The present invention relates to a heat exchanger construction, comprising two plates having a given breadth and with a substantially constant mutual spacing which are wound in the form of a spiral about an axis to form two separate helical fluid loops each with centrally positioned openings, which openings each define inlets and outlets to the two fluid loops.

The invention also relates to a method for the production of the heat exchanger construction, together with an apparatus for the production of a heat exchanger construction. The inventions preferably have to do with an exchanger construction which is to be used as a heat exchanger.

The invention especially has to do with heat exchangers which at the start are constructed as helical heat exchangers.

The object of the present invention is to provide a novel and better construction of a heat exchanger. It is furthermore an object to provide a novel method for the production of a heat exchanger construction, together with an apparatus which is well-suited for such a production.

The heat exchanger construction according to the invention is characterised in that it comprises two exchanger units having mutual mirror-image oriented windings about respective axes, and the two outer plates in the one unit are connected to, or pass continuously over into, the two equivalent outer plates in the other

unit, and in a contact line or contact surface, (which for example extends substantially coaxially), between the helical units there is a fluid tight sealing between the units. By mirror-image orientation is meant that the units are arranged symmetrically about an imaginary plane (a mirror plane) which is tangent to the contact line between the units, or passes through the contact surface between the units. The units are consequently turned or inverted relative to each other.

According to a preferred construction, the two exchanger units comprise a like or different number of windings. Additional preferred constructions of the heat exchanger according to the invention are evident from the remaining dependent product claims.

The method according to the invention is characterised in that a band-shaped plate having a given breadth is joined end edge to end edge to form an endless band of the plate, that each end of the band-shaped plate loop is introduced into a gap between two substantially parallel elongate cores, the two pairs of cores are guided from each other in order to brace the band, that the two pairs of cores are rotated about an axis in order to wind the band about the two cores to form two helical coils, at the same time as the core pairs are moved towards each other as a substantially constant tension is maintained in the band, there being established a tight sealing in the line or surface where the two coils contact each other, and the two core pairs are extracted from the coils.

Preferred embodiments of the method according to the invention are evident from the remaining dependent method claims.

The apparatus according to the invention is characterised in that it comprises two holder units each comprising a pair of two mutually parallel elongate cores, which form between them a gap, the two pairs of cores being mutually parallel, that each holder unit is adapted to rotate the pair of cores about an axis which passes

approximately through the gap parallel to the cores, and means for displacing the two holder units towards and away from each other.

Preferred constructions of this apparatus according to the invention are evident from the remaining dependent apparatus claims.

The invention will now be explained further with reference to the enclosed Figures, wherein: Figure 1 shows schematically a side view of a construction of a plate-helical heat exchanger according to the invention (cp. Figure 6).

Figure 2 shows the introductory step for the production of the heat exchanger according to the invention, that is to say the initial bracing of the endless band for the start of the production.

Figure 3-6 show the stepwise coiling up of the band to a heat exchanger, Figure 6 illustrating the band ready coiled to a first preferred embodiment of a heat exchanger construction having the basic design which is shown in perspective in Figure 1.

Figure 7 shows another alternative form of a heat exchanger construction.

Figure 8 shows how the heat exchanger according to Fig. 6 is commissioned for use.

Figures 9 and 10 show a side section and a plan section respectively of an apparatus for the production of the heat exchanger according to the invention.

Figure 11 shows details of devices in connection with the apparatus for a change of the diameter of the roller, that is to say that when the core/roller is released the radius must be reduced.

Figure 12 shows a section of an alternative construction for the commissioning of the heat exchanger, with reference to Figure 8b.

Figures 13,14 and 15 show dissimilar constructions of spacing pieces for establishing constant plate spacings x.

By way of introduction Figure 2 is referred to, which illustrates the introductory step for the production of the heat exchanger 10 according to the invention. A band 12, in the form of an elongate plate, such as metal or plastic, having a given length is joined end-to-end so that an endless band is formed. The plate band has the breadth B as is evident from Figure 1, and the thickness of the plate can vary. The invention is best suited constructed with so-called thin plates.

Figure 2 shows the initial bracing of the endless band 12 with mounted on spacing elements, in order to start the production of the heat exchanger construction.

The spacing elements which guarantee a constant band spacing distance in the finished product, are arranged in the band in advance. The band 12 is clamped between two of cores 14,18 of the core pairs 14,16 and 18,20 respectively, where each pair of cores is mounted to respective holder units 84, 86. The cores comprise preferably mutually parallel and fixed rollers 14,16 and 18,20 respectively. Stated in another way then the band is threaded into the gap between the two associated rollers.

Each holder 84,86 is adapted to rotate each roller pair 14,16; 18,20 about an axis parallel to the longitudinal direction of the rollers, which axis is located at the approximately tangential point 22 (or in the gap) between the rollers. Further the roller pairs 14,16 and 18,20 respectively are adapted to be moved (on the holders 84, 86) laterally along a straight plane 24 between the tangential points 22a, 22b, that is to say coinciding with the one (lower) stretch 26 of band. Each side surface of the band comprises spacing elements, such as regularly shaped recesses which cause there to become a fixed distance X between adjacent band plates when the band is coiled up, cp. the Figures 13-15.

By virtue of varying diameters there is required an overlength corresponding to the height H of the outer stretch 26 of plate which goes to zero when the band is coiled ready, cp. the Figures 3-6. This also provides a designed tension for a compact heat exchanger product which is guaranteed in coiled up form with band tape or the like.

After the endless band 12 is arranged between the rollers 14,16 and 18,20 respectively, the roller pairs are guided from each other in order to provide the necessary tension, cp. Figure 2, plus apparatus Figure 9.

Now the coiling up starts in that the roller pairs 14,16 and 18,20 respectively rotate about their axes 22 against each other, that is to say in a counterclockwise direction on the left side and in a clockwise direction on the right side as is illustrated by the arrows 28,30 in Figure 1. When a constant tension is to be maintained the whole time in the upper 27 and lower 26 stretches of band, the axes 22 of rotation must be moved towards each other.

The two parallel stretches of band are wound around the cores so that the pairs of cores or rollers finally become located at the centre of each coil. Further outer and inner plates come into a mutual position so that they have a constant spacing equal to x. The coiling up now continues as is illustrated in Figures 3,4,5,6 and 7, whereby the unit is rotated 90°, about 260°, about 440°, about 620°, and about 800°.

Thus there are formed first and second coils 32,34 which gradually move towards each other along the line 26, at the same time as H gradually goes towards zero. The coiling up continues right up to the two coils 32,34 thrust against and are tangential to each other along a line 36 parallel to the axis 22, as is evident from Figure 6. In the contact line/surface 36 between the two coils 32,34 there is now established a sealing, such as by soldering or an attachment means, such as a cementing glue. It is also of interest to establish a tight line or

surface contact between the coils by wrapping a band or a tape or equivalent around the unit. Now the rollers 14,16 and 18,20 respectively are drawn out of the coils, the diameters of the rollers being first reduced, and thereby there is formed a heat exchanger comprising two helical units/coils 32,34 which are mutually connected via the two outermost located band loops 40,42 and via the contact line 36 (Figure 6) or surface 44 (Figure 7) between the two coils 32,34. The spacing elements cause the bands to have a constant mutual spacing. How large such a coil becomes, depends upon the length of the band loop which is mounted according to Figure 2.

In the construction which is shown in Figure 6 the four rollers 14,16 and 18,20 respectively are lying in a plane through the centre of each coil.

When there is sufficient band length the coils can be rotated further so that the relative setting between the pairs of rollers 14,16 and 18,20 is changed. In Figure 7 a solution is evident where the coils contact each other via a surface 44 and the two core rollers are parallel to each other.

In the method according to the invention there is produced a heat exchanger construction where the removable rollers 14,16 and 18,20 respectively themselves define the two inlets and the two outlets for two fluids to/from the heat exchanger.

In Figure 1 there is thus illustrated as an example the inlet 46 for the first fluid loop emphasised by black shading which extends in spiral form outwards from the centre of the first coil 32, over"the joint region" between the coils 32,34 and in spiral form inwards towards the centre of the other coil 34 and to the outlet 48.

Correspondingly there is shown the inlet 50 for the second fluid loop illustrated in white which extends in spiral form outwards from the centre of the second coil 34, over "the joint region"between the coils 34,32 and so further in spiral form inwards towards the centre of the

first coil 32 to the outlet 52. Now when fluid is supplied to the two circuits, the heat exchanger will according to this example, function according to the counter-current principle. Alternatively the two fluid streams can be adapted co-currently, in that the inlets to the two loops lie in the one coil half while the outlets from the loops lie in the other coil half.

In Figure 8a and 8b is shown how there is added on each side surface of the heat exchanger a plate 60,70 with holes 62,64,66,68 which are accurately adapted to the corresponding inlets/outlets 46,52,50,48. The plates are designed and adapted to the heat exchanger construction 10 so that they seal well up to the spiral-forming side edges of the band, so that any leakage between the fluid circuits does not occur.

Now the heat exchanger is ready for the set of hoses or pipes to be coupled to the inlet 46 and the outlet 48 for axial supply and discharge respectively of a first in the first fluid loop, and also in order for the set of hoses or pipes to be coupled to the inlet 50 and the outlet 52 for supply and discharge respectively of a second fluid in the second fluid loop. The in/outlet regions by way of example lie on both sides of the heat exchanger, so that the fluid can be supplied and released from both sides. According to an alternative solution the one of the plates 60,70 can according to Figure 8a be without holes and covers the side edge of the heat exchanger completely so that the fluid is only supplied/ discharged from the one side of the heat exchanger according to the desired arrangement. As is evident from Figure 1, the axially directed inlets/outlets represent a larger area than the spiral loops. The axial inward and outward flow speed of a fluid (for example a liquid) can/will therefore be lower than the spiral fluid speed.

Figures 9 and 10 show respectively a side section and a plan section of an apparatus 70 which is employed in the

method for the production of the heat exchanger according to the invention.

The apparatus comprises two parallel rails 72,74 arranged on a pedestal (not shown). Two separate and parallel travelling carriages 76,78 comprising cross-bars, are mounted at each of their ends on the two rails 72,74.

The travelling carriages can be moved towards each other and away from each other on the rails 72,74. Each end of the travelling carriages is connected to the respective rail via a set of wheels (not shown further). Further the travelling carriages comprise a device which maintains a given band tension. A mounting unit or a holder 84,86 for the two pairs of rollers 18,20 and 14,16 respectively (cp.

Figure 2) is connected to its respective travelling carriage 76,78 via a pedestal 80,82. The pairs of rollers 18,20 and 14,16 respectively are mounted to the mounting unit (the holder) 84,86 so that they are mutually parallel with each other and with the longitudinal direction of the travelling carriages. The pairs of rollers are further adapted to be conducted forwards and backwards in a direction along the longitudinal direction of the travelling carriages between a rest position 88 and a working position 90. As is evident from Figure 10 the pedestal 80 with the roller mounting unit 84 is arranged at the end of the travelling carriage 76 which is adjacent to the first rail 74, while the other pedestal 82 with the associated roller mounting unit 86 is arranged at the end of the travelling carriage 78 which is adjacent to the second rail 72. The pairs of rollers 18,20 and 14,16 thus turn inwardly towards each other and towards the middle region between the rails 72,74. This organising of the pairs of rollers on their respective travelling carriages gives the necessary balance of the forces which the apparatus is exposed to during the coiling. Figure 10 shows this clearly, the plate band being braced and coiled centrally between the rails in the middle region of the apparatus.

Each unit 84,86 comprises a drive means 92,94 in the form of motors for rotation of the respective pairs of rollers 18,20 and 14,16 about a rotational axis 22a and 22b respectively.

The travelling carriages 80,82 have drive means, especially in the form of motors 91,93 connected to the wheels so that the travelling carriages can establish an outwardly directed force on the band and tighten up the latter, and further in order to provide a sufficient braking force on the carriages when these are moved towards each other during the coiling so that a predetermined tension is maintained in the band. Both the operation of the rotation drive means 92,94 for the cores and the motors 91,93 for driving the travelling carriages are connected into a data system so that the driving of these can be accurately controlled. The object of this is there shall be maintained a satisfactory tension in the plate band loop during the coiling up of the heat exchanger.

There shall now be described how the apparatus according to the invention is applied to produce a heat exchanger of an elongate band-shaped plate the end edges of which are joined to form an endless band 12. The band has a breadth equal to B.

The respective pairs of rollers 18,20 and 14,16 are now conducted forwards viewed relatively towards each other from their rest position 88 to their working position 90. The band 12 is then installed in the gap between each roller of a pair of rollers so that the one roller 14,18 on each side is located within the loop, while the other is located outside. The travelling carriages 76,78 are now led away from each other so that the band is tightened up to a satisfactory tension. The upper stretch of plate band is arranged with an overlength corresponding to the height H as mentioned above. Now the clockwise/counterclockwise rotation of the respective roller pairs 18,20 and 14,16 about respective rotational

axes 22a and 22b starts simultaneously. During the rotation the travelling carriage device maintains the necessary band tension in that there is exerted a controlled braking effect via the motors 91,93 on the movement of the travelling carriages towards each other.

The band is coiled up into two coils 32,34 as is shown in the Figures 2-7, of desired size. How many turns in spiral form the bands are coiled around the core rollers, depends upon the length of the band. During the coiling the band exerts a gradually increasing tightening around the rollers so that they will hardly be able to be extracted without their outer diameters being reduced when the coiling is finished. See Figure 11 which shows a mechanism with which such a diameter reduction can be carried out.

The rollers are extracted and there is established a fluid-tight joint between the point of contact 36/44 of the coils 32,34, such as by welding, gluing or the like.

The pairs of rollers are now drawn back, and the apparatus is ready for a new coiling process. In order to be able to draw the core rollers back, it is often necessary to reduce their diameters, since the band by degrees will more strongly tighten around the rollers in the centre. It is therefore preferred that the diameters of the rollers can be reduced, more specifically that the rollers can be readjusted between a maximum diameter when the band is mounted, and a minimum diameter which is produced when they are to be extracted from the coil.

In Fig. 11 there is shown a construction for changing the diameter of the roller. According to a preferred design the roller surface is formed of a number of elongate arcuate segments 94 which squeezed together form a sleeve having a uniformly cylindrical surface. Four such sections 94 are shown lowermost in Figure 11, and here they are outstretched in the position they have during the coiling. The sections are arranged around a roller axle 96 and are held in place peripherally around the axle by means of a number of peripherally extending annular

springs, especially two springs 98,100, which are arranged each in its annular groove 97,99 recessed in the peripheral surface of the sections/rollers. The sections form a sleeve having a substantially circular cross- section. The inner end of the axle towards the unit 88 comprises conical surfaces 95. A removable end cap 102 comprises equivalent conical surfaces 104 on the inner end while its outer end forms an annular stopper flange 101.

The cap is hollow, and comprises a transversely extending rod 110 which can be hooked fast in a hook-forming recessed groove 112 in the axle 96 of the roller. When the rollers are prepared for a coiling process, the sleeve sections are installed on the axle, and by means of the cap 102 the sleeve is pushed in towards the conical surface (konflaten) 95. Each sleeve end now presses against conical surfaces, and this leads to end portions of the sections being pressed radially outwards parallel to the axle 96. Thereafter the cap is locked fixed to the axle 96 in that the cap is twisted and activates a bayonet coupling. Thereby the roller in its outer position is ready for the coiling process. After the coiling process the cap is loosened, the sections are drawn radially inwards so that the sleeve is loosened, and it can then be extracted from the finished heat exchanger.

Figure 12 shows an alternative construction of the end plates according to Figure 8a, b. Here there is shown an end plate where the surface which is to be installed against end surfaces of the heat exchanger, comprises a hardenable material, such as plastic, rubber or epoxy. The sealing is ensured when the substance hardens. It is also possible to hold the end plates mutually together by means of through-going bolts so that the plates are pressed together against a packing of soft rubber/plastic.

In Figures 13-15 several alternative means are shown for maintaining a constant spacing between the plates in the finished heat exchanger construction.

A preferred construction is illustrated in Figure 13

in the form of hemispherical recesses 110 which are designed, for example by stamping, in a regular or irregular pattern in the plate band ahead of the coiling process. The Figure shows a partial cross-section of a finished heat exchanger with a number of such recesses in each plate formed by the continuous band.

Figure 14 shows four alternative constructions of spacing elements between the plates. To the left a construction is illustrated of a compact spacing element 112 of quadratic cross-section, a hollow element 116 of rectangular cross-section, a hollow element 114 of circular cross-section, or as an elongate spiral 118 in the form of a helical spring. The spacing elements can comprise smaller single bits (cubes) which are installed between the plates, or as long strands which are stitched fast to the surface of the band/plate in its longitudinal direction before the coiling starts. It can be sufficient to lay such a spacing element at each edge portion of the plate/band, or several rows of spacing elements between the plates, dependent on the breadth B of the plate.

An especially preferred construction is shown schematically to the right in Figure 14. The spacing element is preferably formed of an elongate helical spring which is placed (such as by being glued fast on) the band surfaces in the longitudinal direction of the band. Such a spring is especially favourable because it can be stretched both in the longitudinal direction and partially extended radially, and can thereby be bent and stretched in step with the bending of the band during coiling up.

Figure 15 shows a cross-section of a U-shaped profile strip 119 of rubber or plastic. Such a U-profile is placed so that the longitudinal side edge of the band lies down in the U-form. Such a U-profile strip of thickness X is mounted on the band edge over the full length of the latter before the coiling up. During the coiling up the U- profile strip is bent in step with the bending of the band, and after the coiling up outer sides of the profile

strips are mutually squeezed together, and sealing is obtained thereby, so that leakage of fluid between the helical loops is avoided. The U-shaped strips are thereby a combined element which both function as spacing element and as sealing means between the fluid loops.

Figure 16 shows a construction where adjacent plate edges can be deflected towards each other, shown at 120, and welded so as to define the one fluid run after coiling up. Alternatively a strip of rectangular profile can be arranged in a weldable material 121 in the intermediate space between two band/plates, and welded fast in order thereby to seal the intermediate space.

According to yet another construction there is shown in Figure 17 that the plate edges can be cast or pressed into the end plates 122 after which there is established a thermal press sealing. End plates are made having shape and grooves for plate edges in the basic material correspondingly as employed in a coiled plate. The solution according to Figure 17 applies to heavier and thicker coiled plates.

According to an alternative construction the heat exchanger can be made by extruding with an optional length, and which thereafter is cut to the desired breadth, for example with the breadth B of Figure 1.

The novel heat exchanger construction makes possible a new and flow-correct method for obtaining heat exchange between two fluids. By flow-correct is meant in this connection that a fluid which is to emit heat to the other fluid, can utilise the length optimum of the novel heat exchanger, that is to say that by the countercurrent function the ingoing fluid meets the outgoing fluid in the region where the ingoing fluid starts the contact for the transfer of heat. Theoretically the heat transfer effect can be very high, something which is confirmed by tests, but is obviously dependent upon the choice of material.

The contact time between the two fluids can be extended with the new construction.

As a heat exchanger the exchanger according to the invention can be arranged for the fluid-combinations gas/gas; gas/liquid; liquid/liquid. The two side plates 60,70 can, when they are screwed to side surfaces of the heat exchanger, be readily removed and one then gets access to the interior of the heat exchanger which thereby can be cleaned such as by flushing.

Besides the heat exchanger according to the invention can be used during processes where it is operated with heat exchanging (as a heat exchanger), settling, flotation, and separation, or for filtering, moistening/ demoistening and drying.