FIELD OF THE INVENTION

The present invention relates to heat exchangers and, more particularly, to concentric tubular heat exchangers enclosing an ascending central heat source with a radially arranged heat exchange tube configuration inside the outer tube periphery.

BACKGROUND OF THE INVENTION

In the field of heat exchangers, several problems have arisen with some of the present designs. The biggest problem with virtually all heat exchangers is the lack of serviceability due to their rigid welded construction, preventing disassembly necessary to clean residual combustion byproducts from the internal surfaces of such heat exchangers. Additionally, the heat exchanger is generally located somewhat remotely from the heat source allowing a certain amount heat loss, depending on the particular design of the furnace.

In the field of heat exchangers, a need has arisen for a heat exchanger that is easily serviceable as well as extremely efficient. A major drawback of conventional heat exchangers is a lack of serviceability due to their rigid welded construction, preventing internal accessibility which is necessary to clean residual combustion byproducts from the internal surfaces of such heat exchangers. Additionally, conventional heat exchangers are generally located remotely from the heat source due to their enclosed configurations, which can allow for a loss of heat.

Most heat exchangers are mechanically welded and not conducive to disassembly and cleaning, reducing overall efficiency gradually throughout the life of the unit, which is particularly disadvantageous when used in conjunction with solid fuel and bio-mass type fuels which generally produce more combustion byproducts than liquid and gaseous fuels.

Conventional heat exchangers generally don't enclose the entire heat source resulting in greater heat loss.

Conventional heat exchangers generally require more space than the present invention for an equivalent amount of heat exchange.

It is thus a primary object of the present invention to provide a novel tubular heat exchanger.

It is further an object of the present invention to provide such a novel tubular heat exchanger which is of simple construction.

It is further an object of the present invention to provide such a novel tubular heat exchanger which can be quickly and easily internally accessed to facilitate convenient cleaning of the internal surfaces of the heat exchanger.

It is further an object of the present invention to provide such a novel tubular heat exchanger which is small in size, relatively inexpensive, and extremely efficient in its operation.

It is further an object of the present invention to provide such a novel tubular heat exchanger of an optimum design which surrounds and encloses a centrally located heat source.

It is further an object of the present invention to provide such a novel tubular heat exchanger design that can be easily expanded to increase the amount of heat exchange area by merely lengthening the tubular components.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a tubular heat exchanger wherein a central tube is employed to enclose an ascending internal heated fluid. The heated fluid is radially disbursed as it converges toward the internal surface of the top cover of the heat exchanger assembly. The heated fluid is forced outwardly below the top flange of the top cover assembly by the updraft flow of the heated fluid, which thereby forces the heated fluid downwardly, apportioning the heated fluid around radially spaced axially arranged heat exchange tubes which are inside of an outer tube, both of which are in sealed engagement with the annular flange of the top cover assembly. The heat exchange tubes concentrically surround the central tube of the heat exchanger assembly and attach at the bottom in sealing engagement with the bottom of the exhaust collection manifold. The heated fluid descends around the heat exchange tubes, gradually disbursing heat inwardly through the walls of the heat exchange tubes. The mostly cooled heated fluid is then collected and recombined below in the exhaust collection manifold which is attached in sealing relation with the exhaust outlet pipe or pipes which vents the mostly spent heated fluid into the atmosphere.

The heat transfer fluid is forced or drawn by mechanical means or other methods of draft induction into the space inside a lower plenum under the bottom of the exhaust collection manifold and a portion of it is forced or drawn into the equally spaced radially arranged heat transfer tubes which extend from the bottom of the exhaust collection manifold to the top of the annular top flange. As the heat transfer fluid ascends inside the heat exchanger tubes, it is gradually heated by the heat transferred from the descending heated fluid outside the heat transfer tubes, which heat is conducted through the walls of the heat exchange tubes. As the heat transfer fluid ascends toward the annular top flange, it is forced upwardly out of the heat exchange tubes to be recollected in the upper plenum which encompasses the top of the heat exchanger adjacent to the top cover from which additional heat is transferred into the heat transfer fluid. The now fully heated internal portion of the heat transfer fluid continues ascending into an upper plenum.

Additionally, another heat exchange function will be occurring simultaneously beginning with the heat transfer fluid entering the lower plenum below the exhaust collection manifold, wherein some of the heat transfer fluid will be directed around the outer surface of the exhaust collection manifold conducting some of the residual heat still remaining in the heated fluid inside the exhaust collection manifold as it recombines and exits the system from the exhaust collection manifold into the connected exhaust pipe. This outer portion of the heat transfer fluid initially ascends upwardly around the sides of the exhaust collection manifold and then is directed inwardly by an outer heat shield towards the outer tube of the heat exchanger. The heat exchange fluid then ascends vertically in the space surrounding the outer tube of the heat exchanger inside the cylindrical section of the outer heat shield which is radially spaced from the outer tube of the heat exchanger to provide an annular cavity between the outside of the outer tube of the heat exchanger and between the inside of the cylindrical section of the heat shield. As this outer portion of the heat exchange fluid ascends in the space provided between the outer tube of the heat exchanger and the cylindrical section of the heat shield, the heat exchange fluid is increasingly heated by the descending heated fluid inside the outer tube of the heat exchanger. As the outer portion of the heat transfer fluid ascends past the annular top flange which is connected to the outer tube of the heat exchanger, being fully heated, it then exits into the upper plenum area above the top cover of the heat exchanger to be recombined with the inner portion of the heat exchange fluid which is exiting upwardly out of the inside of the heat exchanger tubes for utilization in a heating system.

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which:

FIG. 1 is a longitudinal cross sectional view of a tubular heat exchanger assembly according to the teachings of the present invention;

FIG. 2 is a cross sectional view of a heat exchanger assembly of FIG. 1 according to section line 2-2 of FIG. 1;

FIG. 3 is a cross sectional view of a heat exchanger assembly of FIG. 1 and FIG. 2 according to 3-3 of FIG. 2;

FIG. 4 is an exploded isometric view of an elements depicted in FIG. 1, FIG. 2, and FIG. 3 to enhance the clarity of the relationship of the elements;

FIG. 5 is a longitudinal cross sectional view of a tubular heat exchanger assembly according to the teachings of the present invention;

FIG. 6 is a cross sectional view of a heat exchanger assembly of FIG. 5 according to section line 6-6 of FIG. 5;

FIG. 7 is a cross sectional view of a heat exchanger assembly of FIG. 5 and FIG. 6 according to 7-7 of FIG. 6; and

FIG. 8 is an exploded isometric view of an elements depicted in FIG. 5, FIG. 6, and FIG. 7 to enhance the clarity of the relationship of the elements.

For purposes of clarity and brevity, like elements and components will bear the same designations and numbering throughout the FIGURES.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the teachings of the present invention, there is shown in the drawings a heat exchanger assembly, generally designated 10. There is provided a tubular heat exchanger assembly wherein a central tube 11 is attached securely in rigid sealing engagement with the bottom of an exhaust collection manifold 16 assembly. The exhaust collection manifold 16 assembly is also is connected in sealing engagement via its end flanges 19 with the exhaust outlet pipes 17 and the lower plenum 18 by a series of spaced screws 20. Arranged in equally spaced configuration and in press fit side sealing engagement with the removable top flange 13 and also with the bottom of the exhaust collection manifold 16 are twenty-four radially spaced axially arranged heat exchange tubes 12. Also attached in face sealing relation to the removable top flange 13 by a series of radially spaced screws 21 is the removable top cover 14. The outer periphery of the removable top flange 13 is connected in sealing relation with the top of the outer tube 15. The bottom of the outer tube 15 is connected in rigid sealing relation with the top of the exhaust collection manifold 16. Surrounding the outer tube 15 of the heat exchanger core assembly is the outer heat shield 34 which is attached by its lower flange 35 to the tops of the end flanges 19 of the exhaust collection manifold 16 by a group of four fasteners 40. Also attached below the exhaust collection manifold 16 assembly to the end flanges 19 thereof by a series of spaced screws 20 is the lower plenum 18. The outer heat shield 34 assembly is spaced above the top of the exhaust collection manifold 16 and outwardly from the outer tube 15 to provide an external fluid flow path from the lower plenum 18 around and above the exhaust collection manifold 16 into the space between the cylindrical upper section of the outer heat shield 34 and the outer tube 15 of the heat exchanger core. This flow path then ascends into the upper plenum region 37 of the outer heat shield 34 assembly.

The basic embodiment of the heat exchanger assembly provides for a continuous internal flow passage for a heated fluid from above the separator plate 27 of the central tube 11, ascending vertically inside the central tube 11 to the space underneath the removable top cover 14 wherein the heated fluid is disbursed outwardly below the removable top flange 13 then descending axially around the heat exchange tubes 12 and from there flowing into the exhaust collection manifold 16 assembly and after that into the exhaust outlet pipes 17 and finally venting into the atmosphere. This internal flow path is sealed from the external areas around these core components allowing only the heat to be transferred by conduction through the walls of the components, particularly the heat exchange tubes 12, into the internally and externally flowing heat transfer fluid flowing internally through the heat exchange tubes 12 and also externally around the outsides of the outer tube 15, generally flowing in a direction opposite of the internal flow of the heated fluid. This heat transfer fluid is most often external air forced or drawn into the internal cavity of the lower plenum 18 by mechanical means such as a fan or fans or by convection draft. As previously stated, the heat transfer fluid basically flows in an external flow path around the heat exchanger core in a direction opposite from the flow direction of the internal heated fluid, which is the optimum flow relationship for the most efficient heat transfer.

Thus the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the present description as well as the appended claims, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

In accordance with the present invention, there is provided a tubular heat exchanger wherein a central tube 11 is employed to enclose an internal heated fluid which ascends inside the aforementioned central tube 11. The heated fluid is then radially disbursed as it ascends toward the internal surface of the top cover 14 assembly of the heat exchanger assembly. The heated fluid is then forced or drawn outwardly to the internal space under the removable top flange 13 by the updraft flow of the heated fluid, which thereby forces the heated fluid downwardly into the space outside of the central tube 11 and inside of the outer tube 15, apportioning the heated fluid around equally radially spaced axially arranged heat exchange tubes 12 which are in sealed engagement with the annular removable top flange 13 of the top cover 14 assembly to which connected to the top cover 14 in sealed engagement by a series of radially spaced screws 21. The aforementioned heat exchange tubes 12 concentrically surround the central tube 11 of the heat exchanger assembly, radially spaced from the central tube 11, and attach at the bottom in sealing engagement with bottom of the the exhaust collection manifold 16. The heated fluid descends around and through the gaps between the heat exchange tubes 12, gradually transferring heat inwardly through the walls of the heat exchange tubes 12 as it descends. The mostly cooled heated fluid is then collected and recombined below in the exhaust collection manifold 16 which is attached in sealing relation with the outer tube 15 as well as the exhaust outlet pipes 17 from which the mostly spent heated fluid is exhausted into the atmosphere.

The heat transfer fluid is forced or drawn by mechanical means or other methods of draft induction, into the space inside the lower plenum 18 under the bottom of the exhaust collection manifold 16 and is forced or drawn into the bottoms of the radially spaced axially arranged heat exchange tubes 12 which extend from the bottom of the exhaust collection manifold 16 to the top of the annular removable top flange 13 of the top cover 14 assembly. As this inner portion of the heat transfer fluid enters and ascends inside the heat exchange tubes 12, it is gradually heated by the heat transferred from the descending heated fluid outside the heat exchange tubes 12 which is conducted inwardly through the walls of the heat exchange tubes 12. As the heat transfer fluid ascends inside the heat exchange tubes 12 towards the annular removable top flange 13, it is forced or drawn upwardly out of the heat exchange tubes 12 to be collected and recombined in the upper plenum region 37 of the outer heat shield 34 which encompasses the top of the heat exchanger adjacent to the top cover 14 assembly, drawing even more heat radiating from the top cover 14 assembly, from which the now fully heated internal portion of the heat transfer fluid continues ascending into the upper plenum region 37 of the outer heat shield 34.

Additionally, another heat exchange function will be occurring simultaneously beginning with the heat transfer fluid entering the lower plenum 18 below the exhaust collection manifold 16 wherein the outer portion of the heat transfer fluid will be directed around the outer surfaces of the exhaust collection manifold 16 conducting some of the residual heat still remaining in the mostly spent heated fluid as it recombines and exits the exhaust collection system from the exhaust collection manifold 16 into the connected exhaust pipe. This aforementioned outer portion of the heat transfer fluid initially ascends upwardly around the outsides of the exhaust collection manifold 16, within the plenum, and then is directed inwardly by the lower flanged section of the outer heat shield 34 towards the outer tube 15 of the heat exchanger core. The heat exchange fluid then ascends axially in the annular space surrounding the outer tube 15 of the heat exchanger core inside the cylindrical section 36 of the outer heat shield 34 which is radially spaced outwardly from the outer tube 15 of the heat exchanger to provide an annular space between the outside of the outer tube 15 of the heat exchanger core and between the inside of the cylindrical section 36 of the outer heat shield 34. As the aforementioned external portion of the heat exchange fluid ascends in this space provided between the outer tube 15 of the heat exchanger core and the cylindrical section 36 of the outer heat shield 34, the heat transfer fluid is increasingly heated by the descending heated fluid inside the outer tube 15 of the heat exchanger conducting heat outwardly through the wall of the outer tube 15. As the external portion of heat transfer fluid ascends past the annular removable top flange 13 of the top cover 14 assembly, being sufficiently heated, it then enters into the upper plenum region 37 of the outer heat shield 34 above of the heat exchanger core to be recombined with the internal portion of the heat exchange fluid which is exiting upwardly out of the insides of the heat exchanger tubes. This now recombined and fully heated heat exchange fluid ascends out of the upper plenum region 37 of the outer heat shield 34 for utilization in a heating system.

It should be understood that while the preferred embodiment of the present invention utilizes both an inner portion and an outer portion of the heat exchange fluid from the lower plenum 18 to the upper plenum region 37 to optimize efficiency, that either the inner portion or the outer portion of the heat exchange fluid can facilitate a complete heat exchange system by themselves.

The heat exchanger assembly can utilize either an internal or external heat source for the heated fluid, as explained below.

As shown in FIGS. 1,2,3,4, an optional inlet pipe 24 can be employed to provide an entrance for heated fluid from an external source such as an external combustor or biofuel gasifier into the central tube 11 through the attached separator plate 27, whereby additional air can be added via the optional air inlet holes 38 in the separator plate 27 to enable a secondary combustion process within the central tube 11 above the separator plate 27, which may or may not require a secondary ignition system, depending on the application. The use of a secondary combustion process in conjunction with biomass type fuels is desirable to promote complete combustion to reduce or eliminate harmful exhaust emissions.

Also shown in FIGS. 5, 6, 7, 8 is an optional typical fuel combustion arrangement for the heated fluid source featuring a fuel line 30, fuel nozzle 28, ignition electrodes 32 and combustion air inlet holes 38 extending through the separator plate 27 of the central tube 11 assembly assembly, which, in conjunction with the tubular heat exchanger assembly, essentially form a complete furnace.

The unique design of the present invention provides convenient access to the internal surface areas of the heat exchanger via the removable top cover 14 assembly of the center tube assembly as well as the removable exhaust outlet pipes 17 of the exhaust collection manifold 16 assembly. This convenient internal accessibility allows for simple cleaning of the internal surfaces of the heat exchanger using brushes and various other types of common utensils to remove built up residual combustion byproducts from the internal surfaces of the tubes and other components of the heat exchanger to maintain maximum heat transfer efficiency throughout the life of the unit.

Also to be noted is that as with the Type 1 heat exchanger assembly, the present invention referred to as the Type 2 heat exchanger assembly configuration has also been designed to be utilized in conjunction with gas turbine powered electrical generator basically according to the teachings of the previous invention, but not in any way limited to that application.

Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.

Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims.