GB2116305A

GB2116305A - Heat exchanger

Info

Publication number: GB2116305A
Application number: GB08207213A
Authority: GB
Inventors: Hugh Barrie Doyle
Original assignee: PACKAGED AIR CONDITIONING EQUI
Current assignee: PACKAGED AIR CONDITIONING EQUI
Priority date: 1982-03-11
Filing date: 1982-03-11
Publication date: 1983-09-21

Abstract

The heat exchange device comprises a plurality of fluid permeable thermal sinks 16 arranged on an endless belt 18 capable of being driven so as to move the thermal sinks 16 successively from a warmer fluid stream 10 where they pick up heat to a cooler fluid stream 12 where they give up the heat. The thermal sinks 16 may be constructed from a number of parallel sheets or laminae 20 of material having a high heat absorption capacity such as copper arranged so as to allow the fluid to pass therethrough presenting as little resistance to flow as possible. A supply of flushing air may be provided to remove dust and other contaminants from the thermal sinks as they pass from one fluid stream to the other. <IMAGE>

Description

SPECIFICATION Heat exchanger This invention relates to a heat exchanger and in particular to a heat exchanger in compact form for use in fluid carrying ducts.

In air conditioning and heating systems in buildings cool air from the outside is often brought in and filtered, heated, circulated within the building and then extracted to the outside once more. Where the temperature within the building is greater than the outside temperature this involves energy costs owing to the ventilation heat loss, and it has been proposed to reduce the heat loss by inserting a heat exchanging device to transfer some of the heat from the outgoing warm air to the incoming cool air. However, currently available devices for achieving this end are inconvenient in that their shape does not conform to the ducting normally employed and so part of the air passage-way is inevitably obstructed. The loss of duct cross-sectional area can be as high as 30 to 40% which results in a significant reduction in the efficiency of the system.

The invention seeks to provide a form of heat exchanger capable of fitting into fluid ducting, especially heating and ventilation systems, which will provide the minimum loss of duct crosssectional area.

According to the present invention, there is provided a heat exchange device which comprises a plurality of fluid permeable thermal sinks arranged on an endless belt capable of being.

driven so as to move the thermal sinks successively from a warmer fluid stream where they pick up heat to a cooler fluid stream where they give up the heat.

The thermal sinks are preferably blocks made up of sheets of material having high thermal capacity, for example sheets of metallic material such as copper. The sheets are spaced apart so as to allow the fluid to pass therebetween thus ensuring good thermal contact between the sheets and the fluid. The sheets may be assembled into roughly rectangular blocks arranged successively on an endless belt so that, on a straight run of the endless belt, each successive block is closely adjacent its neighbour and an effectively continuous surface of the thermal sink is presented to the fluid.The heat exchanger device of the invention is particular suited to use with heating and ventilation ducts of air conditioning systems and, since these are generally rectangular in section, the device of the invention can be constructed so as to fill virtually the whole cross-sectional area of a duct reducing the obstructed area to less than 10%.

Where the thermal sinks are mounted on an endless belt naturally this must also be fluid permeable, and indeed the endless belt can be constructed by merely linking adjacent thermal sinks to one another in a corrugated chain arrangement.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevational view, partly in section, of a device constructed in accordance with the invention in position in a heating ventilation duct system; Figure 2 is a diagrammatic representation of the change in temperature gradient; Figure 3 is a front elevation of the apparatus of Figure 1; and Figure 4 is a plan view of the apparatus of Figure 1.

Refering to the drawings, ducts 10 and 12 represent, respectively, an exhaust duct for warm used air from a building, and an inlet duct for cool fresh air from outside. The two ducts are positioned adjacent one another as illustrated and positioned within them is a device constructed in accordance with the invention. The device, generally designated 14 comprises a plurality of thermal sinks 16 linked together to form an endless belt 18. Each of the thermal sinks 16 is a block made of sheets or lamina 20 of a material having a high absorption capacity, Normally metals would be employed and a metal such as copper would be particularly preferred, although a non-metallic material can be used for a TOTAL HEAT recovery application.As can be seen from Figure 1 the sinks 16 in the bulk of the device are arranged so that the lamina 20 are parallel to the direction of the air flow thus presenting as little resistance to the air flow as possible in conjunction with presenting the maximum surface area to the air passing through.

The endless belt 18 is mounted on suitable sprockets 22 driven by a motor 24 which is preferably a variable speed electric motor.

In use, the endless belt 18 is driven in a counter-clockwise direction as indicated by the arrows in Figure 1. Warm extract air passes in the direction of arrow A through the thermal sinks 1 6 which extract heat from the air and move into the inlet duct 12 where cool inlet air then passes through them warming up as it does so. This is shown schematically in Figure 2 where the thermal gradient of both the exhaust air and inlet air are illustrated. In order to help prevent dust or the like from the exhaust air contaminating the inlet air a flushing arrangement may be provided as follows.

A barrier 26 is provided to help prevent intermixing of the inlet and exhaust air within the device 14, but a small quantity of inlet air represented by the arrows B may be directed through the thermal sinks 1 6 close to the bar;ier 26, through a duct 28 and back into the exhaust stream. This will flush any dust or other contaminats out of the successive blocks 1 6 as they enter the inlet duct 12 and prevent contamination of the inlet air. As can be seen from the elevational view of Figure 3 the thermal sink blocks 16 form a substantially continuous heat exchanger surface filling the full width of the duct and the greater portion of its depth, the only obstruction occuring at the extreme top and bottom of the run of the endless belt 1 8. Thus, the device of the invention will fit into widely used ducting in heating and ventilation systems without causing unacceptable obstruction thereof and allows a great deal of otherwise wasted heat to be re-cycled.

Claims

1. A heat exchange device which comprises a plurality of fluid permeable thermal sinks arranged on endless belt capable of being driven so as to move the thermal sinks successively from a warmer fluid stream where they pick up heat to a cooler fluid stream where they give up the heat.

2. A device as claimed in claim 1 in which the thermal sinks are blocks made up of sheets of material having high thermal capacity.

3. A device as claimed in claim 2 in which the sheets are of metallic material.

4. A device as claimed in claim 3 in which the metallic material is copper.

5. A device as claimed in any one of claims 1 to 4 in which the sheets are spaced apart so as to allow the fluid to pass therebetween ensuring good thermal contact between the sheets and the fluid.

6. A device as claimed in any one of claims 1 to 5 in which the sheets are assembled into rectangular blocks arranged successively on an endless belt so that, on a straight run of the endless belt, each successive block is closely adjacent its neighbour and an effectively continuous surface of thermal sink is presented to the fluid.

7. A device as claimed in any one of claims 1 to 6 in which the endless belt is constructed by linking adjacent thermal sinks to one another in a corrugated chain arrangement.

8. A device as claimed in any one of claims 1 to 7 in which, in order to prevent dust or other contaminants being carried from the warm stream to the cold stream by way of the thermal sinks, a flushing air stream is directed at the thermal sinks as they cross the boundary from the warmer fluid stream into the coolerfluid stream.

9. A heat exchange device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.