Abstract:
An apparatus is provided employing multi-tube heat exchangers that include turbulence promoters, which are easy to clean, thus maintaining sanitary conditions; prevent catching or trapping of product flowing or pumping through the tubes; and aid in maximizing heating and cooling efficiency of flowable or pumpable product flowing within the apparatus.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 U.S.C. 119(e) and 37 C.F.R. 1.78(b) based upon copending U.S. Provisional Application Ser. No. 60/902,449 for Apparatus for Multi-tube Heat Exchanger with Turbulence Promoters filed Feb. 21, 2007 and which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to multi-tube heat exchangers, and more particularly to multi-tube heat exchangers having turbulence promoter fins that promote turbulence for passing liquid or flowable product thus increasing heating or cooling efficiency. 
       BACKGROUND 
       [0003]    Currently, multi-tube heat exchangers are used in various industries to heat or cool products passing through tubes. For example, the food and beverage, pharmaceutical and chemical industries use such devices because of a basic and important need to subject products to varying temperatures. Multi-tube heat exchangers provide an efficient and effective means to accomplish such needs. Typically, a multi-tube heat exchanger is configured so that a first concentric tube is placed within the hollow section of a second concentric tube. Hot or cold media flows within the hollow section of the first concentric tube in a direction counter to the flow of product. Product flows in the annular space created between the outer surface of the first concentric tube and the inner surface of the second concentric tube. In this way, product and heating or cooling medium do not come in contact with each other thus preserving the purity and sanitation of the product. A third concentric tube may enclose the second concentric tube to create yet another temperature gradient for the product. Multi-tube heat exchangers and their use is well known in the art. Previously, as in U.S. Pat. No. 5,174,369, product would pass through tubes relatively undisturbed. Except for the occasional bend or curve brought about by connecting joints or fittings, the product path through a multi-tube heat exchanger was relatively straight, smooth and undisturbed. One major reason for this design was to facilitate the product&#39;s movement through the tube. The movement of semi-solid product may be problematic if a tube surface is rough or partially occluded by obstacles. In addition, another reason for this smooth tube design was to prevent the tubes from “catching” or accumulating residue of the product within the hollow section of the tubes. The accumulation of product residue is undesirable, especially in the food and beverage industry, because it causes unsanitary conditions. Bacterial and mold growth within the hollow section of the tubes are just two of the possible problems caused by the accumulation of product. 
         [0004]    Although the smooth tube design of multi-tube heat exchangers holds many advantages, it also possess disadvantages. For example, since the hollow section of the tubes are linear and smooth, product passes along the tubes mostly undisturbed in laminar flow. As such, product initially traveling closer to the surface of the tube containing the heating or cooling media remains closer to the heating or cooling tube throughout the path of the tube. The product traveling closer to the heating or cooling tube is thus heated or cooled more so than product traveling further away from such tube as it is exposed for a prolonged period of time and distance to the heating or cooling tube. Since there is little to no product turnover within the tubes, this causes a temperature gradient across the flow path of the product. To address this problem, several improvements have been made to the multi-tube heat exchanger. One such improvement is the inclusion of turbulence promoters within the hollow section or outer surfaces of the tubes. Turbulence promoters are structures disposed on the outer or inner surface of concentric tubes which disrupt the laminar flow of product or media. 
         [0005]    For example, U.S. Pat. No. 4,258,782 discloses a heat exchange device with a cylinder having “turbulators” arranged helically around the cylinder. The turbulators are used to improve heat transfer to viscous liquid flowing in a tube. However, a disadvantage of the turbulators is that “raised fins” create numerous areas where product may catch and is difficult to dislodge or clean. This type of design is extremely difficult to remove trapped product and moreover causes the unsanitary conditions previously discussed above. 
         [0006]    U.S. Pat. No. 5,375,654 attempts to address the shortcomings of U.S. Pat. No. 4,258,782 by disclosing smooth raised “dimples” disposed along the path of product. The dimples are smooth raised surfaces and create turbulence for product placed within the tube. In addition, no dimples are placed along the bottom or six o&#39;clock drainage path of the product. This allows easy clean-up of the tube and prevents product from catching. However, despite the improvements made by U.S. Pat. No. 5,375,654, there is still a need for a more efficient turbulence structure which allows for maximum heat transfer to the product while maintaining sanitary conditions and facilitating easy cleaning of the inside of the tubes. 
       SUMMARY OF THE INVENTION 
       [0007]    The present disclosure describes a greatly improved apparatus for increasing heat exchange when using multiple tubes. An embodiment of the multi-tube heat exchanger has a first tube for receiving a heating or cooling medium. The first tube has a first end and a second end wherein the first end and the second end provide a medium inlet and a medium outlet, an outer surface, and a plurality of turbulence inducers wherein a single turbulence inducer is a smooth raised fin disposed on the outer surface of the first tube and further wherein the plurality of turbulence inducers are disposed in rows around the outer surface of the first tube with the rows arranged perpendicular to a laminar flow direction of a flowable or pumpable product. 
         [0008]    A second tube is disposed about and concentric with the first tube for receiving a flowable or pumpable product. The second tube has a first end and a second end wherein the first end and the second end provide a product inlet and a product outlet, a securing clamp adjacent the first end of the second tube wherein the securing clamp secures the first end of the second tube to the first tube, a seal assembly adjacent the second end of the second tube wherein the seal assembly seals the second end of the second tube to the first tube. 
         [0009]    The product outlet of the second tube is in tubular form and has an angled outlet portion extending toward the securing clamp adjacent the first end of the second tube and the product inlet of the second tube is in tubular form and has an angled inlet portion extending toward the seal assembly adjacent the second end of the second tube, with each of the product inlet and the product outlet having a portion extending radially outward of the angled outlet portion and the angled inlet portion. 
         [0010]    Various objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. 
         [0011]    The drawings, including  FIGS. 1 and 2  constitute a part of this specification, include exemplary embodiments of the present invention, and illustrate various objects and features thereof. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a first embodiment of turbulence promoters according to the invention; 
           [0013]      FIG. 2  is a sectional view of a multi-tube heat exchanger with turbulence promoters according to the invention with walls broken away to illustrate details thereof. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
         [0015]    Referring to  FIG. 1 , an embodiment of the invention is shown comprising a tube  10  having sets or rows of turbulence promoters  10   a ,  10   b . The tube  10  may be any suitable material for transporting liquids or flowable product such as metals, metal alloys, plastic, PVC pipe, etc. The tube  10  has an outer surface  20  and an inner surface  30 . The tube  10  also has a hollow section  40  through which product or media may travel. As an example, in  FIG. 1 , cooling or heating media may travel through the hollow section  40  of the tube  10 . Product, in the form of a liquid or semi-solid flowable product, would travel in a direction counter to the cooling or heating media along the outer surface  20  of the tube  10  shown by dashed line  50 . On the other hand, cooling or heating media would flow along a path shown by dashed line  60  that is in a direction counter to the direction of media flowing in the hollow section  40  of the tube  10 . Not shown in  FIG. 1  is a second concentric tube which would enclose and completely cover the outer surface  20  of the tube  10 . The annular space between the outer surface of the first concentric tube and the inner surface of the second concentric tube (not shown) is the space in which the product flows. 
         [0016]      FIG. 1  further shows an embodiment of the structure of the turbulence promoters  10   a ,  10   b  according to the invention. The turbulence promoters  10   a ,  10   b  are disposed on the outer surface  20  of the tube  10 . One advantage of the present invention is that the turbulence promoters  10   a ,  10   b  may be formed by either casting or forging. In forging, the turbulence promoters  10   a ,  10   b  may be “stamped” into the sides of the tube during the formation of the tube itself. The advantages of forging are numerous including greater strength and integrity of a metal. In casting, metal bits may be welded onto the outer surface of the tube  10  to form the turbulence promoters  10   a ,  10   b . A cast as illustrated in  FIG. 1  may be butt-welded to other cast units or plain tubing of appropriate size. The advantages of casting include ease of manufacturing and lower cost. Yet another advantage of the present invention is that the turbulence promoters  10   a ,  10   b  may be placed anywhere along the tube  10  as determined by a manufacturer. The frequency of sets of turbulence promoters  10   a ,  10   b  may be determined based on amount of product turbulence desired, type of product passing through the heat exchanger, and speed in which product must pass through the heat exchanger. A manufacturer or user of the present invention is not limited to a certain number of turbulence promoters, but is free to choose the frequency of turbulence promoters in order to optimize his or her application and use of a multi-tube heat exchanger. The turbulence promoters  10   a ,  10   b  may take the form of smooth raised fins. Although a raised fin shape is described and shown in  FIG. 1 , the present invention is in no ways limited to that shape and the turbulence promoters  10   a ,  10   b  may take any smooth shape that aids in promoting product turbulence and efficient clean-up of the multi-tube heat exchanger. The height of the turbulence promoters  10   a ,  10   b  may be specified based on the manufacturer&#39;s engineering design for a multi-tube heat exchanger. As is shown in  FIG. 1 , the turbulence promoters  10   a ,  10   b  are disposed at varying angles to the direction of the flow of product. For example, at first, product moving inside the annular space in the direction of dotted line  50 , is relatively undisturbed and is in laminar flow. However, upon encountering the first set of turbulence promoters  10   a  the angle of such turbulence promoters  10   a  causes flowing product or liquid to deflect both in the direction of the angled turbulence promoter  10   a  and in addition upwards and over the turbulence promoters  10   a . Immediately thereafter, the flowing product or liquid encounters another set of turbulence promoters  10   b . Again, the flowing product or liquid is deflected upwards and at an angle determined by the turbulence promoters  10   b  disposed upon the tube  10 . If one assumes that the initial direction of flowing product is parallel to the tube  10  and assigns it 0 degrees, the first set of turbulence promoters  10   a  may be set at an angle of 135 degrees relative to the flow of product. The second set of turbulence promoters  10   b  may be formed at an angle of 225 degrees relative to the flow of product. Irregardless of the measurement of the turbulence promoter angles  10   a ,  10   b  more important is that the first set of turbulence promoters  10   a  are set at a different angle from the second set of turbulence promoters  10   b . Any angle may be chosen by the manufacturer in forming the sets of turbulence promoters  10   a ,  10   b . It is contemplated that varying angles may be employed in forming the sets of turbulence promoters  10   a ,  10   b . Furthermore, although only two sets of turbulence promoters  10   a ,  10   b  are shown in  FIG. 1 , any number of sets of such turbulence promoters may be used depending on a users application for the multi-tube heat exchanger and the speed in which the user desires product to pass through it. Using a greater number of sets of turbulence promoters will result in decreased flow rate of product passing through the multi-tube heat exchanger because of the obstacles presented by the turbulence promoters. This may or may not be desirable depending on the product used in the heat exchanger. The different angles between the two sets of turbulence promoters  10   a ,  10   b  increases product turbulence and thus increases heating or cooling efficiency. In addition, the smooth raised fin shape of the turbulence promoters  10   a ,  10   b  prevents product from catching or being trapped inside the annular space. Furthermore, the smooth raised fin shape allows for easy cleaning of the annular space after product has passed through a multi-tube heat exchanger. This is important to prevent contamination of the multi-tube heat exchanger. 
         [0017]    Referring now to  FIG. 2 , an embodiment of the invention is shown with a section of a multi-tube heat exchanger having three concentric tubes  10 ,  110 ,  120  and the turbulence promoters  10   a ,  10   b  described previously. Product flows in the annular space between the outer surface  20  of the tube  10  and the inner surface  130  of a second concentric tube  110 . The sets of turbulence promoters  10   a ,  10   b  cause turbulence to the product flowing in the annular space between the tube  10  and second concentric tube  110 . 
         [0018]    In the foregoing description, certain terms have been used for brevity, clearness and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed. Moreover, the description and illustration of the inventions is by way of example, and the scope of the inventions is not limited to the exact details shown or described. 
         [0019]    Certain changes may be made in embodying the above invention, and in the construction thereof, without departing from the spirit and scope of the invention. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not meant in a limiting sense.