Abstract:
A fluid flow moderator for a plate heat exchange device comprises an open-sided fluid conduit adapted for positioning adjacent to a fluid port of a plate heat exchange device wherein said fluid conduit has a fluid deflection surface for moderating fluid flow. A method of moderating fluid flow in a plate heat exchange device comprises positioning an open-sided fluid conduit adjacent to a fluid port of a plate heat exchange device wherein said fluid conduit has a surface for deflecting a fluid and moderating fluid flow in said heat exchange device.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention generally relates to heat exchange devices for fluids. In particular, the invention relates to a fluid flow moderator for a plate heat exchange device, a plate heat exchange device containing the fluid flow moderator and to a method of moderating fluid flow. 
       BACKGROUND OF THE INVENTION 
       [0002]    Generally, plate heat exchange devices for fluids are assembled from a series of metallic plates packed vertically in sequence to form a series of fluid chambers. 
         [0003]    The fluid chambers in a plate heat exchange device may alternately contain two fluids between which heat is to be exchanged. 
         [0004]    Normally, fluid ports may be positioned adjacent the corners of the plates to form a manifold through the device which allows the flow (eg, by mechanical pumping) of fluid through and between the alternating fluid chambers. In this manner, each plate provides a heat exchange interface between the two fluids. This facilitates heat transfer between the fluids as they flow through the device cooling the higher temperature fluid while simultaneously heating the lower temperature fluid. 
         [0005]    In certain circumstances, when fluid flows through the chambers, because of frictional effects localised areas of fluid turbulence can form due to irregularly-shaped features (eg, channels, indentations) present on the internal surface of the chambers and around the fluid ports. Energy is dissipated from the areas of fluid turbulence (also referred to as an eddy), which causes fluid pressure loss in the heat exchange device and hinders fluid flow. This can have a detrimental effect on heat transfer efficiency in the device. 
         [0006]    Furthermore, in conventional plate heat exchange devices, the distribution of fluid over the surfaces of the heat-conducting plates can be uneven resulting in the fluid not always obtaining optimum exposure to the surface of the plate in order to facilitate efficient heat transfer. Again, this can have a detrimental effect on the overall heat transfer efficiency of the device. 
         [0007]    Accordingly, a means for ameliorating these problems has been sought. 
       SUMMARY 
       [0008]    According to the invention there is provided a fluid flow moderator for a plate heat exchange device comprising an open-sided fluid conduit adapted for positioning adjacent to a fluid port of a plate heat exchange device wherein said fluid conduit has a fluid deflection surface for moderating fluid flow. 
         [0009]    It has surprisingly been found that the fluid flow moderator of the invention reduces localised areas of fluid turbulence in a plate heat exchange device and also provides a means for obtaining improved evenness of fluid distribution over the plates compared to conventional plate heat exchange devices. 
         [0010]    This surprising effect is achieved by positioning the fluid flow moderator of the invention adjacent a fluid port of a fluid chamber in a plate heat exchange device so that fluid flows through the fluid conduit and is deflected by the inner surface of the conduit as it enters the chamber. In this manner, localised areas of fluid turbulence caused by frictional effects are minimised resulting in a reduced loss in fluid pressure. This also has the effect of more evenly distributing the fluid across the surface of a heat-conducting plate when the fluid is deflected because it is forced to flow in a radial direction from the open-sided portion of the conduit. Also, due to the even fluid flow distribution across the surface of the heat-conducting plate, improved heat exchange is observed. 
         [0011]    Further according to the invention there is provided a plate heat exchange device comprising a fluid flow moderator, wherein said fluid flow moderator comprises an open-sided fluid conduit positioned adjacent to a fluid port of the plate heat exchange device wherein said fluid conduit has a fluid deflection surface for moderating fluid flow. 
         [0012]    Even further according to the invention there is provided a method of moderating fluid flow in a plate heat exchange device, the method comprising positioning an open-sided fluid conduit adjacent to a fluid port of a plate heat exchange device wherein said fluid conduit has a surface for deflecting a fluid and moderating fluid flow in said heat exchange device. 
         [0013]    According to some aspects of the invention, the fluid conduit may be a partial cylinder. In particular, the fluid conduit may be an open-ended and hollow partial cylinder. This provides a fluid conduit with an internal deflection surface which is arcuate, which assists deflection of the fluid in a controlled radial direction through a fluid port and into the fluid chamber through the open-ended portion of the cylinder. For clarification, it should be understood that arcuate means shapes which may correspond to partial circles or partial ellipses. U- or V-shaped internal surfaces for the fluid conduit may also be considered to be within the scope of the invention. 
         [0014]    In some aspects of the invention, the open-sided portion of the fluid conduit can be an opening with parallel edges (eg, a longitudinal opening), which assists in the even distribution of the fluid in a fluid chamber by complementing the radial deflection of fluid from an arcuate deflection surface. 
         [0015]    In some aspects of the invention, the open-sided fluid conduit may include a conduit which has a side wall which is only partially open. To exemplify, this may be a fluid conduit which is an open-ended hollow cylinder with one or more holes and/or slits present in its side wall. These holes and/or slits may be provided at locations in the wall which direct fluid flow in a desired direction. The term open-sided fluid conduit is intended to include all of the above-described constructions and any equivalents providing the same function. 
         [0016]    The fluid conduit may be formed of a metallic material. However, in certain circumstances the fluid conduit may be formed of a plastics or other synthetic material for use in conditions where for example corrosive fluids are being cooled or heated. In any case, the skilled person will be able to select the material and dimensions for the fluid conduit dependent upon the environment in which it will be used. 
         [0017]    According to some aspects of the invention, the fluid conduit may have a sealing ring to provide a seal between the fluid conduit and the fluid port. This can help to ensure that substantially all of the fluid flowing through a fluid port flows through the fluid conduit so that fluid flow remains controlled, homogeneous and without fluid turbulence. This is because fluid flowing between an external surface of a fluid conduit and a rim of a fluid port may create conditions of fluid turbulence. 
         [0018]    The sealing ring may be welded on to the fluid conduit or otherwise connected to the fluid conduit by any other suitable means known to the person skilled in the art. The sealing ring may be constructed from a resilient temperature- and/or corrosion-resistant rubber material or a metallic material. 
         [0019]    In some aspects of the invention, the fluid conduit may also be provided with a handle which provides a convenient means for removing the fluid flow moderator from a heat exchange device. The handle may be integral with the sealing ring or be attached to the fluid conduit separately. 
         [0020]    According to some aspects of the invention, the fluid deflection surface is provided with indentations, corrugations and/or holes. These features can be arranged in a manner which assists in optimising flow distribution over the heat-exchange plates. 
         [0021]    According to some aspects of the invention, an arcuate fluid deflection surface may be provided which subtends an angle of less than 360°, less than or equal to 270°, less than or equal to 180°, or less than or equal to 90°. Depending on the angle subtended by the arcuate deflection surface, fluid flow distribution over a heat-exchange plate can be modified to suit the requirements of the heat exchange device. 
         [0022]    According to some aspects of the invention, a plate heat exchange device may be provided with a fluid flow moderator positioned adjacent a fluid port to moderate fluid flow as a fluid enters and/or exits a fluid port of a heat exchange plate in the heat exchange device. 
         [0023]    According to some aspects of the invention, the plate heat exchange device may be provided with a series of heat exchange plates with fluid ports assembled to form a manifold defining flow passages for fluid flow through the heat exchange device. 
         [0024]    The fluid used in accordance with the present invention may be a liquid or a gas. Furthermore, the fluid flow moderator, heat exchange device and method of moderating fluid flow in accordance with the invention are equally applicable both to processes in which a high-temperature fluid is cooled and to processes in which a low temperature fluid is heated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  shows a plan view of a conventional plate heat exchange device; 
           [0026]      FIG. 2  shows a partial schematic view of heat exchange plates packed inside the plate heat exchange device of  FIG. 1  forming fluid chambers and a counterflow arrangement of fluids through the chambers; 
           [0027]      FIG. 3  shows partial diagrammatic representations of a conventional plate heat exchange device without a fluid flow moderator according to the invention ( FIG. 3A ) and a plate heat exchange device with a fluid flow moderator according to the invention ( FIG. 3B ); 
           [0028]      FIG. 4  shows a plan view of a first embodiment of the fluid flow moderator of the invention; 
           [0029]      FIG. 5  shows cross-sectional views of second ( FIG. 5A ), third ( FIG. 5B ) and fourth ( FIG. 5C ) embodiments of the fluid flow moderator according to the invention; 
           [0030]      FIG. 6  shows plan views of fluid distribution over the surface of a heat exchange plate in a heat exchange device according to the invention having the fluid flow moderators of  FIGS. 5A  ( FIG. 6A ),  5 B ( FIG. 6B) and 5C  ( FIG. 6C ), respectively, fitted; and 
           [0031]      FIG. 7  shows a cross-sectional view of a fluid flow moderator according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    In  FIG. 1 , there is shown a plate heat exchange device  1  for heat exchange between two fluids flowing through the device whereby the higher temperature fluid is cooled and the lower temperature fluid is heated. The device  1  has a head support  5 , an end support  10 , a top carrying bar  15  and a bottom carrying bar  20 . 
         [0033]    Heat exchange plates (not shown) are vertically packed between head support  5  and end support  10  and secured by tie bars  21  on opposing sides of plate heat exchange device  1  to define a series of narrow fluid chambers (not shown) through which the two fluids can flow. 
         [0034]    In this embodiment, fluid inlet ports  25 , 26  and fluid outlet ports  30 , 31  located on head support  5  provide a counterflow arrangement where one fluid flows between fluid inlet port  25  and fluid outlet port  30 , and the other fluid flows between fluid inlet port  26  and fluid outlet port  31 . As an alternative, the fluids may not be in a counterflow arrangement and can flow in the same direction through the fluid chambers  40 . 
         [0035]    Referring to  FIG. 2 , there are heat exchange plates  35  arranged in a sequence internally within the plate heat exchange device of  FIG. 1  (not shown) to define a series of fluid chambers  40 . Heat exchange plates  35  provide a heat exchange interface between fluid chambers  40  and have fluid ports  45  for the flow of a fluid between the fluid chambers  40 . 
         [0036]    The fluid chambers  40  alternately provide a fluid flow passage for a first fluid  50  (fluid chambers  40   a ) and a second fluid  55  (fluid chambers  40   b ). The fluid flow direction of fluids  50  and  55  through fluid chambers  40  is shown by arrows  60  and  65 , respectively. 
         [0037]    Fluid  50  enters heat exchange device  1  at fluid inlet port  25  near the top of heat exchange device  1  and exits at fluid outlet port  30  near the bottom of heat exchange device  1 . Fluid  55  enters heat exchange device  1  at fluid inlet port  26  near the bottom of heat exchange device  1  and exits at fluid outlet port  31  near the top of heat exchange device  1 . This provides a fluid counterflow arrangement of the two fluids  50 , 55  in heat exchange device  1 . 
         [0038]    In use, when fluid  50 , 55  contact opposing surfaces  70  of heat exchange plates  35 , heat is exchanged across the plates  35  between the fluids  50 , 55  such that the higher temperature fluid is cooled and the lower temperature fluid is heated. 
         [0039]      FIG. 3A  shows heat exchange plates  35  of heat exchange device  1  separated by gaskets  75  and fluid  55  flowing through ports  45  in the direction of arrow  65 . Channels  76  are present adjacent gaskets  75  resulting in localised turbulence of fluid  55  as shown by curved arrows  80 . Arrows  85  show the direction of the flow of fluid  55  through fluid chambers  40   b . For clarification, the independent fluid flow system of fluid chambers  40   a  containing cooling fluid  50  is also shown. 
         [0040]    Referring to  FIG. 4 , there is shown a fluid flow moderator  90  which has a partially cylindrical fluid conduit  95  with an arcuate internal deflection surface  100  and a longitudinal opening  110  defined by edges  115 . Deflection surface  100  has indentations  105 . 
         [0041]      FIG. 3B  shows fluid flow moderator  90  positioned adjacent ports  45 . In use, fluid  55  is blocked from migrating into channels  76  by deflection surface  100 , thereby reducing fluid turbulence and improving the flow efficiency of fluid  55  through plate heat exchange device  1 . Reduced loss of fluid pressure occurs and heat exchange from fluid  55  in fluid chambers  40   b  to fluid  50  in fluid chambers  40   a  is improved. 
         [0042]    Referring to  FIGS. 5A to 5C , there are shown further embodiments of fluid flow moderators  90 . Fluid flow moderator  90  of  FIG. 5A  has a fluid conduit  96  with an arcuate deflection surface  101  subtending an angle of less than 180°. Fluid flow moderator  90  of  FIG. 5B  has a fluid conduit  97  with an arcuate deflection surface  102  subtending an angle of between 180° and 270°. Fluid flow moderator  90  of  FIG. 5C  has a fluid conduit  98  with an arcuate deflection surface  103  subtending an angle of between 180° and 270° and also has perforations  120 . The different angles and surface features of the arcuate deflection surface  101 , 102 , 103  provide fluid flow moderators  90  with different deflection properties to suit individual fluid flow distribution requirements. This provides versatility and adaptability to the present invention. 
         [0043]    Referring to each of  FIGS. 6A to 6C , there is shown a heat exchange plate  35  with fluid ports  45  and fluid flow moderators  90 . 
         [0044]    Referring now to  FIG. 6A , to optimise heat exchange across heat exchange plate  35 , fluid flow should be distributed over heat exchange plate  35  in the directions A and B shown by arrows  125  and  130 , respectively. In the absence of fluid flow moderator  90 , flow is predominantly in direction A (ie, arrow  125 ), because this flow direction provides the least overall resistance between the vertically oriented fluid ports  45 . This results in an uneven distribution of fluid over heat exchange plate  40  resulting in inefficient heat exchange. By using fluid flow moderator  90 , fluid (not shown) entering a fluid chamber (not shown) through port  45  is deflected by the arcuate deflection surface  101  evenly in the directions A and B. 
         [0045]    Likewise, as shown in  FIGS. 6B and 6C , by using fluid flow moderator  90 , fluid (not shown) entering a fluid chamber (not shown) through a port  45  is deflected by the arcuate deflection surfaces  102  and  103  in a radial pattern over a wide area of heat exchange plate  40  in the direction of arrows  105 . Thus, the fluid is evenly distributed as it flows over heat exchange plate  35  providing an optimal level of contact with heat exchange plate  35  and efficient heat exchange. 
         [0046]    With reference to  FIG. 7 , there is shown a fluid flow moderator  90  with fluid conduit  95  having fluid deflection surface  100  positioned adjacent fluid ports  45  with sealing rings  140  attached to the ends  101  of fluid conduit  95 . Sealing ring  140  provides a seal between fluid conduit  95  and fluid port  45  so that substantially all of the fluid (not shown) is directed through fluid flow moderator  90 . The sealing rings  110  are made from a temperature- and chemical resistant rubber and provide a tight seal of fluid conduit  90  with ports  45  (not shown). Alternatively, sealing ring  140  is made of a metallic material and is welded to fluid conduit  95 . 
         [0047]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.