US20180172361A1

US20180172361A1 - Heat exchanger

Info

Publication number: US20180172361A1
Application number: US15/836,968
Authority: US
Inventors: Neil BASINI
Original assignee: HS Marston Aerospace Ltd
Current assignee: HS Marston Aerospace Ltd
Priority date: 2016-12-16
Filing date: 2017-12-11
Publication date: 2018-06-21
Also published as: EP3336474A1; EP3336474B1

Abstract

A heat exchanger comprises a conduit with an interior surface which defines a first flow passage. A first plurality of fins project inwardly from the interior surface of the conduit. The first plurality of fins are angled relative to a longitudinal axis (X) of the conduit so as to form helical flowpaths for fluid flowing through the first flow passage. A second flow passage disposed outwardly of the interior surface and radially outwardly of the first plurality of fins.

Description

FOREIGN PRIORITY

This application claims priority to European Patent Application No. 16275174.7 filed Dec. 16, 2016, the entire contents of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a heat exchanger.

BACKGROUND

It is well-known in the art of fluid control to use a matrix or lattice within a component to maximise a contact area for interacting with a fluid flow. Increasing the contact area by using a matrix improves, for example, the rate of heat exchange or chemical reaction between the fluid flow and the component.
Components using a matrix typically comprise a conduit for providing fluid flow to an inlet of the matrix. Typically, the conduit cross-sectional area is less than that of the matrix inlet. The matrix and the conduit are sized such that a flow from the conduit can disperse throughout the entire matrix volume to maximise the contact area. As such, providing a relatively wide conduit with a slow fluid flow allows the flow to disperse evenly.
However, some applications may require a narrow conduit. This can result in a faster-moving fluid flow that does not disperse fully across the matrix volume. This, in turn, can result in a reduced efficiency and/or increased wear of the matrix.
Additionally, in fluid control applications using a matrix as described above, there may be a need to impart or remove heat from the fluid.

SUMMARY

According to an exemplary embodiment of the present disclosure, there is provided a heat exchanger comprising a conduit with an interior surface. The interior surface defines a first flow passage. A first plurality of fins projects inwardly from the interior surface of the conduit. The first plurality of fins are angled relative to a longitudinal axis of the conduit so as to form helical flowpaths for fluid flowing through the first flow passage. A second flow passage is disposed outwardly of the interior surface and radially outwardly of the first plurality of fins.
The fins may be straight along their length.
Alternatively, the fins may be at least partially curved. The fins may be curved along their entire length, or the fins may be straight at an inlet to the conduit and gradually curve to be angled at the exit to the conduit.
Alternatively, the fins may be corrugated.
The first plurality of fins may be distributed around the entire circumference of the interior surface of the conduit.
Alternatively, the fins may be distributed around less than 50% of the circumference of the interior surface of the conduit, for example around 25% of the circumference of the interior surface of the conduit.
The second flow passage may extend around the entire circumference of the conduit. Alternatively the second flow passage may extend around less than 50% of the circumference of the conduit.
The second flow passage may be circumferentially coterminous with the fins.
The conduit may further comprise an exterior surface, wherein the second flow passage is disposed between the interior surface and exterior surface of the conduit.
The conduit may comprise a second plurality of fins which project into the second flow passage.
The second plurality of fins may be aligned with the first plurality of fins. The second plurality of fins may be extensions of the first plurality of fins.
The conduit cross-section may have a maximum diameter of less than 200 mm. In certain embodiments, the conduit may have a diameter of between 50 mm and 150 mm.
The conduit may further comprise an outlet, wherein an angle formed between the fins and the longitudinal axis of the conduit at the outlet is between 10° and 45°, for example between 10° and 20°.
The heat exchanger cross-section may be annular.
The heat exchanger may be an air-liquid heat exchanger.
The plurality of fins may project less than 50% of the radial distance between the interior surface and a centre of the conduit, for example between 25% and 50% of the radius of the conduit.
The fins may be evenly distributed on the interior surface of the conduit.
In a further exemplary embodiment of the disclosure, a system comprises the heat exchanger as described above. A matrix with an inlet is disposed downstream of the first flow passage to receive the flow from the first flow passage.
The matrix may be one of a heat exchanger matrix or an ozone converter matrix.
The heat exchanger or system may be part of an aircraft environmental control system.
In a further exemplary embodiment of the disclosure, a method of operating the heat exchanger as described above comprises the steps of providing a first fluid flow to an inlet of the first flow passage, and a second fluid flow to an inlet of the second flow passage, swirling the fluid flow in the helical flowpaths in the first flow passage, and exchanging heat between the first fluid flow and the second fluid flow.
In a further exemplary embodiment of the disclosure, a method of operating the system as described above comprises the steps of providing a first fluid flow to an inlet of the first flow passage, and a second fluid flow to an inlet of the second flow passage, swirling the fluid flow in the helical flowpaths in the first flow passage, exchanging heat between the first fluid flow and the second fluid flow, and admitting the first fluid flow into the inlet of the matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 3 show sectional views of heat exchangers in accordance with this disclosure.

FIGS. 4A and 5A show oblique views of arrangements of the conduit of the heat exchanger of FIG. 1.

FIGS. 4B and 5B show plan views of the conduits of FIGS. 4A and 5A along lines 1-1 and 2-2 respectively.

FIGS. 4C and 5C show partial, enlarged views of the conduits of FIGS. 4A and 5A respectively.

FIG. 6 shows an oblique view of a swirled flow dispersing from a conduit into a downstream matrix inlet.

FIG. 7 shows an axial view of the swirled flow of FIG. 6.

DETAILED DESCRIPTION

FIG. 1 shows an example heat exchanger in accordance with this disclosure. The heat exchanger comprises a conduit 16. In this embodiment the conduit 16 is annular, and comprises an interior surface 18 and an exterior surface 20. The conduit 16 has a longitudinal axis X. A first flow passage 22 is defined by an interior surface 18 of the conduit 16. A second flow passage 24 is formed radially outwardly of the interior surface 18. In this embodiment, the second flow passage 24 extends around less than 50% of the circumference of the conduit 16, for example between 25% and 30% of the circumference. In this example, the second flow passage 24 is disposed between the interior surface 18 and the exterior surface 20. In other examples, the second flow passage 24 may be disposed outwardly of the exterior surface 20 and formed by a separate member suitably attached to the conduit 16.
Heat exchange fins 26 project from the interior surface 18 into the first flow passage 22. The fins 26 are distributed around the circumference of the conduit 16, extending inwardly from the portion of the conduit 16 where the second flow passage 24 is disposed. Hence, the fins 26 also extend around less than 50% of the circumference of the conduit 16. In the example shown, the fins 26 extend less than 50% of the distance between the interior surface 18 and the centre of the conduit 16. For example, the fins may extend inwardly between 25 and 50% of the conduit radius.
Heat is exchanged between the first flow passage 22 and the second flow passage 24 through the fins 26. Hence, substantial heat exchange only occurs in the portion of the conduit 16 in which the fins 26 and the second flow passage 24 are disposed.
FIG. 2 shows another exemplary heat exchanger. In this example, both the fins 26 and the second flow passage 24 extend around the entire circumference of the conduit 16. Hence, heat exchange occurs around the entire circumference of the conduit 16.
FIG. 3 shows another exemplary heat exchanger. In this example, second flow passage 24 extends around less than 50% of the conduit 16. The heat exchanger comprises both heat exchange fins 26, which are disposed around the portion of the conduit 16 where the second flow passage 24 is present, and non-exchange fins 28, which are distributed around the remaining portion of the circumference of the conduit 16. Heat exchange only occurs in the portion of the conduit 16 where the second flow passage 24 is disposed. The non-exchange fins 28 largely only act to guide flow (as will be discussed below).
With reference to FIGS. 4A-C, there is shown an embodiment of a heat exchanger consistent with FIG. 1. The embodiment of FIG. 1 is used only as an example, and the features described below could similarly be present in any of the examples of FIG. 2 or 3.
FIG. 4A shows an oblique view of the heat exchanger of FIG. 1. The conduit 16 has an inlet 30 and an outlet 32, and is generally of the form as discussed above in relation to FIGS. 1-3.
The fins 26 are angled relative to a longitudinal axis X of the conduit 16 in order to direct and swirl the flow in the first flow passage 22. The fins 26 form helical flowpaths 27 therebetween in order to direct the flow. The flow in the first flow passage 22 is imparted with an angular momentum in order to ‘spin’ outward from the outlet 32 of the conduit 16 to an inlet of a downstream matrix (not shown). By this mechanism, the flow is more evenly distributed across an inlet of the matrix, particularly at the points of the matrix inlet furthest from the centre of the outlet 32 of the conduit 16. Such an arrangement is illustrated schematically in FIGS. 6 and 7, which show a swirled fluid flow from a conduit 2 entering a matrix 4. The flow from the conduit 2 is imparted with an angular momentum by the fins of the heat exchanger. By this mechanism, the flow is dispersed downstream to an inlet 6 of the matrix 4.
The matrix could be for the purpose of heat exchange or facilitating a chemical reaction. It is envisaged that the matrix could form part of a heat exchanger or ozone converter for an environmental control system of an aircraft.
As can be seen in FIGS. 4A-C, the fins 26 are straight along their length. The fins 26 form an angle with the longitudinal axis X at the outlet 32 of the conduit 30. This angle may be between 10° and 45°. In some examples, the angle may be between 10° and 20°.
FIGS. 5A-C show an exemplary heat exchanger. The heat exchanger is similar to that of FIGS. 4A-C, but in this example fins 26 are curved along their length. The fins 26 are straight at the inlet 30 of the conduit 16, and curve to be angled at the outlet 32. Again, the fins 26 form an angle with the longitudinal axis X of the conduit 16 at the outlet 32. The angle may be the same as that discussed in the above “straight-fin” embodiment.
In an example not shown in the figures, the fins 26 could be corrugated along their length to provide increased heat-transfer interaction with the flow in the first flow passage 22. The fins would further be arranged to form a helical flowpath 27 in order to swirl the flow, as discussed above.
Although not shown, non-exchange fins 28 could have the form of either of the heat exchange fins 26 of FIG. 4A or 5A. These non-exchange fins 28 would also serve to swirl the flow through the first flow passage 22 as discussed above in relation to the heat exchange fins 26.
In further embodiments, a second set of fins 25 may project into the second flow passage 24. This would provide increased interaction with the fluid flow in the second flow passage 24 to improve heat exchange with a fluid therein. The second set of fins 25 may be aligned with the heat exchange fins 26, or be an extension of the heat exchange fins 26 through the interior surface 18 of the conduit 16. Such an embodiment is illustrated schematically by dotted lines in FIGS. 4C and 5C.
In an arrangement not shown, the fins of the second set of fins 25 may be circumferentially offset from the first set of fins 26. For example, they may be positioned circumferentially between the first fins.
In accordance with the present disclosure, therefore, heat-exchanger fins can be arranged on the interior surface of a conduit which supplies a fluid to a matrix. The fins are angled to form a helical flowpath and thereby as a flow swirler. Hence, the conduit can swirl flow for a downstream matrix and provide for heat-exchange.
Although the figures and the accompanying description describe particular embodiments and examples, it is to be understood that the scope of this disclosure is not to be limited to such specific embodiments, and is, instead, to be determined by the following claims.

Claims

1. A heat exchanger comprising:

a conduit with an interior surface, wherein the interior surface defines a first flow passage;

a first plurality of fins projecting inwardly from the interior surface of the conduit, wherein the plurality of fins are angled relative to a longitudinal axis (X) of the conduit so as to form helical flowpaths for fluid flowing through the first flow passage; and

a second flow passage disposed outwardly of the interior surface and radially outwardly of the plurality of fins.

2. The heat exchanger of claim 1, wherein the first plurality of fins are straight along their length.

3. The heat exchanger of claim 1, wherein the first plurality of fins are at least partially curved along their length.

4. The heat exchanger of claim 1, wherein the first plurality of fins are corrugated along their length.

5. The heat exchanger of claim 1, wherein the first plurality of fins are distributed circumferentially around the interior surface of the conduit.

6. The heat exchanger of claim 1, wherein the first plurality of fins are distributed circumferentially around less than 50% of the interior surface of the conduit.

7. The heat exchanger of claim 1, wherein the second flow passage extends around less than 50% of the circumference of the conduit.

8. The heat exchanger of claim 1, wherein the conduit further comprises an exterior surface, and wherein the second flow passage is disposed between the interior surface and exterior surface of the conduit.

9. The heat exchanger of claim 1, wherein a second plurality of fins project into the second flow passage, wherein, optionally, the second plurality of fins are aligned with and/or are extensions of said first plurality of fins.

10. The heat exchanger of claim 1, wherein the conduit cross-section has a maximum diameter of less than 200 mm.

11. The heat exchanger of claim 1, wherein the conduit further comprises an outlet, and wherein an angle formed between the first plurality of fins and the longitudinal axis (X) of the conduit is between 10° and 45°, optionally wherein the angle formed is between 10° and 20°.

12. A system comprising:

a heat exchanger that includes:

a second flow passage disposed outwardly of the interior surface and radially outwardly of the plurality of fins; and

a matrix with an inlet disposed downstream of the first flow passage to receive the flow from the first flow passage.

13. The system of claim 12, wherein the matrix is one of a heat exchanger matrix or an ozone converter matrix.

14. A method of operating the heat exchanger of claim 1, the method comprising the steps of:

providing a first fluid flow to an inlet of the first flow passage, and a second fluid flow to an inlet of the second flow passage;

swirling the fluid flow in the helical flowpaths in the first flow passage; and

exchanging heat between the first fluid flow and the second fluid flow.

15. A method of operating the system of claim 12, the method comprising the steps of:

swirling the fluid flow in the helical flowpaths in the first flow passage;

exchanging heat between the first fluid flow and the second fluid flow; and

admitting the first fluid flow into the inlet of the matrix.