GB2118708A - Heat exchanger for a gas fired heater - Google Patents
Heat exchanger for a gas fired heater Download PDFInfo
- Publication number
- GB2118708A GB2118708A GB08211720A GB8211720A GB2118708A GB 2118708 A GB2118708 A GB 2118708A GB 08211720 A GB08211720 A GB 08211720A GB 8211720 A GB8211720 A GB 8211720A GB 2118708 A GB2118708 A GB 2118708A
- Authority
- GB
- United Kingdom
- Prior art keywords
- heat exchange
- intermediate portion
- panels
- convergent
- panel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000012530 fluid Substances 0.000 claims abstract description 34
- 238000002485 combustion reaction Methods 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 3
- 229910001209 Low-carbon steel Inorganic materials 0.000 claims description 2
- 239000004411 aluminium Substances 0.000 claims description 2
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims description 2
- 238000007906 compression Methods 0.000 claims description 2
- 238000010276 construction Methods 0.000 claims description 2
- 229910003460 diamond Inorganic materials 0.000 claims description 2
- 239000010432 diamond Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 claims description 2
- 238000000034 method Methods 0.000 claims description 2
- 230000010355 oscillation Effects 0.000 claims description 2
- 238000013021 overheating Methods 0.000 claims description 2
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
- F28F13/06—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media
- F28F13/08—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media by varying the cross-section of the flow channels
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
- F24H1/22—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating
- F24H1/38—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water contained in separate elements, e.g. radiator-type element
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
Abstract
A heat exchange element comprises a first convergent portion, adapted to receive a primary heat exchange fluid, a second intermediate portion adapted to exchange heat, and a third divergent portion for interconnection with a flue; intermediate portion is convergent over at least 30% of its length, thereby to provide a venturi within the second intermediate portion. In a preferred embodiment the intermediate portion is convergent over 30 to 70% of its length and most preferably 40 to 60% of its length. Values of 50% and 60% are also particularly suitable. <IMAGE>
Description
SPECIFICATION
Heat exchanger particularly for a gas heater
The present invention relates to heat exchange units, particularly, although not exclusively, for fan-assisted gas fired heaters.
Fan assisted gas fired heaters are generally provided with a casing upon which is mounted a fan which impells air through a heat exchange compartment; said compartment being provided with a number of heat exchange elements. The interior of each element carries a primary heat exchange fluid, usually in the form of combustion products from a gas burner, position below said compartment, and thus sad element acts both as a duct for said products and as a heat exchanger.
The products are flued by conventional means on leaving the heat exchange element.
Such an arrangement is, for example, shown in
British Patent No: 1,115,111. This arrangement operates generally satsfactorily, but is comparatively inefficient.
The present invention seeks to provide an improved heat exchange element, particularly, but not exclusively, for use in gas or similar heaters, which provides a greater heat output for a given size of unit. One of the difficulties associated with heaters of the prior art type lies in that they tend to overheat at the top end of their output range because the heat exchangers, being generally planar, cannot transfer heat to the impelled air sufficiently fast, even when the fan speed is increased.
Further, the practice of uniformly reducing the cross-section of heat exchange elements within the heat transfer compartment of such a heater has now been shown to impart a significant degree of inefficiency to the system.
Accordingly, the present invention provides a heat exchange element comprising a first convergent portion, adapted to receive a primary heat exchange fluid, a second intermediate portion adapted to exchange heat, and a third divergent portion for interconnection with a flue; characterized in that the second intermediate portion is convergent over at least 30% of its length, thereby to provide a venturi within the second intermediate portion. In a preferred embodiment the intermediate portion is convergent over 30 to 70% of its length and most preferably 40 to 60% of its length. Values of 50% and 60% are also particularly suitable.
The provision of a venturi within the intermediate portion ensures that the point of maximum heating is in use, located within the main fluid flow path of the secondary heat exchange fluid passing over the element.
Although heat exchange elements which are substantially circular in cross section can be used in some circumstances, it is preferred to use elements which are generally planar and may be utilized as a plurality of panels in a generally parallel array. In such a plurality, spaces are formed between adjacent elements of the parallel array, said spaces serving as a conduit for secondary heat exchange fluid; usually air impelled by a fan. The cross-section of the conduits so formed is preferably at its greatest at or toward the narrowest point of the intermediate portion, whereby the point of maximum heat output coincides with a point of maximum secondary heat exchange fluid flow.
In a particularly preferred embodiment, the conduit has a generally elongate diamond-shape configuration in cross-section.
In a further feature of the present invention, there is provided a heat exchange element adapted to receive a primary heat exchange fluid comprising a first convergent portion, a second intermediate portion adapted to exchange heat, and a third divergent portion for interconnection with the flue; characterized in that the second intermediate portion is corrugated along its surface in the direction at least substantially parallel to the direction of flow of the primary heat exchange fluid within the intermediate portion.
In a preferred form of the invention a plurality of such elements are provided in the general form of heat exchange panels in substantially parallel array, and the corrugations are so arranged to the exterior of each heat exchange element that together with adjacent elements they form a serpentine flow path for the secondary heat exchange fluid.
The corrugations and serpentine flow paths serve, not only to increase the heat exchange area, but also in the case of the serpentine path, to increase the heat exchange rate by increasing turbulence in a measured fashion, thereby to reduce portions of the boundary layers adjacent the corrugations.
In a most preferred embodiment the heat exchange elements include both the foregoing features of convergent intermediate portions and corrugations.
In a particular embodiment of the present invention there is provided a gas heater comprising a casing provided with a fan adapted to impell air through a heat exchange compartment, said compartment being provided with a plurality of heat exchange elements, each element being adapted to receive a primary heat exchange fluid and being provided with a first convergent portion, a second intermediate portion and a third divergent portion adapted for interconnection with a flue, characterized in that said intermediate portion is provided with a venturi disposed within said heat exchange compartment and/or with corrugations as hereinbefore set forth.
Aspects of the present invention will now be described, by way of illustration only, with reference to the accompanying drawings, wherein:
Figure 1 is a vertical elevation of a heat exchange panel in accord with the invention,
Figure 2 is a transverse cross section of the panel of Figure 1, along lines A:A and B:B respectively,
Figure 3 shows a transverse cross section of a panel of Figure 1 along a line C:C,
Figure 4 shows a plan view from above of a heat exchange unit including a plurality of heat exchange panels in accord with Figures 1 to 3,
Figure 5 shows a front view in part section of an air heater including a heat exchange panel in accord with Figures 1 to 3, and
Figure 6 shows a transverse cross section along a line A:A of Figure 5.
With reference to Figures 1 to 3, particularly, a heat exchange panel 1 is provided with a lower convergent panel portion 2, an intermediate portion 3, and an upper divergent panel portion 4.
The panel walls 7A and 7B are first pressed from a suitable metal, such as mild steel and aluminium of a desired gauge, and welded along seam weld 8 thereby to provide a sealed unit opened at its upper and lower ends. The cross section of the heat exchange panels at section "A:A" and "B:B" is substantially identical as can be seen from Figure 2. However, the point of maximum heat exchange is to be found about the point at which section "B:B" is taken, being the entrance to the venturi in the intermediate portion.
Corrugations 6 extend generally vertically in
Figure 1 and hence, primary heat exchange fluid flowing upwardly from a burner, positioned below the lower panel portion 2 (not shown) proceeds upwardly in a smooth and substantially unimpeded fashion until reaching the proximity of the venturi 5. The compression of the heat exchange fluid in the venturi thereby allows output of the maximum amount of heat at the point of maximum flow of the secondary heat exchange fluid impelled by the fan. A dimple 9 is provided in order to space the walls 7A and 7B to their correct gap and may be through welded to locate the same. The dimple 9 also serves to prevent any unwanted oscillation between the walls 7A and 7B.
With reference to Figure 4, a heat exchange unit is shown in plan comprising a plurality of heat exchange panels 1 disposed at the uppermost edges in a frame 10 of a generally rectangular configuration. The corrugation 6 taken with the the corrugation 6 of adjacent panels forms a serpentine flow path for heat exchange fluid flowing from left to right of the figure 4. This flow causes a measure of turbulence along the panels, thereby affecting boundary layers to increase heat exchange.
Panels such as that shown in Figure 4 may be positioned in a fan assisted gas heater as shown in Figures 5 and 6. Such a heater comprises an outer casing 20, supported on generally upright casing supports 1 8 and is provided with a fan and mounting 27 toward its rear face, said fan including an impellor 21. The forward face of the casing shown at 23 is provided with a substantially rectangular vane frame 1 5 bearing vanes 1 7 thereon. The vanes 1 7 may, if desired be made adjustable.
Below the vane frame 15 is positioned a combustion air intake 22. Top and bottom panels 1 6A and 1 6B respectively, locate the casing supports 18 to form a stable unit. The top plate 1 6A bears thereon a flue spigot 25 which communicates with a space 24 into which spent heat exchange fluid is exhausted from the panels 1.
Below the units 1 are disposed a plurality of burner units 13, supported on a channel-shaped support 14. A burner unit is provided for each panel 1, said burner element extending substantially throughout the length of the panel 1, thereby providing heated combustion products throughout the length of the interior of the panel.
Air is withdrawn from the exterior via the combustion air intake 22, the air intake being positioned as remotely as possible from the fan 27, so that the air input is not affected thereby.
It will be appreciated that the space 24 and the burners 13 are in compartments which are isolated from the secondary heating air spaces 11, such that there can be no intermixing of the two fluid streams.
In use, with the blade 21 actuated by the motor 27, air is forced between the panels 4 in the spaces 11 which are generally of a diamond shape. The gas burners 1 3 are actuated in a conventional fashion and the gas flow is adjusted to provide flames of a suitable heat. An electrical control panel is provided at 1 9 and is connected inter alia with thermostats to ensure that the secondary air flow produced by the blade 21 is matched to the heat output from the burner 1 3.
This is conveniently effected by means of thermostats and/or thermocouples.
The combustion products of the gas flame from burners 13 arises into lower portion 2 of the panel 1 and then passes from the portion 2 into the intermediate portion 3 which is almost in its entirety within the heat exchange spaced defined by the inner upper frame 10 and the lower frame 28. Thus, the combustion products flow upwardly into the venturi 5 and into the divergent portion 4 where, substantially cooled, they flow to the flue space 24 and spigot 25.
It will be appreciated that by arranging for a greater heat exchange area, and by controlling the position of highest heat exchange temperature to within the intermediate portion, higher heat outputs per unit can be achieved without any overheating, and without "over-engineering" the device. Accordingly, the panels of the present invention and the gas heaters comprising them can be of lighter construction and more economical to manufacture.
The present invention extends, therefore, to heat exchange elements and panels themselves, to heat exchange devices such as fan assisted gas heaters utilizing said elements or panels, and to methods of controlling heat exchangers utilizing the panels of the present invention.
Claims (Filed on 22.4.83)
1. A heat exchange element comprising a first
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (8)
1. A heat exchange element comprising a first
convergent portion, adapted to receive a primary heat exchange fluid, a second intermediate portion adapted to exchange heat, and a third divergent portion for interconnection with a flue; characterised in that the second intermediate portion is convergent over at least 30% of its length, thereby to provide a venturi within the second intermediate portion.
2. An element according to claim 1 wherein the intermediate portion is convergent over 30 to 70% of its length.
3. A plurality of elements according to claims 1 or 2, said plurality being assembled in a generally parallel array to provide spaces serving as a conduit for secondary heat exchange fluid.
4. A plurality of elements according to claim 3 wherein the cross-section of the conduits so formed is at its greatest at or toward the narrowest point of the intermediate portion, whereby the point of maximum heat output coincides with a point of maximum secondary heat exchange fluid flow.
5. A plurality of elements according to claim 4 wherein the conduit has a generally elongate diamond-shape configuration in cross-section.
6. A heat exchange element adapted to receive a primary heat exchange fluid comprising a first convergent portion, a second intermediate portion adapted to exchange heat, and a third divergent portion for interconnection with the flue; characterised in that the second intermediate portion is corrugated along its surface in the direction at least substantially parallel to the direction of flow of the primary heat exchange fluid within the intermediate portion.
7. An element according to claim 6 wherein a plurality of such elements is provided in the general form of heat exchange panels in substantially parallel array, and the corrugations are so arranged to the exterior of each heat exchange element that together with adjacent elements they form a serpentine flow path for the secondary heat exchange fluid.
8. A gas heater comprising a casing provided with a fan adapted to impel air through a heat exchange compartment, said compartment being provided with a plurality of heat exchange elements, each element being adapted to receive a primary heat exchange fluid and being provided with a first convergent portion, a second intermediate portion and a third divergent portion adapted for interconnection with a flue, characterised in that said intermediate portion provides a constriction within said heat exchange compartment and/or with corrugations as hereinbefore set forth, said first portion being convergent for at most 30% to 70% of the length of the elements to provide a point of maximum heat output intermediate the length of the element.
8. A gas heater comprising a casing provided with a fan adapted to impel air through a heat exchange compartment, said compartment being provided with a plurality of heat exchange elements, each element being adapted to receive a primary heat exchange fluid and being provided with a first convergent portion, a second intermediate portion and a third divergent portion adapted for interconnection with a flue, characterised in that said intermediate portion is provided with a venturi disposed within said heat exchange compartment and/or with corrugations as hereinbefore set forth.
9. A heat exchange element substantially as hereinbefore set forth with reference to the accompanying drawings.
New claims or amendments to claims filed on 22nd July 1983
Superseded claims 1, 2, 6 and 8.
New or amended claims
1. A heat exchange element comprising a first convergent portion, adapted to receive a primary heat exchange fluid, a second intermediate portion having substantially parallel walls and adapted to exchange heat, and a third divergent portion for interconnection with a flue; characterised in that the first portion is convergent over at most 30% to 70% of the length of the element whereby the second intermediate portion provides a point of maximum heat output intermediate the length of the element.
2. An element according to Claim 1 wherein the first portion is convergent over 40% to 60% of the length of the element.
6. A heat exchange element adapted to receive a primary heat exchange fluid comprising a first convergent portion, a second intermediate portion having substantially parallel walls adapted to exchange heat, and a third divergent portion for interconnection with the flue; characterised in that the second intermediate portion is corrugated along its surface in the direction at least substantially parallel to the direction of flow of the primary heat exchange fluid within the intermediate portion, and in that the first portion is convergent for at most 30% to 70% of the length of the element to provide a point of maximum heat output intermediate the length of the element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08211720A GB2118708A (en) | 1982-04-22 | 1982-04-22 | Heat exchanger for a gas fired heater |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08211720A GB2118708A (en) | 1982-04-22 | 1982-04-22 | Heat exchanger for a gas fired heater |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2118708A true GB2118708A (en) | 1983-11-02 |
Family
ID=10529879
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08211720A Withdrawn GB2118708A (en) | 1982-04-22 | 1982-04-22 | Heat exchanger for a gas fired heater |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2118708A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL2011539C2 (en) * | 2013-10-02 | 2015-04-07 | Intergas Heating Assets B V | HEAT EXCHANGER WITH A PIPE WITH AN ALTHANS PARTIALLY VARIABLE SECTION. |
| CN108662762A (en) * | 2017-04-01 | 2018-10-16 | 芜湖美的厨卫电器制造有限公司 | Positive displacement heat-exchanger rig and water heater with it |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB563074A (en) * | 1943-04-15 | 1944-07-27 | Calvert & Co Ab | Improvements in economisers and similar heat exchange apparatus |
| GB651775A (en) * | 1946-11-19 | 1951-04-11 | Calumet And Hecla Cons Copper | Improvements in or relating to a method of forming integral finned tube |
| GB653570A (en) * | 1948-05-21 | 1951-05-16 | Heat Exchangers Ltd | Improvements in surface apparatus for effecting transfer of heat between fluids |
| GB1089409A (en) * | 1965-11-02 | 1967-11-01 | Int Standard Electric Corp | Sheet metal heat exchange fire tube for gas fired hot air furnaces |
| GB1115111A (en) * | 1965-03-30 | 1968-05-29 | Carrier Corp | Fuel gas burning apparatus |
| GB1220867A (en) * | 1967-05-05 | 1971-01-27 | Von Roll Ag | Tubular heat exchange assembly |
| GB1430364A (en) * | 1972-07-07 | 1976-03-31 | Std Services Ltd | Fluid-carrying pipe assembly |
-
1982
- 1982-04-22 GB GB08211720A patent/GB2118708A/en not_active Withdrawn
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB563074A (en) * | 1943-04-15 | 1944-07-27 | Calvert & Co Ab | Improvements in economisers and similar heat exchange apparatus |
| GB651775A (en) * | 1946-11-19 | 1951-04-11 | Calumet And Hecla Cons Copper | Improvements in or relating to a method of forming integral finned tube |
| GB653570A (en) * | 1948-05-21 | 1951-05-16 | Heat Exchangers Ltd | Improvements in surface apparatus for effecting transfer of heat between fluids |
| GB1115111A (en) * | 1965-03-30 | 1968-05-29 | Carrier Corp | Fuel gas burning apparatus |
| GB1089409A (en) * | 1965-11-02 | 1967-11-01 | Int Standard Electric Corp | Sheet metal heat exchange fire tube for gas fired hot air furnaces |
| GB1220867A (en) * | 1967-05-05 | 1971-01-27 | Von Roll Ag | Tubular heat exchange assembly |
| GB1430364A (en) * | 1972-07-07 | 1976-03-31 | Std Services Ltd | Fluid-carrying pipe assembly |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL2011539C2 (en) * | 2013-10-02 | 2015-04-07 | Intergas Heating Assets B V | HEAT EXCHANGER WITH A PIPE WITH AN ALTHANS PARTIALLY VARIABLE SECTION. |
| WO2015050441A1 (en) * | 2013-10-02 | 2015-04-09 | Intergas Heating Assets B.V. | Tube for a heat exchanger with an at least partially variable cross-section, and heat exchanger equipped therewith |
| RU2674850C2 (en) * | 2013-10-02 | 2018-12-13 | Интергэс Хитинг Эссетс Б.В. | Tube for heat exchanger with at least partially variable cross-section and heat exchanger equipped therewith |
| US10760857B2 (en) | 2013-10-02 | 2020-09-01 | Intergas Heating Assets B.V. | Tube for a heat exchanger with an at least partially variable cross-section, and heat exchanger equipped therewith |
| CN108662762A (en) * | 2017-04-01 | 2018-10-16 | 芜湖美的厨卫电器制造有限公司 | Positive displacement heat-exchanger rig and water heater with it |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |