Patent Publication Number: US-2010116479-A1

Title: Heat exchanger of crossflow type

Description:
FIELD OF THE INVENTION 
     The present invention relates to a heat exchanger of crossflow type for heat exchange between different media according to the preamble of claim  1 . 
     BACKGROUND TO THE INVENTION 
     European patent specification EP 0984239 B1 refers to a heat exchanger of crossflow type. The heat exchanger according to EP 0984239 B1 is composed of two plate types placed alternately on one another to form a plate stack. Ducts are disposed between two adjacent plates. The heat exchanger is adapted to receiving two media for heat transfer between the two media. The ducts all have substantially the same volume as one another. The fact that media may differ in density makes it impossible to utilise heat exchange between two media effectively enough when the respective ducts have the same volume. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a heat exchanger capable of maximum and optimum heat transfer between two media which flow in two ducts and are subject to heat transfer through a duct wall. 
     A further object of the invention is to provide a device and a method which are cost-effective compared with the state of the art, which device is easy to construct, thereby making it possible to optimise cost and time. 
     The aforesaid and other objects are achieved according to the invention by the device described in the introduction having the characteristics indicated in claim  1 . 
     An advantage achieved with a device according to the characterising part of claim  1  is that optimum heat transfer between two different media of different densities becomes possible. 
     Preferred embodiments of the device according to the invention further have the characteristics indicated in subclaims  2 - 12 . 
     According to an embodiment of the invention, a first edge region in the first plane is disposed round respective portholes in the first plate type and constitutes an abutment surface against a second edge region disposed round respective portholes in the second plate type, which second plate type is disposed on the first plate type in the plate stack, whereby side A of the first plate type is connected and adjacent to side B of the second plate type. A first throughflow duct is thus formed between two adjacent plate types. 
     According to a further embodiment of the invention, a divider, preferably stamped or pressed, is disposed in the heat transfer surface of one plate type, preferably the first plate type, and extends from the short side where said portholes are situated towards the other short side, which divider is shorter than said long sides and is disposed between them and disposed parallel between said long sides. An advantage of a divider in a plate type in a heat exchanger is that it stiffens the structure of the plate stack. 
     According to a further embodiment of the invention, the divider in the plate comprises a ridge or bottom situated in the second plane on a side B of the first plate type, whereby the divider is connected to side A of an adjacent second plate type, thereby forming between two plate types a passage between the free end of the divider and a short side of the plate types. Said ridge or bottom of the divider has a contact surface connecting to the adjacent second plate type. The connection between two plate types is by technology already known to one skilled in the art, e.g. soldering, welding, adhesive, bonding etc. 
     According to a further embodiment of the invention, the first throughflow duct is disposed between respective long sides and disposed between two adjacent plate types which are connected to one another in said first plane. As previously mentioned, the divider extends from the first plane towards the second plane on a side B of a first plate type. This means that on side A of the first plate type the divider does not protrude from the surface and has no effect on a flow on the side of the first plate type. As previously mentioned, side A of a first plate type is connected to side B of a second plate type, thereby forming said first throughflow duct between said plate types. As the divider does not affect the flow in the first throughflow duct, the duct may be disposed between respective long sides of said adjacent plate types. 
     According to a further embodiment of the invention, the second throughflow duct is disposed in the second plane and extends between said ports, whereby said second throughflow duct extends from the first short side situated adjacent to the first port towards the second short side between the divider and one long side, through the passage disposed between the free end of the divider and the second short side, and towards the first short side between the second side of the divider and the second long side, which first short side is also adjacent to the second port, whereby said second throughflow duct thus extends in a U shape from the first port round the divider and back on the second side of the divider to the second port. The throughflow duct extending in a U shape results in a longer flow path for the medium in the second throughflow duct. 
     According to a further embodiment of the invention, the third edge region of the first plate type is disposed in the second plane of the plate type and extends round said plate type both along each long side and along each short side, which edge regions constitute an abutment surface against the edge region of the second plate type which on the second plate type is disposed in a corresponding manner, which second plate type is placed under the first plate type in the plate stack. Side B of the first plate type connects to side A of the second plate type in a second plane, thus forming said second throughflow duct. This duct thus has an inlet via the first porthole and an outlet via the second porthole. 
     According to a further embodiment of the invention, each plate type has a rim disposed on each short side. The rim constitutes an abutment surface adapted to connecting to an adjacent plate type in the plate stack. 
     According to a further embodiment of the invention, a number of ducts are disposed in a region where the dimples are adjacent to the edge region of a port, whereby said ducts communicate with the porthole to which the ducts lead. The ducts help to lead medium out from the port to regions of the respective plate type to which it is difficult to cause distribution of a medium. Rendering these regions easier for a medium to reach may result in better utilisation of the total heat exchange surface of the respective plate type, through the medium being caused to spread and be distributed over a larger area of the heat exchange surface because the ducts lead part of the medium to regions of the heat exchange surface to which access is difficult. 
     According to a further embodiment of the invention, a draining duct is disposed in the rim, or in the immediate vicinity of the rim, and communicates with ducts formed between two adjacent plates. The draining duct takes the form of a hole arranged through a plate type. The draining duct communicates with the first throughflow duct. In the first throughflow duct, medium may be stationary during operation at the short end of two connected plate types. This is because part of a medium which flows through first throughflow ducts between long sides of the plate types may remain between the plate types, e.g. because the medium condenses. Hence the need for a draining duct which can lead superfluous or stationary medium away from the heat exchanger. 
     According to a further embodiment of the invention, the configuration of the pattern of dimples in the first plate type is such that the peaks of two adjacent dimples pointing in the same direction have, disposed between them at a level below the peaks, a valley situated higher than the bottoms of two other adjacent dimples, which bottoms point in the opposite direction from that of the peaks. The dimples contribute to the heat exchange surface being larger than if it was flat. 
     According to a further embodiment of the invention, the dimples of the second plate type point on side A from the second plane towards the first plane. On side A of said second plate type in the second plane, flat regions are disposed between the dimples. These flat regions constitute an abutment surface for peaks of dimples belonging to the first plate type which connects to the second plate type. On side A of the second plate type, the flat regions are so disposed that a peak portion of the divider on a second plate type can be placed against said regions and be connected to them. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the device according to the invention is described below in more detail with reference to the attached schematic drawings, which only show the parts needed for understanding the invention. 
         FIG. 1  depicts a view of a plate stack for a heat exchanger. 
         FIG. 2  depicts a view of the plate stack where the constituent plate types parted from one another for the sake of clarity. 
         FIG. 3  depicts a view of a first plate type. 
         FIG. 4  depicts a section through the first plate type. 
         FIG. 5  depicts a view of a second plate type. 
         FIG. 6  depicts a section through the second plate type. 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION 
       FIG. 1  depicts a heat exchanger ( 1 ) comprising a plate stack ( 2 ). The plate stack ( 2 ) is made up of a number of heat transfer plates, some comprising a first plate type ( 3 ) and some a second plate type ( 4 ). 
     The heat exchanger ( 1 ) according to  FIG. 1  is of crossflow type. The plate types ( 3 ,  4 ) are so disposed in the heat exchanger ( 1 ) that their long sides ( 5   a, b ) are open, whereby a medium can flow through the heat exchanger ( 1 ) from a long side ( 5   a ) to another long side ( 5   b ). Short sides ( 6   a, b ) are with advantage connected to one another between adjacent plate types ( 3 ,  4 ). 
       FIG. 2  depicts a view of the plate stack ( 2 ) where the plate types ( 3 ,  4 ) are separated from one another in order to make clear their positions and how respective media flow between respective pairs of plates.  FIG. 2  shows the plate stack ( 2 ) made up of two plate types ( 3 ,  4 ) stacked alternately on one another. Each plate type ( 3 ,  4 ) has first and second portholes ( 7 ,  8 ). Said portholes ( 7 ,  8 ) are situated near a short side ( 6   a ) of the respective plate type. Each plate type ( 3 ,  4 ) has a heat exchange surface ( 9 ). Said heat exchange surface ( 9 ) has a pattern ( 10   a, b ) comprising a number of dimples ( 11 ). The configuration of the dimples differs between the respective plate types ( 3 ,  4 ). This is explained in more detail below.  FIG. 2  illustrates how the respective media flow through the heat exchanger ( 1 ). It shows clearly that the flows cross one another in the heat exchanger ( 1 ), hence the name heat exchanger of crossflow type. 
       FIG. 3  depicts a first plate type ( 3 ). The pattern ( 10   a ) of the first plate type ( 3 ) extends between a first plane ( 12 ) and a second plane ( 13 ). This is illustrated in  FIG. 4 , which depicts a section through the first plate type ( 3 ) parallel with the short sides ( 6   a, b ) and through the respective portholes ( 7 ,  8 ). The first plate type has a side A and a side B. In FIG.  3 , side A is the side of the first plate type ( 3 ) which is visible to the reader. Side B constitutes the underside of the first plate type ( 3 ) in  FIG. 3 . 
       FIG. 5  depicts a second plate type ( 4 ). The pattern ( 10   b ) of the second plate type ( 4 ) extends in a manner corresponding to that of the first plate type ( 3 ) between second and first planes ( 13 ,  12 ). Upon abutment between two plate types ( 3 ,  4 ) which constitute a pair of plates, the planes ( 12 ,  13 ) of a pair of plates coincide. This means that in a plate pair it is possible, for example, for the two plate types to relate to either of the planes ( 12 ,  13 ). The first and second planes ( 12 ,  13 ) of the second plate type ( 4 ) are illustrated in  FIG. 6 , which depicts a section through the second plate type ( 4 ) parallel with the short sides ( 6   a, b ) and through the respective portholes ( 7 ,  8 ). The second plate type has a side A and a side B. In  FIG. 5 , side A is the side of the second plate type ( 4 ) which is visible to a reader. Side B constitutes the underside of the second plate type ( 4 ) in  FIG. 5 . 
     In the plate stack, side A of the first plate type ( 3 ) forms together with side B of the adjacent second plate type a first throughflow duct ( 14 , see  FIG. 2 ). Side B of the first plate type ( 3 ) and side A of the second plate type form together a second throughflow duct ( 15 , see  FIG. 2 ). A first medium ( 16 ) flows in the first throughflow duct ( 14 ). A second medium ( 17 ) flows in the second throughflow duct ( 15 ). Said first and second media ( 16 ,  17 ) are subject to heat exchange between them through the respective plate types ( 3 ,  4 ). 
     The first plate type ( 3 ) has round each porthole a first edge region ( 18 , see  FIGS. 3 ,  4 ). This first edge region ( 18 ) is situated in the first plane ( 12 ) of the plate type ( 3 ). Said first edge region ( 18 ) has the function of an abutment surface. This is because the first edge region ( 18 ) is adapted to abutting against a second edge region ( 19 ). This second edge region ( 19 ) is situated round the respective portholes of an adjacent second plate type ( 4 , see  FIGS. 5 ,  6 ) in the plate stack ( 2 ). Said second edge region ( 19 ) is situated in the first plane ( 12 ) of the second plate type ( 4 ). Upon abutment between the two plate types ( 3 ,  4 ) said edge regions ( 18 ,  19 ) coincide and are adjacent to one another in the same first plane ( 12 ). The short sides ( 6   a, b ) of said adjacent plate types ( 3 ,  4 ) are with advantage connected to one another in the first plane ( 12 ). The first throughflow duct ( 14 ) is disposed between said adjacent plate types ( 3 ,  4 , see  FIG. 2 ). 
     A divider ( 20 ) is disposed in the first plate type ( 3 , see  FIG. 3 ). This divider ( 20 ) is with advantage pressed or stamped in the first plate type ( 3 ). Alternatively a separate divider may be fitted permanently to the heat exchange surface ( 9 ) of the first plate type ( 3 ). The divider ( 20 ) extends from one short side ( 6   a ) towards the other short side ( 6   b ) between and parallel with the long sides ( 5   a, b ) and between the portholes ( 7 ,  8 ). The divider ( 20 ) has a bottom ( 21 ) situated in the second plane ( 13 ) of the first plate type ( 3 , see  FIG. 4 ). 
     Said divider ( 20 ) with its bottom ( 21 ) on side B of the first plate type ( 3 ) is adapted to abutting against a side A of the second plate type ( 4 ). As previously mentioned, upon contact between side B of a first plate type ( 3 ) and side A of a second plate type ( 4 ) the bottom ( 21 ) of the divider ( 20 ) connects to side B of said second plate type ( 4 ). The long sides ( 5   a, b ) and short sides ( 6   a, b ) of adjacent plate types ( 3 ,  4 ) connect to one another with advantage in the second plane ( 13 ). The divider ( 20 ) is shorter than the long sides ( 5   a, b ). The divider ( 20 ) has a free end ( 22 ). The fact that the divider ( 20 ) is shorter than the long sides ( 5   a, b ) results in there being a passage between the free end ( 22 ) of the divider ( 20 ) and the other short side  6   b  between side B of a first plate type ( 3 ) and side A of a second plate type ( 4 ). The second throughflow duct ( 15 ) is disposed between said plate types ( 3 ,  4 ). The first porthole ( 7 ) communicates with the second porthole ( 8 ) via a medium which flows in the second throughflow duct ( 15 ). 
     A third edge region ( 23 ) extends along the respective long sides ( 5   a, b ) and short sides ( 6   a, b ) of both the first and second plate types ( 3 ,  4 ). This third edge region ( 23 ) is situated in the second plane ( 13 ) of the respective plate types ( 3 ,  4 ). The respective third edge regions ( 23 ) of the respective plate types ( 3 ,  4 ) are adapted to abutting against and being connected to one another. 
     A rim ( 24 ) is disposed on the respective short sides ( 6   a, b ) of the respective plate types ( 3 ,  4 ). The respective rims ( 24 ) on respective adjacent plate types ( 3 ,  4 ) are so disposed that the rims ( 24 ) can abut against and be connected to one another. A draining duct ( 25 ) is disposed in the rim ( 24 ) along the second short side ( 6   b ) of the first plate type ( 3 , see  FIG. 3 ). The draining duct ( 25 ) takes the form of a hole through the rim ( 24 ) of the first plate type ( 3 ). It is thus possible to remove via the draining duct ( 25 ) any medium remaining in a plate pair, e.g. as a result of condensation. In an alternative embodiment (not shown in the figures) the respective short sides between adjacent plates in the plate stack are open, whereby adjacent rims on the short sides do not seal against each other. 
     A number of distribution ducts ( 26   a - d , see  FIG. 5 ) situated in the second plate type ( 4 ) extend from the respective first and second edge regions ( 14 ,  15 ) round the respective portholes ( 7 ,  8 ) to a number of dimples situated round said portholes ( 7 ,  8 ) in the heat exchange surface ( 9 ). The distribution ducts ( 26   a - d ) lead medium from the ports ( 7 ,  8 ) to the parts of the heat exchange surface ( 9 ) which are difficult for the flow to reach. The distribution ducts ( 26   a - d ) are pressed or stamped in the second plate type ( 4 ). 
     The dimples of the first plate type ( 3 ) differ in configuration from the dimples of the second plate type ( 4 ). The result in each throughflow duct ( 14 ,  15 ) is duct surface irregularity which helps to increase the turbulence of a medium flowing through said throughflow ducts ( 14 ,  15 ). 
     The invention is not limited to the embodiment referred to but may be varied and modified within the scopes of the claims set out below, as partly described above.