GB1561981A - Plate heat exchangers - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO PLATE HEAT EXCHANGERS (71) We, THE A.P.V. COMPANY LIMI TED, a British Company of P.O. Box. No. 4 Manor Royal, Crawley, Sussex RH10 2QB, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to plate heat exhangers.

A plate heat exchanger normally comprises a pack of plates arranged in spaced face-to-face relationship to form flow spaces between adjacent plates. The flow spaces are bounded by peripheral gaskets on the plates. Supply and discharge of heat exchange media are through supply and discharge ports defined by aligned apertures in the plates, and gasketing is arranged so that alternate flow spaces connect the supply and discharge ports for one medium and the intervening flow spaces connect the supply and discharge ports for the other medium.In order to create turbulence in the flow spaces to increase the heat transfer, the plates are usually provided with ribs and troughs which in some cases intermate to provide an undulating flow path, but in the type of exchanger to which the present invention relates, they cross and abut to provide a flow regime with turbulence created by continued sub-division and commingling of the flow, and with closely spaced points of abutment of adjacent plates, whereby good interplate support is achieved, so that the heat exchanger can be used with comparatively high operating pressures.

It will be understood that the form, and particularly the angle, of the ribs and troughs, has a considerable influence on the flow regime within the flow space and hence on the heat transfer characteristics of the exchanger.

It is necessary, when designing a heat exchanger, to be able to adjust the heat transfer characteristics to the requirements of the duty in hand. It is not normally possible to design a plate for a particular duty, so that when calculating the total heat transfer area required it is necessary to choose the type of plate from only a small selection of standard plates, each of which is normally designed for a particular frame.

The required heat transfer and pressure drop performance is then obtained by arranging the chosen plate in a multipass arrangement, i.e. with the correct number and size of passes to conform to the required duty.

However, particularly when using large sizes of plates. it is desirable to avoid having connection to the movable follower of the heat exchanger frame, so that multi-pass operation is to be avoided. Thus, the flexibility this gives is denied to the designer, who therefore has to choose a single pass to give the desired performance characteristic.

An object of the invention is to provide a heat exchanger which can be used to provide a greater degree of flexibility than is possible with the conventional plate heat exchangers.

Accordingly, the present invention consists in a plate heat exchanger comprising a pack of spaced-apart corrugated plates wherein a flow space zone is defined between each adjacent pair of plates and wherein in each flow space zone, the corrugations of adjacent plates cross and abut, in which a majority of the plates in the pack are of a first type having corrugations which are inclined to transverse and longitudinal lines on the plates, while a minority of plates.

with a minimum of one, are of a second type formed with corrugations running along lines transverse to the plates, a plate of the second type being disposed in the pack only next to a plate of the first type and not adjacent plates of the second type.

The transverse direction of the corrugations means that there is great resistance to flow, so the characteristic of the second type of plates is to increase the heat transfer performance of the exchanger.

Accordingly, the greater the number of plates of the second type, up to one less than one half of the total, the greater the heat transfer performance. The plates of the first type are preferably designed to give a comparatively low heat transfer performance, which can be progressively increased as plates of the second type are included in the pack.

A further trimming of the performance of the heat exchanger as a whole can be obtained if some or all of the plates of the second type are formed with the corrugations which have different radii at the crests and troughs. This has the effect of modifying the shape and size of the flow spaces formed with the adjacent plates of the first type.

The invention will be further described with reference to the diagrammatic drawings accompanying the provisional specification, which drawings show a preferred embodiment of the invention.

In the drawings: Figure 1 is an elevation of a typical form of heat exchanger plate; Figure 2 is a view similar to Figure 1 of a form of plate to be mixed with plates of the Figure 1 type to form a heat exchanger according to a preferred form of the present invention; Figure 3 is an enlarged section on the line a-a of Figure 1; Figure 4 is an enlarged section on the line Fb of Figure 2; Figure 5 is an enlarged section on the line c--e of Figures 1 and 2 showing two plates juxtaposed as in a heat exchanger; and Figure 6 is a view similar to Figure 5 but showing a modification.

Turning first to Figure 1, there is shown a fairly typical form of heat exchange plate 4 having corrugations formed in a chevron pattern as indicated at 1. Distribution zones of a generally triangular shape are shown above and below the pattern of corrugations 1 forming the main heat transfer zone, and these are provided with a pattern of dimples 2. Ports 3 are shown at all four corners of the plate, and it will be appreciated that as is conventional in heat exchangers two of the ports will be connected to a flow space zone and two isolated from it, so that one heat exchange medium flows through alter- nate flow space zones and the other flows through the intervening zones.Gasketing to control this is not illustrated, Outside the peripheral gasket and between each of the upper and lower pairs of ports there is provided a hole 5 spaced at a distance W from the centre line 6 of the plate.

It will be readily apparent that a heat exchanger of the criss-cross type. i.e. with the corrugations crossing and abutting within the flow zone can be formed by a pack of plates of the type illustrated in Figure 1, with alternate plates rotated in their planes through 1800 so that the chevrons point alternatively up and down. The plate of Figure 1 is indicated as the plate 4 in Figures 5 and 6.

Turning now to Figure 2, the plate 7 shown there is generally similar to the plate 4, but it can be seen to have transverse corrugations 8 rather than the chevron type shown in Figure 1. It will be appreciated that plates with such transverse corrugations cannot be assembled to form a heat exchanger of the criss cross type, since rotation of the plates through 1800 will leave the corrugations 8 still parallel with each other and not crossing. In order to prevent plates of the type shown in Figure 2 from being assembled next to each other, it will be seen that they are provided, outside the gaskets, and to one side of the centre line 6, with pips 9 which enter the holes 5 when the plates 7 are correctly assembled next to plates 4 of the type shown in Figure 1.The shape of the pips 9 is so chosen that they do not nest closely but abut the metal of the plate if assembled next to another plate 7, thus preventing closure of the heat exchanger and alerting the engineers to the fact that an incorrect assembly has been made.

The plate 7, with its transverse corrugations, is shown in Figures 5 and 6 in conjunction with a single plate 4 of the Figure 1 type.

It will be appreciated that in a heat exchanger, there will be a considerable number of plates 4, and these will be assembled with a smaller number of plates 7 of the type shown in Figure 2. The effect of including plates of the Figure 2 type is to increase the performance of the pack, and the number of plates 7 used will depend on the performance required.

A further modification of the performance may be achieved by modifying the plates 7 so that the crests and troughs have different curvatures, as illustrated in Figure 6, so that a flow space formed between the two sides of the plate 7 and the cooperating sides of adjacent plates 4 have somewhat different characteristics.

Various modifications may be made within the scope of the invention. It may be that the combination of inclined and transverse troughed plates may not give the precise required basic thermal performance specified for the plate, and this can be achieved by inserting supplementary depressions in the transverse grooves which will affect the flow Dattern and thereby modify the thermal and pressure drop characteristics. In addition, the plate can, if necessary, be mechanically strengthened by the addition of full or partial depth grooves which extend longitudinally along the whole or part of the corrugated zone.

WHAT WE CLAIM IS:- 1. A plate heat exchanger comprising a pack of spaced-apart corrugated plates wherein a flow space zone is defined between each adjacent pair of plates and wherein in each flow space zone, the corrugations of adjacent plates cross and abut, in which a majority of the plates in the pack are of a first type having corrugations which are inclined to transverse and longitudinal lines on the plates, while a minority of plates, with a minimum of one, are of a second type formed with corrugations running along lines transverse to the plates, a plate of the second type being disposed in the pack only next to a plate of the first type and not adjacent plates of the second type.

2. A plate heat exchanger as claimed in claim 1, in which the plates of the second type are formed with the corrugations which have different radii at the crests and troughs.

3. A plate heat exchanger as claimed in claim 1 or 2, comprising means for preventing assembly of the exchanger with two plates of the second type adjacent each other.

4. A plate heat exchanger as claimed in claim 3, dn which the said means comprises projections on the plates of the second type which match holes in the next plate or plates of the first type but abut metal and prevent closure of the exchanger if two plates of the second type are juxtaposed.

5. A plate heat exchanger substantially as hereinbefore described with reference to the drawings accompanying the provisional specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. the plate can, if necessary, be mechanically strengthened by the addition of full or partial depth grooves which extend longitudinally along the whole or part of the corrugated zone. WHAT WE CLAIM IS:-

1. A plate heat exchanger comprising a pack of spaced-apart corrugated plates wherein a flow space zone is defined between each adjacent pair of plates and wherein in each flow space zone, the corrugations of adjacent plates cross and abut, in which a majority of the plates in the pack are of a first type having corrugations which are inclined to transverse and longitudinal lines on the plates, while a minority of plates, with a minimum of one, are of a second type formed with corrugations running along lines transverse to the plates, a plate of the second type being disposed in the pack only next to a plate of the first type and not adjacent plates of the second type.

2. A plate heat exchanger as claimed in claim 1, in which the plates of the second type are formed with the corrugations which have different radii at the crests and troughs.

3. A plate heat exchanger as claimed in claim 1 or 2, comprising means for preventing assembly of the exchanger with two plates of the second type adjacent each other.

4. A plate heat exchanger as claimed in claim 3, dn which the said means comprises projections on the plates of the second type which match holes in the next plate or plates of the first type but abut metal and prevent closure of the exchanger if two plates of the second type are juxtaposed.

5. A plate heat exchanger substantially as hereinbefore described with reference to the drawings accompanying the provisional specification.