Abstract:
A mass transfer device having a fluid permeable core wound with many stands of a hollow fiber. A bulk fluid enters the interior of the core, passes through the side wall of the core, and along the outer surfaces of the hollow fibers. A baffle positioned in the center of the core so that the bulk fluid passes outwardly upstream of the baffle and inwardly through the core along the downstream of the block.

Description:
BACKGROUND OF THE INVENTION 
   The field of the invention is mass transfer devices and the invention relates more particularly to devices that are constructed to pass a bulk fluid along the exterior surface of a plurality of hollow fibers. One such device is shown in U.S. Pat. No. 3,794,468. A porous cylindrical core is wound with a single length of capillary tubing as the core is being turned. A core insert directs the bulk fluid from the interior of the porous core over the exterior of the capillary tubes and out of the outlet tubes. A second fluid passes counter currently through the interior of the capillary tubes. 
   Another process for making a fiber bundle is shown in U.S. Pat. No. 4,572,446. Again, a bundle of hollow fibers are wound around a length of a core. 
   A similar design is shown in U.S. Pat. No. 5,299,749. Continuous lengths of filament are laid down on a core around a length of a core. 
   The flow of fluid within the hollow fibers and the fluid flowing on the outside of the hollow fibers is almost counter current. For some separation processes, it is beneficial that the flow be more across the axis of the hollow fiber rather than along the axis of the hollow fiber. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is for a mass transfer device having a fluid permeable core for the passage of a bulk fluid. The core has a bulk fluid inlet end and a bulk fluid outlet end. The core is surrounded by a bundle of hollow fibers. The core is fabricated from a sintered plastic or metal material having pores ranging in porosity from about 50 microns to about 200 microns. A baffle is positioned within the hollow center of the core so that fluid pumped into the inlet end of the core must pass outwardly through the walls of the core to get around the baffle. The fiber bundle is surrounded by a housing which forces the bulk fluid back into the side walls of the core downstream of the baffle. The fiber bundle is made from a first and a second plurality of semi permeable hollow fibers wound around the exterior of the core so that the first and second plurality of fibers form an angle between 20 and 60 degrees and preferably about 35 degrees with respect to one another. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is a cross-sectional view of the mass transfer device of the present invention. 
       FIG. 2  is a side view with the facing side of the housing removed from the mass transfer device of  FIG. 1 . 
       FIG. 3  is an enlarged diagrammatical view taken along line  3 — 3  of  FIG. 2 . 
       FIG. 4  is a side view showing the winding of hollow fibers around a core in the production of the mass transfer device of  FIG. 1 . 
       FIG. 5  is a view analogous to  FIG. 4 , but showing additional winding. 
       FIG. 6  is a diagrammatical view of the mass transfer device of  FIG. 1  affixed to input and output streams. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The mass transfer device of the present invention is indicated in cross-sectional view in  FIG. 1  by reference character  10 . Device  10  has a fluid permeable core  11 . Hollow fiber bundle  12  is wrapped around exterior surface  13  of core  11 . Core  11  has an inner surface  14  which surrounds an inner passageway  15 . Permeable core  11  is in two halves and is joined by the ends of baffle  16 . Baffle  16  is sealed to bore  11  by O-rings  16 ′. 
   A baffle  16  blocks the flow of fluid in inner passageway  15 . Thus, bulk fluid entering the device, as indicated by reference character  17  through bulk fluid inlet fitting  17 ′, must pass through the side walls of core  11 , as indicated by arrows  17 . Core  11  has a bulk fluid inlet end  32  and a bulk fluid outlet end  33 . The fluid flow path  17  passes completely through fiber bundle  12  to an outer gap  12 ′ between the outer edge of the bundle  12  and the inner surface of housing  20 . 
   The details of the fluid passageway around the exterior of hollow fiber bundle  12  is shown best in  FIG. 3  and discussed below. Broadly, however, bulk fluid passes back into interior passageway  15 , as indicated by arrows  18 , and leaves through bulk fluid outlet fitting  19 . 
   Hollow fiber bundle  12  is surrounded by housing  20  which has a housing inlet end  21  and a housing outlet end  22 . 
   Hollow fiber bundle  12  is subjected to the flow of bulk fluid around the exterior surfaces of the individual hollow fibers. A bore fluid flows through the interior of the hollow fiber bundle. This is accomplished by potting the ends of the bundle in a curable sealant  23  at a bore fluid exit end  24 . Similarly, a curable sealant  25  is sealed around the bore fluid entrance end  26 . A bore fluid exit manifold  27  surrounds the exterior open ends of the hollow fibers and a bore fluid entrance manifold  28  surrounds the open ends of the hollow fiber bundle  12 . Thus, bore fluid enters the device through bore fluid entrance fitting  29  and exits the device through bore fluid exit fitting  30 . The device and the core have a longitudinal axis indicated by reference character  31 . 
   The mass transfer device  10  is shown in side view in  FIG. 2  with the housing  20  cut away. Two sets of hollow fibers  32  and  33 , one upwardly wound and one downwardly wound, are shown spaced apart a distance about equal to the width of one set. These are also indicated in  FIG. 4  in an initial winding step discussed below. 
   An enlarged view of a portion of the fiber indicated by arrow  3  in  FIG. 2  is shown in  FIG. 3 . In  FIG. 3  the bulk fluid N is indicated by the shaded arrows  17 . The bulk fluid passes into inner passageway  15 . The bulk fluid  17  then passes outwardly through the side walls of the sintered fluid permeable core  11 . It then passes across the outer surface of the hollow fiber bundle  12 . This is shown in enlarged view in  FIG. 3  where a hollow fiber is indicated by reference character  35 . It then, having been forced around baffle  16 , passes through the side walls of fluid permeable core  11  and continues to the bulk fluid outlet fitting  19 . As can be seen in  FIG. 3 , the fluid tends to flow across the outer surface of the hollow fibers  35  more than it flows along parallel to the outer surfaces as generally taught by the prior art. It is believed that this provides a further anti-fouling scrubbing action of the bulk fluid against the outer surface of the fibers and helps the flow of a portion of bore fluid  34  through the walls of hollow fibers  35  and into the bulk fluid. 
   The winding process of the present invention is indicated in  FIG. 4  where fiber feeding shuttle  36  can guide from 1 to 16 individual hollow fibers  35  in a set  37  of hollow fibers. Set  37  has a width  38 . Each set  37  is spaced from an adjacent set by a space  39  which is preferably about equal to the width of a set. The set indicated in  FIG. 4  is wound at an angle “a” to the longitudinal axis  31  of core  11 . Then the winding process is reversed and a second set of hollow fibers is wound as indicated in  FIG. 5 . The second set is wound at an angle indicated by reference character b in  FIG. 5 . Angles a &amp; b are arranged so that the angle between the set indicated by reference character  37  and the set indicated by reference character  40  are at an angle of about 35 degrees indicated by reference character “c”. This angle can range between 20 and 60 degrees, but keeping this angle well below 180 degrees provides a crossflow rather than a longitudinal/tangential flow of the fluid passing within the hollow fibers and the bulk fluid passing over the exterior of the hollow fibers. 
   A schematic view of a laboratory setup is shown in  FIG. 6 . A bulk fluid container  41  contains bulk fluid  42 . This is passed through pump  43 , pressure gauge  44 , and into bulk fluid entrance fitting  17 ′. It passes upwardly through the mass transfer device  10  and out of bulk fluid exit fitting  19 . While the bulk of the above discussion has indicated counter-current flow, the diagram of  FIG. 6  depicts co-current flow. Thus, the bore fluid passes into inlet fitting  29  through the center of the hollow bores and hollow fibers  35  and out the bore fluid outlet fitting  30 . The bore fluid is indicated by reference character  45 . 
   The present embodiments of this invention are thus to be considered in all respects as illustrative and not restrictive; the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.