GB2458710A

GB2458710A - Heat exchanger with parallel passageways formed by ribs between walls

Info

Publication number: GB2458710A
Application number: GB0809104A
Authority: GB
Inventors: David John Stone
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-03-26
Filing date: 2008-05-20
Publication date: 2009-09-30
Also published as: GB0805459D0; GB0809104D0

Abstract

The heat exchanger 1 has a pair of spaced circular inner and outer walls 4,5 joined by a series of spaced ribs 6 extending in an axial direction between the opposite ends 2, 3 to form a series of parallel passageways 7. Interconnecting ports (e.g. 14a, fig 3) are milled or formed between adjacent passageways (fig 3), or groups of adjacent passageways (fig 4), at opposite ends of the extrusion, such that in one embodiment the fluid flows in opposite directions in the adjacent passageways or groups of adjacent passageways. A pair of end caps 9,10 close the ends 2,3 and have a respective fluid inlet 11 and a fluid outlet 12. An alternative embodiment (fig 5) has helical passageways. The heat exchanger may be an extrusion, moulding or welded; may be transparent or partially/wholly coloured black to absorb heat; and can be cylindrical, curved or flat. The ribs may be inclined to form a triangular cross-section passage (fig 7). The heat exchanger may be a radiator, solar panel, fireproof wall or part of a food processing machine; or cool a horticultural or industrial light bulb, or a chimney.

Description

HEAT EXCHANGERS

TECHNICAL FIELD OF THE INVENTION

This invention relates to heat exchangers.

BACKGROUND

It is known to provide cooling jackets to remove heat from items which become hot in use. One such example relates to high power industrial and horticultural lamps which may be surrounded by a transparent cylindrical jacket through which water is pumped to remove heat from the lamp.

In practice, such cooling jackets tend to suffer from localised build-up of pressure due to the hydraulic ram effect. This puts pressure on the seals, which can cause leaks. Furthermore, it is difficult to produce an even flow of water through the jacket, which may result in hot spots and premature failure of the lamp. The cooling jackets also tend to be expensive since they must be rated to withstand the highest temperature which they are likely to encounter.

Apart from the problem of local overheating it is also important that cooling jackets which surround such light sources do not cause a large amount of -2.

attenuation and/or refraction of light passing through the jacket.

The present invention seeks to provide a new and inventive form of heat exchanger which is capable of achieving improved efficiency, which can achieve low light attenuation and/or refraction, and which is also relatively inexpensive to manufacture.

SUMMARY OF THE INVENTION

The present invention proposes a heat exchanger having: -a heat exchange body which includes a pair of spaced walls and a plurality of spacing ribs which bridge the walls and extend between opposite ends of the body to form a plurality of substantially parallel passageways; -a pair of end caps sealably secured to said opposite ends of the body; -a fluid inlet for introducing a fluid into the space formed by said passageways; and -a fluid outlet for removing fluid from said space; in which interconnecting ports are formed between adjacent passageways, or groups of adjacent passageways, at said opposite ends of the body, such that the fluid flows in opposite directions in said adjacent passageways or groups of adjacent passageways.

The interconnecting ports may be arranged to cause the direction of flow to be reversed at alternate ends of the body.

In a preferred form of the heat exchanger the body is formed from a length of a single extrusion. The interconnecting ports are preferably formed by removing -3.

part of the spacing ribs between the respective adjacent passageways or groups of passageways.

Preferably, when the heat exchanger is viewed in cross-section transverse to the passageways, the walls are formed into a closed shape, e.g. a square or circle, surrounding an internal space for receiving an object to be cooled.

The invention also provides a heat exchanger having a heat exchange body formed of a light-transmitting material which includes a pair of spaced walls and a plurality of spacing ribs which bridge the walls to form a plurality of substantially parallel passageways which are interconnected to conduct a heat-exchange fluid through the body.

Preferably, the transparent heat exchange body is shaped to surround an internal space which may contain a light source. In one embodiment of the transparent heat exchanger the passageways each substantially surround the internal space. In a particularly preferred form of such a transparent heat exchanger the passageways are interconnected such that they travel in a substantially helical configuration around the internal space.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is a general view of a first form of cylindrical heat exchanger in accordance with the invention; figure 2 is a sectional view of the heat exchanger transverse to the direction of the cooling passageways; Figure 3 is a diagrammatic representation of the heat exchanger showing the flow path through the unit; Figure 4 is a diagrammatic representation of a modified form of the heat exchanger; fjgure 5 is a general view of a second form of cylindrical heat exchanger in accordance with the invention; figure 6 is an axial section through one side of the second form of heat exchanger; and Figure 7 is a similar sectional view showing an alternative configuration of the heat exchanger.

DETAILED DESCRIPTION OF THE DRAWINGS

The heat exchangers described below are suitable for cooling a horticultural or industrial light bulb, although the heat exchanger could also be used to remove heat from other objects such as a chimney for example.

Referring to Fig.s 1 and 2, the heat exchanger is formed from a cylindrical plastic extrusion 1 having opposite ends 2 and 3 cut to an appropriate length. When the heat exchanger is required to transmit light the extrusion may be formed of a transparent material, but in some applications it may be advantageous to form the extrusion from a darkly coloured plastic, preferably black, or colour part of the extrusion to assist heat absorption. High temperature plastics are available enabling the heat exchanger to be direct flame tested to temperatures as high as 1,300 °C. The extrusion includes a pair of uniformly spaced circular inner and outer walls 4 and 5 which are mutually joined by a series of equally-spaced ribs 6, extending in an axial direction between the opposite ends 2 and 3 to form a series of substantially parallel passageways 7. A pair of end caps 9 and 10 sea lably close the opposite ends 2 and 3. In a basic form, the end caps could be a pair of annular rings which are adhesively bonded to the inner and outer walls 4 and 5 and (except as explained below) to the internal spacing ribs 6. The two end caps 9 and 10 are provided with a respective fluid inlet 11 and a fluid outlet 12 to conduct a cooling fluid (preferably a liquid but possibly also a gas) in and out of the heat exchanger.

The diagrammatic representation of Fig. 3 shows the basic internal configuration of a single unit heat exchanger with the extrusion 1 shown flattened out in two dimensions for clarity. The diagram shows that the inlet 11 communicates with a first internal passageway 7a while the outlet 12 communicates with the last passageway 7f (which will of course be next to the first passageway 7a in the true three-dimensional configuration). Considering the first two adjacent passageways 7a and 7b, these are mutually interconnected adjacent to the end 3 by milling out or otherwise removing a portion of the intermediate spacing rib 6a to form an interconnecting port 14a. At the opposite end 2 the passageway 7b is interconnected with the next adjacent passageway 7c by removing a portion of the intermediate rib 6b to form an interconnecting port 14b.

Returning again to the opposite end 2, passageway 7c is similarly connected to the next adjacent passageway 7d, and this is repeated at alternate ends of the extrusion until the last passageway 7f exits through the outlet 12.

It will now be appreciated that if the heat exchanger is placed around a high power cylindrical light bulb and a suitable cooling fluid is pumped between the inlet and the outlet the fluid will flow in opposite directions through each adjacent pair of passageways, travelling back-and-forth until the warmed fluid reaches the outlet 12. Such an arrangement has been found to produce very efficient and uniform cooling, with the flow rates and pressures being substantially equal in all the passageways.

It will be noted that in the example of Fig. 3 the extrusion contains an even number of passageways and the inlet and outlet 11 and 12 are therefore located at the same end 2 of the extrusion. However, if the extrusion contains an odd number of passageways between the inlet and outlet these can be made to exit at different ends when more convenient, as shown in FIg. 1. A single cylindrical heat exchanger could be formed from two or more cooling units of the kind shown in Fig. 3 with the outlet of one unit disposed adjacent to the inlet of the next unit. Such an arrangement would provide a lower temperature difference between the inlet and outlet compared with a single unit heat exchanger, and may provide more efficient cooling in some circumstances.

Another possible configuration of the heat exchanger is shown in Fig. 4, which would allow greater flow rates to be achieved for a given cross-sectional area of the passageways. In this embodiment the passageways are connected in groups of two, with each pair of passageways such as 7j and 7k being interconnected at both ends by milling out or otherwise removing a portion of the intermediate spacing rib 6i to form interconnecting ports 14f and 14g. The ports therefore connect the passageways in parallel, so that the direction of fluid flow is the same within each group. The spacing rib 6j between paired passageways 7j, 7k and the next adjacent pair 71 and 7m has a portion of the rib removed at one end only, to form an interconnecting port 14h. This is repeated at the opposite end for the spacing rib 61 between pair 71 and 7m and the next adjacent pair 7n and 7o, and so on, with each parallel pair of passageways being connected to the next pair at alternate ends of the extrusion. In order that the increased flow rate is not impeded, two or more inlets ha and lib may interconnect with adjacent, or separated, passageways, as shown. Similarly, two or more outlets 12a and 12b may interconnect with passageways 7p and 7q.

Although the inner and outer walls 4, 5 and the ribs 6 are conveniently and inexpensively formed as a continuous extrusion the heat exchange body may also be constructed from a number of individually formed components which are bonded together.

It is not essential for the Units of Fig.s 3 and 4 to be formed into a tube. In other applications the heat exchanger units can be used in the form of a flat or curved panel, for example solar panels, radiators, underfloor heating panels, fireproof walls, or cooling fins.

Fig..s 5 and 6 show another configuration of cylindrical heat exchanger which can be used to surround and cool a light source. This heat exchanger is formed of a transparent material such as a high temperature plastics, although in some applications the heat exchanger may be formed of a darkly coloured material to assist heat absorption. The body 21 of the heat exchanger is shaped to enclose an internal space 22 for receiving a light source, and includes a pair of uniformly spaced cylindrical inner and outer walls 24 and 25 which are mutually joined by a continuous connecting rib 26. This rib extends in a helical configuration between the walls 24 and 25 to create a single continuous passageway 27 which travels in a helical path around the space 22 terminating at opposite ends in a fluid inlet 31 and a fluid outlet 32 to conduct a cooling fluid in and out of the heat exchanger.

When the heat exchanger is placed around a high power cylindrical light bulb and a suitable cooling fluid is pumped between the inlet 31 and the outlet 32 the fluid will flow in a helical path until the warmed fluid reaches the outlet 32.

This configuration again has the advantage that the flow rates and pressures are substantially equal throughout the length of the passageway 27. Furthermore, the provision for heat exchange between adjacent helical sections of the passageway 27 through the common dividing rib 26 helps to reduce the occurrence of localised hot spots.

In this form of the heat exchanger it is possible to provide two or more mutually separate helical pathways which run together in a side-by-side configuration between a corresponding number of inlets 31 and a corresponding number of outlets 32.

Fig. 7 shows an alternative configuration in which the dividing wall joining the spaced inner and outer walls is inclined in a sawtooth shape to form a series of passages of triangular cross-sectional shape. Such an arrangement could be used in the heat exchanger of Fig.s 1 to 4 or that of Fig.s 5 and 6.

The heat exchangers described above have the advantage that, for any particular kind of plastic material and heat exchange fluid, light passing through the wall of the heat exchange body is subjected to a minimum amount of refraction and attenuation.

The heat exchangers described above may be formed of polycarbonate or other materials which depend upon the particular application, such as food grade plastics, heat resistant plastics, thermosetting plastics, bendable plastics and insert plastics, rubbers, metals etc. They may be extruded, injection moulded, welded etc. so that the heat exchanger may be highly resistant to attack by chemicals, salt water, acids etc. The connections may be pressure tested prior to use to ensure reliability.

The heat exchangers can be used to harvest unused heat from an item such as a horticultural lamp, allowing the heat to be stored for use at night.

Appropriate precautionary measures may be included, such as a safety cutout to shut down the lamp in the event of a pump failure.

Other possible uses include solar heating panels installed in lofts, temperature regulation panels (heating or cooling) or fire-proof cladding panels for use in walls, floors, ceilings, chimneys etc. They could be used to make rooms more thermally efficient by removing excess heat and returning heat to the room when required, e.g. at night. If made from food-grade plastics the heat exchangers could be used for heating milk as an alternative to stainless steel pasteurisation units, condensers, or water heaters for sterilisation, cooking etc. The forms of heat exchanger described herein overcome problems with localised pressure build-up and produce a substantially even flow in all areas of the heat exchanger. The flow path does not have any large changes in cross-sectional area, and the flow rate is relatively low so that an adequate flow can be achieved using a relatively small pump (e.g. a 5 watt aquarium-type pump).

The heat exchanger is also very light and strong compared with existing glass cooling jackets.

Suitable heat exchange fluids for use in the heat exchangers described herein include liquids such as water or oils, gases, or liquefied gases such as liquid helium.

Whilst the above description places emphasis on the areas which are believed to be new and addresses specific problems which have been identified, it is intended that the features disclosed herein may be used in any combination which is capable of providing a new and useful advance in the art.

* * * * * * * *

Claims

CLAIMS1. A heat exchanger having: -a heat exchange body which includes a pair of spaced walls and a plurality of spacing ribs which bridge the walls and extend between opposite ends of the body to form a plurality of substantially parallel passageways; -a pair of end caps sealably secured to said opposite ends of the body; -a fluid inlet for introducing a fluid into the space formed by said passageways; and -a fluid outlet for removing fluid from said space; in which interconnecting ports are formed between adjacent passageways, or groups of adjacent passageways, at said opposite ends of the body, such that the fluid flows in opposite directions in said adjacent passageways or groups of adjacent passageways.
2. A heat exchanger according to Claim 1 in which the interconnecting ports are arranged to cause the direction of flow to be reversed at alternate ends of the heat exchange body.
3. A heat exchanger according to Claim 1 or 2 in which the heat exchange body is formed from a length of a single extrusion.
4. A heat exchanger according to Claim 3 in which the interconnecting ports are formed by removing part of the spacing ribs between the respective adjacent passageways or groups of passageways.
5. A heat exchanger according to any preceding claim in which, when the heat exchanger is viewed in cross-section transverse to the passageways, the walls are formed into a closed shape surrounding an internal space for receiving an object to be cooled.
6. A heat exchanger according to any preceding claim in which the heat exchange body is formed of a light-transmitting material.
7. A heat exchanger having a heat exchange body formed of a light-transmitting material which includes a pair of spaced walls and a plurality of spacing ribs which bridge the walls to form a plurality of substantially parallel passageways which are interconnected to conduct a heat-exchange fluid through the body.
8. A heat exchanger according to Claim 7 in which the heat exchange body is shaped to surround an internal space which may contain a light source.
9. A heat exchanger according to Claim 8 in which the passageways each substantially surround the internal space.
10. A heat exchanger according to Claim 9 in which the passageways are interconnected such that they travel in a substantially helical configuration around the internal space.
11. A heat exchanger substantially as described with reference to the drawings.* * * * * * * *