Air heating apparatus and method

An improved air heating apparatus comprising:

• a longitudinally extending cylindrical outer casing having an air inlet at one end thereof and an air outlet at the other end thereof;
• a longitudinally extending cylindrical combustion drum disposed within said outer casing, said drum being sized relative said casing to define a flow-through annular passage therebetween and having the end closest to said air outlet of said outer casing closed;
• a frusto-conical combustion chamber wall disposed with said combustion drum at the end opposite said closed end including a cylindrical burner tube extending through the apex portion thereof;
• a combustion air inlet tube communicating with said frusto-conical combustion chamber;
• a plurality of spaced combustion gas outlet openings in said combustion drum extending in spaced relation around the base of said frusto-conical combustion chamber;
• an annular exhaust gas header disposed within said outer casing spaced from said closed end of said combustion drum, said header being connected by an exhaust gas conduit to an exhaust gas outlet in said outer casing;
• a plurality of spaced heat exchange tubes longitudinally extending in said flow-through annular passage between said outer casing and said combustion drum to surround said drum, one end of each tube being connected to a combustion gas opening in said combustion drum and the other end to said annular exhaust gas header;
• an axial blower positioned in said outer casing to move air through said flow-through passage from said air inlet in said outer casing to said spaced air outlet of said casing substantially in the same flow direction as the flow of combustion gas in said heat exchange tubes;
• a support member extending from the closed end of said combustion drum to slidably and matingly engage in the passage defined by said annular exhaust header;
• and,
• a support cradle mounted in the lower section of said outer casing to nestingly and supportively receive the lower of said heat exchange tubes to thus floatingly support said combustion drum surrounded thereby.

A method for heating ventilating air in a heater having a casing with a combustion drum disposed therein in spaced relation therefrom to create a flow-through passage around the drum, the drum having a closed downstream end and an upstream burner with a combustion gas header downstream of the closed downstream end of the drum comprising:

• directing a flame of combustion products toward the closed downstream end of said drum while evacuating said gases from the peripheral region of the drum at the upstream end of said drum to effect a reverse flow of combustion gases surrounding the flame within said drum at the upstream end of said drum;
• conducting said combustion gases in separate, enclosed fluid communication passages through said flow-through passage between and in spaced relation with both said drum and said outside casing to said header from the upstream end of said combustion drum;
• moving an air stream through said flow-through passage in separate surrounding heat exchange relation with said enclosed fluid combustion gases and;
• supporting said fluid communication passages to allow relative movement thereof.