GB2333352A

GB2333352A - A heat exchange unit uing peltier devices

Info

Publication number: GB2333352A
Application number: GB9717916A
Authority: GB
Inventors: Paul Harris; John Ward
Original assignee: ICEE Ltd
Current assignee: ICEE Ltd
Priority date: 1997-08-22
Filing date: 1997-08-22
Publication date: 1999-07-21
Anticipated expiration: 2017-08-22
Also published as: GB2333352B; GB9717916D0

Abstract

A cooling unit 10 comprises a stack of manifolds 11, 12 and 13 with peltier devices 14 sandwiched between each juxtaposed pair of the manifolds 11 and 12, 12 and 13. The peltier devices 14 are spaced from one another and arranged in rows along the length of the manifolds 11 to 13. A DC electrical potential is applied across each of the peltier devices 14. The cold faces of the peltier devices 14 of each row abut the adjacent faces of the middle manifold 12 and the hot faces of those peltier devices 14 abut the adjacent surfaces of the outer manifolds 11 and 12. The manifolds and peltier devices are held together using a fixing arrangment which utilises Belleville washers (32) to allow for thermal expansion and contraction.

Description

A HEAT EXCHANGE UNIT This invention relates to a heat exchange unit and more particularly to a cooling unit for use in an enclosed space or in other enclosures such as in computer housings or in computer rooms to achieve an optimum working temperature for communication equipment. Such equipment can be run satisfactorily at higher temperatures but its life span will be cut down progressively as those temperatures are increased.

It is preferable to use air to air heat exchange units rather than domestic air conditioning units for cooling enclosures within which electronic apparatus is stored. This is because domestic air conditioning units liberate water in their operation so that cool air they would direct around the electronic apparatus is damp. Hence provision needs to be made to collect the water and for its drainage which adds to expense. However, air to air heat exchange units have their limitations because they are only effective to maintain an air flow within an enclosure at a level which is approximately 150C above ambient temperature. As a result on hot days in a temperate climate or frequently in mediterranean or tropical climates, the temperature within an enclosure is excessive for electronic apparatus within that enclosure even when it is cooled by such air to air heat exchange units.

An alternative form of cooling which can be used is natural air convection, air being circulated by a fan. This can be satisfactory but its effect varies with ambient temperature and it suffers because it causes ingress of moisture, dust, dirt and wildlife such as insects.

Systems which use domestic air conditioning units or air to air heat exchanger units are closed systems, the cooling unit being housed within the enclosure. Hence that enclosure has an oven effect, heat being generated within it by operation of electrical equipment within it. This is compounded by the effect of solar gain on the exterior of the enclosure when the latter is outside. This results in necessary cooling apparatus being large if the required cooling level is to be achieved. That can be a problem, as in certain installations, such as roadside apparatus, there may be space constraints. This leads to two irreconcilable conflicting requirements, the desire to maximise space within the enclosure for the electrical equipment it is to house on the one hand and the need to provide space for the necessary large cooling apparatus on the other hand.

An object of this invention is to provide cooling equipment which is economical in space, which is more effective than an air to air heat exchanger within an enclosed cabinet, and which will not create moisture by its operation.

According to this invention there is provided a heat exchange unit comprising a row of peltier devices sandwiched between a pair of manifolds, each peltier device being adapted to be cannected across an electrical potential so that it has a hot face and a cold face when it is so connected, the manifolds being arranged so that each surface of one of them is in intimate thermal contact with the surfaces of each of the peltier devices that are the hot faces when the electrical potential is connected across them and so that a surface of the other of the manifolds is in intimate thermal contact with the other surfaces of each of the peltier devices, and each of the manifolds having a coolant flow passage formed in it so that the coolant flow passages extend alongside the row of peltier devices whereby coolant fluid passed through the coolant flow passage in said one manifold is heated by heat transferred to it from the hot faces of the peltier devices through intervening structure of said one manifold and coolant fluid passed through the coolant flow passage in said other manifold is cooled by heat exchange with the cold faces of the peltier devices through intervening structure of said other manifold.

Preferably there are three such manifolds and two rows of peltier devices, the cold faces of the peltier devices each being in intimate thermal contact with the adjacent surface of one of the three manifolds which is positioned between the other two manifolds which in turn are each in intimate thermal contact with the hot faces of a respective one of the rows of peltier devices.

Conveniently each of said other two manifolds is provided with two laterally projecting flanges which extend one on either side of it, generally in the direction in which the coolant flow passages extend, the two flanges on either side of the stack of three manifolds and two rows of peltier devices being joined together by a respective fixing arrangement. In a preferred embodiment means such as Belleville washers, are incorporated in each such fixing arrangement in order to allow for thermal expansion of the stack. The fixing arrangements are either spaced from or are thermally insulated from said other manifold.

In the preferred embodiment means are provided to cause turbulent flow of coolant through each of the coolant flow passages.

One form of cooling unit which embodies this invention and which is for use to cool the interior of a roadside cabinet which accommodates telecommunication equipment, is described now by way of example with reference to the accompanying drawings of which: Figure 1 is a diagrammatic representation of the cooling unit connected into electrical and cooling fluid circuitry; Figure 2 is an end view of the cooling unit illustrated diagrammatically in Figure 1; Figure 3 is a side elevation of the central manifold of the cooling unit shown in Figure 2; and Figure 4 is a fragmentary view on arrow A in Figure 3.

Figure 1 diagrammatically illustrates a cooling system for installation in a roadside cabinet which houses telecommunications equipment. The cooling system comprises a cooling unit 10 which comprises a stack of three manifolds 11, 12 and 13 with peltier devices 14 sandwiched between each juxtaposed pair of the manifolds 11 and 12, 12 and 13. The peltier devices 14 between each pair of manifolds 11 and 12, 12 and 13 are spaced from one another and arranged in a row along the length of the manifolds 11 to 13.

A DC electrical potential from any suitable source is applied across each of the peltier devices 14, as is shown diagrammatically at 15, 16 in Figure 1. Each peltier device 14 has an opposed pair of faces. Due the peltier effect, one of those faces is a hot face and the other is a cold face.

The cold faces of the peltier devices 14 of each row abut the adjacent surface of the middle manifold 12 of the stack and the hot faces of those peltier devices 14 abut the adjacent surface of the nearer one of the two outer manifolds 11 and 13.

Figures 2 and 3 show that each manifold 11 to 13 is a metal block which has three through bores 17, 18 and 19 formed in it from end to end. The block also has two blind ended lateral bores 21 and 22 (see Figure 3) formed in it, one adjacent either end of that block. Each lateral bore 21, 22 intersects each of the through bores 17 to 19 and receives a fluid connector (not shown) in its mouth which opens in a side wall of the block. Each through bore 17 to 19 has a wire insert (not shown) fitted into it and is plugged at either end.

The external surfaces of the manifolds 11 to 13 that are abutted by the adjacent peltier devices 14 are formed with a high quality finish, say by fly cutting or lapping, so that an intimate thermal contact is established between each peltier device 14 and the respective manifold 11 to 13.

Each of the upper and lower manifolds 11 and 13 has flanges 23 and 24, 25 and 26 which project outwardly from each of its side walls and which are fixed together to complete assembly of the stack. The flanges 23 and 25, 24 and 26 on either side of the stack are fixed together by nuts 27 and 28 and bolts 29 and 31 which have long shanks.

A Belleville washer 32 is fitted between each nut 27, 28 and adjacent flange 23, 24 so as to allow for thermal expansion and contraction. The shank of the bolts 29 and 31 is spaced from the middle manifold 12 so that there is no heat bridge therebetween.

Figure 1 shows that the fluid connector at one end of the middle manifold 12 is connected to the output of a water pump 32 which is operable to draw water from a reservoir 33 and pump it through the passages formed by the three bores 17 to 19 of the middle manifold 12. The wire insert fitted into each of those bores 17 to 19 ensures that water flow through those passages is turbulent. Hence, as it flows through the middle manifold 12, that water is cooled by heat exchange with the structure of the middle manifold 12 which is cooled by the intimate contact with the cold faces of the peltier devices 14. The cooled water emerges from the middle manifold 12 through the fluid connector at its other end from where it is conveyed to a heat exchanger 34 which is located within the compartment within the cabinet in which the telecommunications equipment is housed. Air within that compartment is cooled by heat exchange with the cooled water that flows through the heat exchanger 34. Water which emerges from the heat exchanger 34 is returned to the reservoir 33.

Fans may be provided within the compartment for circulating air cooled by heat exchange with the heat exchanger 34.

The fluid connectors at one end of each of the upper and lower manifolds 11 and 13 are connected in parallel to the output of a pump 35 which is operable to draw water from a reservoir 36 and pump it through the passages 17 to 19 of the upper and lower manifolds 11 and 13. The wire insert fitted into each of those bores 17 to 19 ensures that water flow through those passages is turbulent. Hence, as it flows through the upper and lower manifolds 11 and 13, that water extracts heat from the structure of the manifolds 11 and 13 and thus takes heat away from the hot faces of the peltier devices 14 so that the cooling effect of those peltier devices 14 on the middle manifold 12 is maintained. The water that emerges from the upper and lower manifolds 11 and 13 through the fluid connectors at their other end is conveyed in parallel to a heat exchanger 37 which is mounted so as to be exposed to ambient atmosphere. As a result that water is cooled by passage through the heat exchanger 37 by heat exchange with ambient air. Water emerging from the heat exchanger 37 is returned to the reservoir 36.

Anti-freeze may be added to the water in each of the two water cooling systems.

Claims

CLAIMS 1. A heat exchange unit comprising a row of peltier devices sandwiched between a pair of manifolds, each peltier device being adapted to be connected across an electrical potential so that it has a hot face and a cold face when it is so connected, the manifolds being arranged so that a surface of one of them is in intimate thermal contact with the surfaces of each of the peltier devices that are the hot faces when the electrical potential is connected across them and so that a surface of the other of the manifolds is in intimate thermal contact with the other surfaces of each of the peltier devices, and each of the manifolds having a coolant flow passage formed in it so that the coolant flow passages extend alongside the row of peltier devices whereby coolant fluid passed through the coolant flow passage in said one manifold is heated by heat transferred to it from the hot faces of the peltier devices through intervening structure of said one manifold and coolant fluid passed through the coolant flow passage in said other manifold is cooled by heat exchange with the cold faces of the peltier devices through intervening structure of said other manifold.
2. A heat exchange unit according to claim 1, wherein there are three such manifolds and two rows of peltier devices, the cold faces of the peltier devices each being in intimate thermal contact with the adjacent surface of one of the three manifolds which is positioned between the other two manifolds which in turn are each in intimate thermal contact with the hot faces of a respective one of the rows of peltier devices.
3. A heat exchange unit'according to claim 2, wherein each of said other two manifolds is provided with two laterally projecting flanges which extend one on either side of it, generally in the direction in which the coolant flow passages extend, the two flanges on either side of the stack of three manifolds and two rows of peltier devices being joined together by a respective fixing arrangement.
4. A heat exchange unit according to claim 3, wherein means are incorporated in each such fixing arrangement in order to allow for thermal expansion of the stack.
5. A heat exchange unit according to claim 4, wherein said means comprise Belleville washers.
6. A heat exchange unit according to any one of claims 3 to 5, wherein the fixing arrangements are spaced from said other manifolds.
7. A heat exchange unit accorfding to any one of claims 3 to 5, wherein the fixing arrangements are thermally insulated from said other manifolds.
8. A heat exchange unit according to any one of claims 1 to 8, wherein means are provided to cause turbulent flow of coolant through each of the coolant flow passages.
9. A heat exchange unit substantially as described hereinbefore with reference to and as shown in the accompanying drawings.