US2696369A - Heat exchanger - Google Patents

Description

Dec. 7, 1954 J. P. MORLEY ET AL HEAT EXCHANGER Filed Jan. 4, 1951 HEAT EXCHANGER Application January 4, 1951, Serial No. 204,370 Claims. (Cl. 257-164) This invention relates to a heat exchanger.

An object of the invention is the provision of a heat exchanger having a novel construction for producing unusually effective heat transfer between its interior and exterior.

Another object is the provision of a heat exchanger including a front heat transfer wall for exposure to a space to be heated and so formed as to provide increased heat transfer surface, and including a novel arrangement for directing gases flowing therethrough into contact wtih the front wall with consequent more effective heat transfer between the interior and exterior of the device.

.Still another object is the provision of a heat exchanger for use in a heater adapted to be arranged in vertical position for upward flow of heated gases therethrough, the walls of which converge upwardly and thereby effectively force the gases into heat transfer contact with the walls.

A further object is the provision of a heat exchanger adapted to be arranged in vertical position for upward flow of gases therethrough, provided with baflles for forcing the gases into heat transfer contact with the walls of the exchanger, the walls of which converge'upwardly and thereby aid in the baffling effect, whereby a lesser number of baffles is required than would be required for a similar baffling effect in a heat exchanger of uniform dimension.

Another object of the invention is the provision of a heat exchanger of novel construction having upright walls, one of which is vertical and the other inclined from the vertical toward the vertical wall, the inclined wall having baffles mounted therein forming constructions with the vertical Wall whereby heated gases on flowing upward therethrough are effectively bafiled by the inclined wall and baflles toward the vertical wall for efficient heat transfer contact therewith.

A further object adapted for upward flow of heated gases therethrough having vertical corrugations therein and including a novel baffle arrangement for bafiling the heated gases into efiicient heat transfer contact with the vertical corrugations.

Other objects will be apparent from the following descriptiontaken in conjunction with the accompanying drawings in which:

is the provision of a heat exchanger United StatesPatent O Figure l is a perspective view of a unitary heater I embodying the novel tion;

Fig. 2 is slightly enlarged front elevational view' of the heat exchanger unit;

Fig. 3 is a top view of the heat exchanger unit; and

Fig.4 is a vertical sectional view taken on line 44 of Fig. 2.

A heater and heat exchanger structure, embodying the principles of our invention, is shown as a whole in Fig. l and, as will be seen therein, takes the form of a unitary structure adapted to be set in place as a unit in location for heating. The heater may be formed principally of sheet metal members secured together to form the unitary structure. Heaters of this type are sometimes referred to as wall heaters and are especially adapted for emplacement in a wall niche which may be enclosed by an-open-work grill (not shown) partially concealing the heater in the niche, but freely permitting radiant and convected heat therethrough. The heater however may be placed in any desired location or heating arrangement other than a wall niche as desired.

Theheater as shown in Fig. 1 includes a heat exheat exchanger unit of our inven- 2 changer unit 10 mounted in a heater casing or shell 12, together making up the unitary heater referred to, adapted for emplacement in a wall niche or other appropriate location. The heater casing or shell 12 includes a back wall 16, side walls 18 and is open at the front whereby when the heater is disposed in a desired heating location the open front is directed toward the, space to be heated, such as for example being directed outwardly of a niche when the heater is placed therein. The shell 12 includes a reflector element 20, extendingthe greater part of the height thereof, which may also be of sheet metal making up a form of liner for the shell and curved to present a concave reflecting surface directed outwardly through the The concave surface of the 1 open front of the heater. reflector may be polished for more effective heat reflection. The reflector 20 is secured to the appropriate portions of the shell 12 by any desired means, such as by spot welding.

The novel heat exchanger unit 10 is stantially vertical position in the shell tion that the reflector 20 partially surrounds it for reflecting heat therefrom through the open side of the heater. The details of construction of the heat exchanger are shown in Figs. 2, 3 and 4 and include a front 24, a back wall 26 and side walls 28. The back and side walls may be formed from a single integral piece for convenience if desired. The front wall 24 is corrugated as shown most clearly in Figs. 2 and 3, for producing an effect to be described later herein, having vertical or upright corrugations 30 extending throughout the full vertical length of the heat exchanger. The corrugations preferably are of angular form with adjacent wall surfaces thereof making approximately 90 angles. At the lateral edges the front wall is provided with flanges 32 for engagement with cooperating flanges 34 on the side Walls 28, the flanges 34 being of lesser transverse dirnension than the flanges 32, whereby the flanges 32 may be rolled over and crimped on the flanges 34, if desired, for forming trim appearing seams. If desired, the respective flanges 32 and 34 may also be spot welded for more rigidly securing the parts of the heat exchanger together. The back wall 26 of the heat exchanger is inclined from the vertical toward the front wall as show in Figs. 3 and 4 forming an upwardly converging chamber-like interior or passage for the flow of gases therethrough, the bottom and top of the heat exchanger being open for that purpose. As viewed in Fig. 4the front wall 24 is disposed vertically indicating the position assumed by the heat exchanger when mounted in the structure 12 as will be referred to later. The innermost points of the corrugations 30 are disposed substantially in the plane of the inner surface of the flanges 32, this plane being the plane of connection between the front wall and the counterpart made up of the back and side wa s.

A novel bafiling effect of the gases is produced in the heat exchanger unit for bringing about greater heat transfer between the gases and the front wall 24 of the heat exchanger. To this end a plurality of baflles 36, in this case two, are mounted in the interior or chamber of the heat exchanger unit. The baffles 36 take the disposed in subform of substantially horizontal partitions provided with vertical flanges where convenient for securement to the back wall and the side walls, as desired, so that the partitions or baffles are in substantially gas-tight engagement with the back and side walls. The baflles or partitions 36 terminate, or have their extended forward edges adjacent the innermost points of the corrugations 30, thus forming constrictions in the passage of the heat exchanger which, in the construction disclosed, consist of the spaces between the corrugations, with the result that gases flowing past the partitions are baflied or directed through the spaces between the corrugations, producing a scouring or sweeping effect on the front wall'24, carrying away the insulating film that tends to form on the wall, and thereby producing more efficient heat transfer between the gases and the wall.

The heater structure is provided with appropriate structural elements for mounting the heat exchanger horizontal panel or floor 38,

12 in such pos1- wall and in elevated position with respect to the bottom of the structure or the surface on which the structure rests. Such elements also include an upper horizontal panel 40 disposed adjacent to but below the top of the heater and secured to the shell are provided with appropriate openings for receiving the respective ends of the heat exchanger 22. The particular means for mounting the heat exchanger in the openings may take any desired form, .such asv for example spot welding the exchanger is, thus maintained in vertical position, when considered as a unit, the front wall 24 being vertical I the vertical toward the front .wall at, the top.

Means vfor directly supporting the heater structure, and for mounting a burner, comprises a stand :42 "disposed belowv and engaging the undersurface of the panel 38, made upof legs or upright members 44 upon which is secured a deck 46 secured to or formed integral with'the back wall 16. The deck 46 is utilized for inclosing a conventional burner 48 such as, a gas burner positioned for emitting heated gases into. the. opening in the panel 38 and therefore into the interior of the heat exchanger unit 10, which burner may be secured to the stand 42.

The heater when placed in location for heating is disposed in proper position for directmgthe heated gases or fluegases out through a stack (not shown).

14 of the heater by any .preferred means, such as by spot welding. The panels 38 and 40 respective interengaging elements. The heat.

upright or substantially 1 and. the rear wall being inclined from advantages attainable by the use exchanger.

. inner surfaces of the It occasionally happens that downdrafts through the stack occur and it is desired to prevent such downdrafts from being propagated through the heat'exchanger and into the burner. For this purposea draft diverter 49 is adjacent the top'of the heater and mounted above the heatexchanger in connection with other elements'of con struction which include in the upper end of the shell 14. Thepariel 50 as shown may have a peripheral flange 52 mounting the panel in the shell, the flange being secured to the Walls of the shell as by spot welding. The panel 50 is provided with a central opening 54'for permitting flow of gases therethrough and so through the stack. .The panel 50, as will be noted, is spaced above the upper panel 40, being additionally supported by supplemental members 58 secured between the two panels and and spaced transversely of the heater, the panels .40 and 0 forming a space therebetween indicated generally at 56. The draft diverter proper 49 takes the form of a horizontal baflle or plate 49 disposed in vertical alignment with the opening 54 and preferably also in vertical alignment with the upper end of the heat, exchanger unit 10. This baffie or plate 49 members 58 and is, of course, disposed intermediate the two panels 40 and 50 and correspondingly spaced from both .of,the openings referred to. A deflector 62 is secured to the front edge of the panel 40 and inclined upwardly and rearwardly partiallycovering the upper open end of the heat exchanger unit and concealing it from view in ordinary usage.

The draft diverter plate 49 is spaced from the back wall 16 whereby heated gases rising from the heat exchanger unit are permitted to flow past the draft diverter on both the front and rear sides thereof, the tendency being toward the rear .side because of the from the exterior into 1the;sp'ace V ward drafts through the stack. Uponthe occurrence of downdraftsthrough the stack, which occur at times due to peculiar atmosphericconditions in the'exterior'adjacent the stack, the downfiow'bf air passing through the opening 54 is diverted by the plate 49 out through the open front side of the heater ,into the room or space in which the heater is located, and prevented from flowing down through the heat exchanger to the burner.

The heat exchanger is formed of good heat conducting material, e g., sheet metal, for conductance of heat from the gases in the interior thereof to the exterior. In the construction and use of the heater as described above,

56 due to normal up.-

the front wall 24 of the heat exchanger is exposed directly heating to the space to be heated and is effective for the space by both radiation and convection. The rear and side walls are also effective for heating the space by way of radiation and convection of heat, the radiant heat therefrom being reflected by the reflector 20, and convected heat being carried by air currents from the space between the heat exchanger and reflector.

It is desired to point out by way of summary certain provided a top horizontal panel 50 secured is secured to the upright for the purpose of of the heat exchanger and heater embodying the invention, so that the specific embodiment of the invention {described above will be given as full significance as possible.

The corrugated form of the front wall provides an especially efficient transfer of heat from the interior to the exterior of the heat exchanger.

The angular form 'of the corrugations with the adjacent surfaces thereof extending at approximately right angles still further improves the efliciency of the heat transfer.

The heated gases from the burner 48 flow upward through the heat exchanger and are baffled by the baflles or partitions 36-'and, as a consequence, the gases are prevented from flowing in a center line through the heat In this connection, it is pointed out that in the case of a device such as a heat exchanger, or flue or stack, if the inner surface is smooth and unobstructed, the gases adjacent the inner walls tend to cling thereto and form an insulating film, while the main portion of the gases flow 'up through the passage in a center line.

Under such conditions the heat transfer from'the main portion of the gases to the walls of the.device is quite inefficient. On the other hand, baffles in such a pasasge force the gases into sweeping or scouring contact with the walls and prevent, to a high degree, the accumulation of such insulating film. In the present instance, thebatfles'or partitions 36 are effective for that purpose,-namely,-for forcing the gases into good heat transfer contact with particularly the front wall 24; this wall is exposed directly to the space to be heated and therefore most efficient heat transfer from the interior of the heat exchanger to the exterior is effected. More specifically, the'gases are forced'through the c'onstric tions formed between the corrugations30 by the battles or partitions 36. Such constrictions 'are of considerably less total'area than the cross-sectional area of the heat exchanger, and consequently the gases flow through the constrictions at a more rapid rate than in'the remaining portions of the heat exchanger, resulting in the desired sweeping and scouring action between the gases and the front wall.

The sweeping and scouring action above referred to is made especially effective by thenovel arrangement of elements of construction of the heat exchanger of our invention. Because'of the forward inclination of the back -wall 26 with respect-to the front wall the gases flowing through the heat exchanger tend to flow by relation toward the back wall, that is, gases normally flow vertically and the back wall being inclined is disposed in such positionthat the gases flowing vertically actually flow toward the inclined wall. The baffies together with the rear and side walls form pockets into which the gases flow, and the gases are thereby temporarily trapped producing a slight back pressure. As a result the gases are forced toward the front wall into heat transfer contact therewith. This action of the gases in contacting the front wall is effective substantially throughout the full vertical extent of the pockets, that is, the full vertical extent of the space, between the two baffles or that space between the lower baffle and the lower end of the heat exchanger, The sweeping and scouring action therefore 15 made effective. to a maximum extent throughout wall and the corrugations the vertical height of the front therein. v

Trapping of the gases in the pockets under the baffles 36, as above described, creates a turbulent condition in the gases in the heat exchanger. The turbulent action causes the gases to be deflected with some degree of force to contact with the front wall 24. Such turbulence eliminates the center line flow and destroys the insulating film above referred to. r

The upwardly converging shape of the heat exchanger produces a result not attainable in connection with previously known heat exchangers. As is well known, gases in their upward flow in a heat exchanger are gradually cooled and therefore gradually contracted in volume. Therefore as the gases approach the upper end of the heat exchanger they flow more slowly and result in less efiicient heat transfer because of their slower movement. This condition is compensated for by the convergence of the front and rear walls of the heat exchanger of our invention. As the gases cool and contract their tendency to fiowslower is counteracted by the gradually decreasing cross-sectional area of the heat exchanger in an upward di rection. Because of this progressive decrease in crosssectional area of the heat exchanger, the gases, although cooled and tending to flow slower, are caused to flow relatively fast with consequent more effective heat transfer contact with the walls of the heat exchanger.

Another advantage of the upward convergence of the heat exchanger is that fewer baffles or partitions such as 36 are required than would be required in a device having uniform cross-sectional area. The inclined rear wall itself acts as a bafile in producing turbulence, and this bafiling and turbulence augments that produced by the actual baffles 36.

It is also contemplated within the scope of the present invention that the heater as a whole may be surrounded on the sides and rear by insulating material such as refractory material for insulating purposes and for directing the greatest amount of heat directly into the space to be heated as intended. If the heater is disposed, for example, in a wall niche, the surfaces of the niche itself may be effective for the purpose stated. But if the heater is positioned entirely in the space to be heated a greater part of the heat will be emitted from the sides and rear than when insulation is provided and a substantial amount of heat will be transmitted from this source directly to the s ace.

Although the above description has to do with a heat exchanger as employed in a heater in such a way that the heat is to be transferred from the heat exchanger to the exterior space, it is also contemplated that the device can be used equally well for the reverse action. The device is usable in connection with transferring heat from an exterior space to the interior of the heat exchanger, whereby the gases flowing therethrough convey the heat thus transferred. It is intended, therefore, that although the heat exchanger is described as an element of a heater, such is to be interpreted as only one embodiment of the invention, and that the invention is not limited to its use in a heater.

It is understood that changes may be made in the specific device disclosed within the scope of the appended claims.

We claim:

1. A heat exchanger comprising a unit having surrounding upright walls at least one of which is of high heat conducting material, defining a chamber-like passage having a bottom opening and a top opening for the flow of gases therethrough, one of said walls having upright corrugations therein and relatively converging upwardly with the opposite wall, and a plurality of horizontal partitions in the chamber extending from the innermost portions of said corrugations to said other upright walls and defining constrictions in the unit consisting solely of the spaces between the corrugations of the front wall.

2. A heat exchanger comprising a unit having surrounding upright walls at least one of which is of high heat conducting material, defining a chamber-like passage and having a bottom opening and a top opening for the flow of gases therethrough, a pair of opposite ones of said walls converging in an upward direction, the one of said walls which is of high heat-conducting material; having upright corrugations therein, said corrugations being formed by wall elements adjacent ones of which are disposed at approximately 90 angles, and the corrugations terminating outwardly at the junctures of the wall elements, and a plurality of horizontal partitions in said passage extending from the innermost portions of said corrugations to said other upright walls and defining constrictions adjacent the corrugated wall.

3. A heat exchanger comprising a unit having a front, a rear, and side upright walls defining a chamber-like passage and having a bottom opening and a top opening for the flow of gases therethrough, said front wall having upright corrugations therein, said rear wall being inclined upwardly and forwardly toward the front wall, and a plurality of horizontal partitions in said passage extending from the innermost portions of said corrugations to said rear and side upright walls and defining constrictions therein adjacent said front wall.

4. A heat exchanger comprising a unit having a front, a rear, and side upright walls defining a passage and having a bottom opening and a top opening for the flow of gases therethrough, said front wall having upright corrugations therein, said rear wall being inclined upwardly and forwardly toward the front wall, and a plurality of horizontal imperforate baflles in said passage having gas-tight engagement with the rear and side walls and terminating substantially in abutting relation to the innermost points of the corrugations of said front wall and thereby establishing constrictions in the spaces between said corrugations.

5. A heat exchanger comprising an upright tubular member defining a generally vertical passage having bottom and top openings and converging upwardly, said member being formed with a wall portion having upright corrugations therein defining a plurality of parallel vertical passages, and a plurality of vertically spaced partitions each extending horizontally across said tubular member and into abutment with the wall of said tubular member in substantially gas tight relation except at said corrugated portion, each of said partitions terminating substantially in abutting relation to the innermost portions of said corrugations thereby to prevent the passage of hot gases past said partitions except through the passages defined by said corrugations.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Mar. 23, 1906

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