Vortical flow aerothermodynamic fireplace unit

Abstract

A heat exchanger particularly for use in a circulating hot air fireplace is constructed to induce vorticity in the flame and/or hot combustion gases at a position in proximity to a heat exchange surface to enhance residence time and thermal transfer to the circulating air. The vorticity pattern acts as a self-adjusting flow controller.

I claim: 
     
       1. A heat exchange structure for use .[.in a fireplace.]. .Iadd.with a firebox .Iaddend.of the type including an enclosure for a fire producing a hot thermally donative gas, said enclosure comprising side walls, a back wall, and a top wall, a flue opening in said top wall for exhausting said donative gas,   an outer enclosure comprising walls spaced outwardly from said fire enclosure walls and defining therebetween passages for a thermally recipient air,   a front wall extending downwardly from a front portion of said top wall and including a fire enclosure opening therein,   means communicating air from said thermally recipient air passages through said front wall, said means comprising a duct extending between junctures with said back and front walls through a central portion of said fire enclosure,   said structure further characterized in that   said duct has a bottom surface comprising a flame plate for exposure to said donative gas in said enclosure, said flame plate being slanted upwardly toward one of said junctures to define throughout the extent of said one juncture a laterally extensive thermally donative air vorticity area throughout which the donative air is induced to whirl in a stable vortex proximate to and in heat exchange relationship to said flame plate and said wall structure.   
     
     
       2. The structure of claim 1 wherein said flame plate includes a free edge spaced from a contiguous portion of said fire enclosure side wall to define a portion of said donative gas flow path therebetween, said flame plate being pitched in a direction transverse to said slant and toward said free edge whereby the axis of the induced vortical pattern is pitched in the general direction of gas flow and terminated beyond said free edge. 
     
     
       3. The structure of claim 2 wherein the cross-sectional area of said portion of said donative gas flow defined by said free edge and said contiguous enclosure wall portion bears a substantially equal relationship to the cross-sectional area of said exhaust flue opening. 
     
     
       4. The structure of claim 1 wherein said flame plate includes two free edges each spaced from the respective contiguous portions of said fire enclosure walls to define on either side of said duct a pair of portions of said donative gas flow paths therebetween, said pitch of said flame plate diverging laterally outwardly from a longitudinal central portion thereof to each said free edge. 
     
     
       5. The structure of claim 4 wherein the sum of the cross-sectional areas of said donative gas flow paths on either side of said duct bears a substantially equal relationship to the cross-sectional area of said exhaust flue opening. 
     
     
       6. The structure of claim 4 wherein the width of same flame plate is at least 1/4 the width of said flame enclosure. 
     
     
       7. The structure of claim 4 wherein said pitch is substantially 15°. 
     
     
       8. The structure of claim 7 wherein the ratio of said slant angle to said pitch is substantially within the range of 0.5 to 2. 
     
     
       9. The structure of claim 1 wherein said exhaust opening has its major area disposed downstream of said one juncture. 
     
     
       10. The structure of claim 9 wherein said exhaust flue opening has at least a portion thereof of substantially triangular cross-sectional configuration, the base of said triangular constituting said major area and the apex extending away from said one juncture toward the other of said junctures downstream thereof. 
     
     
       11. The structure of claim 1 wherein said flame plate includes lateral fins projecting downwardly into said fire enclosure and extending substantially parallel to and spaced from said junctures, said fins coacting with said flame plate surface to define additional areas for vorticity patterns of donative gas flow. 
     
     
       12. The structure of claim 1 wherein said front wall includes an additional portion comprising a barrier lip extending upwardly from said fire enclosure bottom, said barrier lip being adjustable in height. 
     
     
       13. The structure of claim 1 wherein said fire enclosure bottom includes spaced elongated hollow grates extending from front to rear, said grates comprising inverted channel shaped elements having at least a portion of the underside of said channel open through said bottom and being open to communicate with said passage for thermally recipient air. 
     
     
       14. The structure of claim 13 wherein said tubular grate elements include a draft opening in a side of said tubular element for communicating a portion of the accepted ambient room air with the lower portion of said fire enclosure. 
     
     
       15. The structure of claim 14 wherein said draft opening includes a flow control vane, said vane being controlled by a thermally sensitive element. 
     
     
       16. The structure of claim 1 wherein said front wall includes an additional portion comprising a barrier lip extending upwardly from said fire enclosure bottom, and wherein said fire enclosure includes spaced grate elements extending from front to rear, said grate elements each comprising a tubular member open through said barrier lip to accept ambient room air and open through said enclosure rear wall to discharge air to the rear said passage for thermally recipient air. 
     
     
       17. The structure of claim 16 wherein said tubular grate elements include air forcing means disposed within said tubular element near said opening through said barrier lip. 
     
     
       18. The structure of claim 1 wherein said front wall has a recess adjacent to said fire enclosure opening, said structure including a door assembly movable from a closed position covering said flame opening to a stored position within said additional opening. 
     
     
       19. The structure of claim 18 wherein said recess is disposed within said recipient air passage, a horizontal track is disposed within said recess, a carrier is slidably mounted upon said track, and said door assembly is pivotally mounted to and carried by said carriage for pivotal movement from said closed position to an open position aligned with said recess, and said carrier is movable from an extended to a retracted position within said recess to totally confine said door assembly within said recess. 
     
     
       20. The structure of claim 9 wherein said door assembly comprises a folding door composed of at least two panels, one said panel having one end pivotally supported by said carrier and another said panel being hingedly connected to the unsupported end of said one panel, a handle element rigidly secured to the hingedly connected end of said another panel whereby said handle may be used for movement of said door assembly between said closed, open and stored positions. 
     
     
       21. A heat exchange structure for use .[.in a fireplace.]. .Iadd.with a firebox .Iaddend.of the type including .Iadd.an .Iaddend.enclosure for a fire producing hot, thermally donative gas,   a flue opening for exhausting said gas,   means for conducting ambient room air in heat recipient relationship to said hot, thermally donative gas,   said structure characterized in the inclusion of   means to divert at least a portion of said thermally donative gas in a vortical pattern, said means comprising   a duct comprising a portion of said recipient gas conducting means, said duct having a bottom surface comprising a flame plate exposed to said donative gas in said enclosure to form a partial barrier to the flow of said donative gas to said flue opening,   additional partial barrier means comprising a surface extending toward said donative gas source and intersecting said bottom surface to form therewith a juncture defining a laterally extensive thermally donative air vorticity area throughout which donative air is induced to whirl in a stable vortex proximate to and in heat exchange relationship to said flame plate.