Abstract:
The invention disclosed herein is a method and apparatus for use therewith for creating flow passages of approximately equal cross section whereby a flow of a fluid through any passage will be approximately equal to the flow of a fluid through another passage.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is generally directed to equalizing the flow within a plurality of passages, and more specifically to extending a pattern defined by a tube bundle into the housing into which the tube bundle is positioned.  
         BACKGROUND OF THE INVENTION  
         [0002]    A catalytic reactor is a device that has a catalyst therein that facilitates a chemical reaction. Generally, the main components of a catalytic reactor are a housing surrounding a support onto which the catalyst is positioned. The support is commonly referred to as a substrate. Substrates vary widely. Some of the more basic substrates are pellets, monoliths, gauzes or screens. More complex substrates can be enclosed passages such as tubes.  
           [0003]    Catalytic reactors that employ enclosed passages are disclosed in U.S. patent application Ser. No. 09/527,708 entitled “Method and Apparatus for a Fuel-Rich Catalytic Reactor” and U.S. Pat. No. 6,174,159 entitled “Method and Apparatus for a Catalytic Firebox Reactor,” both assigned to the assignee of the present application, namely Precision Combustion, Inc., and both incorporated herein by reference in their entirety. Both of these catalytic reactors use elongated bodies having passages, e.g. tubes, spaced apart relative one to the other and positioned within a housing thereby defining a single flow channel. The catalyst is positioned on the outer surface of at least one tube within the single flow channel.  
           [0004]    When similar tubes, e.g. straight with a circular cross section, are packed to form a bundle within a housing such as in the above-identified catalytic reactors, interstitial areas are created. More specifically, the tubes in the bundle are positioned along a coordinate direction longitudinal of the housing with the interstitial areas being between the tubes and best visualized along a plane perpendicular to the coordinate direction. There are two general categories of interstitial areas—those between the tubes relative one to the other and those between the tubes and the housing.  
           [0005]    In a uniform tube-packing scheme, i.e. where the tubes are uniformly spaced one to the other, the interstitial areas between the tubes are of uniform cross section and in turn define interstitial passages of uniform cross section. When the bundle is placed within the housing, the interstitial areas defined by the tubes and housing can be of any cross section but will be different from the cross section of the interstitial areas between the tubes. If the housing is uniform around the bundle, the interstitial areas defined by the tubes and the housing will be uniform. As a result of the cross-sectional differences between the interstitial areas, at least two different type flow channels within the housing are defined. Therefore, when these tube type reactors are placed in a fluid flow stream, the different flow channels impart to a fluid flowing therethrough distinctly different flow characteristics.  
           [0006]    In the above-identified tube reactors, the fluid flowing in the single flow passage will be combined with another fluid flowing in the tubes at the reactor&#39;s downstream exit. This is accomplished by co-locating and interspersing the exits of each flow channel within the single flow channel and the exits of the tubes creating a point of confluence for the two fluid streams. If the flow characteristics of the flow channels are not uniform, mixing of the fluid exiting the flow channels with the fluid exiting the tubes will not be uniform potentially causing the two fluid streams to not mix as desired.  
           [0007]    Based on the foregoing, it is the general object of the present invention to provide an apparatus that overcomes the problems and drawbacks of the prior art.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention is directed in one aspect to an apparatus for defining relatively similar interstitial passages. The apparatus has a housing with a plurality of tubes defining a bundle wherein the tubes cooperate to define a repeating interstitial pattern. In the apparatus, the housing is contoured such that the repeating interstitial pattern defined by the tubes is continued in the area between the bundle and the housing. While the invention is being depicted in the context of a catalytic reactor the invention should not be so limited as it could also find utility in heat exchangers and other similar devices wherein there is a defined repeating interstitial pattern.  
           [0009]    In the present invention, a plurality of tubes in the form of a bundle are positioned within a housing along a coordinate direction longitudinal of the housing. The tubes are positioned in a pattern such that there is a generally uniform repeating interstitial area between adjacent tubes in a cross section taken perpendicular to the coordinate direction, which define generally identical flow channels. The bundle has a perimeter defined by an outer row of tubes and the housing is contoured such that the contours and the outer row of tubes establish the same pattern formed between adjacent tube rows within the bundle, i.e. a pattern consistent with a next hypothetical row of tubes that would form part of the bundle.  
           [0010]    The tubes can be positioned in almost any repeating pattern such as triangles and rectangles. Non-uniform patterns that produce a repeating pattern of interstitial areas are also permitted. The tubes can touch to define discrete flow passages or can be positioned to define a single flow channel such as depicted in the incorporated application and patent.  
           [0011]    There is considerable flexibility permitted in the contouring of the housing. For example, the contouring may be done throughout the length of the bundle or only within a portion of the length of the bundle. It is also possible to continue the contouring originating within the length of the bundle outside the length of the bundle. In some cases it might be desirable to only have the housing contoured in the area of the end of the bundle.  
           [0012]    The housing can be contoured in numerous ways. For example, a body can be either attached to or made part of the housing with each body having a profile that is the same as the profile of the next hypothetical tube. The housing could also be cased or machined to have the contours. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a cross-sectional view of an apparatus of the present invention.  
         [0014]    [0014]FIG. 2 is an end view of the apparatus of FIG. 1.  
         [0015]    [0015]FIG. 3 is an end view of a second embodiment of the apparatus.  
         [0016]    [0016]FIG. 4 is an cross-sectional view of a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]    As shown in FIG. 1, the apparatus generally denoted by reference number  9  is comprised of a plurality of tubes  10  defining a bundle  11  positioned within a volume  12  defined by housing  14  having an inner surface  16  and a length  18 . Each tube  10  has an outer surface  20  and a length  22 . Referring to FIG. 2, the apparatus has seven tubes  10  in a close packed configuration, meaning that the outer surfaces  20  of adjacent tubes  10  are in contact and the outer surface  20  of the tubes  10  adjacent to the inner surface  16  and the inner surface  16  are in contact. A body  24  is attached to the inner surface  16  having a terminus  26  positioned approximately at a tube outlet  28 .  
         [0018]    Continuing with FIG. 2, the apparatus  9  has seven tubes  10  configured in a pattern of a ring of six tubes  10  around a single center tube  10 . Adding additional rings of tubes could extend this pattern. The outer surfaces  20  of the tubes  10  in the ring define a perimeter  31 . This pattern defines two interstitial areas, the first interstitial areas  30  and the second interstitial areas  32 . The first interstitial areas  30  are defined by the outer surfaces  20  of adjacent tubes  10 . The second interstitial areas  32  are defined by the outer surfaces  20  of tubes  10  closest to the inner surface  16  and by the inner surface  16 . The second interstitial areas  32  are of a different cross section than the first interstitial areas  30 .  
         [0019]    The tubes  10  define a uniform repeating first interstitial pattern. However, this is not a requirement of the invention as any repeating first interstitial pattern is acceptable. In addition while the term tube has a cylindrical connotation, that is not considered a limitation of this invention, and the term tube should not be so limited.  
         [0020]    Referring to FIG. 2, a catalyst  36  is positioned on the outer surface  20  of a tube  10 . It is understood, however, that positioning of a catalyst  36  at the outer surface  20  is not required, nor should the invention be considered so limited. The catalyst  36  can be positioned on any surface of the tube  10 . As those skilled in the art will readily recognize there are numerous ways to position a catalyst  36  at the surface of the tube including but not limited to deposition on to the tube material and integration into the tube material.  
         [0021]    A body  24  is disposed in fixed position within each second interstitial area  32 . The body is fixed in position relative to the inner surface  16  of the housing  14 . The body  24  has a cross-section  40  that is the same as the cross section a hypothetical tube  10  would have if positioned in this location to continue the tube pattern. The body  24  further sub-divides the second interstitial areas  32  creating a third interstitial area  42  having a cross-section similar to, if not identical to, the first interstitial areas  30 .  
         [0022]    As shown in FIG. 1, the body  24  has a length  46  that places the body  24  at the tube outlets  28 . This is not a requirement as the length and position of the body  28  can be adjusted based on the application. In some applications, the body  24  might extend the length of the bundle  11 , or only a portion of the bundle  11 . In addition, the body  24  might extend from along the length of the bundle  11  to outside the bundle  11  or be intermittently placed along the bundle  11 . The body  24  need only continue the pattern within at least one cross section within the housing  14 .  
         [0023]    [0023]FIG. 3 shows the tubes  10  packed within a hexagonal housing  14 . It should be noted that a body  24  is not placed within every second interstitial area  32 , such as the interstitial areas at the corners of the hexagon. While it is preferred that all second interstitial areas  32  be sub-dividable into third interstitial areas  42  consistent with the interstitial pattern, it is not required. For the invention, only a majority of the second interstitial area  32  is required to be divided. Where a second interstitial area  32  can not be properly subdivided, consideration should be given to blocking that flow channel.  
         [0024]    [0024]FIG. 4 depicts a tube packing arrangement wherein the tube  10  outer surfaces  20  do not touch and the tube outer surfaces  20  do not touch the housing inner surface  38 . The tube pattern defines first interstitial areas  38 , denoted by dotted lines  48  and  50 , and second interstitial areas  32 , and denoted by dotted lines  50  and  52 . Note that in this arrangement the various interstitial areas are in fluid communication. Placement of the bodies  24  subdivides the second interstitial areas  32  into third interstitial areas  42 , denoted by dotted lines  50  and  54 , and  52  and  54 . Note how the third interstitial areas  42  have similar cross-sections  56  and  58  to the first interstitial areas  30 .  
         [0025]    Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.