Abstract:
The invention relates to a plate heat exchanger comprising a plurality of plates having flow channels, wherein a first plate has a front side having at least one flow channel for a first fluid and a second plate has a front side having at least one flow channel for a second fluid, and wherein the plates have through openings via which the flow channels for the same fluid are respectively connected to one another, wherein a front plate, which is placed in front of the front side of the first plate, has ports for the first fluid and for the second fluid, wherein an end plate forms the end of the aligned plates, wherein the plates and ports are formed from plastic, and wherein the plates are bonded or welded tightly together.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a plate heat exchanger comprising a plurality of plates having flow channels, wherein a first plate has a front side having at least one flow channel for a first fluid and a second plate has a front side having at least one flow channel for a second fluid, and wherein the plates have through openings via which the flow channels for the same fluid are respectively connected to one another. 
         [0003]    2. Description of the Related Art 
         [0004]    In pharmacy, biotechnology and in the food industry, gaseous or perhaps liquid mediums frequently have to be heated or cooled. In order to perform such thermal processes, heat exchangers are normally used. Heat is here transported from the warmer medium to the colder medium. The mediums are mutually separated. In this context, there is a need for heat exchangers which are very cheap in terms of material and production. 
         [0005]    DE 10 2006 013 503 A1 discloses a plate heat exchanger comprising plates having a plurality of flow channels. A first plate here has at least one flow channel for a first fluid and a second plate here has at least one flow channel for a second fluid. The plates have through openings via which the flow channels for the same fluid are respectively connected to one another. 
         [0006]    A drawback in this case is that the plates are mutually sealed in a relatively complex manner by means of seals, or, insofar as they are formed from a ceramic material, it is known to join them integrally in a complex process to form a monolithic block. Both apparatuses which are produced according to this process are correspondingly complex and expensive to make. 
         [0007]    From EP 0 038 454 A2, a plate heat exchanger consisting of a multiplicity of extruded individual plates made of polycarbonate is known. 
         [0008]    A drawback in this case is that the plates have no internal flow distributor or flow guide. Further complex components for the fluid distribution thus have to be provided. In the course of assembly, difficulties arise in ensuring a leak-tightness necessary for sterile applications. 
         [0009]    The object of the present invention is therefore to provide a plate heat exchanger which is of simple and cost-effective configuration in terms of material and production. 
       SUMMARY OF THE INVENTION 
       [0010]    The invention relates to a plate heat exchanger with a first plate having a front side with at least one flow channel for a first fluid and a second plate having a front side with at least one flow channel for a second fluid. The plates have openings via which the flow channels for the same fluid are connected. A front plate, which is placed in front of the front side of the first plate, has ports for the first fluid and for the second fluid, that an end plate forms the end of the aligned plates, that the plates and ports are formed from plastic, and that the plates are bonded or welded tightly together. 
         [0011]    The plate heat exchanger according to the invention is of simple construction and can be cost-effectively made by simple production of its plastics plates, for example by injection molding of the plates. Through the bonding together or connection of the plates in a plastic welding process, seals can be dispensed with. The plate heat exchangers can be produced so cheaply that they can be used as disposable heat exchangers. Complex cleaning, or even disassembly, can thereby be dispensed with. By virtue of their construction, the plate heat exchangers according to the invention are suitable for applications from the pharmaceutical, biotechnology and food sectors. 
         [0012]    According to a preferred embodiment of the invention, the plates, on their rear sides facing away from the front sides, are configured flat. This has the advantage that the plates can be lined up in any chosen order. 
         [0013]    According to a further preferred embodiment of the invention, the plates, on their rear sides facing away from the front sides, have mirror-symmetrical flow channels corresponding to the flow channels of the adjacent front sides. 
         [0014]    It is thereby possible, in particular, to configure the first plates and the second plates such that they are structurally identical, wherein the second plates are mounted such that they are turned correspondingly through 180° in relation to the first plates. As a result, only one mold is required for the first and second plates, which makes production considerably simpler. 
         [0015]    According to a preferred embodiment of the invention, the flow channels of the plates respectively have flow guides. The flow guides are here configured as barriers or partitions disposed in the flow channels. The partitions of flow channels for the first fluid and of flow channels for the second fluid are preferably arranged perpendicular to each other. This contributes to a better heat exchange. 
         [0016]    According to a further preferred embodiment of the invention, the plates have a collecting space. The collecting space is located at the bottom in the vertical direction. Insofar as a gas is conducted through the first flow channel, which gas condenses due to cooling, the condensate collects in the collecting space and is led off via a condensate port in the front plate. 
         [0017]    According to a further preferred embodiment of the invention, the plates and ports are formed from a sterilizable plastic. It is thereby possible to supply the plate heat exchanger sterile-packed. 
         [0018]    Insofar as the plates and ports are produced from polycarbonate (PC), polyethylene terephthalate (PET), acrylonitrile-butadiene styrene (ABS), polyphenylene ether (PPE) or polyphenylene sulphide (PPS), the plate heat exchangers can be sterilized by irradiation with gamma or beta rays. It is also possible to sterilize the plate heat exchangers by autoclaving with superheated steam. 
         [0019]    According to a further preferred embodiment of the invention, the plate heat exchanger is connected to a bioreactor, which preferably is likewise sterilizable. 
         [0020]    Thus, for the exhaust gas cooling of a gas to be evacuated from the bioreactor, the port for the entry of the first fluid is connected to an exhaust gas line of the bioreactor and the port for the exit of the first fluid is connectable to an inlet of a sterile filter, whilst the ports for the second fluid can be connected to a cooling circuit. 
         [0021]    Liquid vapors which are absorbed when gas is introduced into the bioreactor are condensed and the condensate is fed back to the bioreactor, whereupon the dried exhaust gas can now be evacuated without difficulty via a sterile filter without blocking the latter as a result of condensed liquid. 
         [0022]    According to a further preferred embodiment of the invention, for the preheating of a medium which is to be fed to the bioreactor, the port for the entry of the first fluid is connected to a medium supply line for supplying the medium and the port for the exit of the first fluid is connected to an inflow port of the bioreactor, wherein the ports for the second fluid are connected to a temperature control circuit. 
         [0023]    In particular, long heating times of the filled bioreactor can thereby be avoided. 
         [0024]    Further features of the invention emerge from the following detailed description and the appended drawings, in which preferred embodiments of the invention are illustrated by way of example. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0025]      FIG. 1  is an exploded perspective view of a plate heat exchanger. 
           [0026]      FIG. 2  is a front view of a plate of a plate heat exchanger in a further preferred embodiment, having a flow channel for a first fluid. 
           [0027]      FIG. 3  is a rear view of the plate of  FIG. 2 . 
           [0028]      FIG. 4  is a front view of a front plate of a plate heat exchanger having ports for a first fluid, for a second fluid and having a condensate port, 
           [0029]      FIG. 5  is a rear view of the front plate of  FIG. 4  having a flow channel for a first fluid, which flow channel is configured in mirror symmetry to the flow channel of  FIG. 2 . 
           [0030]      FIG. 6  is a front view of an end plate of a plate heat exchanger having a flow channel for a first fluid, 
           [0031]      FIG. 7  is a schematic representation of a process diagram of a bioreactor connected to a plate heat exchanger configured as an exhaust gas cooler. 
           [0032]      FIG. 8  is a process diagram of a bioreactor connected to a plate heat exchanger as a medium heating apparatus for preheating during filling of the bioreactor. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    A plate heat exchanger  1  substantially consists of a plurality of first plates  40  and second plates  50  having flow channels  4 ,  5 , a front plate  6  and an end plate  7 . 
         [0034]    The first plate  40  has a front side  2  and a rear side  41 . In the vertical direction, the first plate  40  has in its corners at bottom left and top left through openings  8 ,  9  for a first fluid. On the front side  2  of the plate  40  is disposed a planar depression, which forms the flow channel  4  and extends into the through openings  8 ,  9 . In the horizontal direction away from the side walls, the flow channel  4  has flow barriers  10 ,  11  of a flow guide  12 , which overlap in the horizontal direction and thus form a serpentine flow channel  4 . The rear side  41  is configured flat, i.e. without a flow channel. 
         [0035]    Outside the flow channel  4 , the first plate  40  has through openings  13 ,  14  respectively at top right and bottom right in the vertical direction. 
         [0036]    The second plate  50  has on its front side  3  a planar depression, which forms the flow channel  5  and extends into the right-hand through openings  17 ,  18 . The flow channel  5  has vertically running flow barriers  15 , which form a flow guide  16 . In the left-hand corners, the plate  50  has outside the flow channel  5  through openings  19 ,  20 , which correspond with the through openings  8 ,  9  of the plate  40 . Correspondingly, the through openings  17 ,  18  of the plate  50  correspond with the through openings  13 ,  14  of the plate  40 . The plate  50  has a rear side  51  facing away from its front side  3 , which rear side is configured flat and thus has no flow channel. 
         [0037]    The plate heat exchanger  1  has on its front side the front plate  6  having its ports  21 ,  22  for the first fluid and ports  23 ,  24  for the second fluid. The port  21  is here connected to the through openings  8 ,  19  and serves to supply the first fluid, which is evacuated again via the port  22  connected to the through openings  9 ,  20 . 
         [0038]    The front plate can optionally have on its rear side (not shown in  FIG. 1 ) a flow channel  4 ′. 
         [0039]    The port  23  is connected to the through openings  14  and  18  and serves to supply the second fluid, whilst the port  24  is connected to the through openings  13  and  17  and is used to lead off the second fluid. 
         [0040]    At its end facing away from the front plate  6 , the plate heat exchanger  1  is closed off by the end plate  7 . The end plate  7  can in this embodiment have a flow channel  4  and in this embodiment has no through openings. 
         [0041]    In one embodiment (not represented) of the end plate  7 , this is structurally identical to the front plate  6  and is disposed in the plate heat exchanger  1  in mirror symmetry to the front plate  6 . 
         [0042]    The front side of the end plate can have a flow channel  4 , as shown in  FIG. 1 , but can also be configured flat and thus without a flow channel  4  and can additionally have through openings (not represented), which correspond with the through openings of the plates  40  and  50 . 
         [0043]    In a particularly preferred embodiment, the front plate  6  and the end plate  7  are respectively provided with through openings in order to enlarge the cross section of the fluid supply without having to change the dimensioning of the ports  21 ,  22 ,  23  and  24 . In this way, the pressure loss in connection with the inflow and outflow of fluids into and out of the heat exchanger  1  can be minimized particularly advantageously. 
         [0044]    As explained above, the plates  40  and  50  are respectively configured flat on their rear sides, whilst the rear side of the front plate  6  and/or the front side of the end plate  7  can be configured plane or can alternatively have a flow channel  4 ,  4 ′. The plates  40 ,  50 ,  6  and  7  are respectively bonded to the plate situated adjacent thereto. 
         [0045]    The illustrative embodiment of  FIG. 2  shows a plate  40 ′ or  50 ′ having a flow channel  4 ′ on its front side  2 ′ for a first fluid in the form, for instance, of a cooling medium. 
         [0046]    In the vertical direction, the first plate  40 ′ or  50 ′ has in its corners at bottom left and top left through openings  8 ′,  9 ′ for the first fluid. On the front side  2 ′ of the plate  40 ′ is disposed the flow channel  4 ′, which is connected to the through openings  8 ′,  9 ′. Outside the flow channel  4 ′, the side  2 ′ has through openings  13 ′,  14 ′ respectively at top and bottom right in the vertical direction. 
         [0047]    The rear side  41 ′ of the first plate  40 ′ (see  FIG. 3 ) has a flow channel  5 ′ for a second fluid. 
         [0048]    The plate  40 ′ and the plate  50 ′ are exactly structurally identical. Analogously to the plate sequence shown in  FIG. 1 , the plates  40 ′ and  50 ′ can be put together to form a plate heat exchanger, wherein the plates  50 ′ are mounted such that they are turned correspondingly through 180° in relation to the structurally identical plates  40 ′. Unlike the embodiment according to  FIG. 1 , in which the rear sides of the plates  40  and  50  are respectively flat, this assembly produces a plate heat exchanger  1  in which the front and the rear side of the assembled plates  40 ′ and  50 ′ respectively have a flow channel  4 ′ and  5 ′. 
         [0049]    The flow channel  5 ′, in the lower region in the vertical direction, has a collecting space  25 , which serves to receive condensate which is evacuated via a condensate port  26  disposed on the front plate  6 ′ (see  FIG. 4 ). The through openings  13 ′ and  14 ′ for the second fluid of the plate  50 ′ are of elongated configuration and correspond with through openings  13 ′,  14 ′ of the plate  40 ′ (see  FIG. 2 ). 
         [0050]    The rear side  51 ′ of the plate  50 ′ (see  FIG. 3 ) has a flow channel for a first fluid, which flow channel corresponds to the flow channel  4 ′ of a further, structurally identical plate  40 ′ or to the flow channel  4 ′ of an end plate  7 ′. 
         [0051]    The plate heat exchangers  1 ,  1 ′ according to the illustrative embodiments of  FIGS. 1 to 6  are formed from polycarbonate (PC). They can readily be irradiated with Gamma rays and are suitable for any sterile application in the temperature range up to 110° C., briefly even up to 125° C. The plate heat exchangers  1 ,  1 ′ can thus also be sterilized with superheated steam. 
         [0052]    According to the illustrative embodiment of  FIG. 7 , the plate heat exchanger  1 ′ is connected to a bioreactor  27 ′ and is used as an exhaust gas cooler. The exhaust gas is conducted from the headspace  28  of the bioreactor  27 ′, via an exhaust gas line  29  connected to the port  23 ′ of the plate heat exchanger  1 ′, into the top of the plate heat exchanger  1 ′. In the plate heat exchanger  1 ′, the gas stream is divided by means of the flow channel  5 ′ over the individual front sides  3 ′ of the plates  50 ′. On the front sides of the plates  3 ′ of the plates  50 ′, the gas stream is cooled as it flows downward on the plate wall, and is evacuated via the port  24 ′ and further delivered to the environment via a sterile filter  30 . As a result of the exhaust gas cooling in the plate heat exchanger  1 ′, the air moisture of the exhaust gas is lowered, whereupon liquid medium accommodated in the bioreactor is condensed, led off via the condensate port  26  and fed back to the bioreactor  27 ′ via a hose pump. 
         [0053]    In counterflow thereto, cooling medium is conducted from the primary cooler  33  from below, via the port  21 ′, into the plate heat exchanger  1 ′. From the through openings  8 ′, the cooling medium is conducted into the individual flow channels  4 ′ and absorbs the heat from the plates  40 ′ and  50 ′. The cooling medium is hereupon heated. The cooling medium is collected in the through opening  9 ′ and conveyed via the port  22 ′ back into the primary cooler  33 . The cooling medium is circulated. 
         [0054]    According to the illustrative embodiment of  FIG. 8 , the plate heat exchanger  1  is connected to the bioreactor  27  via a supply line  31 . The plate heat exchanger  1  is here used to preheat medium which is to be fed to the bioreactor  27 . 
         [0055]    The medium which is to be heated is conducted from a supply reservoir (not represented) into the plate heat exchanger  1  from above, via the port  23 . In the plate heat exchanger  1 , the material stream is distributed, by means of the flow distributor derived from the through openings  14  and  18 , into the individual channels  5 . In the flow guides  12 , the medium current is heated as it flows downward on the plate wall. The medium currents are combined and conducted to the outlet or port  24 . From the port  24 , the preheated medium is conveyed into the bioreactor  27 . 
         [0056]    In counterflow thereto, heating medium is conducted from a thermostat  32  from below, via the port  21 , into the plate heat exchanger  1 . In the flow distributor derived from the through openings  8  and  9 , the heating medium is conducted into the individual channels  4  and delivers the heat to the plates  40  and  50 . The heating medium is conveyed from the outlet or from the port  22  back into the thermostat  32 . The heating medium is circulated.