GB2280256A

GB2280256A - Fluid channelling member for use in heat transfer tubes

Info

Publication number: GB2280256A
Application number: GB9414811A
Authority: GB
Inventors: Graeme Donald Marshall
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-07-23
Filing date: 1994-07-22
Publication date: 1995-01-25
Also published as: GB9414811D0; GB9315346D0

Abstract

A heat transfer device 12 has a tubular casing 14 and a member 16 located in the tube 14. The member 16 is elongate and has radial walls 20 on a central spine 22. The walls 20 are helical to define helical channels 18 along the whole length of the member 16. Lips 26 on each wall increase the surface area for heat transfer. In use, warm fluid passes along the helical paths, to be continually in motion around the spine 16, and coolant passes around the device 12. This makes different portions of the warm fluid come into contact with the tube 14. The member 16 may be made of aluminium which is twisted after extrusion. The member is preferably an interference fit in the tubular casing which may be made of copper. <IMAGE>

Description

Fluid Channelling Means for use in Heat Transfer Apparatus, and a Method of Producing Fluid Channelling Means The present invention relates to fluid channelling means, particularly but not exclusively to a fluid channelling member for use in heat transfer apparatus, and also a method of producing the said means.

Conventional heat transfer apparatus comprises a mesh matrix located at an appropriate position along a pipe. The pipe is surrounded by coolant. As a relatively warm liquid is passed through the pipe, the matrix causes turbulence in the liquid, to facilitate heat transfer between the warm liquid and the coolant, to cool the liquid in the pipe.

It has been found that heat transfer using such conventional means can be inefficient and unsatisfactory.

What is more, the matrix often unsatisfactorily restricts flow of liquid through the pipe, and often becomes blocked, particularly when relatively viscous liquids are being cooled. Furthermore, a "core effect" can occur in conventional apparatus as a result of viscosity changes occurring as the fluid cools. When liquids such as oil are cooled, the relatively cool oil adjacent the inside wall of the pipe becomes more viscous and so less mobile than the relatively warm, less viscous liquid nearer the centre of the pipe. This "core" of relatively warm, low viscosity liquid is insulated from the coolant to a degree by the outer layer of relatively viscous, slow moving liquid, so that the core tends to move relatively fast through the device, and heat transfer is inhibited.

It is an object of the present invention to obviate or mitigate these disadvantages.

According to the present invention there is provided heat transfer apparatus comprising a casing and fluid channelling means located therein, the said channelling means being so formed as to define at least one indirect path through the space within the casing, and along which the channelling means, in use, channels fluid passing through the space.

The term "indirect" is used to refer to any configuration of path which is not completely straight from the start to the finish of the path.

Preferably the fluid channelling means comprises a member locatable within the casing.

Preferably the fluid channelling means comprises at least one twisted channel defining the or each aforesaid path. The or each channel preferably defines a generally helical path, desirably along substantially the whole length of the channelling means.

Preferably the fluid channelling means comprises a spine and walls extending from the spine to define the channel or channels. The walls may diverge in a direction away from the spine. Preferably the walls are arranged around the spine to define a plurality of equispaced channels. There may be six channels extending along the channelling means, twisting around the spine.

The spine is preferably central.

Preferably a rib extends from a wall of the or at least one of the channel(s) to enhance heat exchange.

Preferably a rib is provided on two walls defining the or at least one channel.

Preferably a lip is provided along at least part of the free end of a wall of the or at least one of the channel(s). A lip may be provided on each of two walls defining the or at least one channel.

Preferably two radially diverging walls define the or each channel, with preferably a lip as aforesaid extending from the free end of each wall to give the free end of each wall an enlarged surface area. The free end of each wall is preferably of generally "T"-shaped cross-section. Each wall may define one side of two adjacent channels.

The channelling member is preferably a friction fit within the casing such that the free end of each wall abuts the inside of the casing. Preferably the casing is a tube. The free end of each wall may be arcuate, centred on the axis of the tube.

The channelling means preferably comprises aluminium. The casing preferably comprises copper.

The heat transfer apparatus may further comprise a housing in which at least one device comprising a channelling means within a casing according to the preceding ten paragraphs is located. Means may be provided for the flow of coolant through the housing, around the or each device, whilst relatively warm fluid is passed through the or each device.

Still further according to the present invention there is provided a method of heat transfer, the method comprising passing a fluid of a first temperature through a casing having fluid channelling means located therein, the said channelling means being so formed as to define at least one indirect path along the space within the casing, along which the fluid is channelled through the space, and passing a further fluid of a second temperature around the outside of the casing, whereby heat is transferred through the casing and/or fluid chanelling means, from one fluid to another until the first and second temperatures are substantially equal.

Preferably the said fluid is channelled along at least one twisted path, preferably generally helical path(s), desirably along substantially the whole length of the channelling means.

The said fluid may be channelled along a channel or channels defined by walls extending from a spine of the channelling means preferably diverging in a direction away from the spine.

The said fluid is preferably channelled along a plurality of channels, desirably six, preferably equispaced around the spine.

Preferably a rib extends from a wall of the or at least one of the channel(s) to enhance heat exchange as the said fluid is passed through the casing.

Preferably a lip extends from the free end of each wall to give the free end of each wall an enlarged surface area to facilitate heat transfer as the said fluid is passed through the casing.

The method may comprise passing a coolant through a housing in which one or more devices comprising a channelling means within casing, are located, and passing relatively warm fluid through the or each device, whereby heat is transferred from the relatively warm fluid through the channelling means and/or casing(s), to the coolant.

According to a further aspect of the present invention there is provided a fluid channelling member comprising at least one channel to channel fluid therealong to follow an indirect path from one end of the member to the other.

Preferably the fluid channelling member comprises at least one twisted channel defining the or each aforesaid path. The or each channel preferably defines a generally helical path, desirably along substantially the whole length of the channelling means.

Preferably the fluid channelling member comprises a spine and walls extending from the spine to define the channel or channels. The walls may diverge in a direction away from the spine. Preferably, the walls are arranged around the spine to define a plurality of equispaced channels. There may be six channels extending along the channelling member, twisting around the spine.

The spine is preferably central.

Preferably a rib extends along at least a part of the length of a wall of the or at least one of the channel(s). A rib may extend along each of two walls of the or at least one of the channel(s). Preferably the ribs are generally mutually opposite, within the channel.

A lip may be provided along, at least part of, the free end of a wall of the or at least one of the channel(s) to enlarge the surface area of the free end.

A lip may be provided on each of two walls defining the or at least one of the channel(s). Preferably a lip is provided on both sides of the wall, to give the free end thereof a generally "T"-shaped cross-sections.

Preferably the or each channel is defined by two, radially diverging walls. Adjacent channels may share a common wall.

Preferably the member is adapted to be locatable within a casing, such as a tube, preferably to be a friction fit therein, such that fluid moving through the tube, passes along the channel or channels to follow a generally helical path or paths. Preferably the free end of each wall abuts the inside of the casing. The free end of the walls may be arcuate, centred on the axis of the tube.

According to a further aspect of the present invention there is provided a method of forming channelling means as hereinbefore described, the method comprising extruding material through forming means to form an extrusion of desired cross-section, and twisting the extrusion along at least part of its length.

The material may be heated before or during extrusion. The material is preferably relatively soft.

Preferably the material is an aluminium alloy, and preferably a 6,000 series aluminium alloy, such as 6,063 T4 aluminium alloy.

Preferably the extrusion is stretched following formation, preferably before being twisted. The extrusion is preferably twisted from at least one end.

The extrusion may be twisted cold. The channelling means may be heat treated and/or chemically treated to harden it.

The forming means may be a die.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is the outline of a cross-section along the lines I-I of Fig. 2 of a channelling member according to the present invention; Fig. 2 is a side view of a channelling member according to the present invention; Fig. 3 is the outline of a cross-section of a device according to the present invention; and Fig. 4 is a diagrammatic cross-section of heat transfer apparatus according to the present invention.

Heat transfer apparatus 10 (Fig. 4) comprises a device 12 (Fig. 3) having a tubular casing 14 and a fluid channelling member 16 located in the tube 14.

The member 16 is elongate and comprises six walls 20 extending radially from a central spine 22. The walls 20 are equispaced and follow a helical path around the spine 20, to define six equispaced, helical channels 18, (Figs. 1 and 2) which extend along the whole length of the member 16.

Each wall 20 forms a partition between two adjacent channels 18.

A rib 24 extends from both sides of each of the walls 20. Each rib 24 is located towards the free end of each wall 20, and extends along the length of the wall 20.

Lips 26 extend from each side of each wall 20, at the free end thereof. These lips 26, along with the outer edge of the respective walls 20, provide a surface 28 of greater area than the corresponding area of the cross-section of the wall 20 alone. The cross-section of the free end of each wall 20 is generally "T"-shaped, with each surface 28 being arcuate, centred on the axis of the tube 14, to ensure maximum area of contact between the surface 28 and the inside of the tube 14.

The member 16 is located in the tube 14 by mechanical insertion resulting in a friction fit between the inside of the tube 14 and the surfaces 28 on each wall 20 (Fig. 3).

The tube 14 may be copper and the member 16 may be aluminium, such that during use, the security of the member 16 within the tube 14 increases due to the differences in thermal expansion of the two metals. The aluminium will expand to press tightly against the copper.

The apparatus 10 further comprises a housing 30 (Fig. 4) in which a number of devices 12 as described above may be accommodated. The housing 30 comprises an elongate tube along which the devices 12 extend generally parallel to one another, but preferably with some space therebetween.

One end of each device 12 is connected to a source (not shown) of relatively warm fluid, either liquid or gas. The other end of each device 12 is connected to fluid collecting means (not shown). Similarly, one end of the housing 30 is connected to a fluid coolant source (not shown), the other end to a coolant collecting means (not shown).

In use, relatively warm fluid is passed, preferably with some driving force, through the devices 12, usually by pumping. Coolant is passed around the devices 12, within the housing 30. As the warm liquid moves through the devices 12, it is channelled along the helical paths defined by the members 16. This causes the warm liquid to be continually in motion around the spine 16, such that different portions of the warm liquid are continually coming into contact with the tube 14. The helical path tends to cause the liquid to adopt a cyclic motion whereby liquid is continually being displaced from the centre of the tube towards the outside and back again. This facilitates direct heat transfer from the warm liquid, through the tube 14 to the coolant.It ensures that all the liquid in the device is continually circulated to be brought into contact with the tube 14, thereby preventing the problem of "coring".

Furthermore, the walls 20 and the ribs 24 provide additional surfaces for the transfer of heat from the warm liquid to the member 16. The member 16 transfers heat, by conduction along the ribs 24 and walls 20, to the tube 14 and hence the coolant. The surfaces 28 on the walls 20 of the member 16, provide relatively large contact areas between the member 16 and the tube 14, thereby facilitating heat transfer therebetween.

Manufacturing the member 16 in aluminium further facilitates heat transfer.

It is to be appreciated that the apparatus can be used with both liquid and/or gas. The member can define any number of channels, and the pitch of the twist, whether it be a helical or any other twisted configuration, can be of any desired pitch. That is, the number of turns per unit length of the member is chosen according to the desired application. Other shapes of indirect path could be used, but generally helical paths are preferred in order to provide relatively smooth fluid flow with enhanced heat transfer and reduced or eliminated "coring". The housing may be of any suitable shape and size. The member and casing may be of any suitable material.

The member 16 is formed from an extrusion, formed by forcing material through a die (not shown) having an internal profile corresponding to the profile shown in Fig. 1. The material from which the member 16 is formed is a relatively soft aluminium alloy, such as 6,000 series aluminium alloy. 6,063 T4 condition aluminium alloy has been found to be particularly suitable.

The material is heated before it is extruded through the die. The extrusion which has a cross-section corresponding to that shown in Fig. 1 is then stretched slightly to ensure it is as straight as possible. The extrusion is then twisted mechanically from at least one end to form the member 16. Careful twisting ensures the member has a substantially uniform pitch along its length. Clearly members 16 of any length can be formed using this method, and a plurality of members 16 may be produced from a single extrusion.

It has been found that the extrusion can be twisted cold, and that once twisted the member 16 often has sufficient strength for use. However, conventional techniques may be used to further harden the member 16 if desired. For instance the member 16 may be heat treated and/or chemically treated.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. Heat transfer apparatus comprising a casing and fluid channelling means located therein, the said channelling means being so formed as to define at least one indirect path through the space within the casing, and along which the channelling means, in use, channels fluid passing through the space.

2. Apparatus according to claim 1, in which the fluid channelling means comprises a member locatable within the casing.

3. Apparatus according to claim 1 or claim 2, in which the fluid channelling means comprises at least one twisted channel defining the or each aforesaid path.

4. Apparatus according to claim 3, in which the or each channel defines a generally helical path.

5. Apparatus according to claim 4, in which the or each helical path extends along substantially the whole length of the channelling means.

6. Apparatus according to any of claims 3 to 5, in which the fluid channelling means comprises a spine and walls extending from the spine to define the channel or channels.

7. Apparatus according to claim 6, in which the walls diverge in a direction away from the spine.

8. Apparatus according to claim 6 or claim 7, in which the walls are arranged around the spine to define a plurality of equispaced channels.

9. Apparatus according to any of claims 3 to 8, in which there are six channels extending along the channelling means, twisting around the spine.

10. Apparatus according to any of claims 6 to 9, in which the spine is central.

11. Apparatus according to any of claims 6 to 10, in which a rib extends from a wall of the or at least one of the channel(s) to enhance heat exchange.

12. Apparatus according to claim 11, in which a rib is provided on two walls defining the or at least one channel.

13. Apparatus according to any of claims 6 to 12, in which a lip is provided along at least part of the free end of a wall of the or at least one of the channel(s).

14. Apparatus according to any of claims 6 to 13, in which a lip is provided on each of two walls defining the or at least one channel.

15. Apparatus according to any of claims 6 to 14, in which two radially diverging walls define the or each channel.

16. Apparatus according to any of claims 13 to 15, in which a lip extends from the free end of each wall to give the free end of each wall an enlarged surface area.

17. Apparatus according to any of claims 6 to 16, in which the free end of each wall is of generally "T "-shaped cross-section.

18. Apparatus according to any of claims 6 to 17, in which each wall defines one side of two adjacent channels.

19. Apparatus according to any of claims 6 to 18, in which the channelling member is a friction fit within the casing such that the free end of each wall abuts the inside of the casing.

20. Apparatus according to any preceding claim, in which the casing is a tube.

21. Apparatus according to any of claims 6 to 20, in which the free end of each wall is arcuate.

22. Apparatus according to claim 21, in which the arc of the or each wall is centred on the axis of the tube.

23. Apparatus according to any preceding claim, in which the channelling means comprises aluminium.

24. Apparatus according to any preceding claim, in which the casing comprises copper.

25. Apparatus according to any preceding claim, in which a housing is provided in which at least one device comprising a channelling means within a casing is located.

26. Apparatus according to claim 25, in which means is provided for the flow of coolant through the housing, around the or each device, whilst relatively warm fluid is passed through the or each device.

27. A method of heat transfer, the method comprising passing a fluid of a first temperature through a casing having fluid channelling means located therein, the said channelling means being so formed as to define at least one indirect path along the space within the casing, along which the fluid is channelled through the space, and passing a further fluid of a second temperature around the outside of the casing, whereby heat is transferred through the casing and/or fluid chanelling means, from one fluid to another until the first and second temperatures are substantially equal.

28. A method according to claim 27, in which the said fluid is channelled along at least one twisted path.

29. A method according to claim 28, in which the or at least one of the parths is helical.

30. A method according to any of claims 27 to 29, in which the or each path extends along substantially the whole length of the channelling means.

31. A method according to any of claims 27 to 30, in which the said fluid is channelled along a channel or channels defined by walls extending from a spine of the channelling means.

32. A method according to claim 31, in which the walls diverge in a direction away from the spine.

33. A method according to claim 31 or claim 32, in which the said fluid is channelled along a plurality of channels.

34. A method according to claim 33, in which the fluid is channelled along six channels.

35. A method according to claim 33 or claim 34, in which the channels are equispaced around the spine.

36. A method according to any of claims 31 to 35, in which a rib extends from a wall of the or at least one of the channel(s) to enhance heat exchange as the said fluid is passed through the casing.

37. A method according to any of claims 31 to 36, in which a lip extends from the free end of each wall to give the free end of each wall an enlarged surface area to facilitate heat transfer as the said fluid is passed through the casing.

38. A method according to any of claims 27 to 37, in which a coolant is passed through a housing in which one or more devices comprising a channelling means within casing, are located, and passing relatively warm fluid through the or each device, whereby heat is transferred from the relatively warm fluid through the channelling means and/or casing(s), to the coolant.

39. A fluid channelling member comprising at least one channel to channel fluid therealong to follow an indirect path from one end of the member to the other.

40. A member according to claim 39, in which the fluid channelling member comprises at least one twisted channel defining the or each aforesaid path.

41. A member according to claim 40, in which the or each channel defines a generally helical path.

42. A member according to claim 41, in which the path extends along substantially the whole length of the channelling means.

43. A member according to claims 40 to 42, in which the fluid channelling member comprises a spine and walls extending from the spine to define the channel or channels.

44. A member according to claim 43, in which the walls diverge in a direction away from the spine.

45. A member according to claim 43 or 44, in which the walls are arranged around the spine to define a plurality of equispaced channels.

46. A member according to claim 45, in which six channels extend along the channelling member, twisting around the spine.

47. A member according to any of claims 43 to 46, in which the spine is central.

48. A member according to any of claims 43 to 47, in which a rib extends along at least a part of the length of a wall of the or at least one of the channel(s).

49. A member according to claim 48, in which a rib extends along each of two walls of the or at least one of the channel(s).

50. A member according to claim 49, in which the ribs are generally mutually opposite, within the channel.

51. A member according to claims 43 to 50, in which a lip is provided along, at least part of, the free end of a wall of the or at least one of the channel(s) to enlarge the surface area of the free end.

52. A member according to claim 51, in which a lip is provided on each of two walls defining the or at least one of the channel(s).

53. A member according to claim 51 or 52, in which a lip is provided on both sides of the wall, to give the free end thereof a generally "T"-shaped cross-sections.

54. A member according to any of claims 43 to 53, in which the or each channel is defined by two, radially diverging walls.

55. A member according to any of claims 43 to 54, in which adjacent channels share a common wall.

56. A member according to any of claims 40 to 55, in which the member is adapted to be locatable within a casing, such as a tube, to be a friction fit therein, such that fluid moving through the tube, passes along the channel or channels to follow a generally helical path or paths.

57. A member according to claim 56, in which the free end of each wall abuts the inside of the casing.

58. A member according to claim 56 or 57, in which the free end of the walls is arcuate.

59. A member according to claim 58, in which the arc is centred on the axis of the tube.

60. A method of forming channelling means as defined in claims 39 to 59, the method comprising extruding material through forming means to form an extrusion of desired cross-section, and twisting the extrusion along at least part of its length.

61. A method according to claim 60, in which the material is heated before or during extrusion.

62. A method according to claim 60 or 61, in which the material is relatively soft.

63. A method according to any of claims 60 to 62, in which the material is an aluminium alloy.

64. A method according to claim 63, in which the material is a 6,000 series aluminium alloy, such as 6,063 T4 aluminium alloy.

65. A method according to any of claims 60 to 64, in which the extrusion is stretched following formation.

66. A method according to any of claims 60 to 65, in which the extrusion is stretched before being twisted.

67. A method according to any of claims 60 to 66, in which the extrusion is twisted from at least one end.

68. A method according to any of claims 60 to 67, in which the extrusion is twisted cold.

69. A method according to any of claims 60 to 67, in which the channelling means is heat treated and/or chemically treated to harden it.

70. A method according to any of claims 60 to 67, in which the forming means is a die.

71. Heat transfer apparatus substantially as hereinbefore described with reference to the accompanying drawings.

72. A method of heat transfer substantially as hereinbefore described with reference to the accompanying drawings.

73. A fluid channelling member substantially as hereinbefore described with reference to the accompanying drawings.

74. A method of forming channelling means substantially as hereinbefore described with reference to the accompanying drawings.

75. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.