Abstract:
Scraped surface heat exchanger, the shape of the chamber thereof and the positioning and direction of feed and discharge conduits opening into said chamber being such that, on feeding a liquid through these conduits and the chamber, the flow of said liquid will cover the entire chamber.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a scraped surface heat exchanger having a cylindrical chamber surrounded by heat-exchanging means, at least one feed conduit and at least one discharge conduit for feeding and discharging a product to be treated in that heat exchanger being connected to said chamber, and a rotor provided with scraper elements being rotatably arranged in said chamber. A heat exchanger of this type is known from U.S. Pat. No. 2 188 551. 
     For reasons of increasing hygienic standards and the cleanability of food processing equipment, there is a continuing need for improved heat exchangers of the above type, and in particular equipment suited for in-line cleaning, whereby the frequency of the equipment having to be taken apart may be reduced. 
     It is an aim of the invention to improve the hygiene and the cleanability of the above type of heat exchangers, thereby requiring them to be taken apart at less frequent intervals. 
     Other objects and advantages of the invention will become apparent as the specification proceeds. 
     SUMMARY OF THE INVENTION 
     With the above objects in view, the invention provides a heat exchanger as described hereinbefore, wherein the shape of the chamber is designed such that, and the feed and discharge conduits are arranged such that, on feeding a liquid through said conduits and the chamber, this fluid will be guided in a flow covering the entire chamber. To put it in other words, this means that no dead spots remain if the fluid is fed through the heat exchanger. 
     In an embodiment giving good results in practice, the feed and discharge conduits are arranged such that they put the fluid in a helical flow in the chamber. To that end, these conduits have in particular a tangentially directed component with respect to the cylindrical chamber. 
     It is advisable to give the flow a certain pitch, for which, in a preferred embodiment, said conduits are arranged at a sharp angle with respect to the axis of the chamber. Said angle is preferably from 25° to 70°, and in particular from 40° to 50°. 
     To prevent the disturbance of the flow as much as possible, it is preferable that any joints opening into the chamber, as well as any seals, do not give rise to discontinuity in the internal surface of the chamber. 
     For reliably flushing the chamber with cleaning liquid and removing cleaning liquid and product to be treated as completely as possible, it is advisable that each of the feed and discharge conduits should open into one of the end plates at diametrically opposite positions in a vertical plane and adjacent to the cylindrical wall of the chamber. 
     For testing the tightness of hollow parts, these parts are preferably provided with a conduit leading to the outside of the heat exchanger and communicating, with the cavity inside the part so that the conduit may be closed if required. With this provision, the tightness of said part and the absence or presence of pores, cracks and similar defects may be tested. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be illustrated in the annexed drawings, which is given by way of example only. In the drawings 
     FIG. 1 is a schematic longitudinal section along the line I--I in FIG. 2 showing a heat exchanger according to the invention, 
     FIG. 2 is a front view from the feed end, 
     FIG. 3 is a front view from the discharge end, and 
     FIG. 4 is a cross-sectional view along the line IV--IV in FIG. 1. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the drawings a preferred embodiment of a heat exchanger according to the invention is shown, which heat exchanger is suited, for instance, for manufacturing ice cream. This heat exchanger is provided with an elongate cylindrical chamber 1, mainly confined by a cylindrical wall 2 and two end plates 3,4. One end wall 3 is provided with a feed conduit 5 and the other 4 with a discharge conduit 6 for feeding and discharging, respectively, a product to be treated in the chamber 1. When seen in side view (see FIG. 1), these conduits are at a sharp angle with respect to the axis of the chamber and, when seen in axial view (see FIG. 2 and 3), these conduits are tangentially arranged in the same rotational sense. The feed conduit 5 is arranged at the lowermost and the discharge conduit 6 at the uppermost point of the chamber, in order that any air may escape during use of the heat exchanger while, after shutting down, all liquid will drain off. An additional result is that the entire chamber may be flushed with a liquid and that no dead spots ar formed. 
     A hollow cylindrical rotor 8, provided with scraper blades 7 bearing against the inner wall of the chamber 1, is rotatably arranged in said chamber. In a preferred embodiment, the scraper blades 7 are attached to the rotor 8 as shown in FIGS. 1 and 4. The blades 7 extend axially in the chamber 1 as illustrated in FIG. 1, and as is known in the art to optimize the efficiency of the heat exchanger. The rotor 8 is, at one end, supported by the driving shaft 9, which is rotatably supported in a bearing 10 arranged in the end wall 3. At the other end, the rotor 8 is rotatably supported by a fixed hollow shaft 12 by the intermediate of a suitable bearing 11. 
     In a preferred embodiment shown in FIG. 4, the rotor 8 is provided with a plurality of gaps 8&#39; in the wall of the rotor 8. These gaps 8&#39; may be spaced in the rotor wall as shown in FIG. 4 and as is conventionally known in the art. It may be appreciated that the rotor wall may be constructed without any gaps. 
     The hollow shaft 12 is fixed to the end wall 4 by means of a bolt 13 having an axial bore, which shaft also supports the eccentrically rotatable beater 14, having longitudinal slits arranged in a usual manner, which beater may also be static. By means of the bore 15 in the bolt 13, pressure-testing gear may be connected for testing the tightness of the hollow shaft 12. 
     In the drawing it is clearly shown that surfaces which are exposed to the product to be treated, are connected through rounded corners and are devoid of grooves and ribs and which generally have a smooth shape. Joints between different parts, such as between the cylindrical wall 2 and the end wall 3 are designed such that no discontinuity in the total surface results. Any seal 16 arranged in this joint should conform to this requirement, too. 
     The heat exchanger is, in a usual manner, provided with a jacket 17 for a refrigerant or heating medium.