GB2137328A - Heat Exchanger - Google Patents

Abstract

A heat exchanger is disclosed which uses a plurality of overlayed webs 13 of mesh material 14. The mesh material 14 is of open nature and provides very little restriction to the flow of air therethrough. Cooled water is allowed to flow onto the webs 13 and it flows around the strands of the mesh 14 thus providing a plurality of leading edges to air which is passed through the heat exchanger. This in turn allows for very efficient heat exchange with the air. The mesh material 14 is preferably a continuous length of material which is overlayed to provide the plurality of webs 13. <IMAGE>

Description

SPECIFICATION Heat exchanger This invention relatesto a heatexchangerand 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 after harvest and to maintain such vegetables in a relatively high humidity in the order of 96 to 98% humidity.

It is known thatwhen vegetablessuch 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 quickly.

Accordinglythefield heat of the vegetables is quickly removed by such air handling apparatus so theycan be maintained in as fresh a condition as possible.

Known air handling apparatus usable for the above purposes maintains humidity in the range of 97 to 98% relative humidity. The cooling ofthe air and the raising ofthe humidity (i.e. moisture content) is effected by passing airthrough heat exchangers. Typically water is passed through cooling members which, in turn, are cooled by refrigerant means and then the cooled water is passed through a heat exchanger. Air isthen 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.

Typical examples of air handling apparatus of this type are those made by Co-Ordinated Thermal Systems Pty. Ltd. of 32 MurdockStreet, Clayton, Victoria, Australia and sold under model numbers HH3 through HH36. The numerical ending on the designation signifies the cubic feet per min x 1000/min which is handled by the apparatus.

A problem with the known heat exchangers isthat theyarevery expensive. This is becausetheyare made from individual sheets of corrugated material bonded together. The corrugations are criss-crossed between adjacent sheets so that a tortuous path is provided for air as itflowsthrough the corrugations of the heat exchanger. The corrugated construction of individual sheets and the subsequent assembly into a heat exchanger 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 expensive to manufacture and which in certain circumstances can provide increased humidity (i.e. moisture content) to the air.

Therefore in accordance with a broad aspect of the present invention there may be provided a heat exchangerfor 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 waterwill accumulate and will permit heat transferto the air.

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

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 orderthatthe invention can be more clearly ascertained a preferred construction will now be described with reference to the accompanying drawings wherein: Figure lisa side perspective view of part of a prior art heat exchange member; Figure 2 is a top, end perspective view of a preferred heat exchanger according to the present invention; Figure3 is a close-up plan viewofthe heat exchanger webs; Figure 4 is a close-up end view of part of the 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 of material 1 which are bonded to each other. In Figure 1, only two such webs are shown but in practicethere are a multitude of webs bonded to each other. Each web 1 is made of a material which will not lose its shape when subjected to water and which will not then collapse when 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 corrogations 3.

The webs are placed back to back so thatthe ribs or corrugations 3 on 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 handling apparatus below a series of refrigerant heat exchanger coils. Water is then passed overthe 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 ofthe webs 1. The direction offlow ofwaterwhich is applied to the webs 1 is shown by arrows A. Air is then passed through the bottom ofthe heat exchanger and through the passageways which are defined therein. Typicallythe airflowing through the passageways moves in a helical convoluted path as diagrammatically 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).

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 material which will not deteriorate. Typical examples may be stainless steel, plastics, suitably treated wood, such as treated pine and the like. In Figures 2 through 5 the box shaped frame 10 is made from lengths of stainless steel angle which are welded together at theirends.Theframe 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 mate rial. Frame 10, in turn, supports a plurality of webs of mesh material. 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 lOto the width ofthewebs of mesh 13, a generally plantar web 13 can be provided. Such web 13, in turn, will be inhibited from sagging over a period oftime because of the biaxially oriented nature ofthe web material. A plurality of overlayed webs 13 are provided by a single continuousweb of mesh which has been folded into layers 1 4which lie spaced but on top of each other. This is clearly shown in Figure 4.

Each ofthe layers 14 is separated by a spacing member 15 at each end ofthe frame 10. The spacing members 15 arethen collectively sandwiched together in the frame 10 whereby to clampingly engage with the side edges of the web 13. In this mannerapluralityofspacedapartwebs l3ofmesh material are provided.

The heat exchanger is then suitably placed 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 perpendiculartothe plane of each ofthe layers 14 ofthe webs 13 of mesh. The water is first passed over refrigerant cooling coils whereby to cool the water and then allowed to strikethe individual edges of strands of the mesh material. The water tends to flow completely around the surfaces ofthe strands ofthe mesh and thereby provides a considerable surface area of water 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 ofthe strands of mesh of each web 13 in turn provide a leading edge to the air flow whereby to provide for efficient heat exchange and humidification (i.e. increase in moisture content) ofthe air.

Typically the mesh is 8mm square mesh and the spacing apart ofthe webs 13 ofthe mesh is 3.65 mm.

Such 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 is presented to the air as it flows through the heat exchangerthan in the prior art heat exchanger. It also should be appreciated that considerably greater contact is made with the cooled waterthan in the prior art as there are now provided a considerable number of wetted leading edges defined by the water on each ofthe strands of the mesh whereas in the prior art there is no leading edge as such but merelycon tinuous wetted surfaces in the passageways. The proposal herein therefore provides for a more efficient heat exchanger.

twill be appreciated thatthe heat exchanger will be useful not only in the art of cooling but also in the art of heating.Typicallythecooling and/or heating medium may not be water but may be other liquids as desired Modifications relay be made to the invention as would be apparentto persons skilled in the heat exchanger art. Forexamplethewebs of mesh may not be planar in nature but may be provided by a roll of mesh 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 distinctfrom passing end on through each layer.

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

Claims (8)

1. A heat exchangerfor an air handling apparatus ofthe 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 bythe mesh surfaces upon which waterwill accumulate and will permit heat transferto the air.

2. A heat exchanger as claimed in Claim 1 wherein the pluralityofwebs of mesh are formed bya 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 orientated in orderto inhibit sagging or stretching.

4. Aheatexchanger as claimed in anyone ofthe preceding claims wherein said webs are supported by a rectangular box shaped frame.

5. Aheatexchangerasclaimed in Claim 4wherein said box shaped frame is made as an open-sided, open-ended frame within which substantially all of said plurality of webs are positioned.

6. 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 ofthe 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.

7. A heat exchanger as claimed in any one ofthe preceding claimsfitted in an air handling apparatus so that water at a desired temperature is allowed to pass through the webs in a direction generally perpendicu- larto the plane of each web, as distinctfrom 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.

8. A heat exchanger substantially as herein described with reference to the accompanying drawings.