TECHNICAL FIELD

The present invention relates to a heat exchanger device for transferring thermal energy between a first and a second fluid, a system comprising a heat exchanger device, and a method for producing a heat exchanger device. ' PRIOR ART

Several methods and devices for passive heat transfer driven by a temperature difference between two or more fluids are known in the art. One common device is a plate heat exchanger, which comprises a set of plates shaped to form two separate channels for two fluid flows, where the spaces formed between every two pairs of neighbouring plates are alternately interconnected to form a channel, and allowing a transfer of heat through the plates in their thickness direction. The plates are normally very thin to allow an efficient heat transfer, and may in some instances also be provided with surface enhancements, such as indentures or nanoparticles, to increase the surface areas contacting the fluids. Plate heat exchangers are usually considered the preferred choice for liquid to liquid applications. For liquid to air applications it is also known to solder a number of flanges onto a pipe, with the liquid running inside the pipe and the enhanced surface area of the flanges interacting with surrounding air or gas.

One area of application for heat exchangers is ventilation systems for buildings, in which indoor air is replaced with outdoor air. By performing a heat exchange between an outgoing and an incoming air flow, the temperature of the incoming air will be brought closer to the indoor temperature, resulting in passive heating and/ or cooling in order to make cost savings. One common type of heat exchanger for ventilation systems utilises a liquid carrier to carry thermal energy from one ventilation flow to another.

In DE 10054695, there is shown a heat exchanger made of plates comprising a U-shaped part arranged to keep the plates at a distance from each other, by the U-shaped part making contact with a plane surface of a neighbouring plate.

SUMMARY OF THE INVENTION

One objective of the present invention is to indicate a new type of heat exchanger, which is inexpensive to manufacture, has low operation costs and which is reliable. Another objective of the invention is to indicate a heat exchanger device suitable for use in ventilation applications.

According to a first aspect of the invention at least one of these objectives is achieved with the heat exchanger device according to the preamble of claim 1, which is further arranged in accordance with the characterizing part of the same claim.

According to a second aspect of the invention at least one of these objectives is also achieved with the heat exchanger system according to claim 10.

According to the first and second aspects of the invention a heat exchanger device for transfer of thermal energy between a first and second fluid flow comprises a first fluid chamber for the first fluid, a second fluid chamber for the second fluid, and a set of heat conducting plate members arranged to be in contact with both the first and the second fluids to admit thermal transfer there between through the material of the plate members. The plate members are further shaped so that each plate member comprises a middle portion arranged to bridge a distance between the first and second channels, a first portion arranged to jut out from the middle portion and to reside inside the first channel, and a second portion arranged to jut out from the middle portion and to reside inside the second channel, and shaped so that thermal transfer is performed mainly along a direction perpendicular to a thickness direction of the plate members. Preferably, the plate members are shaped by one or more deformation operations. Such plate members are very easy and quick to manufacture, especially by a deformation operation. Also, such plate members are very easy and quick to assemble into a heat exchanging device. Since the thermal transfer is mainly carried out along a direction perpendicular to the thickness direction of the plate member it is easier to match the surface area of the plate member being in direct contact with the fluid and the resulting heat transfer from the fluid to the plate member, with the heat conduction through the plate member along its length direction. In traditional plate members the heat conduction coefficient is much higher inside the plate relative to the heat conduction coefficient over the intersection between the fluid and the plate, leading to inefficiencies. Also, the operation of the heat exchange device is very reliable.

The limiting factor for efficient thermal transfer is very often the interface in the contact area between the fluid and the heat conductor. By letting the first and second portions jut out from the middle portion and into the body of the fluid inside the respective chambers, the surface area of the parts of the plates being in contact with the fluids in the first and second chambers, respectively, becomes very large. Preferably, the plates are shaped such that the first and second portion juts out longer than or equal to half the width of the respective chambers.

That the thermal transfer is mainly carried out along a direction perpendicular to the thickness direction of the plate members preferably includes that the transfer is carried out along the length and/or width direction of the first, second and middle portions. Since the thermal transfer takes place along the length and/ or width direction of the plates, high standards are set for the heat conducting properties of the material of the plates. The material of the plates should have a higher than average value for the constant of heat conduction relative to the value of the constant for heat conduction of plates normally used when the heat conduction takes place along the thickness direction of the plates. This in turn normally also requires the material of the plates to be of a higher quality and purity than what can usually be accepted for plates in which the heat conduction takes place in their thickness direction.

Preferably, the first and second portions are formed from respective end portions of the plate members. Preferably, the first and second portions are arranged to jut out into the space formed inside each chamber, respectively. Thus the fluids inside the chambers contact both sides of each first and second portion, effectively doubling the available surface area between the fluid and the plate member. Preferably, the plates are shaped such that the first and second portion juts out longer than or equal to 80 % of the width of the respective channels. Hence it is ensured that a large part of the fluid in the chamber is in contact with the plates and thus subjected to the heat transfer. Also it is ensured that the contact area is large for high thermal transfer. In one embodiment the heat exchanging device is adapted for ventilation of a non-inhabited area of a building. By ventilating non-inhabited cellars, attics, building foundations, and/ or the area beneath buildings there is both a decreased hazard of damages from damp, and also a decreased impact on health from earth emission gases, such as radon. However, the ventilation of these parts may entail heat energy losses to the environment, leading to higher heating costs. The increased cost due to the heat loss in these areas is however in general not sufficiently large to motivate the costly measures of heat transfer and heat recovery as are known within standard ventilation. Due to the extremely low cost of manufacturing the device and system according to the present invention, the device and system may be sufficiently cost effective for allowing economical use also when ventilating non-inhabited spaces normally having a temperature intermediate between normal indoor temperature and outdoor temperature. With the inexpensive device according to the invention it thus becomes economically efficient to recover heat also in applications where less heated areas of a building are ventilated.

According to one embodiment the plate member is made from a plate sheet, which is then deformed into a desired shape for the plate member. The deformation preferably comprises bending of the plate sheet into the shape of the plate member. In one embodiment the deformation operation of a plate sheet comprises one or more of bending, pressing and deep-drawing. In a preferred embodiment the deforming of the plate sheet comprises bending and/or pressing. In a preferred embodiment the deformation comprises mainly bending of the plate sheet. In one embodiment the plate member is also punched into a desired shape before the deformation operation and/ or so as to be provided with holes or other similar openings of a desired shape going through the plate.

The first and second portions are preferably long and wide relative to their thicknesses, so that they provide a large surface area for emission or absorption of heat to or from the fluid in the chamber relative to their cross- sectional area in the direction of heat transfer within the material of the first and second portions. Preferably, the first and second portions retain their original plate shape so that they are thin, preferably thinner than or equal to 5 mm. The first and second portions thus jut out from the middle portion in the form of wings or flanges. Preferably, said first and second portions are also flat. However, depending on the application and geometry of a particular environment, the first and second portions may also be curved or fitted with another suitable shape, such as being corrugated to enhance the surface area.

Preferably, the first and second portions are formed on either side of the middle portion. The middle portion is then located in between the first and second portions, and so that the middle portion connects the first and second portions with each other. In a preferred embodiment the first and second portions are shaped as plate sheets, or flanges, jutting out from the middle portion. Preferably, the set of plate members are shaped to be arranged in a stack so that their middle portions are aligned with each other and form a connection between the plate members. Preferably the extensions of the first and second portions substantially define a plane, and the middle portion is shaped to extend at an angle relative to that plane, preferably substantially orthogonally. Preferably, the widths of the first and second portions are longer than both the height and the width of the middle portion. Preferably, the first, second and middle portions are formed from one, single original plate sheet, so that the plate member is made as an integrated piece of material. Preferably, the middle portion also retains its original plate shape, though it is bent, so that it remains thin in its thickness direction, preferably thinner than or equal to 5 mm. Preferably, each individual plate member comprises only one first portion and only one second portion. Thus it is ensured that the thickness of the middle portion is sufficient to be able conduct the thermal energy collected and emitted by said first and second portions.

According to one embodiment the set of plate members are arranged in a stack so that their middle portions bear against each other. Thus there is only need to make room for one path of passage for the middle portions of all plate members in a set. Preferably the first and second chambers are separated by an internal wall, wherein the internal wall comprising a gap or opening and the plate members are arranged so that their middle portions pass through said gap or opening. According to one embodiment the set of plate members are stacked so that the first and second portions form spaced apart flanges in said first and second chambers respectively. Thus the first and second portions may absorb and emit thermal energy homogeneously throughout a large volume of fluid. According to one embodiment the plate members are provided with line segments forming openings going through the plate member in its thickness direction, which line segments divides the plate members into plate sections having low thermal conductivity between adjacent plate sections. Hence fast arranging of several sections of plate members along the flow directions of the fluids is possible, while restricting any heat exchange between different fluid packages within the same fluid flow. By arranging two or more sections of plates along a flow direction, and with low thermal transfer between the plate sections, the thermal transfer between two fluid flows is improved, since the heat transfer is driven by the temperature difference between the flows.

According to one embodiment the middle portions of said set of plate members are shaped having a receiving portion and a protruding portion, wherein the protruding portion of one plate member is shaped to fit into the receiving portion of a neighbouring plate member. The middle portions of the plates in said set are thus shaped to be stackable with each other so as to form a pile. Preferably, the receiving portion is shaped to receive a protruding part of a neighbouring plate which is arranged on top of or below the plate, and vice versa. The receiving/protruding portion thus forms a connection that holds the plate members together in the set of plate members, and prevents relative movement in at least a lateral direction, giving structural rigidity. According to one preferred embodiment the receiving and protruding portions are formed as two mutually opposed, shaped surfaces of the middle portion, wherein the outer surface of the shaped middle portion forms the protruding portion and the inner surface of the shaped middle portion forms the receiving portion. Thus there is cost economy when manufacturing the set of plate members, and also, the assembly of the set of plate members likewise becomes easy and fast to achieve by stacking the plates one on top of the other. According to one embodiment the middle portions of the plates in said set are shaped with recessed, receiving sections having gradually decreasing height and/ or gradually increasing widths for each subsequent plate member in the stack of plate members, thus achieving that the first and second portions of neighbouring plates are spaced apart when assembled. The need for increasing width corresponds to the thickness of the material in the middle portions, so that the protruding part of one plate fits inside the recessed receiving part of its neighbouring plate throughout the entire stack of plate members. According to one embodiment the middle portions of said set of plate members are U-shaped. Preferably the first and second portions jut out from the middle portion from the legs of the U-shape, preferably from the ends (feet) of the U-shape. A U-shape is very easy and cost effective to produce relative to other shapes from plates. Also it is very easy to adapt the measures of the U-shape for particular embodiments, purposes, or geometries. According to one embodiment the heat exchanger comprises a set of stackable plates, and the width and depth of the U-shaped middle portions are adapted so that the outer surface of one plate member fit into the inner surface formed by the U-shape of a neighbouring plate member. Preferably, the widths and heights of the U-shape are gradually decreasing for each subsequent neighbouring plate member in the set of plate members. In yet another embodiment the middle portion is straight, and the first and second portions jut out from the ends of the middle portion, so that each plate member is U-shaped. Manufacturing a U-shaped plate member only requires two bending operations. Preferably, a fastener is then used to keep the U- shaped plate members from sliding relative to each other in the stack. In another embodiment the middle portion is V-shaped. Manufacturing a V- shape requires a lesser number of operations but is more demanding in terms of tolerances.

According to one embodiment the heat exchanger further comprises an intermediate element arranged to lie in between each pair of plate members. Preferably, the intermediate element is arranged to lie in between two stacked plate members so as to form a distance between them. Preferably, the intermediate element is arranged to lie in between the middle portions of the pair of plate members. Preferably, the intermediate element is then arranged with a similar shape as the middle portions of the plate members. The intermediate element is arranged to keep the pair of plate members apart, so as to increase the spacing between the respective first and second portions of the first and second plate members. In a preferred embodiment the middle portions of the plate members are of the same size and shape. The thickness of the intermediate element then determines the spacing between the respective first and second portions of the first and second plate members. It is then not necessary to employ different tool sizes in the production of the plate members. In case the middle portion is V-shaped, the intermediate element may also be V-shaped. In a preferred embodiment the V-shapes are then all of the same size, so that the thickness of the V-shaped intermediate element determines said spacing. By using an intermediate member to create the desired distance it is not necessary to manufacture plate members with different shapes or dimensions in order to stack the plate members so that the first and second portions are spaced apart. Thus the number of tools needed in the manufacturing process is decreased.

According to one embodiment the heat exchanging device is provided with a moisture addition arrangement arranged to add moisture to a gas flow, which preferably is an air flow. Preferably, the moisture is added to a gas flow which is to be cooled. Preferably the moisture is then added to the gas flow upstream of the set of plates. By introducing moisture into the gas flow the moisture condenses on the plates, which increases removal of heat from that gas flow. This is advantageous if, for example, it is intended to cool incoming air, where it is more important to remove heat rather than to recover heat. According to one embodiment the heat exchanger device is provided with a drying arrangement arranged to remove moisture from at least one of the fluid flows. This is important if, for example, incoming air is very humid, or if the area into which the air is to be introduced should be dry. The drying arrangement may comprise a cloth absorbing moisture from the gas flow and carrying the moisture to a tapping point or sink. Alternatively, the drying arrangement may comprise silica or some other substance with capacity to absorb moisture.

According to one embodiment the first chamber is shaped to be connected with a first ventilation channel carrying a first ventilation flow, and the second chamber is shaped to be connected with a second ventilation channel carrying a second ventilation flow. Preferably, the heat exchange device is adapted to achieve a heat exchange between an incoming and an outgoing ventilation flow carried by the first and second ventilation channels respectively.

According to one embodiment of the invention the device, or system, is designed for use for climate control of a building or construction. In one embodiment the heat exchanger device, or heat exchanger system, is designed for use for regular ventilation of the normally inhabited area of a building. Preferably, at least one of said first or second fluid flows is a ventilation flow, such as an incoming or an outgoing ventilation air flow. In another embodiment the device, or system, is adapted for ventilation of cellars, foundations of buildings, or areas beneath buildings, such as beneath a foundation of a building.

According to one embodiment the first chamber is shaped to be connected with a first ventilation channel carrying a first ventilation flow, and the second chamber is shaped to store the second fluid in order to admit accumulation of heat in the second fluid, wherein the heat exchanging device further comprises a third chamber shaped to be connected with a second ventilation channel carrying a second ventilation flow, and a second set of plate members shaped in the same manner as the first set of plate members and arranged with their first portions residing in the second chamber and their second portions residing in the third chamber. Preferably the heat exchanging device is further adapted to be connected with a heat pump and to provide the second fluid in the second chamber as a heat source for the heat pump. A heat pump retrieving thermal energy from an outgoing ventilation flow is normally only run intermittently, meaning that when the heat pump is passive the heat in the outgoing ventilation flow is lost to the outside. With the invention the heat of the outgoing ventilation flow is conducted by the first set of plate members to the second fluid in the second chamber, where the heat is stored. Thus there is less heat loss to the environment. Preferably the heat exchanging device comprises a fluid conductor being in thermal contact with the second chamber and which is adapted to conduct a heat transfer fluid between the heat pump and the second chamber. According to a third aspect of the invention this objective is further achieved with the method for producing a heat exchanger according to claim 11. According to one embodiment the method for producing a heat exchanger comprises

- deforming a plate sheet along a first line to form a first portion jutting out from a middle portion of the plate,

- deforming the plate sheet along a second line to form a second portion jutting out from the middle portion of the plate, and

- arranging the plate sheet with a plurality of similar plate sheets to form a stack of plate sheets inside a housing having first and second chambers, so that the first portions of the plates reside inside the first chamber and the second portions of the plates reside inside the second chamber.

One advantage with the design of the heat exchanging device and the method for producing the heat exchanging device according to the invention is that it is very simple to manufacture, giving extremely low manufacturing costs.

According to one embodiment the method for producing a heat exchanger comprises deforming the plate or plate sheet along at least one line so as to form a receiving portion and a protruding portion. Preferably, the method comprises deforming the plate sheet along a third and a fourth line, which third and fourth lines are parallel and positioned inside the first and second lines, so as to form a U-shaped middle portion. Preferably the third and fourth lines are also parallel with the first and second lines.

In another embodiment the method for producing a heat exchanger comprises deforming the plate sheet along a third line, which third line is parallel with the first and second lines and is positioned inside the first and second lines, so as to form a V-shaped middle portion.

According to one embodiment the method for producing a heat exchanger comprises removing material so as to form line segments in the plate sheet, which line segments divides the plate sheet into plate sections, and the line segments forming openings going through the plate sheet in its thickness direction. The line segments then defines sections of the plates, which sections forms separate sections of the plate members when assembled. Preferably, this step comprises punching the line segments. In another embodiment the removal of material comprises cutting or sawing. Preferably, this step comprises removing material so as to form line segments which jointly extend over almost the entire width of the plate apart from one or more connecting bridges. The bridges are formed by material that is not removed and that connects the sections of the plate members separated by the punched out line segments. The sections are then held together so that a single deformation operation, such as a bending operation, may shape all sections of the plate member simultaneously.

In one embodiment the bridges may be left intact, keeping the plate sheet in one piece. During assembly of the intact plate sheets by stacking, several stacks of sections of plate members are thus formed at once with one single operation. Since the bridges are very small the heat conduction through the bridges is very small, and may for less demanding applications be ignored. The separation of the stacked sections achieved by the incomplete punched line segments may therefore be sufficient in order to decrease any heat conduction in the direction between the sections or stacks of plates in the length direction of the heat exchanger. Preferably, the bridges are between 0.3 to 1 mm in width, preferably 0.5 mm. In one embodiment the method comprises breaking the bridges after the deforming steps have been completed, so that the sections form completely separated stacks of plate members. This is advantages if arranging a plurality of stacks of plate members in compartments inside for example a heat accumulation tank.

BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS

The invention is now to be described as a number of non-limiting examples of the invention with reference to the attached drawings. Fig. 1 shows a first example of a heat exchanger device according to the invention.

Fig. 2 shows one example of a plate sheet for a heat exchanging device according to the invention.

Fig. 3 shows a heat exchanger system comprising a heat exchanger device according to the invention. ^{" "} Fig. 4 shows another example of a heat exchanger device and system.

Fig. 5 shows one example of a method for producing a heat exchanger device. Fig. 6 shows further examples of possible shapes for the plate sheet and plate members.

DETAILED DESCRIPTION In fig. 1 one example of a heat exchanger device 1 according to a first example of the invention is shown. In fig. 2 plate sheets 5 forming plate members 7 shaped to be arranged inside the heat exchanger device of fig. 1 are shown, and in fig. 3 the heat exchanger device 1 is shown installed in a heat exchanger system 3. In this example the heat exchanger device 1 is adapted for use in a ventilation system 9 for a building. The heat exchanger device and the ventilation system could then be adapted for ventilation of the indoor, inhabitable area 1 1 inside the building, or, as shown here in a preferred alternative, for ventilation of the non-inhabited area 13 beneath the building, or for ventilation of a cellar, or a combination thereof. In an exemplary application, the heat exchanger device is used for removal of radon and moisture from the area beneath a building. However, it should be noted that the heat exchanger device could also be used in other applications, and could then be subjected to one or more adaptations by a man skilled in the art. The heat exchanger device comprises a housing 15 having outer walls 17 encasing the heat exchanger device. Inside the housing there are arranged a first 19 and second 21 chambers for first and second fluids, respectively. The first and second chambers are here shaped as part of two ventilation channels intended to carry one ventilation fluid flow each. The chambers are therefore for ease of use in this example arranged in parallel with and lying next to each other. The chambers 19, 21 are housed inside the same housing, and the walls of the housing also forms the walls lining the chambers, which allows a saving in the amount of materials needed to construct the device. In this example the heat exchanger device 1 comprises an internal wall 23 separating the first and second chambers. The housing further comprises four inlet/outlet openings into the chambers in the respective ends of the housing to allow inflow and outflow of the first and second fluid flows. The two channels are adapted in size and shape for allowing a flow of ventilation air comprising one incoming airflow and one outgoing airflow, respectively. The sizes of the chambers are in turn adapted to the size of the ventilation channels in the building and on the specific ventilation requirements. The ventilation airflows are furthermore here intended to flow in opposite directions relative to each other inside the two chambers and channels. This is natural, since the incoming and outgoing airflows should already be directed in opposite directions to enter or being exhausted from the building, and an opposite flow also allows for a more efficient heat transfer. In this respect the first chamber is shaped to be connected with a first ventilation channel carrying a first ventilation flow, and the second chamber is shaped to be connected with a second ventilation channel carrying a second ventilation flow. The heat exchange device is thus adapted to carry out a heat exchange between the incoming and the outgoing ventilation flow.

The heat exchanger system 3 further comprises a first 27a and second 27b driving arrangements to drive said fluid flows, in this example fans. In another example the fans are instead provided by the ventilation system into which the heat exchanger system is installed. In yet another example the fans are included within the heat exchanger device 1. In yet another alternative the fluid flows could also be achieved by some other driving arrangements, such as by pumps in case of liquids, thermal convection, gravity, natural or artificial pressure differences, screws, etc.

In order to allow transfer of thermal energy between the first and second chambers, and therefore between the first and second fluid flows, the heat exchanger device comprises a set of plate members 7 arranged to conduct heat from a warmer fluid package in one of the fluid flows and which is in contact with the plate in one location, to a cooler fluid package in the other fluid flow and which is in contact with the same plate in another location. The set of plates are therefore arranged to simultaneously be in contact with both the first and second fluid flows, and to admit thermal transfer between the first and second flows through the material of the plates. The plate members 7 are further shaped so that each plate member has a middle portion 29 arranged to bridge a distance between the first and second chambers, a first portion 31 arranged to jut out from the middle portion 29 and to reside inside the first chamber 19 in order to be in contact with the first fluid flow, and a second portion 33 arranged to jut out from the middle portion 29 and reside inside the second chamber 21 in order to be in contact with the second fluid flow, so that thermal transfer is admitted between the first and second flows in said chambers along a length direction of the plates.

The general shape of the plates is shown in more detail in fig. 3. In this example each individual plate 7 comprises only one first portion 31 and one second portion 33, respectively. At least a majority of the plates 7 is in this example made from an originally flat plate sheet 5 of a highly conducting metal, which is then formed by bending the plate sheet 5 so that the first and second portions jut out from the middle portion. In this example, the first and second portions are formed out of a respective end of the plate sheet. In this example the first and second portions are formed as parts of the thin plate, having first and second, mutually opposed surfaces 77, 79 defining the extension of the respective first and second portions, and a thickness there between. The fluid thus flows on both sides of each portion, so that the fluid is in contact with both the first and second surfaces, allowing a very large contact surface between the portions and the fluids. The first and second portions are thin with low thickness relative to their extension. This is advantageous since the bottle-neck in heat transfer applications normally is constituted by the interface between the fluid and the heat conducting plates. The length and width of each portion are longer than the corresponding thickness. In a preferred example the length of the first and second portions (corresponding to a direction perpendicular to the fluid flow or length of the chambers) is 35-65 cm, the width (coinciding with the direction of fluid flow or length of the chambers) is 4-7 cm, and the thickness is 1-3 mm. (The dimensions shown in the drawings are chosen to simplify understanding of the principles and not to illustrate the dimensions in a real device.) The first and second portions are thus plate-shaped and form wings or flanges jutting out into the first and second chambers, and therefore into the streams of the fluid flows.

In this example the first and second portions are arranged to jut out from the middle portion and into the chamber a distance corresponding to at least half the width of the chamber. Preferably the first and second portions are arranged to jut out a distance which longer than or equal to at least 70 % of the width of the chamber. Thus it is ensured that the surface is large, and also that a larger part of the fluid flow will be subjected to the heat transfer. The first and second portions thus jut out into the space formed by the chambers, in particular, into the space enclosed by the walls of the chambers. In this example the first and second portions are substantially flat. However, in another application the first and second portions are curved, for example in order to better fit the geometry of a chamber. In yet another example the first and second portions are corrugated in order to increase the surface area being in contact with the fluids even more. The middle portion 29 of the plates is in this example U-shaped. The middle portion thus comprises a recessed receiving part 81, corresponding to the inside of the U, and a protruding part, corresponding to the outside surface of the U. The plates are arranged stackable with each other, wherein the protruding part 82 of one plate is fitted inside the recessed receiving part of its next, neighbouring plate. This means that the plates are held together and are locked against lateral motion, giving structural rigidity. In this example, to accommodate for the material thickness of the plates, the width of the U- shape is widened for each subsequent plate (taken in the order from bottom up in the figure, or narrowed if going from top to bottom), so as to allow the protruding part of one plate admittance into the recessed receiving part of the next plate. Furthermore, the height of the U-shape is likewise gradually shortened, so that the first and second portions of neighbouring plates are arranged at a regular distance from each other when the plates are assembled. In this example the first and second portions are arranged to jut out from the feet of the U-shaped middle portion, since this allows a very simple manufacturing process for the plates. The distance between the first and second portions of subsequent plates thus corresponds directly to the change in height. In this respect the plates in said set are shaped stackable so that the top of a protruding part is substantially in contact with the bottom of the subsequent receiving part. However, if each of the U-shaped middle portions is formed with a gradually narrowing configuration, there may remain a distance between these parts when the plates are stacked. In this example, the bottommost plate in said set of plates comprises a receiving section arranged to receive at least a part of said inner wall.

In the example above the middle portion of the plate is U-shaped. However, other shapes are also conceivable for the middle portion without necessarily departing from the scope of the invention. In one example, the middle portion is V-shaped, which leads to a slightly different size, but is faster to manufacture since only one bending operation is needed instead of two. Other shapes allowing stacking of the plates so that the first and second portions of neighbouring plates are arranged at suitable distances are also considered part of the invention, but are too numerous to make an exhaustive list.

In operation, heat is absorbed from a fluid by one of the first or second portions of a plate, the heat is transported through the middle portion driven by thermal difference, and further to the other of the first or second portion where the heat is absorbed by the other fluid flow. Heat is thus conducted in a longitudinal or length direction along the extension of the plate members 9.

The heat exchanging device according to this example comprises at least one stack of plates 35 as described above. In this example the heat exchanging device however comprises several such stacks of plates 35, arranged in a row one after the other along the flow paths of the first and second fluid flows, that is, along the length of the first and second chambers. Since the fluids flow in the opposite direction relative to each other the total heat exchange thus becomes more efficient, with the ability to transfer a larger amount of the thermal energy from one flow to the other. This is due to that there is no heat conduction in the flow direction inside the plates, which would otherwise lower the temperature difference between the flows and therefore the heat transfer. The first and second portions of each plate is furthermore arranged to jut out in a general direction perpendicular to each flow path or chamber. In this example each plate member 9 in a stack of plates 35 is connected with a plate member in a neighbouring stack of plates 35 via connecting bridges 37. These bridges are due only to manufacturing concerns as will be described later. Alternatively, the bridges may be broken or removed before assembly of the heat exchanger.

The internal wall 23 separating the first and second chambers is furthermore slightly lower in height than the height of the respective chambers, leaving a gap 38 between the top of the inner wall 23 and the ceiling of the housing. The middle portions of the sets of plates are arranged to pass through said gap. Preferably the size of the gap is adapted to correspond to the combined thickness of the middle portions of the stack of plates, so that the gap is closed after the heat exchanger is assembled. Furthermore, the depth of the recessed receiving part, that is the height of the U-shaped part, of the bottommost plate is equal to or slightly less than the height of the inner wall, and the width is likewise adapted to the width of the inner wall, so as to admit the bottommost plate to be positioned on top of the inner wall. In another example the inner wall may also be completely made up by the middle portions of said stacks of plates. The heat exchanger device and/ or heat exchanger system further comprises a by-pass channel 39 admitting passage of a flow without incurring a heat exchange. This is advantageous in case the temperature of a target body of the fluid or some other location affected by the heat exchanging device is already at a desired level.

The heat exchanger device or heat exchanger system further comprises a moisture addition device 41 arranged to add moisture to one of the fluid flows, in this example to the incoming air flow. In case of a desire to cool the incoming air an addition of moisture to the incoming air flow upstream of the heat exchanger plates leads to that the moisture is condensed on the plates. This in turn leads to a significant removal of energy and a subsequent decrease in temperature, in addition to the heat exchanger device. The temperature is therefore reduced even more than what would have been achieved with the heat exchange alone.

In this example the heat exchanging device comprises a drying arrangement 43 arranged to dry one of the fluid flows from moisture. The drying arrangement comprises in this example a moisture absorbing textile or cloth. The textile then leads the moisture to a tapping point or an evaporation point. This is advantageous for example if ventilating the area beneath a building of a cellar, where it is important that the incoming air is dry. Of course depending on application a heat exchanger device may also comprise any combinations of a by-pass channel 39, a moisture adding device and a drying arrangement.

In fig. 4 another example of a heat exchanging device 83 and ventilation system 85 is shown. The heat exchanging device comprises a first chamber 91 shaped to be connected with a first ventilation channel carrying a first ventilation flow, a second chamber 93 shaped to store a second fluid 97 in order to admit accumulation of heat in the second fluid, and a third chamber 95 shaped to be connected with a second ventilation channel carrying a second ventilation flow. The heat exchanging device further comprises a first set of plate members 99 shaped by a deformation operation so that each plate member comprises a middle portion 103 arranged to bridge a distance between the first 1 and second 93 chambers, a first portion 101 arranged to jut out from the middle portion 103 and to reside inside the first chamber 91, and a second portion 105 arranged to jut out from the middle portion 103 and to reside inside the second chamber 93. The heat exchanging device further comprises a second set of plate members 107 correspondingly shaped by a deformation operation so that each plate member comprises a middle portion 109 arranged to bridge a distance between the second 93 and third 95 chambers, a first portion 111 arranged to jut out from the middle portion 109 and to reside inside the second chamber 93, and a second portion 113 arranged to jut out from the middle portion 103 and to reside inside the third chamber 95. Thus heat is conducted between the first and second ventilation flows via the combination of the first and second set of plate members and the second fluid in the second chamber.

The ventilation system further comprises a heat pump 115 arranged to supply heat to the building in which the ventilation system is installed via a heat pump mechanism. The heat exchanging device is further adapted to be connected with the heat pump and to provide the second fluid in the second chamber as a heat source for the heat pump. In this example the heat exchanging device comprises a fluid conductor 1 17 in the form of a pipe being in thermal contact with the second chamber and arranged to conduct a heat transfer fluid between the heat pump and the second chamber. The heat exchanging device is thus arranged to function both as a heat source for the heat pump and for transferring heat between the incoming and outgoing ventilation flows.

In fig. 5 one example of a method for producing the heat exchanging device is shown.

In a first, optional step 45 the method comprises providing a housing 15 for the heat exchanger device. In this example the method comprises providing an upper part of the housing intended to form a ceiling/roof for the housing. The method also comprises providing a lower part of the housing, comprising a floor portion 47, and two parallel side walls 49. The lower part also comprises an inner wall 23 parallel with the side walls, and separating the interior of the housing into two separate chambers. The inner wall 23 has a height lower than the height of said side walls, so as to leave a gap between the top of the inner wall 23 and the ceiling. The gap allows passage of the set of plate sheets so that the plates may extend between the chambers. In this example the housing comprises no end walls, letting the ends of the housing open for forming inlet/outlet openings for easy access to said chambers. However the housing could also be provided with end walls, provided that these end walls comprises suitable inlet/outlet openings to a corresponding channel, or the end walls are closed for the chamber to provide a closed off storage container for the fluid. The method preferably comprises forming the housing from metal sheets. However, the housing could also be provided in another type of material. Optionally, the housing could also be provided by an external supplier.

In a second step 51 the method comprises providing a plate sheet 5 of highly, thermally conductive material. The method optionally comprises cutting the plate sheet into appropriate dimensions. In this example the plate sheet is cut to an appropriate length, which is slightly less than the length of the chambers in said housing, so that the stack of plates to be made from the plate sheet can be fitted inside the chambers. The method further optionally comprises cutting the plate sheet into an appropriate width, such that the width is sufficient for forming the lengths of the first and second portions and of the middle portion, and also sufficiently short so that the plates made of the plate sheet can be fitted inside the housing. Preferably, the plate sheet is cut so that the length of the first and second portions extends for at least 50 % of the widths of the chambers, respectively, and more preferably for at least 70 % of the widths of the chambers.

In a third step 53 the method comprises removing material so as to form line segments 55 through the plate sheet in its width direction. The line segments are thus arranged orthogonally to the intended flow direction inside the heat exchanger. Preferably the removal of material comprises cutting, or even more preferably punching, the line segments. The line segments forms open holes going through the material of the plate sheet, and thus hinders thermal conduction in a direction across the line segments. The line segments are further positioned so as to form a number of distinct plate sections 57 of the plate sheet. Each plate section is intended to form its own plate in the finished heat exchanging device. Hence, thermal transfer is mostly limited to take place within a plate section and not between plate sections. In this example the line segments are cut or punched so that there remain bridges 37 of intact material between line segments arranged along the same line, functioning to keep the plate sections 55 of the plate sheet together also after the line segments have been formed. Preferably, at least two line segments, but less than six line segments are formed along in each line, resulting in between one and seven bridges depending on if bridges are also left on the very edges of the plate sheet or not. By letting bridges 37 remain the plate sections 37 that will form one distinct plate member each are held together so that all plate sections of the same plate sheet can be bent simultaneously in one single bending operation. In a fourth step 59 the method comprises bending the plate sheet 5 along at least one line so as to form a middle portion comprising a recessed receiving part and a protruding part. In this example the fourth step 59 of the method comprises bending the plate sheet along a first 61 and second 63 middle lines arranged along the length direction of the plate sheet, in order to form a U- shaped middle portions from the plate sections of the plate sheet. The first and second middle lines are therefore parallel and positioned at a distance from each other defining the width of the U. In this example the method comprises bending the third and fourth lines to an angle between 80- 110 degrees, preferably close to 90 degrees, apart from standard machining deviations. In another example of the invention the fourth step may instead include bending the plate sheet along only one middle line, so as to form a V- shaped middle portion. In a fifth step 69 the method comprises bending the plate sheet 5 so as to form a first 31 and second 33 portion jutting out from the middle portion for each section of the plate sheet. In this example the method comprises bending the plate sheet along a first 65 and second 67 outer lines arranged along the length direction of the plate sheet. The first and second outer lines are here located outside of the first and second middle lines. When bending the plate sheet along the first and second outer lines said first and second portions jutting out from the middle portion are formed. The distance between the first outer 65 and the first middle line, and correspondingly between the second outer and the second middle line, defines the height of the U-shaped middle portion. In this example the method comprises bending the first 65 and second 67 outer lines to an angle between 80- 1 10 degrees, preferably close to 90 degrees, apart from standard machining deviations. The plate sheet is thus bent into the shape of a middle U-shaped portion having two wing-shaped, first and second portions jutting out 90 degrees from the feet of the U-shape.

In a sixth step 71 the method comprises assembling the heat exchanger device. In this example the assembling step comprises arranging the shaped plate sheet 5 with a plurality of similar shaped plate sheets to form a stack of plate sheets 5 inside the housing, so that the first portions 31 are positioned inside the first chamber 19, the second portions 23 are positioned inside the second chambers 21, and so that the middle portions 29 span the distance between the first and second chambers by being positioned on said inner wall. The U-shaped middle portion of the lowermost plate sheet is turned with the mouth of its U-shape meeting the top of the inner wall, and pushed onto the inner wall so that the inner wall is received inside the U-shape. The next plate sheet is then stacked onto the lowermost plate sheet by pushing the U- shape of the next sheet plate onto the U-shape of the lowermost plate sheet in a corresponding manner, and so on until the entire stack of plate sheets is formed. Since the plate sheet is held together by said bridges, all separate stacks of plate members 7 of the heat exchanging device are assembled simultaneously. In another example the plate sheet may instead first be separated into its individual plate members 7 by breaking said bridges, and then be assembled into separate stacks of plates. In this embodiment however the assembly becomes more expensive, but the heat conduction in a longitudinal direction between neighbouring stacks of plates is decreased.

In a seventh step 73 the method comprises attaching a lid 75 onto the housing, forming the ceiling of the heat exchanger device. The lid 75 may be attached by any appropriate method, such as by welding, brazing, riveting screwing etc. The lid is preferably attached tightly, so as to form a sealed engagement relative to the housing, and also sealed against the top of the middle portions of the topmost plates, so as to prevent any leakages between the first and second chambers. In fig. 6a there is shown plate members 119 shaped with a V-shaped middle portion 121, and first 123 and second 125 portions jutting out from the end of the legs constituting the V- shape. The plate members are stackable with each other by the apex of the V-shaped middle portion of one plate member being insertible into the V-shaped middle portion of a neighbouring plate member. By shaping the V-shape with different sizes the first and second portions of neighbouring plate members are spaced apart inside the first and second chambers.

In fig. 6b there is shown a different example of the plate members if fig. 6a. In this example the heat exchanger also comprises an intermediate element 124 intended to lie between each pair of plate members 119. The intermediate element is arranged to lie in between two stacked plate members 119 so as to form a distance between them, in this example between the middle portions 121 of the pair of plate members. Hence the plate members 1 19 are arranged at a distance from each other so as to form the spacing between the two first and the two second portions, respectively. In this case the middle portions are V-shaped and the intermediate element is also V-shaped. The V-shaped middle portions and intermediate element are of the same size, so that the thickness of the V-shaped intermediate element determines said spacing. The intermediate element 124 is arranged to form a connection between the middle portions of neighbouring plate members, so as to hold them together when stacked. The intermediate element thus comprises a protruding portion and a recessed portion, arranged to be inserted into and to receive, corresponding recessed and protruding portions of the immediate plate members. The heat exchanger may further comprise an inner wall also shaped in the same way as the intermediate element, onto which the most underlying plate member may be piled. In fig. 6c there is shown a plate member 127 which is U-shaped. The middle portion 129 is straight and traverses a distance between the first and second chambers. The first 131 and second 133 portions are formed by bending a plate sheet so that the first and second portions jut out from the respective ends of the middle portion 129. The first and second portions thus form flanges inside the first and second chambers. Adjacent plate members are shaped with increasing length of the middle portion, so that when assembled in the heat exchanging device the first portions of neighbouring plate members are spaced apart. Since the plate members are not secured from lateral movement by their own design they are accompanied with a fastener 135 to hold the plate members 127 together.

The invention is not limited to the examples and embodiments shown but may be varied freely within the framework of the following claims. For example, the plates in said set may be shaped so that their middle portions jointly form an inner wall at least partly separating the first and second chambers from each other. Furthermore, features shown exclusively for one example or embodiment in the description may be equally used in another embodiment or example.