The invention relates to a connection element for connecting cores of hollow-core plates. The invention relates more particularly to a system of a number of connection elements for connecting cores of hollow-core plates, wherein these connection elements can be closed with an enclosing profile.

In addition, the invention relates to a connection element for beginning or ending a core in a hollow-core plate for the purpose of connecting and controlling flows in the hollow-core plate .

Diverse heat exchangers are described in the prior art, wherein generally chosen as construction materials are materials which have a high coefficient of heat transfer. This is because the heat transfer is generally proportional to this coefficient of heat transfer and other factors. Such materials, usually metals, are in general relatively expensive.

An alternative to a heat exchanger is described in the Netherlands patent NL1034648. In this patent hollow-core plates are provided on the end surfaces with U-shaped profiles. In order to provide a zigzag pattern in the hollow-core plate the intermediate walls between the cores of the hollow-core plate are partially removed alternately on either side of the hollow-core plate.

Such a heat exchanger is relatively difficult to connect, it is inconvenient to provide the recesses in the intermediate walls and it is relatively difficult to obtain a good seal.

The invention therefore has for its object to provide a heat exchanger which does not have, or at least partially obviates, the above stated drawbacks and/or other drawbacks while the advantages thereof are at least partially retained. The invention also has for its object to provide a heat exchanger which is simple and advantageous such that a higher coefficient of heat transfer is more than compensated by the price of the construction materials, and also enables applications in environments harmful to metal-containing heat exchangers.

At least one of these and/or other objects are achieved with a connection element suitable for connecting cores of hollow-core plates, comprising a first insert part fitting into a core of a hollow-core plate, a second insert part fitting into a core of a hollow-core plate, a first connecting chamber, wherein the first insert part comprises a first passage, wherein the second insert part comprises a second passage and wherein the first and second passages debouch in the first connecting chamber .

As a result of this connection element hollow-core plates can be used as heat exchanger or flow reactors. Hollow-core plates are generally manufactured from thermoplastic polymers such as polycarbonate, which has a lower coefficient of heat transfer than most metals. Although the specific heat transfer is hereby lower, much larger heat exchangers can be produced due to the lower manufacturing costs, which more than compensates this effect. Through the use of these connection elements larger heat exchangers with a higher overall heat transfer can therefore be manufactured at lower cost than heat exchangers manufactured from conventional materials. This can be advantageous for instance in applications where differences in height or temperature have to be bridged, such as in greenhouses.

The above described connection element can further comprise: a third insert part fitting into a core of a hollow-core plate, a fourth insert part fitting into a core of a hollow-core plate, a second connecting chamber, wherein the third insert part comprises a third passage, the fourth insert part comprises a fourth passage and wherein the third and the fourth passages debouch in the second connecting chamber.

By placing a plurality of connection elements offset relative to each other in the cores on either side of the hollow-core plate a fluid connection can hereby be obtained running zigzag through the hollow-core plate and skipping one core at a time.

When the connection elements are not placed offset relative to each other on either side of the hollow-core plate, this results in a series of parallel loops of in each case two closed cores which are connected to each other on either side.

When the connection elements are placed offset every other core relative to each other on either side of the hollow-core plate, this results alternately in one first zigzag fluid channel and a series of parallel loops of in each case two closed cores which are connected to each other on either side. One core of the loops is here situated in each case between a meander of the zigzag core.

When the connection elements are placed offset every two cores relative to each other on either side of the hollow-core plate, this results in two zigzag fluid channels. A meander of the second zigzag core is situated here in each case between a meander of the first zigzag core.

The different possibilities for placing of the connection elements therefore provide a great freedom of connection of the cores. Using the same basic construction elements, i.e. a series of connection elements and one or more hollow-core plates, a wide variety of heat exchangers can hereby be constructed. An alternative embodiment of the invention is a connection element suitable for connecting cores of hollow-core plates, comprising a first insert part fitting into a core of a hollow-core plate, a second insert part fitting into a core of a hollow-core plate, a first connecting chamber, wherein the first insert part comprises a first passage, wherein the second insert part comprises a second passage, wherein the first and second passages debouch in the first connecting chamber, a third insert part fitting into a core of a hollow-core plate, a fourth insert part fitting into a core of a hollow-core plate, a second connecting chamber, wherein the third insert part comprises a third passage, wherein the fourth insert part comprises a fourth passage, wherein the third and the fourth passages debouch in the second connecting chamber and wherein at least one of the passages is sealed or omitted.

Owing to this configuration this connection element can be applied at the beginning or the end of a formed core, wherein leakage and/or dead volumes in the hollow-core plate can be prevented. Different configurations of flow channels can be obtained in the hollow-core plates through targeted sealing of the passages.

The seal in one or more passages can comprise a fitting and closely connecting plug or a preformed seal. If plugs are used, the various insert parts can then hereby be closed as desired. This can realize a wide variety of configurations of the flow channels in the hollow-core plate.

Should preformed seals be used in the connection elements, secure and durable seals can then be obtained.

The connection element can further comprise:

a third insert part fitting into a core of a hollow-core plate, a fourth insert part fitting into a core of a hollow-core plate, a second connecting chamber, wherein the third insert part can comprise a third passage, wherein the fourth insert part can comprise a fourth passage and wherein the third and the fourth passages can debouch in the second connecting chamber.

In the connection element the third insert part can be located between the first insert part and the second insert part, and the second insert part can be located between the third and fourth insert parts.

The first connecting chamber and the second connecting chamber can each lie with a sealed rear side offset against each other substantially over the width of a core of a hollow-core plate.

The invention also relates to an assembly of at least two above described connection elements and a hollow-core plate, wherein at a first open end of the hollow-core plate a first connection element and at a second open end of the hollow-core plate a second connection element can be arranged with the insert parts of the respective connection elements in the cores of the hollow-core plate

At a first outer end the first insert part of the connection element can be arranged in a first core of the hollow-core plate, the third insert part of the connection element in a second core of the hollow-core plate, the second insert part of the connection element in a third core of the hollow-core plate and the fourth insert part of the connection element in a fourth core of the hollow-core plate, and at a second outer end a first insert part of a connection element can be arranged in the second core of the hollow-core plate, a third insert part of the connection element in the third core of the hollow-core plate, a second insert part in the fourth core of the hollow-core plate and a fourth insert part of the connection element in a fifth core of the hollow-core plate, whereby a first continuous fluid connection can be obtained in the hollow-core plate which runs zigzag through the hollow-core plate and which connects a core, a connecting chamber, then a core, subsequently a connecting chamber, once again a core, again a connecting chamber, a core and a connecting chamber.

At a first outer end in the assembly the second insert part of the connection element can be arranged in a first core of the hollow-core plate, the fourth insert part of the connection element in a second core of the hollow-core plate, a first insert part of a connection element in a third core of the hollow-core plate, the third insert part of the connection element in a fourth core of the hollow-core plate, a second insert part of the connection element can be arranged in a fifth core of the hollow-core plate and a fourth insert part of the connection element in a sixth core of the hollow-core plate, wherein at a second outer end a first insert part of a connection element can be arranged in the first core of the hollow-core plate, a third insert part of the connection element in the second core of the hollow-core plate, a second insert part in the third core of the hollow-core plate and a fourth insert part of the connection element in a fourth core of the hollow-core plate, whereby a first continuous fluid connection can be obtained in the hollow-core plate which runs zigzag through the hollow-core plate and which connects connecting chambers and cores and wherein a second continuous fluid connection runs zigzag through the hollow-core plate and is offset one core relative to the first continuous fluid connection and which connects the remaining connecting chambers and cores.

In the above described assembly a first U-shaped profile can be arranged closing round the connecting chambers of the connection elements and a second U-shaped profile can be arranged closing round the connecting chambers of the connection elements .

The insert parts can be connected at least partially to the inner walls of the cores with an adhesive. An adhesive can be used here which has a viscosity lower than water, whereby it can penetrate more easily between the outer walls of the insert parts and the inner walls of the cores of the hollow-core plate.

The U-shaped profiles can be connected to the connecting parts by means of an adhesive mass. This adhesive mass can have rubber-like properties for good sealing in changing temperature ranges. The adhesive mass can act here as expansion compensation while a good sealing remains possible.

In the above described assembly according to the invention the seal can also be arranged in one or more of the cores (7A-7H) of the hollow-core plate (6) instead of in one or more of the passages of the connection elements (1A-1D) . This sealing can for instance be realized with a construction or sealing compound, wherein wholly filling a core of a hollow-core plate could contribute toward the strength and/or other structural possibilities of the hollow-core plate. Connecting means such as screws can thus be arranged more easily in a core sealed with compound. The ϋ-shaped profiles can comprise an inlet and an outlet which can each form a passage into at least one of the connecting chambers. The profiles can also comprise a plurality of inlets and/or outlets.

The above described assembly can be used as heat exchanger or reactor.

The invention also relates to a method for exchanging heat between two fluids, comprising the following steps, to be performed in suitable sequence, of: A) providing a heat exchanger as described above, B) arranging a first fluid flow with a temperature T via a first inlet through a first fluid passage of the heat exchanger, C) arranging a second fluid flow with a temperature differing from the temperature T of the first fluid flow through a second fluid passage or along the outer side of at least one hollow-core plate of the heat exchanger, D) allowing transfer of heat through the intermediate walls and/or the outer walls of the hollow-core plates from the first fluid flow to the second fluid flow, or vice versa.

The invention relates to a core exchange system for applying in for instance hollow-core plate with two or more walls. The invention is devised for use in combination with polycarbonate or acrylate hollow-core plates with two or more walls. In a great improvement in the application of the hollow-core plates with two or more walls, the invention can be provided as heat exchanger.

The heat exchanger newly realized in this manner can be used for climate control of buildings and spaces. It can thus be used, among other reasons, because of the possibility of generating and utilizing heat and/or cold, optionally in combination with intermediate storage thereof.

The basic materials generally used for the hollow-core plates, polycarbonate or acrylate, are suitable for both inside and outside use. The hollow-core plates with two or more walls are constructed from walls and connecting ribs. In the standard manufactured sizes of hollow-core plate the wall thickness of the ribs is generally thinner than the side walls. Transfer of heat and/or cold can therefore progress more rapidly through the ribs than along the side walls. The fluids are only separated in the heat exchanger by an intermediate wall with a wall thickness of for instance 0.25-0.65 mm. Owing to the great strength of the material used, for instance acrylate or polycarbonate, the walls and ribs can withstand an internal pressure up to 8 bar.

Liquid (s) and/or gas(es) can for instance flow alternately through the separate cores. These liquids and/or gases can have different temperatures. The intention of the core exchange system is to equalize or optimize these temperature differences.

The alternate flows through the cores can be controlled by a (plastic) component designed for this purpose, such as an above described connection element.

Despite the low lambda value (coefficient of heat transfer) of plastics as in the case of the polycarbonate or acrylate used for the hollow-core plates, exchange of heat is very well possible as a result of the thin walls and the (counter) flow of gas and/or liquid along the walls.

The flow speed of both the liquid and the gas also determines the transfer of heat. The more rapid the flow, the higher the speed of transfer. Particularly at high air speeds a part of the energy added for this purpose is converted into heat. This frictional heat occurs during the direct contact between the flow and the walls and ribs. This energy partially enhances the production of warm water.

The design of the connection element is such that a number of aspects can be taken into account:

- that the outer ends of the cores can be closed against undesirable throughflow or leakage. This can for instance be done using a U-profile and a sealing compound.

- that the throughflow capacity is not much less than that of the cores themselves. Throughflow capacities of for instance at least 40 litres per minute can be achieved in a standard hollow-core plate of 10 x 10 cm.

- that the seal of the U-profile on each side of the hollow-core plate only comes into contact with one liquid and/or gas. The left side of the profile can for instance thus be the feed/discharge side for air and the right side of the U-profile for instance the throughfeed for (ground) water . This selection option may be significant in enabling feed of a liquid or gas to or from a feed/discharge core running at right angles to the cores. Process-influencing agents can for instance be added here in a closed continuous photocatalytic reactor. Samples can likewise hereby be taken at multiple locations along the profile.

- that this core connected at right angles can have a plurality of connections. The same liquid or the same gas at the same temperature can hereby be injected and/or discharged at different levels in the heat exchanger. The U-profiles on the outer ends of the hollow-core plates can also be connected to each other using for instance a rubber O-ring and associated pinch construction. The optionally desired distance between the hollow-core plates can be spanned or connected using a (plastic) component and 0-rings .

- that the construction of the connection element is such that different flows/loops are created when one or two cores are displaced relative to the opposite connection element. Depending on the application, it is hereby possible to opt for vertical and/or horizontal core flows.

- that the cost of realizing the mould for the above described connection element is low. This is certainly the case when compared to the cost of developing the components and apparatus required for the application of other heat exchangers available on the market.

Two designs of a connection element are described by way of illustration. The first (basic) connection element is a symmetrical component which can be made with a small injection mould. The component is suitable for the first production series of connection elements for the different applications and the installation of pilots. This can enhance the start-up options for the invention. The connection element is designed such that it can form an endless series with similar connection elements.

The exchange of differences in temperature between for instance outside and inside air or the groundwater temperature and heat in buildings such as greenhouses can, as has meanwhile been demonstrated with other heat exchangers, produce considerable energy-savings.

The invention can considerably improve the operation of the heat exchange in hollow-core plates with two or more walls, and thereby increase energy-saving. This can be achieved by more efficient heat exchange. By having a liquid or gas flow alternately through the cores formed by the walls and ribs a forced heat/cold contact can be obtained on the ribs of the hollow-core plates. The liquid or gas flow can run here in the parallel cores inside the same plate with two or more walls. Heat exchange can take place here via the intermediate walls and/or the outer walls.

The flows of liquid and/or gas can run here in the same or opposite direction. Through counterflow of warm inside air and cold outside air the heat of a space can be relinquished to the cold outside air even before the warm air flows outside or cold air flows inside. Owing to the thin size of the hollow-core plates with two or more walls a heat exchanger created in this way can for instance be built into the cavity wall, a so-called breathing wall, of a building. Placing along a wall or as dividing wall, optionally provided with a colour or decoration, can also be envisaged. Applications can be envisaged wherein the heat exchanger is concealed in furniture or integrated with the construction of a cabinet or with the ceiling covering. It can be useful here to arrange a discharge for draining possibly formed condensed water.

A heat exchanger can also be constructed for use in greenhouses by forming a tube-type chimney with two or more parallel/coupled hollow-core plates. The airflow supplied from the top of the greenhouse can here be introduced or discharged at different heights through a parallel core. (Ground) water for instance can hereby be enclosed along a plurality of sides with a continuous warm/cold airflow. The water can here have a longer throughflow time than the air. The flow rate of air and water can be set and controlled independently of each other. This hollow-core plate heat exchanger can for instance be a component of a closed greenhouse.

The hollow-core plate heat exchanger can also be placed outside. The heat exchanger can for instance be connected to a system filled with a glycol solution. This glycol solution can be used to make the system frost-resistant. Heat irradiation by sunlight, optionally combined with an airflow, can heat the glycol diluted with water. The heated glycol solution is stored and used to heat a building, optionally in combination with a heat pump. An additional advantage is the low price of the hollow-core plates with two or more walls and the proven weather-resistant properties of this material. The system can conversely also provide for cooling of the building.

The hollow-core plate heat exchanger can be immersed in a cold or warm, optionally artificial reservoir (rainwater storage, lake, sea or river) in order to transfer the temperature to the filling liquid or gas. The filling liquid or gas, optionally with intermediate storage or further influencing of temperature, can then cool and/or heat a building or space.

Industrial residual heat, such as for instance the cooling water at -28 °C which is drained in large amounts to the surface water by nuclear power stations, can be stored and/or used by means of this heat exchanger.

Another possibility enabling further applications is the perforation of one of the two core systems on the left or right-hand side. A hollow-core plate with two or more walls, whether or not it forms part of a construction, can hereby be made moisture and/or nutrient-regulating (for the purpose of drainage or watering) . The other, non-perforated core system can simultaneously heat and/or cool the environment of use. Envisage here for instance culture trays for plants or crops.

Suctioning of air and/or gas into the cores can also be realized by perforating the cores. A contribution can hereby be made to the capacity of the heat exchanger.

Owing to the smooth and straight walls of the hollow-core plates the electricity consumption for the displacement of air between the hollow-core plates and in the cores is low. Together with the thin walls, this enhances the ratio of energy supply and yield. A consumption of 25 W has for instance thus been measured in 100 cores of 10 x 10 mm with a length of 4 metres at a speed of 6 m/s. A hollow-core plate heat exchanger with exchange system provided with 180 cores of this length (4 m) can at an airspeed of 4-5 m/s have a cooling capacity of 18 kW. In combination with the raw material and processing costs, this provides a favourable competitive position.

The invention will be further elucidated on the basis of embodiments shown in the drawing. In the drawing:

figure 1 is a schematic perspective rear view of the connection element according to a first embodiment,

figure 1A is a detail view of the connection element of figure

1,

figure 2 is a schematic perspective front view of the connection element,

figure 3 is a schematic cross-section through lines A-A of the connecting block according to figure 1 in a first application,

figure 4 is a schematic perspective view of a heat exchanger according to a further embodiment of the invention,

figure 5 shows a schematic front view, a top view and two side views of a heat exchanger according to a further embodiment of the invention,

figure 6A shows a schematic cross-section of an embodiment of a connection of the heat exchanger according to figure 5, figure 6B shows a schematic cross-section of a further embodiment of a connection of the heat exchanger according to figure 5,

figure 7A is a schematic side view of a series of connection elements according to figure 1,

figure 7B is a schematic top view of a series of connection elements according to figure 1,

figure 8 is a schematic perspective, cross-sectional view of the connection element according to figure 1,

figure 9 is a schematic view of the first embodiment of an assembly of a set of connection elements and a hollow-core plate, with a schematic representation of a fluid flow,

figure 10 is a schematic view of a second embodiment of an assembly of a set of connection elements and a hollow-core plate, with a schematic representation of two fluid flows,

figure 11 is a schematic perspective view of a third embodiment of a connection element,

figure 12 is a schematic perspective view of a fourth embodiment of a connection element,

figures 13A and 13B are schematic views of a fifth embodiment of a connection element,

figure 14 shows an exemplary embodiment of a connection with connection elements with selectively sealed cores as shown in figures 11 to 13B, and

figures 15A and 15B show an embodiment of an alternative sealing of a connection element according to the invention.

It is noted that the drawing is only a schematic

representation of preferred embodiments of the invention. The drawing should in no way be interpreted as limitative for the invention. The same or similar components are designated in the figures with corresponding reference numerals.

The term "hollow-core plate" used in the specification and/or the claims should be interpreted as, but is by no means limited to, a plate-like structure with a series of parallel cores situated adjacently of each other. Such plates are generally obtained by means of extrusion and optional deep-drawing .

Figure 1 shows a schematic perspective view of a connection element 1. This connection element is provided with four insert parts 2A, 2B, 2C and 2D, each with a respective passage 4A, 4B, AC and 4D. Each of the insert parts 2A-2D is provided with a peripheral form substantially corresponding to the inner peripheral form of a core of a hollow-core plate. Insert parts 2A-2D are arranged in a row and have a substantially rectangular peripheral form, wherein at the open outer end of the insert part two opposite walls 26 and 29 are provided with tongues 24 extending in the length of the insert part and the walls 27 and 28 lying at right angles thereto are provided with curved recessed edges.

Owing to the configuration of extending tongues and recessed edges a good closure can be obtained in a core of a hollow-core plate. The outer edge formed by the extending tongues 24 and the recessed edges 25 is shown in detail in figure 1A. In this figure can be seen that the outer edge has an inward chamfering. Due to this chamfering the insert part can be placed more easily in a core and, when an adhesive is used to obtain a good connection between the outer edge of the insert part and the inner edge of a core of a hollow-core plate, can prevent adhesive residues entering the passage 4A of the insert part.

The connection element can be manufactured from a thermoplastic plastic such as ABS, PVC or blends with polycarbonate. Connection element 1 of figure 1 is further provided with two connecting chambers 3A and 3B. The first connecting chamber 3B is connected to passages 4A and 4B of the respective insert parts 2A and 2B. Connecting chamber 3B is connected to passages 4C and 4D of the respective insert parts 2C and 2D. Both connecting chambers are connected side-by-side to each other in offset manner via rear walls 5A and 5B. Every alternate passage of the insert parts can hereby be connected to each other via connecting chambers 3A and 3B. The connecting chambers and the passages can be dimensioned such that a liquid flow rate of 40 litres per minute can flow through the cores.

Arranged on the upper side of the rear walls is a first adhesive core along the top of the element and a second adhesive core to the left of connecting chamber 3A. These cores can distribute the adhesive mass and discharge the excess applied adhesive to a drain between the hollow-core plate and the U-profile. After curing of the adhesive mass present therein, these cores can bring about a seal between the connecting chambers and prevent air or water passing between the U-profile and the element. The core on the left can for instance obviate leakage of the throughfeed chambers on one and the same side of a U-profile.

Figure 3 shows a cross-section of connection element 1 of figure 1 along line A-A in installed position. The connection between connecting chamber 3A and passage 4A of insert part 2A is visible in figure 3. Insert part 2A is arranged in a core 7A of a hollow-core plate 6. Insulating plates 20 and 21 are arranged on either side of hollow-core plate 6. In the application as heat exchanger the insulating layer can be arranged to preserve the energy of a heated space by heat transfer to cold ventilation air .

Arranged round connection element 1 is a U-shaped angular profile 17 connected with an adhesive mass 19 to connecting part 1. Adhesive mass 19 can realize a liquid and gastight seal between the walls of U-shaped profile 17 and connecting part 1. The adhesive mass can be a compound such as a silicone compound.

Inlets and outlets can be arranged in the U-shaped profile which extend through the wall of the profile. By selecting a sufficient thickness for the wall of the profile the inlets and outlets can be fixed therein. Connections of for instance ¾-inch can be applied here.

The U-shaped profile can alternatively also be provided with milled recesses, which are in contact with one connecting chamber of a connection element at a time. Figure 4 shows a perspective view of a heat exchanger on the basis of a hollow-core plate. The side walls of the hollow-core plate are covered here with insulating plates 20 and 21 and the end surfaces of the hollow-core plate are provided with a row of connection elements as shown in figures 7A and 7B, wherein these rows are in turn enclosed and closed by means of U-shaped angular profiles 17 and 18. An inlet 22 and an outlet 23 are arranged in profile 17. This inlet and outlet are arranged through the wall of profile 17 and each extend into a connecting chamber 3A or 3B of one of the connection elements 1. Further corresponding connections can be provided on the rear side in order to obtain a counterflow system.

Figure 5 shows an alternative embodiment of a heat exchanger wherein two substantially parallel hollow-core plates are connected in the same manner as described above. In this embodiment the intermediate space between the two hollow-core plates can likewise be used as a fluid channel.

This embodiment can for instance be applied in greenhouses. Figures 6A and 6B show detail views of the heat exchanger of figure 5.

Figure 7A relates to an embodiment in which a plurality of connection elements are placed successively. The elements can here be adhered to each other, or manufactured integrally. The longer core exchange component shown in the views 7A and 7B can be made with a larger, and so more expensive injection mould. This can form the basis if larger projects have to be realized with the hollow-core plate heat exchanger. This longer component may also still only involve a relatively low investment.

Figure 9 shows the flow as this occurs when the core exchange components placed opposite each other are offset one step relative to each other. The liquid or the gas flows through on one side. In the illustration this is always the front side of the plate.

Figure 10 shows the flow as this occurs when the core exchange components placed opposite each other are offset two steps relative to each other. Flow hereby takes place through two continuous channels/flow paths at the opposite outer ends of the hollow-core platef alternately the front and the rear side.

Figure 11 shows a schematic perspective view of a third embodiment of a connection element 1'. Only three insert parts 2A, 2B and 2C are available in this connection element. The passages 4A, 4B and 4C are situated in the respective insert parts 2A, 2B and 2C. This connection element can be applied as end connection element in a row of connection elements as shown for instance in figures 7A and 7B. Through the use of three insert parts 2A, 2B and 2C this connection element can be used to bring about the mutual offsetting of connection elements 1A, IB, 1C without an insert part protruding outside the cores 7A-H of hollow-core plate 6. This protruding of an insert part 2A-D is shown for instance in figure 10, in which insert part 10D is situated outside the cores of hollow-core plate 6.

Connection element 1' can in addition bring about a reversal of the flow channel from for instance through the connecting chambers 12A and 3A of connection elements 1A and 1C on the front side of hollow-core plate 6 to connecting chambers 12B and 3B of connection elements 1A and 1C on the rear side of hollow-core plate 6 (see for instance figure 6) . Owing to this reversal of the flow channel fewer inlets 22 and/or outlets 23 for instance need be arranged in the enclosing U-profile 17. And parallel placed hollow-core plates can be connected to each other with a direct connection. Drilling of the connection element to be connected is in this way unnecessary.

In connection element 1* the passages 4A and 4B debouch in connecting chamber 3A and passage 4C debouches in connecting chamber 3B.

If this connection element is applied, and connecting chambers 3A and 3B are enclosed with a U-profile, an inlet 22 or an outlet 23 can then be arranged on the side and at the position of connecting chamber 3B. This inlet 22 or outlet 23 (see figure 4) can then connect a beginning or an end of a core 14, 15 or 16 formed in hollow-core plate 6 to a conduit.

An alternative embodiment of a connection element 1 ' ' is shown in figure 12. In the connection element one of the insert parts 2D is sealed, so that passage 4D has a closed end. Insert part 2D can for instance be situated outside a core 7A-7H of a hollow-core plate 6, while the other insert parts 2A-2C are situated in a core 7A-7H of a hollow-core plate. Because passage 4D is sealed, no gas and/or liquid can escape through this passage 4D, even if it is situated outside a core 7A-7H of a hollow-core plate 6.

Although one passage 4D is sealed in this figure, two or more passages can also be sealed as will be further elucidated below. The sealing can be realized by modif ing the moulding die so that the seal is obtained during forming, for instance by injection moulding. A durable and secure seal can hereby be obtained.

An alternative sealing can be formed by a plug 38 as shown in figures 13A and 13B. This plug is dimensioned such that it fits closely and sealingly in one of the passages 4A-4C. By arranging one or more plugs 38 in one or more passages 4A-4D the passages 4A-4D can be sealed in flexible and randomly desired configuration using one basic connection element 1.

Figure 14 shows such a configuration. In figure 14 the connection elements on either side of hollow-core plate 6 are offset every other core as in figure 9. A meandering core 14 is hereby formed as shown in more detail in figure 9. By sealing insert parts 2A of connection element 1A and insert parts 2'B, 2'C and 2 ' D of connection element IE with plugs 38, no liquid and/or gas can escape from the cores once the ϋ-shaped profiles 17 have been arranged on either side of hollow-core plate 6 round the connecting chambers of connection elements 1A-1E. The hollow-core plate can for instance be configured as heat exchanger by arranging inlets 22 and outlets 23 at the correct position in the U-shaped profiles. Figures 15A-B show an alternative closure of connecting chamber 3A of connection element 1 as shown in, among others, figure 1. A cover 39, which preferably fits closely and sealingly with its peripheral edge 40 in the peripheral edge 41 of connection element 1, can close connecting chamber 3A as shown in figure 15B. This cover can for instance be manufactured from the same material as the connection element, whereby both components comprise substantially the same coefficient of expansion. An advantage hereof can be that no relative displacements can take place between cover 39 and connection element 1. This can provide an improved and durable seal.

One of the peripheral edges 40 or 41 can be provided with a tongue which fits for instance in a groove in the opposite peripheral edge 41 or 40. Peripheral edge 40 of cover 39 can hereby be arranged with a snap connection in peripheral edge 41 of connecting chamber 3A. An advantage of such a connection is that cover 39, after being snapped fixedly, is less likely to fall out of peripheral edge 41 and can be less easily placed too deeply into connecting chamber 3A. The other connecting chambers can be closed in corresponding manner.

Alternatively, cover 39 can be arranged with adhesive in peripheral edge 41 of connecting chamber 3A. As another alternative the cover, instead of dropping into peripheral edge 41, can wholly enclose this edge on the outer side. In all the above stated alternatives the cover 39, its peripheral edge 40 and the peripheral edge 41 of connecting chamber 3A can comprise rounded corners and/or comprise other shapes. Connecting chamber 3A and cover 40 could thus have corresponding round, oval or other shapes .

The sealing of one or more insert parts can alternatively be obtained with a sealing compound. Dead volumes in for instance the outer cores can be avoided by applying the seal in the connection elements. The chance of accumulation of sediment, algal growth and/or bacterial growth is hereby, reduced. The cores in the connection elements can be provided with rounded corners. This can improve throughflow and also avoid the occurrence of dead spaces .

It is noted that the invention is not limited to the above discussed exemplary embodiments. Instead of being manufactured from extruded plastics, the hollow-core plates can thus be manufactured from extruded metals such as aluminium.

Alternatively, additives which enhance the heat transfer can be added to the plastic of the hollow-core plates.

The heat exchanger can alternatively be used as algae breeding reactor or as sun screen. The algae can here for instance absorb a part of the transmitted light.

In addition, the system according to the invention can be used as photocatalytic reactor in waste water cleaning.

The hollow-core plates can be of random dimensions and manufactured from random materials, such as PVC, PMMA, ABS, PE, PP etc. Such plastics can be recycled multiple times. Through the use of plastics the heat exchangers can be used in a possibly corrosive environment. By manufacturing the hollow-core plates from light-transmitting material the heat exchangers produced herefrom can readily be used in agricultural applications such as greenhouses. The plastics used are preferably non-harmful and can optionally be used for food production. The plastics used are substantially free of pores, so that possible algae adhesion can be prevented and the material displays the least possible decrease in light transmission during long-term use.

The materials can be selected such that they are

self-extinguishing. This may be favourable for insurance reasons. The hollow-core plates can also be manufactured from extruded aluminium. The dimensioning of the connection elements can be adapted hereto. Such and other variants will be apparent to the skilled person and are deemed to lie within the scope of the invention as formulated in the following claims.