Self-contained exhaust hood with heat exchanger and method of exhausting air

Claim 1

An exhaust system for the removal of heated, fouled air from a defined work area in a room having air tempering equipment, and having a source of said fouled air located in said defined work area, comprising: a hood structure defining a central, downwardly open space, and first and second chambers adjacent said central space forwardly and rearwardly thereof, respectively; means for supplying make-up air to said hood structure at a first predetermined rate; said first chamber being in communication with said make-up air supply means, and having a heat-insulated front wall and a heat-conducting rear wall; means for exhausting the mixture of make-up air and fouled air from said hood structure at a second predetermined rate; said second chamber being in communication with said exhausting means and having an upwardly and forwardly slanted front wall, and also being in communication with said central space through an aperture in the last-mentioned front wall; and means in said second chamber for removing contaminants from said mixture of make-up air and fouled air; there being provided in the lower portion of the rear wall of said first chamber a diagonally downwardly and rearwardly inclined air flow directing means for projecting all of said make-up air through a portion of said central space toward said fouled air source, the angle of inclination of said directing means being such that said make-up air mixes with the rising heated, fouled air in a zone located below said bottom plane but at a substantial distance above said fouled air source and that the mixture, upon re-entering said central space, in part passes through said removing means to said exhausting means and, to another part, circulates along the upwardly and forwardly slanted front wall of said second chamber towards and along said heat-conducting rear wall of said first chamber so as to pre-heat the make-up air passing through said first chamber.