Gas Flow Conditioner Device for a Heat Exchanger

Abstract

Flow conditioner device (40), for use in a heat exchanger system (10). The flow conditioner device includes a honeycomb structure (42) and a mesh (44). The honeycomb structure is configured for rectifying an incoming gas flow (26), and is formed by walls that border channels extending in a flow direction (X) from inlet apertures at a leading surface, to respective outlet apertures at a trailing surface of the honeycomb structure. The mesh is formed by a plurality of wires that extend along further directions (Y, Z) transverse to the flow direction, and which are mutually spaced to define openings. The mesh is attached directly to the honeycomb structure and abuts the second surface, and cross-sectional areas of the openings defined along the further directions vary as a function of position along at least one of the further directions.

Claims

1. A flow conditioner device (40), for use in a heat exchanger system (10), wherein the flow conditioner device comprises: a honeycomb structure (42) for rectifying an incoming gas flow (26), wherein the honeycomb structure is formed by a plurality of walls (46, 47), which border a plurality of channels (48) that extend in a flow direction (X) from respective inlet apertures (56) at a first surface (52), to respective outlet apertures (58) at a second surface (54) of the honeycomb structure; a mesh (44), formed by a plurality of wires (60, 61), which extend along further directions (Y, Z) transverse to the flow direction, and which are mutually spaced to define a plurality of openings (62); wherein the mesh is attached directly to the honeycomb structure and abuts the second surface, and wherein cross-sectional areas (A.sub.o) of the openings defined along the further directions vary as a function of position along at least one of the further directions.

2. The flow conditioner device (40) according to claim 1, wherein the mesh (44) extends directly across the outlet apertures (58) of the honeycomb structure (42), and is configured to generate turbulences with predetermined length scales in a regularized gas flow (28) downstream of the flow conditioner device.

3. The flow conditioner device (40) according to claim 1, wherein the cross-sectional areas (A.sub.o) of the openings (62) of the mesh (44) are everywhere smaller than cross-sectional areas (A.sub.a) of the outlet apertures (58) of the honeycomb structure (42) defined along the further directions (Y, Z).

4. The flow conditioner device (40) according to claim 1, wherein the cross-sectional areas (A.sub.o) of the openings (62) vary monotonically as a function of position along a line transverse to the flow direction (X).

5. The flow conditioner device (40) according to claim 1, wherein cross-sectional dimensions (D.sub.o1, D.sub.o2) of the openings (62) defined along the further directions (Y, Z) are 10 millimeters or less.

6. The flow conditioner device (40) according to claim 1, wherein the wires (60, 61) in the mesh (44) are arranged to form a grid with quadrilateral openings (62).

7. The flow conditioner device (40) according to claim 1, wherein the walls (46, 47) in the honeycomb structure (42) are arranged to form channels (48) with quadrilateral inlet and outlet apertures (56, 58).

8. The flow conditioner device (40) according to claim 1, wherein the openings (62) in the mesh (44) have shapes that are congruent to the outlet apertures (58) in the honeycomb structure (42), and wherein the wires (60, 61) in the mesh are rotationally displaced over a non-zero angle (1) about a nominal axis along the flow direction (X) relative to the plurality of walls (46, 47) in the honeycomb structure.

9. The flow conditioner device (40) according to claim 1, wherein a length (ΔX1) of the channels (48) along the flow direction (X) is at least four times a transverse dimension (D.sub.a) of the channels.

10. The flow conditioner device (40) according to claim 1, wherein a cross-sectional void fraction of the mesh (44) is in a range of 80% to 90%.

11. The flow conditioner device (40) according to claim 1, wherein the wires (60, 61) of the mesh (44) have diameters (0) of less than 2 millimeters.

12. A heat exchanger system (10) comprising, a heat exchanger device (20) and a flow conditioner device (40) according to claim 1.

13. The heat exchanger system (10) according to claim 12, wherein the flow conditioner device (40) is positioned upstream on a channel entrance side (38) of the heat exchanger device (20).

14. The heat exchanger system (10) according to claim 12, wherein the heat exchanger device (20) is of a plate-type, comprising heat transfer plates (32), wherein each plate extends predominantly in a plane along the flow direction (X) and a first transverse direction (Y), and wherein the plates are mutually spaced along a second transverse direction (Z) to define heat exchanger channels (34, 36) in between the plates; wherein wires (60, 61) in the mesh (44) of the flow conditioner device (40) are arranged to form a grid with rectangular openings (62), and wherein a portion of the wires (61) is oriented along the second transverse direction.

15. The heat exchanger system (10) according to claim 14, wherein the rectangular openings (62) are square openings.

16. The flow conditioner device (40) according to claim 6, wherein the quadrilateral openings (62) are rectangular openings.

17. The flow conditioner device (40) according to claim 6, wherein the quadrilateral openings (62) are square openings.

18. The flow conditioner device (40) according to claim 7, wherein the outlet apertures (56, 58) are rectangular apertures.

19. The flow conditioner device (40) according to claim 7, wherein the outlet apertures (56, 58) are square apertures.

20. The flow conditioner device (40) according to claim 11, wherein the diameters (Ø) range from 500 micrometers to 1 millimeter.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] Embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts. In the drawings, like numerals designate like elements. Multiple instances of an element may each include separate letters appended to the reference number. For example, two instances of a particular element “20” may be labeled as “20a” and “20b”. The reference number may be used without an appended letter (e.g. “20”) to generally refer to an unspecified instance or to all instances of that element, while the reference number will include an appended letter (e.g. “20a”) to refer to a specific instance of the element.

[0025] FIG. 1 schematically shows a portion of a heat transfer system, according to an embodiment;

[0026] FIG. 2 presents a perspective view of a flow conditioner device, according to an embodiment;

[0027] FIG. 3 shows details of the flow conditioner device from FIG. 2.

[0028] The figures are meant for illustrative purposes only, and do not serve as restriction of the scope or the protection as laid down by the claims.

DESCRIPTION OF EMBODIMENTS

[0029] The following is a description of certain embodiments of the invention, given by way of example only and with reference to the figures.

[0030] FIG. 1 schematically shows a perspective view of a portion of a heat transfer system 10. The heat transfer system 10 includes a sequence of conduits 12, which are in fluid communication to define a passage for a flowing gas 26, 28, 30. The conduits 12 are connected to each other, and to a heat exchanger (HE) device 20, and allow the flowing gas to traverse the HE device 20.

[0031] Reference symbol X is used to indicate a longitudinal direction, corresponding with a local direction of macroscopic gas flow. This flow direction X corresponds with the local direction of a sufficiently straight portion of the conduits 12, and may vary along the system of conduits 12. The term “upstream” and “downstream” designate directions opposite to and along with the flow direction X, respectively. Reference symbols Y and Z are used to indicate (local) transversal directions that are perpendicular to X.

[0032] On an upstream region 22 of the conduits relative to HE device 20, the conduits 12 accommodate a flow conditioner (FC) device 40. This FC device 40 allows an incoming gas flow 26 to pass through, and is configured to reduce macroscopic rotation (i.e. “swirl”) and promote uniformity in the velocity distribution of the incoming flow 26. Non-uniform velocity profiles may for instance be caused by a curved section (e.g. a turn) 15 in the upstream region 22 of the conduits 12. The curved section may include a slight turn as shown in FIG. 1, but may alternatively trace out a sharper curve (e.g. a 180° turn), or a sequence of turns in different directions.

[0033] The resulting flow 28 that exits the FC device 40 at the side of the intermediate conduit portion 16 is regularized (i.e. has a more uniform velocity profile and less swirl), before it enters a plurality of first channels 34 that extend through the HE device 20

[0034] FIG. 2 shows the exemplary FC device 40 of FIG. 1 in more detail. The flow conditioner device 40 comprises a flow rectifier 42 and a wire mesh 44. In FIG. 2, the mesh 44 is shown removed from a rear surface 54 of the flow rectifier 42, only for illustrative purposes. In an assembled state of the FC device 40, the mesh 44 is attached directly to the rear surface 54 (i.e. at an outlet side) of the flow rectifier 42, so that the flow rectifier 42 and the mesh 44 abut and form a unit. The mesh 44 may be attached to the flow rectifier 42 by known methods, like bolting, welding, clamping, or equivalent means of attachment.

[0035] The flow rectifier 42 comprises a honeycomb structure, which is configured to rectify (i.e. to reduce or even remove swirling motion from) the incoming flow of gas 26, once it passes through the honeycomb structure 42. This honeycomb structure 42 is formed by a rigid array of walls 46, 47, which extend over a characteristic length ΔX1 along the flow direction X. The walls 46-47 enclose square channels 48 from the transverse directions Y, Z. The walls 46-47 are formed by a structurally rigid and self-supporting material (e.g. carbon steel or stainless steel), and are preferably sufficiently thin (e.g. the order of 2 millimeters or less) to limit flow resistance while reducing the likelihood of deforming under operational conditions.

[0036] The channels 48 extend, from inlet apertures 56 on a leading surface 52 of the honeycomb structure 42, along the flow direction X, to outlet apertures 58 on the rear surface 54 of the honeycomb structure 42. Only one such channel 48a, inlet aperture 56a, and outlet aperture 58a are schematically shown in FIG. 2 for clarity. It should, however, be understood that multiple channels 48 and apertures 56, 58 are present, which define a regular two-dimensional array along the transverse directions Y, Z.

[0037] A cross-sectional area A.sub.a of each channel 48 in the transverse directions Y, Z is essentially constant along the entire length ΔX1 of the channel 48. The channel length ΔX1 is relatively long, relative to a transverse thickness of the walls 46-47, and relative to transverse channel dimensions D.sub.a (e.g. ΔX1>√A.sub.a). In particular, the channel length ΔX1 is at least four times the transverse dimensions D.sub.a of the channels 48, to provide good swirl reduction effects. For rectangular channels 48 with a transverse edge size D.sub.a of 50 millimeters, the channel length ΔX1 may for instance be 200 millimeters or larger.

[0038] The mesh 44 is located on the rear surface 54 of the honeycomb structure 42, and is directly attached to this rear surface 54. The honeycomb structure 42 is thus located directly upstream of the mesh 44, without space in between. The mesh 44 covers the outlet apertures 58 of the honeycomb structure 42, and is configured to generate turbulences with defined length scales in the regularized gas flow 28 that exits the FC device 40 during operation.

[0039] The honeycomb structure 42 also includes peripheral walls 50, 51, and may further include reinforced walls 59a, 59b that extend between the internal walls 46, 47 and diagonally between the peripheral walls 50, 51 to provide additional structural support to the honeycomb structure 42. The trailing surface of these reinforced walls 59 may be used as attachment region for the mesh 44.

[0040] The mesh 44 is formed by a plurality of wires 60, 61, which extend along the transverse directions Y, Z, and which are woven into a grid structure. The first wires 60 and second wires 61 enclose openings 62 in transverse directions Y, Z (again, only one such opening 62a is shown in FIG. 2 for clarity). In this example, the openings 62 have rectangular or square shapes, and also form a two-dimensional array in the transverse directions Y, Z.

[0041] In this example, the wires 60-61 have diameters Ø in a range from 500 micrometers to 1 millimeter. The cross-sectional void fraction of the mesh 44 is preferably in a range of 80% to 90%. Due to crossing of wires 60-61 in the mesh 44, the mesh 44 extends over a mesh length ΔX2 that is at most 2 millimeters along the flow direction X (i.e. ΔX2<<ΔX1).

[0042] Cross-sectional areas A.sub.o of the mesh openings 62 are everywhere smaller than cross-sectional areas A.sub.a of the outlet apertures 58. In the example of FIG. 2, the openings 62 are rectangular, and are smaller towards a lower edge 65 of the mesh 44. This lower edge 65 is associated with a longer outer part of the curved wall section 15 in the conduit system 12 from FIG. 1. As a result, the mesh 44 has a denser region on the lower mesh edge 65, and a courser region on an opposite mesh edge 64.

[0043] As shown in FIG. 2, the FC device 40 is positioned upstream, at a distance ΔX3 from a channel entrance side 38 of the HE device 20. In the case that the HE system 10 includes a plate-type HE device 20 with first fluid channels 34 that extend with a height AZ (i.e. inter-plate distance) along the second transverse direction Z in the order of 10 millimeters, this intermediate spacing ΔX3 is preferably 100 millimeters or less.

[0044] In embodiments wherein the honeycomb structure 42 includes diagonal reinforcing walls 59a, 59b, the FC device 40 may be mechanically fixed onto or integrated with the channel entrance side 38 of the HE device 20 (i.e. ΔX3≈0 millimeter), so that these walls 59 may reinforce the HE device 20 as well.

[0045] Alternatively or in addition, the generation by the mesh 44 of small-scale turbulences in the regularized gas flow 28 can be exploited to improve heat transfer characteristics of the gas flow inside the first HE channels 34 of the HE device 20. This effect becomes more noticeable if the spacing ΔX3 is reduced. In embodiments wherein the FC device 40 is mounted directly to the channel entrance side 38 of the HE device 20 (i.e. ΔX3≈0 millimeter), a second portion of the wires 61 of the mesh 44 is preferably oriented parallel with the second transverse direction Z, so that these wires 61 define fine turbulence-inducing structures that extend perpendicular to the main surfaces of the heat transfer plates 32.

[0046] FIG. 3 shows the honeycomb structure 42 and the mesh 44 in the FC device 40 of FIG. 2 in more detail. In this example, the openings 62 in the mesh 44 have shapes that are congruent to the outlet apertures 58 in the honeycomb structure 42. The wires 60, 61 of the mesh 44 are rotationally displaced relative to the walls 46, 47 of the honeycomb structure 42 over an angle φ≈45° about a nominal axis along the flow direction X. This relative orientation is preferred if diagonal reinforcing walls 59a, 59b are present in the honeycomb structure 42 to provide enhanced structural support.

[0047] The cross-sectional areas A.sub.o of the openings 62 are everywhere smaller than the cross-sectional areas A.sub.a of the outlet apertures 58 of the honeycomb structure 42. The mesh 44 has a non-uniform mesh size, meaning that the spacing between adjacent wires 60-61 and resulting transverse sizes D.sub.o1, D.sub.o2 of the openings 62 vary as a function of position along the mesh surface. As a result, the openings 62 have varying cross-sectional areas A.sub.o1, A.sub.o2. In this example, the mesh 44 has a stepped transition region, which divides the mesh 44 in a rectangular region with a lower mesh density i.e. larger opening area A.sub.o1 on an upper side (associated with the upper mesh edge 64) and a rectangular region with a higher mesh density i.e. smaller opening area A.sub.o2 on a lower side (associated with the lower mesh edge 65). Here, A.sub.o1≈4.Math.A.sub.o2.

[0048] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. It will be apparent to the person skilled in the art that alternative and equivalent embodiments of the invention can be conceived and reduced to practice. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

[0049] The openings in the wire mesh may for instance have triangular, quadrilateral, hexagonal, or other shapes.

[0050] Alternatively or in addition, the mesh may include more than just two mesh density regions, each region including mesh openings with cross-sectional areas A.sub.oi that differ from the other regions. Furthermore, transition(s) in the mesh from a lower mesh density region (i.e. larger opening areas A.sub.o1) to a higher mesh density region (i.e. smaller opening areas A.sub.o2) may be gradual instead of stepped.

[0051] In the example of FIG. 2, the cross-sectional areas A.sub.a of each channel of the honeycomb structure remained constant over the length of the channel, which implied the presence of walls with a rectangular cross-sectional shape along the flow direction. In alternative embodiments, the walls of the honeycomb structure may have an aerodynamic profile along the flow direction, which may include a rounded leading edge and/or a sharp trailing edge.

LIST OF REFERENCE SYMBOLS

[0052] 10 heat exchanger system [0053] 12 conduit assembly [0054] 14 first conduit portion (e.g. supply conduit) [0055] 15 curved conduit section [0056] 16 intermediate conduit portion [0057] 18 second conduit portion (e.g. discharge conduit) [0058] 20 heat exchanger device [0059] 22 upstream region [0060] 24 downstream region [0061] 26 incoming flow [0062] 28 regularized flow [0063] 30 outgoing flow [0064] 32 heat transfer plate [0065] 34 first HE channel (e.g. longitudinal fluid channel) [0066] 36 second HE channel (e.g. transverse cross-flow fluid channel) [0067] 38 HE channel entrance [0068] 40 flow conditioner device [0069] 42 flow rectifier (e.g. honeycomb structure) [0070] 44 wire mesh [0071] 46 wall [0072] 47 further wall [0073] 48 channel [0074] 50 peripheral wall [0075] 51 further peripheral wall [0076] 52 first surface (e.g. leading/front surface) [0077] 54 second surface (e.g. trailing/rear surface) [0078] 56 inlet aperture [0079] 58 outlet aperture [0080] 59 reinforced wall [0081] 60 wire [0082] 61 further wire [0083] 62 opening [0084] 64 mesh edge [0085] 65 further mesh edge [0086] A.sub.a aperture area [0087] A.sub.o opening area [0088] φ displacement angle [0089] X first direction (flow direction) [0090] Y second direction (first transversal direction) [0091] Z third direction (second transversal direction) [0092] ΔX1 channel length [0093] ΔX2 mesh length [0094] ΔX3 intermediate spacing [0095] ΔZ HE channel height [0096] D.sub.a transverse channel edge size [0097] D.sub.o1 first transverse mesh edge size [0098] D.sub.o2 second transverse mesh edge size