Abstract:
A heat exchanger comprises a housing jacket and tube segments disposed concentrically inside the housing jacket. Between two receiving plates, closing the housing jacket on its face ends, the tube segments embody heating chambers and product chambers. While the product to be heated flows in a meandering course through the heat exchanger, the heating medium flows through the heat exchanger over short paths from a medium inlet stub, in the direction of a medium outlet stub. The heat exchanger of the invention is distinguished by a relatively simple construction and is especially suitable for compositions in the candy industry, using steam as the heating medium.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 35 USC 371 application of PCT/DE 02/01689 filed on May 10, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an improved heat exchanger for heating a product, in particular a composition for producing candies. 
   2. Description of the Prior Art 
   One heat exchanger of the type with which this invention is concerned is known from U.S. Pat. No. 5,246,062. In this known heat exchanger, the product is guided within parallel tubes of equal diameter disposed side by side. In the face-end closing elements of the housing jacket of the heat exchanger there are recesses, which together with the tubes form a meandering product path. The inlet for the heating medium is located in the upper part of the cylindrically embodied housing jacket, while the outlet is disposed in the lower part. A disadvantage of the known heat exchanger is that no defined flow path within the housing is created for the heating medium. Instead, the tubes that carry the product protrude transversely into the flow path of the heating medium, so that the heat transfer from the heating medium into the product, and hence the efficiency of the known heat exchanger, are not yet optimal. This is also due to idle spaces, through which heating medium flows only inadequately. Furthermore, a product when it is heated expands inside the tubes. Since the tube diameter for the product is always the same in the known heat exchanger, the pressure of the product thus increases steadily upon heating along the product path, which can lead to a shift in the boiling line of the product and to strength problems and necessitates appropriate dimensioning of the tubes. 
   From German Patent DE 29 07 770 C2, a heat exchanger is also known in which both the product and the heating medium are carried back and forth in a meandering course. However, a disadvantage here, among others, is its relatively complicated structure because of the various meandering flow paths. 
   SUMMARY OF THE INVENTION 
   The heat exchanger of the invention for heating a product, in particular a composition for producing candies, has the advantage over the prior art that because of defined flow paths for the heating medium, it has relatively high efficiency. Moreover, because of widening product path cross sections, it makes relatively little demand in terms of strength and counteracts the shift in the boiling line caused by an otherwise increasing pressure of the product. Finally, it is also structurally relatively simple. 
   If the chambers of annular cross section for the heating medium are closed off with annular closure plates, which in turn communicate with the receiving plates via tubes, then the meandering course for the product can be realized in a structurally simple way. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One exemplary embodiment of the invention is described in further detail below, with reference to the drawings, in which: 
       FIG. 1  is a heat exchanger of the invention in a simplified longitudinal section; and 
       FIG. 2 , a heat exchanger that is modified compared to  FIG. 1 , shown in an exploded view, with the face-end closure caps and several tube segments that embody the heating and product chambers left out. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The heat exchanger  10  shown in the drawings preferably serves to heat a composition for producing candies, such as a solution of sugar and glucose syrup, using steam as the heating medium. The heat exchanger  10  has an outer, preferably cylindrical or tubular housing jacket  11 . On each of the face ends of the housing jacket  11  there is a respective receiving plate  12 ,  13 , which completely covers the respective face end of the housing jacket  11  and is solidly joined to the housing jacket  11 . 
   Tube segments  14 - 20 , each of different diameters, are each disposed concentrically to one another inside the housing jacket  11 . The housing jacket  11  together with the tube segment  14  forms a first heating chamber  21 ; the two tube segments  15 ,  16  form a second heating chamber  22 ; the two tube segments  17 ,  18  form a third heating chamber  23 ; and the two tube segments  19 ,  20  form a fourth heating chamber  24 , the heating chambers  21 - 24  each being annular in cross section. The heating chambers  21 - 24  are bounded on their face ends by circular-annular closure rings or plates  27 - 34 . In the closure plates  27 - 34 , there are bores  36  that are aligned with tube segments  37 ,  38  that are disposed on the side of the closure plates  27 - 34  remote from the heating chambers  21 - 24  and that protrude sealingly into corresponding bores  39  in the receiving plates  12 ,  13 . On the side remote from the heating chambers  21 - 24 , the tube segments  37 ,  38  are flush with the end faces of the receiving plates  12 ,  13 . 
   In the exemplary embodiment, four tube segments  37 ,  38  disposed at regular angular intervals from one another, as can be seen particularly from  FIG. 2 , are connected to each of the closure plates  27 - 34 . To avoid idle spaces for the steam and to carry away the cooled, condensed steam, the arrangement of tube segments  37 ,  38  is selected such that at least one tube segment  37 ,  38  each is disposed in both the upper region and the lower region of the heat exchanger  10 . 
   It is also essential that each of the heating chambers  21 - 24  be coupled with respective short tube segments  37  on one side and respective long tube segments  38  on the opposite side. Moreover, the spacing between two closure plates  27 - 34 , facing one another, of a given heating chamber  21 - 24  is less than the spacing of the two receiving plates  12 ,  13  from one another. Moreover, the closure plates  27 ,  30 ,  31  and  34  communicating with the short tube segments  37  rest directly on the respective receiving plate  12 ,  13  oriented toward it, while the closure plates  28 ,  29 ,  32  and  33  communicating with the long tube segments  38  are spaced apart from the respective receiving plate  12 ,  13  oriented toward them. 
   The tube segment  20 , disposed centrally in the housing jacket  11  and communicating on one side with the closure plate  33 , penetrates the receiving plate  13  in a corresponding bore, and on the side opposite the closure plate  33 , it forms an inlet stub  41 , through which the composition to be heated enters the heat exchanger  10 . The interior of the tube segment  20  forms a first product chamber  42 . Other product chambers  43 ,  44  and  45 , each embodied annularly in cross section and disposed concentrically to one another, are located between the receiving plates  12 ,  13  and are defined by the tube segments  14 - 19 . The outermost product chamber  45  communicates with an outlet stub  46 , through which the composition to be heated emerges from the heat exchanger  10 . The communication with one another of the individual product chambers  42 - 45 , which as already explained are disposed concentrically to one another, is effected via the regions between the closure plates  28 ,  29 ,  32  and  33  and the respective receiving plates  12 ,  13  spaced apart from them. In these overflow regions between the individual product chambers  42 - 45 , only the long tube segments  38  are disposed, which only insignificantly impede any overflow of the composition from one product chamber  42 - 44  into the other product chamber  43 - 45 . 
   The receiving plates  12 ,  13  are covered completely, each by a respective convex closure cap  47 ,  48 , on the side remote from the heating chambers  21 - 24 . One closure cap  48 , together with the receiving plate  13 , defines an entrance chamber  49  for the heating medium, in particular steam, while the other closure cap  47  together with the receiving plate  12  defines an exit chamber  50 . While the inlet stub  41  and the outlet stub  46  penetrate the closure cap  48  without being in contact with the entrance chamber  49 , a medium inlet stub  51  communicates with the closure cap  48  and discharges into the entrance chamber  49 . At the bottom of the closure cap  47 , there is also a medium outlet stub  52 , which communicates with the exit chamber  50 . 
   In  FIG. 2 , the heat exchanger  10  just described is shown in an exploded view to illustrate its structure. In  FIG. 2 , for the sake of greater clarity, however, the closure caps  47 ,  48  and tube segments  17 ,  18  (which are located in the housing jacket  11  and are connected to the receiving plate  12 ) have not be shown. It can also be seen that compared to the heat exchanger of  FIG. 1 , in addition a helically embodied product guide baffle  55  is disposed on the outer circumference of the tube segment  15 . A further product guide baffle  56  is disposed on the outer circumference of the tube segment  19 . These product guide baffles  55 ,  56  are preferably disposed over the entire length of the corresponding product chamber  43 - 45  and also over the entire cross section of the applicable product chamber. With the product guide baffles  55 ,  56 , it is attained that the composition to be heated inside the applicable product chamber  43 - 45  does not flow over the shortest path from the inlet to the corresponding outlet but instead is guided helically along the corresponding product guide baffle  55 ,  56 , so that the flow path of the product or composition is lengthened and thus the flow time is also increased. 
   Moreover, although not shown, so-called mixing bodies may be disposed inside the product chambers  42 - 45 . These mixing bodies, which are already well known, are stationary bodies that serve to improve the mixing of the composition to be heated. 
   The heat exchanger  10  of the invention functions as follows: From a steam generator, not shown, the heating medium (steam) that is under pressure flows via the medium inlet stub  51  into the entrance chamber  49 , where it is distributed uniformly. Over the short tube segments  37  and the long tube segments  38 , the steam reaches the heating chambers  21 - 24 , in which the steam flows in the direction of the receiving plate  12 . The steam then leaves the heating chambers  21 - 24  via the short tube segments  37  and the long tube segments  38  to enter the exit chamber  50 . If after flowing through the heating chambers  21 - 24  the steam has been cooled below its condensation temperature, then the steam emerges as condensate in liquid form from the outlet stub  52 . Thus what is essential in terms of the flow course of the steam or heating medium is that the steam flow rectilinearly and thus in guided fashion through the heat exchanger  10  from the direction of one receiving plate  13  in the direction of the other receiving plate  12 . By comparison, the composition to be heated enters the heat exchanger  10  via the inlet stub  41  and the first product chamber  42 . From there, the composition to be heated flows radially outward via the closure plate  33  into the second product chamber  43 . In the second product chamber  43 , the composition to be heated flows back in the direction of the receiving plate  13 , where it flows radially outward via the closure plate  32  to enter the third product chamber  44 . In the product chamber  44 , the composition flows back in the direction of the receiving plate  12  again, where via the closure plate  29  it flows radially outward into the fourth product chamber  45 . From the fourth product chamber  45 , finally, the composition flows back in the direction of the receiving plate  13 , from where it flows through at least one corresponding opening into the outlet stub  46  and then out of the heat exchanger  10 . To illustrate the above-described meandering flow path of the product and of the composition to be heated, flow arrows  57  are shown in  FIG. 1 , which are meant to illustrate the course of the product through the heat exchanger  10 . If product guide baffles  55 ,  56  are present, then the product to be heated, as already described, does not flow inside the heat exchanger  10  over the direct course inside the product chambers  42 - 45 , but rather over helical courses. While the composition to be heated is flowing through the heat exchanger  10 , its temperature increases as desired, because a heat transfer takes place from the steam, flowing through the heat exchanger  10  in the heating chambers  21 - 24 , into the product chambers  42 - 45 . It is understood that this heat transfer can be varied by means of a suitable choice of material or the thickness of the individual tube segments  14 - 20 . Moreover, the heat transfer is dependent on the throughput quantity of the steam and on the length of the heating chambers  21 - 24 , the number of product chambers  42 - 45 , and the flow quantity of the product to be heated. 
   The heat exchanger  10  described above can be structurally modified in manifold ways. For instance, it is conceivable for the individual heating chambers  21 - 24  to be provided with separate medium inlet stubs, by way of which the heating medium can be carried into the heat exchanger  10  at different temperatures or pressures or with different flow directions. Moreover, a widening or narrowing cross-sectional course may be provided for both the heating chambers  21 - 24  and the product chambers  42 - 45 . The number of heating chambers  21 - 24  and product chambers  42 - 45  can also be different from what is shown and described here for the exemplary embodiment. Finally, it is also conceivable to provide a plurality of outlet stubs  46  for the product, which can optionally communicate with different product chambers  42 - 45  and by suitable connection can create product paths of various lengths. From a production standpoint, the heat exchanger  10  can be embodied either as a welded construction or as a construction that can be dismantled, with suitable screw connections and sealing connections. 
   The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.