WO1990011472A1

WO1990011472A1 - Heat exchanger

Info

Publication number: WO1990011472A1
Application number: PCT/GB1990/000411
Authority: WO
Inventors: Kenneth Edward Hopkinson
Original assignee: Cubit Limited
Priority date: 1989-03-17
Filing date: 1990-03-19
Publication date: 1990-10-04
Also published as: GB8906200D0; AU5274290A

Abstract

A heat exchanger for heating fluid flowing therethrough such as a heat exchanger for heating water to steam temperatures, comprises an outer coil part (13) comprising a plurality of coil windings about a generally horizontal heat exchanger axis (12), an inner coil part (17) located inside the outer coil part (13) and also comprising a plurality of coil windings about the heat exchanger axis (12), means (35) to provide fluid for heating to each of the coil parts (13, 17), and means (24) to provide heat inside a space bounded (28) by the inner coil part (17).

Description

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Title: Heat Exchanger

Description of Invention

This invention relates to a heat exchanger for heating fluid flowing therethrough and more particularly, but not exclusively to a heat exchanger for heating water to steam temperatures.

According to one aspect of the invention we provide a heat exchanger comprising an outer coil part comprising a plurality of coil windings about a generally horizontal heat exchanger axis, an inner coil part located inside the outer coil part and also comprising a plurality of coil windings about the heat exchanger axis, means to provide fluid for heating to each of the coil parts, and means to provide heat inside a space bounded by the inner coil part.

According to a second aspect of the invention, we provide a fluid system including a heat exchanger in accordance with the first aspect of the invention, the system including a flow control device comprising a chamber, an inlet to the chamber, and a plurality of outlets from the chamber, one of the outlets being connected to an inlet of the heat exchanger, and others of the outlets having valve means associated therewith, which may be opened and closed to achieve a desired fluid flow rate to the heat exchanger.

The invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is an illustrative side cross section through a heat exchanqer in accordance with the invention,

FIGURE 2 is an end cross section of the heat exchanger of Fiqure 1, on the lines 2-2,

FIGURE 3 is an end cross section of the heat exchanger of Fiqure 1, on the lines 3-3,

FIGURE 4 is an illustrative drawing of the heat exchanger of Figures 1 to 3 in a fluid system in accordance with the second aspect of the invention.

Referring to figures 1 to 3, a heat exchanqer 10 is contained in an outer casing 11 which in this example is generally elongate and cylindrical, having a central longitudinal axis 12.

An outer heat exchanging coil part 13 comprises a plurality of coil windings about axis 12, with each winding of the coil part 13 being connected to an adjacent winding so that the coil part 13 comprises a continuous tube of windings which extends from a position 14 at or adjacent one end wall 1 5 of the heat exchanger 10, to a second end wall 16 of the casing 11.

Nested inside the outer coil part 13 is an inner coil part 17 which again comprises a plurality of coil windings about axis 12 with each winding being connected to adjacent windings so that the inner coil part 17 also comprises a continuous tube of windings which extends from the second end wall 16 to a position 18 short of the endmost position 14 of the outer coil part 13.

Between the inner 17 and outer 13 coil parts, is an intermediate coil part 19 which also comprises a plurality of coil windings about axis 12 with each winding over a major portion of the length of the coil part 19 only, being connected to adjacent windings. The coil part 19 extends from a position 20 longitudinally between positions 14 and 18 to the second end wall 16 of the housing 11.

The coil parts 17 and 19 are retained in the positions show by stays S, the positions of which are not shown in figure 2.

It can be seen that the windings of the intermediate coil part l^q approaching the second end wall 16 of the housing 11, become spaced apart, the spacial separation between the windings generally increasing towards the end wall 16.

A closure plate 22 is provided adjacent first end wall 15 of the housing 11, to close the space bounded by the intermediate coil part 19 at the one end 20, as shown. The closure plate 22 in the current example comprises a plate 23 of stainless steel clad on either side with heat resistant and insulating material. Plate 22 is shown, cross hatched in figure 2, for clarity.

It can be seen from figures 1 and 3 that an annular space between the outer coil part 13 and the inner coil part 17 is closed by the second end wall 16 of the housing 11. This space is cross hatched in figure 3, for clarity.

Mounted in the second end wall 16 is a burner 24 which may comprise an oil or gas burner for examples, fuel for the burner 24 being fed thereto via a feed line 25 which extends to a nozzle 26 of the burner 24.

Air for combustion is fed into the housing, via openings 27, which are preferably integral with the burner 24 and are arranged so that the proportion of air to fuel can be adjusted to achieve a desired burner output.

Thus a space 28 bounded by the inner coil part 17, comprises a combustion chamber into which a flame 29 is projected to produce heat entrained in products of combustion, which heat flows along the combustion chamber 28 towards the closure plate 22 where it reverses direction to flow back towards the second end wall 16 of the casing 11 through annular space 30 provided between the inner coil part 17 and the intermediate coil part 19.

As the combustion gases approach the second end wall 16 of the housing 11, they reverse direction yet again and flow back towards the one end wall 15 of the housing 11 through annular space 31 provided between the intermediate coil part 19 and the outer coil part 13.

The spacing apart of the windings of the intermediate coil part 19 as it approaches the second end wall 16 of the casing 11, allows the products of combustion to pass through the coil part 19 so that not all the products of combustion must flow to the end of the coil part 19 in order to flow from space 30 into space 31.

A collection space 32 is provided between the closure plate 22 and the first end wall 15 of the housing 11 in which the products of combustion collect and from which the gases are vented from the heat exchanger 10 via a flue 34.

As heat is produced, fluid flows through the coil parts 17,19,13, and each coil part 17,19,13, is fed with fluid from an inlet conduit 35 which is connected to and communicates with each of the coil parts 17,19,13. Similarly, an outlet conduit 36 is provided which is also connected to and communicates with each of the coil parts 17,19,13, to enable the fluid to flow from the heat exchanger 10. Preferably, where the output of the burner 24 is sufficiently high, and the fluid is water, steam issues from the outlet conduit 36. Thus the heat exchanger 10 comprises a steam producing boiler.

Various modifications may be made without departing from the scope of the invention. For example, the burner 24 may be replaced by any other heat providing source although preferably for a steam producing boiler, a burner 24 which is oil or gas fired would need to be provided as described.

Whereas in the present arrangement, the boiler comprises a three pass boiler in that the heat passes along combustion chamber 28, which is one pass, back through space 30 which is the second pass, and then through space 31, which is the third pass, to the collection space 32, if desired, the heat exchanger 10 may provide more passes for the products of combustion by providing additional coil parts, preferably each comprising windings about the horizontal axis 12 of the heat exchanger 10. As shown, the inlet conduit 35 communicates with each of the coil parts 17,19,13, and the outlet conduit 36 also connects the three coil parts, if desired the coil may comprise a continuous coil, in which case the inlet conduit need only communicate with the inner coil Dart 13, for example, and the outlet conduit 36 with outer coil part 17.

Other alternative coil arrangements may be provided.

Referring now to figure 4, a fluid system 40 is provided which incorporates the heat exchanger 10 which is only shown diagrammatically.

The inlet conduit 35 to the heat exchanger 10 is connected to a flow control device 41, and the outlet conduit 36 from the heat exchanger 10 is connected to a steam accumulator 42 from which steam may be drawn along a steam line 43 when a valve 44 is open, for any desired use.

The flow control device 41 comprises a chamber 45 to which the water is fed via an inlet 46. Spaced along chamber 45 are three injector nozzles 47,48, and 49 which preferably are all identically sized, and permit water to flow from the chamber 45 into respective outlets 50,51 and 52. Outlet 52 is connected to the inlet conduit 35 to the heat exchanger 10.

It can be seen that each outlet 50,51, and 52 is double ended, and that in each case, one end is blanked off by a suitable blank 53.

The water to the inlet 46 is provided by a pump 54. The outlet 50 from the chamber 45 is connected directly to a relief means 55, whilst the outlet 51 is connected to the relief means 55 via a valve 56 which may be opened to allow fluid to pass to the relief means 55, or closed to prevent such flow.

It will be appreciated that when the valve 56 is closed, each of the outlets 50 and 52 from the chamber 45, will be provided with identical quantities of fluid, because the injectors 47 and 49 are identically sized. Where the output of the burner 24 of the heat exchanger is sufficiently large, operating the fluid system in this condition may provide for wet steam to issue from the outlet 36.

To provide drier steam it is necessary to reduce the guantity of water being fed into the heat exchanger 10 and this may be achieved by openinq valve 56. In this event, each of the outlets 50,51 and 52 would receive approximately equal quantities of water because the injectors 47,48 and 49 are identically sized. Of course, to achieve this, pump 54 would need to provide sufficient head. More complex control arrangements may be provided to adjust the quality of the steam issuing from outlet 36 of the heat exchanger 10.

In another example (not shown), the outlet 50 may itself be closeable so that the entire quantity of water being pumped into the chamber 45 passes into the outlet 52 and hence to the inlet 35 of the heat exchanger 10. In this event, the heat exchanger 10 may simply provide hot water or very wet steam.

For further description of a fluid system in which the present invention may be used, attention is drawn to our prior published applications G8 2206955, and WO 89/12782.

Claims

1. A heat exchanger comprising an outer coil part comprising a plurality of coil windings about a generally horizontal heat exchanger axis, an inner coil part located inside the outer coil part and also comprising a plurality of coil windings about the heat exchanger axis, means to provide fluid for heating to each of the coil parts, and means to provide heat inside a spaced bounded by the inner coil part.

2. A heat exchanger according to claim 1 wherein an intermediate coil part is provided between the inner and outer coil parts, the intermediate coil part comprising a plurality of coil windings about the heat exchanger axis, there being a flow path for heat from the spaced bounded by the inner coil part into a space between the inner and intermediate coil parts and then into a space between the intermediate and outer coil parts.

3. A heat exchanger according to claim 2 wherein a space bounded by the intermediate coil part is closed at one end of the heat exchanqer beyond an adjacent end of the inner coil part so that heat can flow alonq the space bounded by the inner coil part towards the closed one end, and reverse direction to flow into the space between the inner and intermediate coil parts.

4. An exchanger according to claim 3 wherein an annular space between the outer coil part and the inner coil part is closed at a second opposite end so that heat which flows along the space between the inner and intermediate coil parts towards the closed second end, reverses direction to flow into the space between the inner and outer coil parts.

5. An exchanger according to any one of claims 1 to 4 wherein the coils of the outer and/or inner coil part comprise a plurality of close coil windings with each winding in contact with, and preferably connected to, adjacent coil windings so that the outer and/or inner coil parts comprise tubes of wound coils.

6. An exchanger according to claim 5 where appendant to claim 2 wherein the intermediate coil part also comprises a plurality of close coil windings, each winding being in contact with, and preferably connected to, adjacent coil windings at least along a major portion of its length, but preferably approaching the second end, adjacent windings having spaces between them, which spaces increase in dimension towards the second end so that a proportion of the heat can pass from the space between the inner and intermediate coil parts into the space between the intermediate and outer coil parts without having to flow along the entire lenqth of the space between the inner and intermediate coil parts.

7. An exchanger according to any one of the preceding claims where appendant to claim 3 wherein the entire heat exchanger is contained within a housing which provides a collection space for the heat between the closed one end of the intermediate coil part and an adjacent housing wall.

8. An exchanger according to any one of the preceding claims wherein the heat is provided by a burner such as an oil or gas burner which is located at or adjacent to an end of the heate exchanger, whereby the space bounded by the inner coil part comprises a combustion chamber and the heat exchanger itself comprises part of a boiler in which the heat is entrained in combustion products which flow through the flow path provided between the various parts.

9. An exchanger according to any one of the preceding claims wherein the inner and outer coil parts, and the intermediate coil part where provided, together comprise a continuous coil having a single inlet and a single outlet, with the inlet provided to the outer coil part and the outlet from the inner coil part, or the coil parts each have their own fluid inlets and outlets but being arranged so that fluid can interchange between the respective coil parts.

10. An exhanger according to any one of the preceding claims wherein the fluid comprises water and the heat provided by the heat producinq means is sufficient to produce steam from the water.

11. A fluid system including a heat exchanger in accordance with any one of the preceding claims, the system including a flow control device comprising a .chamber, an inlet to the chamber, and a plurality of outlets from the chamber, one of the outlets being connected to an inlet of the heat exchanger, and others of the outlets having valve means associated therewith, which may be opened and closed to achieve a desired fluid flow rate to the heat exchanger.