Improvements to heat exchange

Abstract

The invention relates to a heat exchanger with inter-connecting cells in a row or block which evenly distribute and transfer heat to a fluid within a cell. Voids between rows or blocks of cells and the heat transfer medium comprise additional means of transferring heat from a heat-transfer medium to the fluid within the cells. The heat exchanger may be used but not limited to applications such as a condenser in an air conditioning unit, a wall heater or an indirect evaporative cooler.

Claims

1. A heat exchanger (60) comprising: at least a first and a second conduit (1) of at least a first row (2); each conduit (1) comprising at least eight sides (4); wherein the internal angles of the conduits (1) are obtuse; each conduit (1) comprising a first fluid flowing within the conduit (1); a first means of heat transfer comprising one or more protrusions (3) extending longitudinally along the inside periphery of the conduit (1); the first and second conduits (1) characterized by: a first side (4) of the first conduit (1) substantially opposite a second side (4) of the first conduit; wherein the first side of the first conduit (1) of conduit 1 is in substantially continuous contact with the second side (4) of a second conduit (1) for at least substantially an eighth of the perimeter of the conduit (1); wherein the shared heat transfer length along both heat transfer lengths of the first and second conduits(1) is constant; a third side of the first conduit (1) adjacent to the first side of the first conduit and a fourth side of the second conduit adjacent to the third side of the first conduit; a heat transfer medium (61); wherein when forming a row of at least two conduits (1), the external surfaces of the third, fourth or more adjacent sides to the third or fourth side and a tangent to the external surface of the conduit (1), the tangent being perpendicular to the first or second side, create a void (8) in thermal contact with the heat transfer medium (61); a second means of heat transfer (5) within void (8); wherein the second means of heat transfer (5) is one or more fins, or thermal mass extending from, or In contact with, the external surfaces of the third, fourth or more sides excluding the first and second sides of conduit (1); wherein the void (8) is blocked from the first fluid.

2. A heat exchanger (60) as claimed in claim 1 for use in a heater (64) in a building (62), comprising: at least one row (2) of the conduits (1) comprising: a first end (45) and a second end (46); wherein the at least one row (2) is fastened to a first end plate (44) at the first end (45); wherein the void (8) is blocked from the first fluid by at least the first end plate (44) or an end cap (25) wherein the conduit (1) comprises eight sides wherein a fifth and a sixth sides (4) are substantially perpendicular to the first side of the conduit (1); wherein the fifth side is opposite the sixth side; wherein at least one of the fifth or the sixth sides (4) are In thermal communication with the heat transfer medium (61); and wherein the first end portion (49) comprises: a first air entry conduit fluidly connecting the first end (45) of the at least one row (2) to the outside air; a first interior air conduit fluidly connecting the second end (46) of the at least one row (2) to the inside of the building (62).

3. A heat exchanger (60) as claimed in claim 1 for use in an Indirect evaporative cooler (94) wherein the indirect evaporative cooler (94) comprises: the one or more conduits (1) arranged substantially horizontally; wherein at least the first and second conduits (1) are vertically aligned in row (2); wherein the sides of the one or more conduits (1), excluding the first and second sides, define a substantially cylindrically shaped side (91) to one side of the first and second sides of the conduit (1) in contact with the heat transfer medium (61); wherein the heat transfer medium (61) is water; one or more rows (2) of the conduits (1); and wherein one or more rows (2) are positioned below one or more water pipes (85) and above a sump (81); the sump (81) comprising one or more air vents (97) extending above the water line of the sump (81); a second void (98) between rows (2) of the conduits (1) and the first void (8); a first air supply (84) fluidly connecting the one of more air vents (97) and the second void (98) between rows (2) to a means of heating air; a first exhaust air conduit (83) fluidly connecting the second void (98) to the exterior above the indirect evaporative cooler (94); a second air supply (75) fluidly connecting the interior (77) of the conduits (1) to the exterior; a second exhaust duct (78) fluidly connecting the interior (77) of the conduits (1) to the building interior.

Description

DEATILED DESCRIPTION OF THE INVENTION

[0056] FIG. 1 discloses a perspective view of an example of a heat exchanger 23 comprising two rows 2 of conduits 1 that form a block. Protrusions 3 extend longitudinally along the inside periphery of conduits 1. The outer perimeter comprises flat face 4 which enables improved proximity and/or points of contact with other octagon cells thereby improving heat exchange.

[0057] The advantage of a block of octagonal conduits as compared to other prismatic conduits in certain applications is that the outer perimeter is spatially compact when accommodated in a square or rectangular insulating cover. Furthermore, it provides a flat surface if the source of heating is along one or more sides of a block of conduits. Also, in the case of a block of conduits that are octagonal, void 8 is formed by adjoining conduits. This allows for an even distribution of heat exchange when void 8 comprises a heat transfer medium 61. If the material chosen has high thermal conductivity, then heating can evenly radiate to all octagonal faces 4 within the block of octagonal conduits.

[0058] The means 5 within void 8 that transfers heat from the medium to the conduits can vary according to the form of heat exchange. It may form a solid surface around the heat source or it may comprise fins extending towards the heat source. Preferable heat transfer means 5 maximizes contact between conduits 1 and the heat exchange medium in order to optimize heat exchange.

[0059] If void 8 contains a copper pipe and the extrusion is aluminium, for example, it would be preferable for the pipe to be in contact with the extrusion to maximize heat transfer. This however can cause problems due to unlike metals and corrosion. One possible solution can be, for example, to encase the pipe in two layers of graphene which can prevent this.

[0060] Screw port 6 is an example of a way to fasten one or more blocks of prismatic conduits to an end plate, but methods could also include, for example, male and female locking devices between blocks of prismatic conduits. Screw port 7 can be useful to fastening a seal to prevent a fluid entering void 8.

[0061] FIGS. 2a and 2b are perspective views of a section of helical fin 9 that can be inserted into the prismatic conduits preferably such that the side edges of helical fin 9 are in contact with protrusions 3. This lengthens the flow path to enable more heat exchange to take place without impeding the flow. It also creates turbulence around the inside periphery of the conduit. It can include side tabs so that it locks into place between the extrusions. Helical fin 9 can be heated. Examples of methods of heating the helical fin include an etched foil heating element or a heated tube 10. If the fin incorporates an etched foil heating element then it could then be corrugated or rippled in order to twist into a helix. Preferably the material of the helix is thermally conductive. Preferably also the etched heating element foil is protected from electricity leakage such as by means of graphene or micathermic sheets.

[0062] FIG. 3 is a perspective view that discloses an example how two different materials can form a block of conduits 1 for heat exchanger 23. For example, an outer casing 11 can be a material such as magnesium oxide which forms sides 4a of conduits 1, with the remaining sides 4b formed by an extrusion in another material such as aluminium. A means of heating 12a can be encased and transfer heat from tubular elements or other form of heating to the fluid flowing within conduits 1. Heating means 12b in void 8 may be in addition or instead of heating means 12a.

[0063] FIG. 4 is a perspective view of another embodiment of heat exchanger 23 comprising conduit 1 in a row of conduits 2. Heating means 13 can be located in close proximity to conduit 1. In this example, heating means 13 comprises etched foil heating elements located on the inside face of heated sheet 14 in the gaps between heated sheet 14 and prismatic conduits 1. The heat transfer medium 61 could also be water pipes or other heat transfer mediums 61. Preferably to avoid electricity leakage, heat transfer strips 15 can be in direct contact with heated sheet 14 and octagonal face 2 to increase the rate of heat exchange with face 4. A means of insulation can be included such as air gap 16 and insulation layer 17 to minimize heat loss away from the conduits.

[0064] FIG. 5 is a perspective view of a portion of prismatic conduit 1. This is an example of outer protrusions 18 extending from the outer periphery of conduit 1 wherein the objective is to maximize heat storage outside conduit 1 within cavities 19 and beyond. Inner protrusions 3 may also extend from the inner periphery of wall 2 and/or a helical ribbon extend longitudinally along conduit 1 thereby contributing further to improved heat transfer to a heat storage medium outside conduit 1.

[0065] FIG. 6 is a perspective view of an inline heat exchanger 101 of heat exchanger 23 as a block of conduits 1 connected to ducts at duct connections 102 and 103 via reducer 21. In this way a fluid flowing through a duct can be efficiently heated within the inline heat exchanger 101 with insulation and/or cover 20. The number and size of blocks of prismatic conduits can vary according to the duct size. To minimize labour costs, conduits can be extruded as a block of conduits, for example four prismatic conduits 1.

[0066] FIG. 7 is a perspective cross-sectional view of heat exchanger 23. This type of heat exchanger could be useful for a condenser in an air conditioner for example. The design of a block of prismatic conduits maximizes inter-connectivity between one or more conduits 1 while also evenly distributing void 8 which comprises a pipe 22 for a heat transfer material 61 such as a refrigerant for example. Preferably heat exchanger 23 is thermally conducting such as aluminium. Protrusions 3 extending longitudinally along octagonal conduit 1 can significantly increase heat exchange from pipes 22 to a fluid flowing through conduits 1. They are shown here to extend in parallel with conduit 1. However, with some manufacturing techniques such as 3D printing, it may be possible for them to also follow a helical trajectory.

[0067] One or more fins 24 between pipe 22 and conduit 1 or other means 5 of heat transfer also serve to exchange heat. For example, a means 5 to transfer heat can be shaped to a conduit as shown in FIG. 1 or it can be made from a different heat conductive material than heat exchanger 23. Means 5 within void 8 to transfer heat from a heat transfer medium 61 to the conduits will depend , for example, on the size and shape of the heat transfer medium 61. Removable helical fins 9 can be inserted into the conduits to improve turbulence and heat exchange with the inner periphery of the conduit wall.

[0068] This design helps to protect heat exchange pipe 22 from pollution. A coating on pipe 22 or the part of the heat exchanger in contact with pipe 22 can protect from corrosion due to dissimilar metals. For example, a coating of a double layer of graphene is known to not only have exceptionally high thermal conductivity but also to protect from metal corrosion on copper pipes.

[0069] Furthermore, conduit 1 which is exposed to constant air flow can be easily accessed and cleaned. The remaining areas of pipe 22 are also easily accessible to clean. Pipe 22 can contain a refrigerant or water for example.

[0070] FIG. 8 is a perspective view of one end of heat exchanger 23. It describes an example of ways to seal the cavity that encloses pipe 22 by means of one or more end caps 25. These can be fastened to conduits 1 by means of screw port 6.

[0071] FIG. 9 is a perspective view of an example of an arrangement of some of the components for a condenser in an air conditioning unit 65 comprising heat exchanger 23 and fan 39. Fan 39 with motor 29 can be, for example, the type of helical fan described in PCT/NZ2018/050010 which has excellent flow rate and pressure. It is shown here as a helical fan of opposite chirality with two exhaust openings 27 at both ends and an intake opening 28. Alternatively another type of fan could be used such as a centrifugal fan. In this example, intake opening 28 is connected to heat exchanger 23 so that fan 39 draws air through heat exchanger 23. A cover and seal can allow air to be drawn from the fan intake only, thereby increasing the flow rate through heat exchanger 23. Grill 30 can be spaced off blocks of conduits 1 to maximize air flow. In another embodiment one or more heat exchanger 23 can be located at the fan outlet such that the fan is driving air through heat exchanger 23 located at one or more fan exhaust openings 27.

[0072] This arrangement would be applicable to an outdoor condenser unit for example. All these components would of course be contained within an outdoor unit along with all other components such as a compressor.

[0073] FIG. 10 is a side profile of an example of a grill 32 with drip seal 33. This can be located in front of blocks of conduits 1 that form the heat exchanger. Top of grill 31 and bottom of grill 34 are curved such that the distance 35 is less than the distance 36.

[0074] FIG. 11 is a perspective view of an evaporator 105 comprising an example of a refrigerant pipe 38 coiled over the intake opening 40 of a fan 41 comprising a rotor and casing. Fan 41 can also be the type of helical fan as described in PCT/NZ2018/050010 with intake opening 40 and exhaust openings 27 which has excellent flow rate and pressure. Alternatively it can be a standard cross flow fan as commonly used in evaporator units.

[0075] In this example, refrigerant pipe 38 coils backwards and forwards over at least intake opening 40 of fan 41 in a FIG. 8 pattern. The refrigerant pipe 38 coils are angled such that it comprises an upper layer 42 and a lower layer 43. The objective is to space refrigerant pipe 38 in such a way as to maximize contact between refrigerant pipe 38 and the air flow without the use of traditional fins to transfer heat. Preferably the spacing allows for easy cleaning of refrigerant pipe 38. Two or more rows of fans 41 can supply the air flow and thermal comfort required with a continuation of refrigerant pipe 38 over intake 40 of the adjoining fan 41. Where there is little air flow between fans 41, refrigerant pipe 38 can discontinue to coil backwards and forwards. It would simply bridge the sections of coiling refrigerant pipe 38.

[0076] FIG. 12a is a perspective view of an embodiment of a row 2 of conduits 1 fastened to an upper and lower end plate 44. One or more sides comprise a heat exchange medium 61. An example of an application for this embodiment is disclosed in FIGS. 12b and 12c showing a wall-mounted heat exchanger. Upper portion 63 can include one or more rows 2 of conduits 1, heat exchange medium 61and end plates 44 enclosed in insulation 53 with air gap 58 and casing along with upper opening 47 and controls. Lower portion 49 can be joined to upper portion 63. A front cover 48 can be removed for example via clips and hinging tabs 54 to access a filter tray 55. In a less polluted environment, filter tray 55 may be a washable pre-filter. FIG. 12c is an example of the back of the wall-panel heat exchanger of FIG. 12b showing a means of fastening 52 to the wall. In this example, air is shown to be sourced externally via duct 50 and cowl 56.

[0077] FIG. 13 is a cross sectional view of this embodiment of lower portion 49. It discloses filter tray 55, clip 54 to lock a cover in place, duct 50 and cowl 56. Lower portion 49 may also contain a fan in a location within either lower portion 49 or duct 50. It is expected that some passive flow will result from heating air in upper portion 63, but lower portion 49 may also contain a fan to aid flow or to supply fresh air when heating is not needed.

[0078] In some environments that are polluted, fresh air requires a higher level of filtration. This necessarily entails increasing the surface area of the filter and fan power. This would require extending the lower portion 49 to include a large filter.

[0079] In some applications, it may be preferable to source and clean stale air. FIG. 14a is a perspective view of a wall-mounted heater with an extended lower portion 49. It includes vents 59 such as those shown in FIG. 14b.

[0080] FIG. 14b is a cross sectional view of an example of a lower portion 49 with an increased surface area for filter 70. Of course higher filtration requires a fan 71 capable of handling greater pressure such as a cross flow fan. A helical cross flow fan of the type described in PCT/NZ2018/050010 by the present inventor has been shown to be capable of relatively high pressure and flow rate.

[0081] In other embodiments of the invention, whether as blocks or single row of conduits, a fluid other than air, such as water or oil, can be heated by means of the heat exchanger described herein.

[0082] FIG. 15a is a perspective cross-sectional view of an indirect evaporative cooler 94 comprising a series of rows 2 of conduits 1. The extent of cooling achieved depends largely on the achieved temperature to dry the air. The ideal heat to dry air is between 60 and 80 degrees and ideally the relative humidity of this air should be under 30%. For this reason, indirect evaporative coolers only work in hot dry areas. They also can use a lot of water which can be a problem in hot dry areas. So in order to widen the geographic reach of evaporative coolers, they need a source of heating to dry air such as solar air heating working in tandem with the indirect evaporative cooler so that they will work when located in hot areas where water, fresh or sea water, isn't an issue.

[0083] A solar air collector such as the one described in PCT/NZ2013/000185 is ideally suited to provide free heat to dry air before it is cooled by means of evaporation. A test of a prototype solar air heater reached 60 C at the outlet providing about 350 m3/hr through natural thermal siphoning. The outside temperature was 25 C, so it is expected the temperature and air flow would increase much further as ambient temperature increased.

[0084] FIG. 15a discloses how a portion 72 of air conduit 83 can dry a section of desiccant wheel 73 as it slowly rotates. This air then passes through cavity 74 where it can either be exhausted to outside or alternatively mix with fresh air flow from opening 75. Fresh air from opening 75 passes through cavity 74, through desiccant wheel 73 where it is dried and then via conduits 1 which form the heat exchanger along air conduit 77 where it is cooled. Cooled air from air conduit 77 then passes through duct 78 to supply cooled air 79 to the building.

[0085] The other portion 80 of air conduit 83 flows through vents 97 in sump 81 and between rows 2 of conduits 1. An opening at close proximity to lid 82 allows moist air to be exhausted to the outside via air conduit 83.

[0086] Water can be pumped up through pipes 85 where is it is sprayed or drips onto pad 88 in physical contact with the outside of the rows 2 of conduits 1. This pad 88 can be water-wicking material that holds water while it evaporates cooling as it flows along air conduit 83. It can be held to the cylindrical sides of the row 2 of conduits 1 by, for example, a series of interconnecting vertical ribs that follow the contour of the cylindrical sides of a row 2 and can be pulled out as one allowing easy replacement of the pad 88. These vertical ribs should still allow air to flow upwards in the gaps between pads 88 of alternate rows 2. In this application, evaporative cooling from water functions as the heat exchange medium 61.

[0087] FIG. 15b is a cross sectional view 89 from FIG. 15a of a row 2 of conduits 1 with flat parallel sides 4. Sides 4 are in physical contact and may contain means of interlocking such as male and female locks 92 and 93. Cylindrical opposing sides 91 allow water in the pads 88 to evenly distribute as it flows down the sides of rows 2 of conduits 1.

[0088] FIG. 16 is a cross-sectional perspective view of an example of an indirect evaporative cooler 94 disclosing rows 2 of conduits 1 spaced apart so that air conduit 83 fluidly connects duct 84, cavity 99, vents 97 above the water line in sump 8, voids 98 between rows 2 of conduits with water wicking material 88 or between a row 2 of conduits and an insulating side 95, and finally to the outside under lid 82. A pump supplies water from pipe 96 to pipes 85.

[0089] This compact design is an example of an indirect evaporative cooler which should economize on water compared with other evaporative coolers. This can be significant for regions where water is in short supply. It can use rain water, or sea water if corrosion is not an issue. Any water that is not used drips back into the sump to be used again. It can also incorporate a PV panel, such as on top of lid 82, in order to run a fan and pump so that it functions entirely independently from the electricity supply.

[0090] The invention may be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features. Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

[0091] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. For example, the heat exchange medium can be changed to cool rather than heat or vice versa. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention.