GB2283087A

GB2283087A - Tubular heat exchanger made from stacked sheets

Info

Publication number: GB2283087A
Application number: GB9321601A
Authority: GB
Inventors: Charles David Belcher
Original assignee: SILAVENT
Current assignee: SILAVENT
Priority date: 1993-10-20
Filing date: 1993-10-20
Publication date: 1995-04-26
Anticipated expiration: 2013-10-20
Also published as: GB2283087B; GB9321601D0

Abstract

A heat exchanger is made by joining a plurality of substantially identical elements (1). Each element (1) comprises a sheet (2) of material having a plurality of wells (3) formed therein. Each well (3) is of open tubular form. A pair of elements (1,1') are joined with the wells (3) of one sheet (1) in registry with corresponding wells (3') of the other sheet (1') to form tubular air paths through the wells. The sheets are preferably made of plastics and the elements are vacuum formed. Location lugs and recesses 4', 5, may be provided. <IMAGE>

Description

HEAT EXCHANGER The present invention relates to a heat exchanger and to a method of manufacturing a heat exchanger.

Various heat exchangers are known in which hot air is passed in one direction over cold air moving in another direction, the hot and cold air flows being separated by a wall which allows heat to pass from the hot air to the cold air in order to recover some of the heat energy which is often otherwise wasted. Many heat exchangers are formed of plates stacked in successive layers, hot air and cold air being passed through respectively alternating layers in the heat exchanger. Materials used for these plate heat exchangers include aluminium or PVC. However, aluminium itself is relatively expensive and, for either material, the assembly process is labour intensive and therefore expensive. In the case of the PVC plate heat exchanger, the individual plates must be welded to each other which is very time-consuming.

According to a first aspect of the present invention, there is provided an element for a heat exchanger, the element comprising a sheet of material having a plurality of wells formed therein, each well being of open tubular form, the element being connectable to at least one other substantially identical element having a corresponding plurality of wells to form an assembled heat exchanger in which respective wells join to form tubular air flow paths through the heat exchanger.

A heat exchanger can be formed from a plurality of substantially identical elements, which of itself keeps down the manufacturing costs. The elements can be simply joined in a manner which is much less time-consuming and therefore less expensive than the prior art proposals.

The element may be made of plastics, for example PVC.

The element may be vacuum formed.

The element may be initially formed with each well having a bottom wall which is then removed to form a well of open tubular form prior to connection with another element.

The sheet may be formed with a locating lug and a locating recess to locate the element in registry with another substantially identical element.

When the elements are assembled into a heat exchanger, the elements may be bonded together. The bonding process may be by at least one of high-frequency welding, solvent bonding, and fusion.

According to a second aspect of the present invention, there is provided a method of manufacturing a heat exchanger, the method comprising the steps of: forming a plurality of substantially identical elements, each element comprising a sheet of material having a plurality of wells formed therein, each well being of open tubular form; and, joining a pair of elements with the wells of one sheet in registry with corresponding wells of the other sheet to form tubular air paths through the wells.

The method may comprise the further step of joining together two pairs of elements which are joined with the sheets face-to-face so that the mouths of corresponding wells meet, the two pairs of elements being joined to each other such that the bottoms of corresponding wells meet to form tubular air paths through the four elements.

Further pairs of elements which are joined with the sheets face-to-face may be joined together to form larger, more extensive heat exchangers.

The elements may be initially formed with closed wells, the bottom walls of the wells being removed to provide wells of open tubular form prior to joining the element with another substantially identical element.

The elements may be made of plastics. The elements may be vacuum formed.

The present invention provides a simple and inexpensive heat exchanger, effectively in modular form.

This allows heat exchangers of any size to be built up.

Smaller versions, perhaps having just four elements described above, may be useful for domestic use in a single home. Larger heat exchangers, made up of many elements joined together, may be used in larger buildings, for example offices.

An example of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a plan view of an element used to make a heat exchanger; and, Fig. 2 is a cross-sectional view through a side of a heat exchanger.

An element 1 for a heat exchanger is formed as a sheet 2 of material which is formed with a plurality of wells 3, all of the wells 3 being formed on the same side of the sheet 2. In the example shown, ten wells 3 are formed in a regular array across the sheet 2. The element 1 may be vacuum formed PVC, the PVC having the useful property of being fire-retardant. When the element 1 is initially vacuum formed, the wells 3 are closed by a bottom wall (not shown). These end walls are removed by a conventional cutter so as to form wells 3 of open tubular form with open lower ends 7. The element 1 is formed with a locating lug 4 and a locating recess 5 in the sheet portion 2.

A heat exchanger is formed by assembling a plurality of elements 1 described above. At least two substantially identical elements 1 are joined. In Figure 2, four substantially identical elements 1 are shown connected to each other to form a cubic heat exchanger of side 15cm.

Elements 1 of different dimensions can be used to make up a heat exchanger of any desired size.

To form the heat exchanger shown in Figure 2, two pairs of elements 1,1';la,la' are joined. Firstly, each pair of elements l,l';la,la' is assembled by placing the sheets 2 face-to-face with the mouths 6 of corresponding wells 3 in registry with each other. Ensuring the registry of the respective wells 3 with each other is facilitated by pressing the locating lugs 4' of one sheet into a corresponding recess 5 of the other sheet and vice versa.

The two elements 1,1' are then joined to each other by high frequency welding of the plastics material of the sheet portions 2. The elements l,l';la,la' may be joined by spot welding the sheets 2 at various locations, but particular attention should be paid to ensuring that the welds around the mouths 6 of the wells 3 are complete to ensure that no air leaks out of the tubes formed by the joined wells 3 in use.

Once the individual pairs of elements l,l';la,la' have been joined, the two pairs of elements can then be joined to each other. This is achieved by joining the open lower ends 7' of one set of wells 3' of one element 1' with the corresponding open lower ends 7a of a set of wells 3a of one element la of the other joined pair of elements la,la'.

This may be facilitated by forming the bottoms of the wells 3 such that they have a step 8 and, for one set of bottom walls 7', leaving the step 8' when the end face is removed and, for the lower end 7a of the adjacent wells 3a, removing the portion having the step 8a when the end walls are cut so that the stepped portion of one set of wells 3' can fit within the end portion 7a of the other set of wells 3a as shown in Figure 2.

Once the lower ends of adjacent wells have been joined, they can be fixed to each other by solvent bonding, for example. Alternatively, high frequency welding can be used although a suitably shaped tool having an appropriate welding tip will be required so that the tool can be inserted through the tubes from one side of the heat exchanger. Once the four elements have been joined together as described above, supporting end walls 9 are fixed to the ends of the exposed wells 3, 3A'. The end walls 9 are formed with apertures 10 corresponding to the wells 3.

In use, warm or hot air which is expelled from a building, for example, may be passed through the tubes formed by the joined wells along a flow path A shown in Figure 2. Cold air which is to be introduced into the building flows at 90 to the flow path A of the hot air, the flow path of the cold air being indicated by B in Figure 1. It will be seen that the cold air flows over and around the tubes formed by the joined wells 3. As the hot and cold air flow over each other, separated by the walls of the wells 3, heat transfers from the hot air to the cold air.

In order to improve the efficiency of the heat exchanger, the walls of the element 1, especially the walls of the wells 3, should be made as thin as possible.

Preferably, if vacuum formed PVC or other plastics is used, the wall thickness should be 500m or less.

The mouths 6 of the wells 3 may have fluted edges which serve to increase the surface area, improving the heat transfer, as well as creating turbulence in the air flow which provides better mixing of the air and therefore ensures a better heat transfer.

Whilst high frequency welding and solvent bonding are mentioned above as methods for fixing the elements 1 together, other techniques such as fusion by melting may be employed, depending upon the materials used.

The heat exchanger of the present invention is simply and inexpensively manufactured and assembled. By virtue of the modular nature of the element 1, the heat exchanger can be built up to any size simply by adding further pairs of elements to increase the lengths of the tubes formed by the joined wells 3. Furthermore, the efficiency may be improved by subdividing the heat exchanger by fixing dividing walls between groups of tubes. For example, in Figure 1, the upper half may be divided from the lower half by a wall. Hot air may flow from right to left around the upper tubes and then be circulated back to flow from left to right around the lower tubes, with cold air being passed through the tubes formed by the wells 3 so that a measure of recirculation is achieved before the hot air, from which a substantial amount of heat has been removed, is finally expelled. The heat exchanger 1 can be subdivided in many ways to provide various recirculation paths according to the efficiency required.

Claims

1. An element for a heat exchanger, the element comprising a sheet of material having a plurality of wells formed therein, each well being of open tubular form, the element being connectable to at least one other substantially identical element having a corresponding plurality of wells to form an assembled heat exchanger in which respective wells join to form tubular air flow paths through the heat exchanger.

2. An element according to claim 1, wherein the element is made of plastics.

3. An element according to claim 2, wherein the element is made of PVC.

4. An element according to claim 2 or claim 3, wherein the element is vacuum formed.

5. An element according to any of claims 1 to 4, wherein the element is initially formed with each well having a bottom wall which is then removed to form a well of open tubular form prior to connection with another element.

6. An element according to any of claims 1 to 5, wherein the sheet is formed with a locating lug and a locating recess to locate the element in registry with another substantially identical element.

7. A heat exchanger comprising a plurality of substantially identical elements according to any of claims 1 to 6.

8. A heat exchanger according to claim 7, wherein the elements are bonded together.

9. A heat exchanger according to claim 8, wherein the bonding process is by at least one of high-frequency welding, solvent bonding, and fusion.

10. A method of manufacturing a heat exchanger, the method comprising the steps of: forming a plurality of substantially identical elements, each element comprising a sheet of material having a plurality of wells formed therein, each well being of open tubular form; and, joining a pair of elements with the wells of one sheet in registry with corresponding wells of the other sheet to form tubular air paths through the wells.

11. A method according to claim 10, comprising the further step of joining together two pairs of elements which are joined with the sheets face-to-face so that the mouths of corresponding wells meet, the two pairs of elements being joined to each other such that the bottoms of corresponding wells meet to form tubular air paths through the four elements.

12. A method according to claim 11, wherein further pairs of elements which are joined with the sheets face-to-face are joined together.

13. A method according to any of claims 10 to 12, wherein the elements are initially formed with closed wells, the bottom walls of the wells being removed to provide wells of open tubular form prior to joining the element with another substantially identical element.

14. A method according to any of claims 10 to 13, wherein the elements are made of plastics.

15. A method according to claim 14, wherein the elements are vacuum formed.

16. An element for a heat exchanger, substantially as described with reference to the accompanying drawings.

17. A heat exchanger, substantially as described with reference to the accompanying drawings.

18. A method of manufacturing a heat exchanger, substantially as described with reference to the accompanying drawings.