above said combustion tube; said burner comprising a vertically oriented burner tube positioned to discharge flames downwardly into said combustion tube; a plurality of vertically oriented heat transfer tubes extending between said tube sheets alongside said combustion tube; a gas reversal chamber communicating the lower end of said combustion tube with the lower ends of said heat transfer tubes, whereby hot combustion gases are caused to travel upwardly through said heat transfer tubes; a manifold connected to said upper tube sheet, in overlying relation to said heat transfer tubes, whereby said combustion gases are discharged from said heat transfer tubes into said manifold; a stack extending from said manifold; a tubular shell spanning said upper and lower tube sheets to define a water chamber surrounding said combustion tube and said heat transfer tubes; a water inlet connected to said tubular shell near said lower tube sheet; a water outlet connected to said tubular shell near said upper tube sheet; said circular combustion tube having a lower end edge located within said gas reversal chamber; and said lower end edge of said combustion tube being acutely angled to a horizontal plane, with the end edge area in nearest proximity to said heat transfer tubes being elevated above the end edge area remote from said heat transfer tubes.