NZ207572A - Heat exchanger for cooling air:water flows over open mesh material - Google Patents

Description

207: II Priority Date(s): ..

Complete Specification Filed: ?/.'.4 Class: Publication Date: ..... J?. P. f£ P.)??/.'.. P.O. Journal, No: PATENTS FORM NO- 5 N.Z. PATENT Of i-iCS - 1 FEB 1985 RECEIVED" PATENTS ACT 1953 COMPLETE SPECIFICATION M TITLE: -f'A'Ie "HEAT EXCHANGER" /" *- , ;Co-Ordinated Thermal Systems Pty' fecwttee^l, an Australian company, of 32 Murdock Street, Clayton 3168, ;Victoria, Australia hereby declare the invention, for which -I/We pray that a patent may be granted to /$e/us, and the method by which it is to be performed to be particularly described in and by the following statement: ;-1- ;This invention relates to a heat exchanger and ;. ;relates particularly but not exclusively to a heat exchanger for use in air handling apparatus. ;The object of such air handling.apparatus is to quickly cool vegetables in a relatively high humidity in the order of 96 to 98% humidity. ;It is known that when vegetables such as lettuce, celery, cabbage, cauliflower and the like are harvested, it is necessary to remove the field heat from them because otherwise they can dehydrate very quickly. ;- - •!- ;r.'uis-X''- ;W-yi ;/ ;y > ' \ ' I , ' ■ V • ' ;- 3 - ;2 0757 2 ;Accordingly the field heat of the vegetables is quickly removed by such air handling apparatus so they can be maintained in as fresh a condition as possible. ;Known air handling apparatus usable for the 5 above purposes maintains humidity in the range of 97 to 98% relative humidity. The cooling of the air and the raising of the humidity (i.e. moisture content) is effected by passing air through heat exchangers. ;Typically water is passed through cooling members which, 10 in turn, are cooled by refrigerant means and then the cooled water is passed through a heat exchanger. Air is then forced through the heat exchange in the reverse direction to which the water is passed, and the air is thereby cooled and its relative humidity is increased. 15 Typical examples of air handling apparatus of this type are those made by Co-Ordinated Thermal Systems Pty. Ltd. of 32 Murdock Street, Clayton, Victoria, Australia and sold under model numbers HH3 through KH36. The numerical ending on the designation signifies the 20 cubic feet per min x 1000/min which is handled by the apparatus. ;A problem'with the known heat exchangers is that they are very expensive. This is because they are made from individual sheets of corrugated material bonded 25 together. The corrugations are criss-crossed between adjacent sheets so that a tortuous path is provided for air as it flows through the corrugations of-the heat exchanger. The corrugated construction of individual sheets and the subsequent assembly into a heat exchanger 30 core is labourious and hence the reason for such expense. ;An object of the present invention is to > provide an improved heat exchanger which, will be less ;;4<#> . . . ;expensive to manufacture and which m certain circumstances can provide increased humidity (i.e. 3 5 moisture content) to the air. ;: / ;V ■ • v--i : " ' ■ ' ■ , " 7 : / ;I ;* -4 - 1 @75 72 Therefore in accordance with a broad aspect of the present invention there may be provided a heat exchanger for an air handling apparatus of the type used in rooms where fresh vegetables are to be stored, comprising, a plurality of overlayed webs of open mesh material, said webs being spaced apart from each other, the arrangement being such that when water is directed through the webs, and air is directed through the webs, there will be a plurality of leading edges defined by the 10 mesh surfaces upon which water will accumulate and will permit heat transfer to the air.

Most preferably the plurality of webs of mesh are formed by a single continuous web which is overlayed to provide the plurality of layers.

Desirably the mesh is made of a non-corrosive material such as polypropylene which has been biaxially oriented in order to inhibit sagging or stretching.

In order that the invention can be more, clearly ascertained a preferred construction will now be 2 0 described with reference to the accompanying drawings wherein:- Figure 1 is a side perspective view of part of a prior art heat exchange member; \- Figure 2 is a top, end perspective view of a 25 preferred heat exchanger according to the present invention; Figure 3 is a close-up plan view of the heat exchanger webs; Figure 4 is a close-up end view of part of the 30 heat exchanger shown in Figure 2; and Figure 5 is a close-up perspective view of a web of material in the heat exchanger.

Referring now to Figure 1 there is shown a prior art heat exchanger made up of a plurality of webs 3 5 of material 1 which are bonded to each other. In Figure r \ ' .r. - - ' ~ - I ' ■' - -.1. ... - , 2 0757 1, only two such webs are shown but in practice there are a multitude of webs bonded to each other. Each web 1 is made of a material which wi3,l not lose its shape when subjected to water and which will not then collapse when 5 air is directed over its surfaces. The material 1 has a plurality of angularly inclined ribs or corrugations 3 thereon. Each of the ribs or corrugations 3 is parallel to the adjacent ribs or corrugations 3. The webs are placed back to back so that the ribs or corrugations 3 on 10 one web 1 run across the ribs or corrugations 3 on the other web 1. The arrangement is such as to provide a plurality of vertical passageways (not clearly shown) through the webs 1.

In use, the heat exchanger is placed in a air 15 handling apparatus below a series of refrigerant heat exchanger coils. Water is than passed over the coils and is allowed to flow onto the heat exchanger material. The water strikes the upper edges of the heat exchanger and then runs down the faces of the webs 1. The direction of 20 flow of water which is applied to the webs 1 is shown by arrows A. Air is then passed through the bottom of the heat exchanger and through the passageways which are defined therein. Typically 'the air flowing through the passageways moves ih a helical convoluted path as 2 5 diagrarnmatically shown by the helical line 5. The direction of air passing through the heat exchanger has been shown by the arrows B. As the air passes through the passageways there is a heat exchange and the air, in turn, increases in humidity (i.e. moisture content). 3 0 The prior art heat exchangers as shown in Figure 1 are extremely costly to manufacture.

The preferred heat exchanger of the present invention is made from a rectangular box shaped frame 10. The box shaped frame 10 is made from a suitable rigid 35 material which will not deteriorate. Typical examples J : 'I'-Z-y. ^':S f: m ~6~ tmsn 1 may be stainless steel, plastics, suitably treated wood, such as treated pine and the like. In Figures 2 through <, the box shaped frame 10 is made from lengths of stainless steel angle which are welded together at their P ends. The frame 10 defines a module of heat exchanger material. A plurality of modules may be stacked one on top of each other and/or side by side to provide a required volume of heat exchanger material. Frame 10, in . i'-'V turn, supports a plurality of webs of mesh material. • \i> '10 Each web of mesh material is shown generally at the top of the frame 10 by numeral 13. The mesh is of a polypropylene material which has been biaxially oriented whereby to inhibit stretching and/or sagging.

Accordingly by appropriately sizing the frame 10 to the 15 width of the webs of mesh 13, a generally planar web 13 can be provided. Such web 13, in turn, will be inhibited ' from sagging over a period of time because of the • biaxially oriented nature of the web material. A plurality of overlayed webs 13 are provided by a single 20 continuous web of mesh which has been folded into layers 14 -which lie spaced but on top of each other. This is clearly shown in Figure 4. Each of the layers 14 is separated by a spacing member 15 at each e;id of the frame 10 . The spacing, members 15 are then collectively 2 5 sandwiched together in the frame 10 whereby to clampingly engage with the side edges of the web 13. In this manner a plurality of spaced apart webs 13 of mesh'material are provided.

The heat exchanger is then suitably placed 30 within known air handling apparatus and water is . preferably passed through the heat exchanger in the direction shown by arrows A. This preferable direction is generally perpendicular to the plane of each of the layers 14 of the webs 13 of mesh. The water is first 3 5 passed over refrigerant cooling coils whereby to cool the ,■> 07572 water and then allowed to strike the individual edges of strands of the mesh material. The water tends to flow completely around the surfaces of the strands of the mesh and thereby provides a considerable surface area of water 5 in the mesh 13. Air is then passed through the heat exchanger preferably in the direction shown by arrows B. This is in the opposite direction to the direction of flow of water. Each of the surfaces of the strands of mesh of each web 13 in turn provide a leading edge to the 10 air flow whereby to provide for efficient heat exchange and humidification (i.e. increase in moisture content) of the air.

Typically the mesh is 8mm square mesh and the spacing apart of the webs 13 of the mesh is v3.65mm. Such 15 is suitable for use in connection with air handling apparatus which is in the range of 14 kilo watts to 100 kilo watts capacity.

It will also be appreciated that with the embodiment proposed herein, considerably less resistance 2 0 is presented to the air as it flows through the heat exchanger than in the prior art heat exchanger. It also should be appreciated that considerably greater contact is made with the cooled water than in the prior art as there are now provided a considerable number of wetted 25 leading edges defined by the water on each of the strands of the mesh whereas in the prior art there is no leading edge as such but merely continuous wetted surfaces in the passageways. The proposal herein therefore provides for a more efficient heat exchanger.

It will be appreciated that the heat exchanger, will be useful not only in the art of cooling but also in the art of heating. Typically the cooling and/or heating medium may not be water but may be other liquids as desired.

- -KW"-™ o'>rf ci t r.' ru >" - 8 - ' 207572 ' ■ ■-!:■'■ .v Modifications may be made to the invention as would be apparent to persons skilled in the heat exchanger art. For example the webs of mesh may not be planar in nature but may be provided by a roll of mesh 5 where each layer in the roll is suitably spaced from adjacent layers.

Preferably in this embodiment the air is directed to pass substantially perpendicularly across the mesh material as distinct from passing end on through • each layer.

These and other modifications may be made without departing from the ambit of the invention the nature of which is to be determined from the foregoing description.

!. I ■' :7 •'

Claims (5)

207572 *Ci /'' WHAT WE CLAIM 15: ^tge

1. A heat exchanger for an air handling apparatus of the type used in rooms where fresh vegetables are to be stored, comprising, a plurality of overlayed webs of open mesh material, said webs being spaced apart from each other, the arrangement being such that when water is directed through the webs, and air is directed through the webs, there will be a plurality of leading edges defined by the mesh surfaces upon which water will accumulate and will permit heat transfer to the air, and the mesh size of the webs being sufficiently open as to provide for substantially unrestricted air flow therethrough.

2. A heat exchanger as claimed in claim 1 wherein the plurality of webs of mesh are farmed by a single continuous web which is overlayed to provide a plurality of layers.

3. A heat exchanger as claimed in claim 1 or claim 2 wherein the mesh is of a substantially non-corrosive synthetic plastics material which has been biaxially oriented in order to inhibit sagging or stretching.

4. A heat exchanger as claimed in any one of the preceding claims wherein said webs are supported by a rectangular box shaped frame.

5. A heat exchanger as claimed in claim ft wherein said box shaped frame is made as an open-sided, open-ended frame within which substantially all of said plurality of webs are positioned. 207572 A heat exchanger as claimed in claim 5, wherein the webs are held spaced from adjacent webs by spacing members placed at a pair of opposite ends of said frame, the arrangement of the spacing members being such that each respective end of the adjacent webs will be spaced apart by a single spacing member, there being a stack of such webs and spacing members at each said respective end, the webs and the spacing members being held in sandwiched relationship. A heat exchanger as claimed in any one of the preceding claims fitted in an air handling apparatus so that water at a desired temperature is allowed to pass through the webs in a direction generally perpendicular to the plane of each web, as distinct from end on to each web and wherein air is directed to pass through said heat exchanger in a direction opposite to the direction of flow of water. A heat exchanger substantially as herein described with reference to figures 2 to 5 of the accompanying drawings. fifty_ iz I'/s/hftr/ti"•!'! if AUt/i r-ev 'o