AU2005202057A1 - An improved evaporator for a heat pump water heater - Google Patents

Description

C05074 1 An improved evaporator for a heat pump water heater Field of the invention [001] The present invention relates to evaporators which can be used for heat pump water heaters, which can also be used to absorb solar energy to assist the evaporator function.

Background of the invention [002] Heat pump water heaters utilise an evaporator to heat a heat transfer fluid, which is then passed to the condenser, whereby heat is extracted from the heat transfer fluid so as to heat water in a tank. Efficiency of such evaporators is a function of the ability of the evaporator plates to absorb energy from the surrounding environment. Thus, there has been a long felt need to improve the efficiency of such evaporator plates, to make more efficient water heaters.

[003] Any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates, at the priority date of this application.

Summary of the invention [004] The present invention provides an evaporator panel having an iinlet and an outlet and at least one channel therebetween, said at least one channel traversing across said panel in a serpentine fashion, said panel including at least one aperture through said panel adjacent said at least one channel.

[005] There can be a plurality of apertures through said panel.

[006] The at least one channel can direct a heat transfer fluid in a first direction past said at least one aperture on one side thereof, and on an opposite side thereof can direct said heat transfer fluid in a second direction opposite to said first direction past said at least one aperture.

[007] There can be a plurality of channels.

[008] The at least one aperture can located between at least two portions of said channel or channels, said portions carrying a heat transfer fluid in the same general direction.

[009] The at least one aperture can be a slot. The slot can extend generally parallel with the length of said channel.

[010] The at least one aperture can one of the following shapes: generally rectangular; generally circular; square; polygonal.

C05074 2 [011] Preferably there is a plurality of said apertures arranged in an array on said plate.

[012] The apertures can be aligned along an imaginary axis which has its direction generally parallel to the direction of said at least one channel.

[013] The apertures can be aligned along an axis which has its direction generally perpendicular to the direction of extension of said at least one channel.

[014] The apertures can be arranged in a first line, with the locations of the apertures displaced in two directions from the location of apertures arranged in a second adjacent line.

[015] A plurality of channels can be provided each having fluid communication, directly or indirectly, to said inlet and outlet, each of said plurality of channels traversing said panel in a direction generally parallel to the other ones of said plurality of channels.

[016] The plurality of channels can have connection passages interconnecting adjacent ones of said plurality of channels.

[017] The panel can manufactured from metal, such as aluminium. The panel can be of a colour or finish which assists in the absorption of electromagnetic radiation.

[018] The at least one channel can be generally hexagonal, polygonal or other appropriate .shape in cross section.

[019] The present invention also provides an evaporator assembly comprised of a plurality of panels as described above. The evaporator assembly can be such that a heat transfer fluid flow path is formed which serpentines laterally and downwardly along a first half of a said device, and laterally and upwardly along a second half of said device.

[020] The present invention also provides a water heater having a tank, a heat pump circuit to heat water held by said tank, said circuit including a heat transfer fluid reservoir, an expansion device, an evaporator, a compressor and a condenser, said condenser being adapted to heat water held in said tank, said water heater being characterised by said evaporator being made from one or more evaporator panels as described above, or having an evaporator assembly as described above. The evaporator can positioned in atmosphere so as to allow said evaporator to absorb heat from solar energy and or from air. Further the evaporator can transmit heat back to moving air when the amount of heat absorbed exceeds what is required for the operation of the heat pump circuit.

[021] The present invention also provides a method of making an evaporator plate, said method including the steps of: manufacturing a plate assembly by joining two adjacent plates C05074 3 together, including or subsequently forming channels in one or both of said plates forming apertures through said plate assembly, said apertures being clear of said channels.

[022] The present invention further provides another method of making an evaporator plate, said method including the steps of: forming a series of apertures in plates to be joined together to form a plate assembly, forming at least one channel in said plates, said channel being adjacent said apertures and joining said plates together by first aligning said apertures on plates to be joined; or positioning channel forming means on one or more of said plates adjacent said apertures, joining said plates and forming said channel.

Brief description of the drawings [023] An embodiment or embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [024] Figure 1 is a schematic view of a heat pump water heater which can utilise the evaporator of the present invention; [025] Figure 2 is a plan view of an evaporator element; [026] Figure 2A is a cross section through a channel; [027] Figure 3 is an assembly of four evaporator elements for use with the heat pump water heater; and [028] Figures 4 and 5 illustrate schematics of alternative arrangements of channels and apertures to produce an evaporator element similar to that of Figure 2.

Detailed description of the embodiment or embodiments [029] Illustrated in Figure 1 is a typical heat pump circuit 1 which includes a water heater tank 17 connected'to a condenser heat exchanger coil 7. The heat pump circuit 1 has a reservoir 2 of a heat transfer fluid or other appropriate fluid which is able to change state from liquid to gas, and an expansion device 3 which allows for expansion of the heat transfer fluid.

Also included are an evaporator 4 and a compressor 5 which are in fluid communication via a fluid line 6. The other devices namely coil 7, receiver 2 and expansion device 3 are also connected via fluid lines but these have not been numbered for clarity reasons.

[030] The coil 7 is located intermediate the compressor 5 and expansion device 3. Coil 7 is housed inside a housing tube 8 which is disposed inside the tank 9. The coil 7 is preferably of copper tubing but can be of aluminium or other material having high thermal transmission C05074 4 coefficient. It is also desirable for it to have a higher thermal expansion coefficient than the housing tube 8. The housing tube 8 is a cylindrical tube which can be formed from sheet metal.

[031] The coil 7 is connected to the heat pump circuit 1 to provide heat for heating water in the tank 17. The top end 19 of the heat exchange coil 7 has an inlet 16 for hot gaseous heat transfer fluid which is compressed by compressor 5 and which is connected to compressor delivery outlet 10. The coil 7 also includes an outlet tube 11 for condensed liquid heat transfer fluid returning to the expansion device 3 to reduce the pressure of the heat transfer fluid downstream of the expansion device 3.

[032] During the condensation process heat is released from gaseous heat transfer fluid in the coil 7 and transferred to water held in the reservoir space 12 through walls 13.

[033] On the heat transfer fluid side (inside housing tube 8) heat is transferred from heat transfer fluid to the housing tube wall 13. On the water side in reservoir space 12, heat is transferred from the surface of the housing tube wall 13 to water in space 12 by natural convection. In the storage tank, the natural stratification formed by layers of heated water at different temperatures is maintained by the upward convection current of hot water to the top of the storage tank. The heat exchanger is constructed with a top down hot to cold flow. The stratification in the storage tank is thus maintained and effective heat exchange thus achieved.

[034] An upper region 19 of coil 7 performs a super heater function, due to the coil 7 being at its hottest in this region, which provides hottest water at the top of the tank. Whereas the bottom region 18 of coil 7 performs a sub-cooler function providing a low temperature condensation which increases the efficiency of the heat pump compressor [035] The evaporator 4 can be constructed from an assembly of evaporator plates 100 illustrated in figure 2. An assembly of such plates 100 is illustrated in figure 3. The evaporator plate 100 of figure 2 is an assembly of 2 bonded plates, of which only the top plate is visible.

More will be said about the manufacturing method below.

[036] In figure 2 it can be seen that the evaporator plate 100 has an inlet 102 and an outlet 104 (whether in use they are actually inlets or outlets will depend upon the connections made thereto as will be explained in more detail later). Between the inlet 102 and outlet 104 is a plurality of channels 106 which traverse the width of the plate 100 from left to right, then downwardly on the right side, then right to left, downwardly on the left side, left to right, downwardly on the right side, right to left, etc, in a serpentine fashion across the plate 100.

C05074 [037] It will be seen from figure 2 that the channels 106 are formed from six discreet channels 108, 110, 112, 114, 116 and 118 which all travel in the same direction, across and down the plate.

[038] Between the inner channels 112 and 118 spaces 120 are provided through which apertures 122 pass. The apertures 122 are spaced in an array across the plate 100 and are aligned horizontally in lines 121, 124, 126,128, 129, 130, 131 down the height of the plate 100.

[039] For the line 121 of apertures 122 at the top of the plate 100 it should be noted that above and below the apertures 122, in the line 121, that the direction of flow of the heat transfer fluid carried by the channels 108 to 118 is in the same direction. Whereas looking at the second line 124 of apertures 122, the flow of heat transfer fluid in channels 114, 116 and 118 above the apertures 122 in the line 124 is in the opposite direction to the direction of flow of heat transfer fluid in the same channels below apertures 122 of the line 124.

[040] It can be seen from figure 2 that line 126 of apertures 122 is similar to the first line 121 in that above and below the apertures of line 126 the heat transfer fluid is flowing in the same direction, that is from right to left. This pattern continues down the height of the panel 100.

[041] As can be seen from figure 2 the apertures 122 in lines 121, 126, 130 and 131 are aligned or are in register from one end of the plate 100 to the other, that is perpendicular to the lines 121, 126, 130 and 131. Whereas the apertures 122 in lines 124, 128 and 129 are in register or aligned also in a parallel direction but in these lines their location is offset from the alignment of apertures 122 in lines i21, 126, 130 and 131 [042] The apertures 122 generally provide for flow-through of air through the plate 100.

When the plate is working at very high temperatures, such as during summer, the heat load can be reduced by means of the apertures 122, whereby they assist in heat transfer to the surrounding air by convection particularly if a wind or breeze is present. This can reduce the risk of over heating. Whereas in winter time, cold air around the plate 100 can sink through the apertures 122, thus increasing heat absorption. The apertures also assist to remove surface water or condensation by providing multiple drains. Such surface condensation or water can decrease the heat absorption capability of the panel 100.

[043] The portions of the plate 100 around the apertures 122 will absorb heat from solar energy and surrounding air, and in some circumstances transfer heat to air. Whereas those portions of the plate 100 away from apertures 122 will absorb heat from solar energy with less effectiveness in absorbing heat from surrounding air, and are less able to transfer heat to the air.

C05074 6 [044] The size of the apertures 122 and the total surface area of apertures through the plate relative to the total surface area of the plate 100 is somewhat dependant upon the operational criteria and the operational environment in which the plate 100 will be utilised. The ratio of the total of the apertures 122 to the general area of the plate 100 illustrated in figure 2 is approximately 3% to but depending upon application this could vary between 2% up to The proportion of apertures to the total surface area will be a function of the energy balance required between absorption from solar energy and absorption from air desired Identifying the appropriate balance will be to some extent a matter of routine experiment.

[045] It can be seen at the right hand side 140 and left hand side 150 of the plate 100 that the channels 108, 110, 112, 114, 116 and 118 are oriented parallel to the edges of the sides of the plates 100 and have equalisation passages 142, 144, 146, and 148 provided. The equalisation passages 142, 144, 146, and 148 help equalise the pressure inside the channels 108, 110, 112, 114, 116 and 118. Such equalisation is useful in cases where part of the evaporator plate 100 is located in bright sunshine while other parts are in shadow.

[046] The plate 100 of figure 2 shows the inlet 102 and outlet 104 as having a "Zshape" configuration. This "Z shape" configuration allows either of the side directed passages to be utilised for interconnection. Alternatively if the top or bottom of the is cut off, such as, for example, by lines 132 and 134, there can be formed a top edge directed opening inlet 102 and a bottom edge directed opening outlet 104. By this relatively convenient means a single plate 100 can be manufactured with provision for a variety of inlet and outlet directions and configurations being possible with very little modification.

[047] Preferably the plate 100 is manufactured by a roll bonding method. As is well known in the art, the roll. bonding method is achieved by the application of a printing ink or similar to a plate of metal such as aluminium, so when another adjacent plate of a like metal is overlaid on the printing and the two plates are bonded by rolling and application of pressure, the ink prevents bonding between the adjacent metal surfaces. Once the bonding has occurred by roll bonding, the manufacturer can apply, in the case of the evaporator plate 100, via the inlet and/or outlet 104, in a mould designed for the purpose, sufficient pressure to expand the plates away from each other along the lines of the printing ink, to thereby form the channels 108 to 118 and the inlets 102 and 104. Typically the cross section of the expanded channels 108, 110, 112, 114, 116 and 118 would look like that depicted in figure 2A. The cross section is preferably hexagonal as illustrated but other shapes could be utilised.

C05074 7 [048] If desired, prior to roll bonding, the apertures 122 can be formed in the plates that make up the plate assembly 100 or alternatively, the apertures 122 can be punched from the surfaces 122 in a later manufacturing step. If the apertures 122 are punched out prior to joining of adjacent plates this can add to the manufacturing costs in that alignment of the plates and the apertures 122 will be required, whereas no such alignment is required if the apertures are formed after the two plates have been joined. Other methods of making the assembly of evaporator plate 100 include pressing and stamping stainless steel plates and interleaving them with a copper shim or by using copper coated stainless steel and brazing them together.

[049] Illustrated in figure 3 isan assembly 500 of four plates 100A, 100B, 100C and 100D. In the assembly 500 of figure 3 a cross-hatch border is illustrated around each of the plates 100. This cross hatch border represents a tooling area through which the plates 100 can be drilled or affixed etc.

[050] As can be seen from figure 3, the plate 100 A interconnects at union 200 with the plate 100B and this is the inlet side of the assembly 500. The heat transfer fluid flows into the plate 100 A as a liquid or liquid and vapour mixture, under the influence of the suction produced by the compressor 5. This liquid or liquid vapour mixture will flow downwardly and in a serpentine fashion across one half of the assembly 500, which transfers solar and atmospheric heat to the liquid heat transfer fluid or heat transfer fluid liquid and vapour mixture thereby evaporating same causing some or all the liquid heat transfer fluid to become vapour. If sufficient solar and or atmospheric heat energy is available, the liquid heat transfer fluid or heat transfer fluid liquid and vapour mixture will be 100% vapour by the time the heat transfer fluid exits the 100B. If insufficient energy is available, conversion of all the liquid heat transfer fluid into vapour may occur in the plates 100 C or 100D.

[051] The vaporised or partially vaporised heat transfer fluid exits the panel 1 OB and enters the panel 100C, on the right hand side. The heat transfer fluid progresses in a serpentine fashion under the influence of the suction from the compressor 5, upwardly and across the right hand half of the assembly 500 and exits the panel 100C at join 202 and enters the panel 100D and finally exits the assembly 500 of four panels via the outlet 206.

[052] It is expected under normal operating and environmental conditions that the heat transfer fluid vapour exiting the panel 100D will be superheated as it returns to the compressor [053] Illustrated in figure 4 is an evaporator panel 1100, which has a right side inlet 1102 and outlet 1104, entry manifold 1103, cross channels 1108 and 1110 above and below a line 1121 of apertures 1122. Interconnecting vertical channels 1142, 1144 and 1146 join C05074 8 channels 1110 and 1108. Below channel 1110 is a cross channel 1112, with the pattern being repeated to the end of the plate 1100.

C [054] It can be seen that each of the channels 1110, 1108, and 1112 open out into an exit manifold 1105 which proceeds to the outlet 1104.

[055] In this embodiment the apertures 1122 are round ended slots and are arranged in horizontal lines 1121, 1124 etc. The individual apertures 1122 in adjacent lines are also aligned V) vertically, unlike the previous embodiment.

[056] Illustrated in figure 5 is an evaporator panel 2100 which has apertures 2122, inlet 2102, outlet 2104 and channels 2108 and 2110. It will be seen that the apertures 2122 are circular and that the channels 2108 and 2110 are substantially straight line paths, with no deviations.

[057] If desired, and depending upon design criteria and conditions, open slots can join adjacent apertures 2122 or single slots extending the length of channels 2108 and 2110 can be substituted.

[058] Where ever it is used, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of'. A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear.

[059] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention.

[060] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.

Claims (20)

1. An evaporator panel having an inlet and an outlet and at least one channel therebetween, said at least one channel traversing across said panel in a serpentine fashion, said panel including at least one aperture through said panel adjacent said at least one channel

2. An evaporator panel as claimed in claim 1, wherein there is a plurality of apertures through said panel.

3. An evaporator panel as claimed in claim 1 or 2, wherein said at least one channel directs a heat transfer fluid in a first direction past said at least one aperture on one side thereof, and on an opposite side thereof directs said heat transfer fluid in a second direction opposite to said first direction past said at least one aperture.

4. An evaporator panel as claimed in any one of claims 1 to 3, wherein there are plurality of channels An evaporator panel as claimed in any one of claims 1 to 4, wherein said at least one aperture is located between at least two portions of said channel, said portions carrying a heat transfer fluid in the same general direction.

6. An evaporator panel as claimed in any one of claims 1 to 4, wherein said at least one aperture is a slot.

7. An evaporator panel as claimed in claim 6, said slot extends generally parallel with the length of said channel.

8. An evaporator panel as claimed in any one of claims 1 to 4, wherein said at least one aperture is one of the following shapes: generally rectangular; generally circular; square; polygonal.

9. An evaporator panel as claimed in claim 8, wherein there is a plurality of said apertures arranged in an array on said plate. An evaporator panel as claimed in claim 8, wherein said apertures are aligned along an imaginary axis which has its direction generally parallel to the direction of said at least one channel.

11. An evaporator panel as claimed in any one of claims 9 or 10, wherein said apertures are aligned along an axis which has its direction generally perpendicular to the direction of extension of said at"least one channel. C05074

12. An evaporator panel as claimed in claim 11, wherein said apertures arranged in a first line, are displaced in two directions from the location of apertures arranged in a second adjacent line.

13. An evaporator panel as claimed in any one of claims 1 to 12, wherein a plurality of channels is provided each having fluid communication, directly or indirectly, to said inlet and outlet, each of said plurality of channels traversing said panel in a direction generally parallel to the other ones of said plurality of channels.

14. An evaporator panel as claimed in claim 13, wherein said plurality of channels have connection passages interconnecting adjacent ones of said plurality of channels. An evaporator panel as claimed in any one of claims 1 to 14, wherein said panel is manufactured from metal, such as aluminium.

16. An evaporator panel as claimed in any one of claims 1 to 15; wherein said panel is of a colour or finish which assists in the absorption of electromagnetic radiation.

17. An evaporator panel as claimed in any one of claims 1 to 16, wherein said at least one channel is one generally hexagonal, polygonal or other appropriate shape in cross section.

18. An evaporator assembly comprised of a plurality of panels as claimed in any one of claims 1 to 17.

19. An evaporator panel as claimed in claim 18, wherein a heat transfer fluid flow path is formed which serpentines laterally and downwardly along a first half of a said device, and laterally and upwardly along a second half of said device. A water heater having a tank, a heat pump circuit to heat water held by said tank, said circuit including a heat transfer fluid reservoir, an expansion device, an evaporator, a compressor and a condenser, said condenser being adapted to heat water held in said tank, said water heater being characterised by said evaporator being made from one or more evaporator panels as claimed in any one of claims 1 to 17, or having an evaporator assembly as claimed in claim 18 or 19.

21. A water heater as claimed in claim 20 wherein said evaporator is positioned in atmosphere so as to allow said evaporator to absorb heat from solar energy and or from air. C05074 11

22. A water heater as claimed in claim 21 wherein said evaporator will transmit heat back to moving air when the amount of heat absorbed exceeds what is required for the operation of the heat pump circuit.

23. A method of making an evaporator plate, said method including the steps of: manufacturing a plate assembly by joining two adjacent plates together, including or subsequently forming channels in one or both of said plates forming apertures through said plate assembly, said apertures being clear of said channels.

24. A method of making an evaporator plate, said method including the steps of: forming a series of apertures in plates to be joined together to form a plate assembly, forming at least one channel in said plates, said channel being adjacent said apertures and joining said plates together by first aligning said apertures on plates to be joined; or positioning channel forming means on one or more of said plates adjacent said apertures, joining said plates and forming said channel. Dated this 13th day of May 2005 Rheem Australia Pty Limited, by its patent attorneys HALFORD CO