US3835922A

US3835922A - Heat exchanger for fluent masses

Info

Publication number: US3835922A
Application number: US00343406A
Authority: US
Inventors: R Raths
Original assignee: LINDT AND SPRUENGLI SCHOKOLADE
Current assignee: LINDT AND SPRUENGLI SCHOKOLADE
Priority date: 1972-03-30
Filing date: 1973-03-21
Publication date: 1974-09-17
Anticipated expiration: 1991-09-17
Also published as: JPS497841A; GB1378996A; CH551605A; DE2215536C2; DK153277B; DE2215536A1; IT980450B; DK153277C

Abstract

A heat exchanger for flowable or fluent masses or media, comprising a hollow cylinder surrounded by a cooling or heating jacket, and a rotor coaxially arranged with respect to the hollow cylinder, rotatable relative thereto, and bounding together with the hollow cylinder a gap. The rotor carries scraper or stripper elements cooperating with the heat exchange surface of the hollow cylinder at the gap, these scraper elements serving to prevent the deposition of particles of the media at the surface. The scraper elements are constructed as plates arranged parallel to tangential planes of the rotor, these plates being radially displaceably guided at the rotor. The plates can be pressed by elastic means against the heat exchange surface of the hollow cylinder so that they bear thereagainst by means of two parallel lengthwise extending edges.

Description

United States atent i 1 Raths [4 1 Sept. 17, 1974 HEAT EXCHANGER FOR FLUENT MASSES [75] Inventor: Rudolf Raths,1(ilchberg,

Switzerland [22] Filed: Mar. 21, 1973 [21] Appl. No.: 343,406

[30] Foreign Application Priority Data Primary Examiner-Manuel A. Antonakas Assistant Examiner-Theophil W. Streule Attorney, Agent, or Firm-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT A heat exchanger for flowable or fluent masses or media, comprising a hollow cylinder surrounded by a cooling or heating jacket, and a rotor coaxially arranged with respect to the hollow cylinder, rotatable relative thereto, and bounding together with the hollow cylinder :1 gap. The rotor carries scraper or strip- Mar. 30, 1972 Germany 2215536 per elements cooperating with the heat exchange sur- 52 U.S. Cl. 165/94, 62/354 face 0f hollow cylinder at P: t [51] Int. Cl. F281 17/00, F28g 3/12 elements E to Prevent the deposmon of parades [58] Field of Search 259/DIG. 18, 32, 34; the med"! at the Surface The elements f l65/86 94 9 62/342 3 6 354 2 4 constructed as plates arranged parallel to tangential l planes of the rotor, these plates being radially dis- [56] References Cited placeagly) guided at the rotor. Tltile tplates C111 be resse e astic means against t e eat exc ange UNITED STATES PATENTS Surface of the hollow cylinder so that they bear there- 2,449,012 9/1948 Schley 165/94 X against by means of two parallel lengthwise extending 3,035,420 5/1962 Stoelting et al edges 3,395,419 8/1968 Munlist et a1 3,587,729 6/1971 Eisenmann 165/94 9 Claims, 6 Drawing Figures I E 1 *2 M i w a N m PAIENIED SEP I 71974 mamzz PAYENIED am 71974 sum ear 3 HEAT EXCHANGER FOR FLUENT MASSES BACKGROUND OF THE INVENTION The present invention relates to a new and improved construction of heat exchanger for fluent or flowable masses or media, comprising a hollow cylinder surrounded by a heat exchange jacket i.e. a cooling or heating jacket, and a rotor coaxially arranged with respect to the hollow cylinder and delimiting with respect thereto a gap or annular space, the rotor being rotatable relative to the hollow cylinder, and further being provided with stripper or scraper elements cooperating at the region of the gap with the heat exchange surface of the hollow cylinder for preventing the deposit of particles of the treated media at the surface.

This piece of equipment is especially intended for the pre-crystallization treatment of molten chocolate masses which, during a subsequent treatment, should be homogeneously solidified and finely crystallized in a state which is as free of thermal energy as possible, in order to obtain final products possessing a hard crunchy break or fracture characteristic and a protective luster as well as good durability or shelf-life. To this end there is required cooling of the mass in the presence of intimate mechanical admixing, by means of which also the heat of fusion (latent heat) must be removed as extensively as possible, and there is brought about crystallization in a crystalline state which is as poor as possible in thermal energy. For cooling there can be only employed low temperature gradients, and

, the particles which have crystallized must be prevented from depositing at the heat transfer or exchange surfaces and growing in size beyond a certain magnitude.

The objective of the invention starts with this in mind and aims at providing a heat exchanger in which all of the particles of the mass or medium are maintained in an intensified movement and uniformly brought into contact with the heat exchange or transfer surface. As

is known, these prerequisites can be fulfilled in an advantageous manner if the fluent mass is guided through a narrow gap, the opposed walls of which are moved relative to one another in the lengthwise direction of the gap, so that there can be generated at the mass in the gap a large velocity gradient transversely with respect to the gap.

In the case of state-of-the-art heat exchangers for molten chocolate masses which operate according to this principle, for instance as exemplified by German patent 950,976 and German patent publication 1,145,468, a cylindrical rotor revolves coaxially within a stationary double-wall hollow cylinder, the inner jacket surface of which is designed as a heat exchange surface. This rotor carries a number of scrapers constructed as flat ledges of rectangular cross-sectional configuration and which continuously wipe the aforementioned heat exchange surface so as to scrape away the mass which deposits thereon. These scrapers extend in radial direction over a large part of the gap area between the rotor surface and the heat exchange surface.

These prior art machines therefore possess compartments or chambers of large radial width which are bounded at the outside by the stationary heat exchange surface, at the inside by the rotor surface, and with respect to the peripheral direction at the front and rear partially by the scrapers which revolve with the rotor. These compartments are interconnected by through passages of slight radial width which are bounded at the inside likewise by the rotor surface, at the outside however by the confronting surfaces of the scrapers connected with the rotor.

Hence, neither at the compartments nor at the passages do there exist to be processed large radial velocity gradients of the mass; in the compartments the cylindrical boundary surfaces which move relative to one another are spaced at a relatively great distance from one another, whereas the boundary walls of the passages conjointly revolve about the axis of the rotor.

SUMMARY OF THE INVENTION Hence, with the foregoing background in mind, it is a primary object of the present invention to provide a new and improved construction of heat exchanger of the aforementioned general type in which the width of the gap area or gap is more uniform and smaller and in which therefore there occur, at a greater part of the periphery, higher radial velocity gradients and therefore a more intensive mechanical admixing and a more uniform heat exchange than is achieved with the aforementioned state-of-the-art heat exchangers.

Now in order to implement this object, and others which will become more readily apparent as the de scription proceeds, the invention provides the scraper elements in the form of plates arranged substantially parallel to tangential planes of the rotor, these plates being radially displaceable guided at the rotor and being urged by elastic means against the heat exchange surface of the hollow cylinder, so that they come to bear thereagainst by means of two lengthwise extending edges.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood, and objects other than those set forth above will become apparent, when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is a longitudinal sectional view of a heat exchanger designed according to the present invention, taken substantially along the line II of FIG. 2;

FIG. 2 illustrates the heat exchanger depicted in FIG. 1 in cross-sectional view, taken substantially along the line II--II of FIG. 1;

FIG. 3 is a cross-sectional view of the heat exchanger depicted in FIG. 1, taken substantially along the line IIIIII thereof;

FIG. 4 illustrates a detail of the heat exchanger depicted in FIG. 2 on an enlarged scale;

FIG. 5 is a partial variant of the heat exchanger depicted in FIGS. 1 to 4, and illustrated in cross-sectional view analogous to the showing of FIG. 4; and

FIG. 6 is a further partial variant, on an enlarged scale, and in longitudinal sectional view analogous to the upper half of the showing of heat exchanger depicted in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The exemplary embodiment of heat exchanger depicted in FIGS. 1-4 embodies a housing in the form of a hollow cylinder 1 which is composed of, for instance, three successively arranged double-

wall housing sections

1a, 1b and 1c, This housing 1 is closed at each of its ends by means of a suitable closure of cover member 4, only one of which is shown.

The hollow cylinder sections la, lb and 1c possess flanges at their respective ends, and by means of these flanges 5 they can be sequentially connected with one another and the cover members 4 by screws 5a or equivalent fastening expedients. Their inner and

outer walls

6 and 7 respectively collectively delimit or bound an annular jacket compartment or chamber 8, which by means of infeed and outfeed lines or conduits 2 and 3 respectively can be selectively supplied with a suitable heat exchanger medium, in other words a cooling or heating medium, for instance cold or hot water, in order to remove or introduce, as the case may be, heat from or to an inner surface 9 of the hollow cylinder 1; this inner surface 9 forms the heat exchange surface of the machine.

Now at both of the cover members 4 there is rotatably mounted a rotor shaft 10 which can be driven in any suitable and therefore not particularly illustrated manner at a low rotational speed, typically for instance by using a suitable drive motor. This shaft 10 carries a rotor 12 which is of essentially cylindrical configuration, but however is flattened for instance at three locations 11 of its periphery over its entire length. The diameter of the rotor 12 at a cylindrical rotor portion 13 between the flattened portions 11 is somewhat less than that of the enclosing heat exchange surface 9 of the hollow cylinder 1.

At this region the rotor jacket surfaces 13 and the heat exchange surface 9 delimit along their entire lengths a rather narrow substantially annular gap or space 14 which is intended to receive a flowable or fluent mass or medium, which has been depicted in the drawings by dot-like points.

In order to prevent deposits of particles of such mass at the heat exchange surface 9 of the hollow cylinder, there is mounted at the rotor 12, at each section 1a, lb, 10 of the hollow cylinder 1, a rectangular plate-shaped scraper 15 over each flattened portion 11 of the rotor jacket or outer surface. Both longitudinal or lengthwise extending edges 16 of each of the scrapers 15 is bevelled or tapered, as shown, at the side confronting the rotor 12 so as to form cutting or knife edges 17, as best seen by referring to FIG. 4.

In the embodiment depicted in FIGS. 1, 2 and 4 the substantially plate-shaped scrapers 15 are each guided at two respective plugs or pins 18 secured by means of nuts 19 in recesses 20 of the confronting flattened portion 11 in such a manner that they are located perpendicular to the axis of the associated recess. Between the floor of each recess 20 and the associated scraper 15 there is inserted a respective or spiral spring 21 which surrounds the associated plug or pin 18. These springs 21 serve to press the associated scraper 15 towards the outside against the heat exchange surface 9 of the corresponding hollow cylindrical section 1a, lb, 10, so that its cutting edges 17 come to bear against the surface.

By means of lock washers or spring rings 26, each of which is seated in a suitable annular or ring-shaped groove provided at the region of the outer end of the corresponding plug or pin 18, the scrapers 15 are thus fixedly retained at the rotor 12 when this has not yet been assembled into the hollow cylinder 1.

Between the neighboring sections 1a, lb and 1c of the hollow cylinder 1 there are inserted metallic ring members 22 having rib members 24a and which are centered, by means of their outer edges, in machined recesses or apertures 23 of the hollow cylinder end surfaces, and which extend by means of their inner edges 24 over the major portion of their periphery up to the region of the cylindrical outer or jacket surface 13 of the rotor 12, as best seen by referring to FIG. 3. Each ring member 22 is provided at the same angular spacing from one another and extends somewhat over more than the width of each scraper 15 with a respective recess or intermediate space 25 which extends to a point behind the heat exchange surface 9 of the hollow cylinder 1.

These recesses 25 of the individual ring members 22 on the one hand, and, on the other hand, the individual scrapers 15 are axially aligned with respect to one another so that the rotor 12, in a suitable rotational position, together with the scrapers 15, and following removal of one of the cover members 4, can be introduced from an end of the hollow cylinder 1 into the latter, and wherein the scrapers 15 are displaced or shifted through the recesses 25 from one hollow cylinder section 1a, lb, 1c into the next hollow cylinder section.

In the variant embodiment depicted in FIG. 5, there are provided, instead of the plugs 18 seated at the rotor 12, two pin members 27 at each scraper 15, which are fixedly connected with the scraper and which extend through a bore 28 towards the inside of the wall of the rotor 12. At this location each pin 25 is provided with a collar 29 at which engages a pressure spring 30 or equivalent. This spring 30 bears by means of its other end against the floor of a spring housing 31 which is secured to the rotor wall. By means of the collar 29 and the pin member 27 the spring 30 presses the associated scraper 15 against the heat exchange surface 9.

According to a further embodiment, as depicted in FIG. 6, there is threadably connected or riveted to each flattened portion 11 of the rotor 12 a blade spring 32 between both of the recesses 20, in which there is seated a respective plug or pin 18 guiding the scraper 15. Both ends 33 of the blade springs 32 are flexed in the direction of the scraper 15 and press the same, in addition to the action exerted by the helical springs 21, against the heat exchange surface 9 of the hollow cylinder 1.

During operation of the machine, for instance for the pre-crystallization of a fator chocolate molten mass, this mass is continuously introduced in a completely molten state, for instance by means of an infeed or delivery conduit 35 connected with one end closure or cover member 4, into the annular gap or slot 14 between the heat exchange surface 9 and the rotor jacket or outer surface 13. In this annular gap 14 the mass, during rotation of the rotor 12, is entrained by frictional forces at the

rotor surfaces

11 and 13 and at the inside of the scrapers 15 which revolve therewith, whereas it is braked between the scrapers and the stationary heat transfer or heat exchange surface 9 and therefore placed into a state of turbulent movement.

Since the ring-shaped or annular gap 14 only possesses a slight width in radial direction, there are formed numerous small turbulent flow pockets by means of which all of the particles of the mass are continuously brought into contact with the heat transfer or exchange surface and again removed therefrom. It is therefore possible to remove large quantities of heat or thermal energy with only slight temperature differences between the mass in the ring-shaped or annular gap 14 and the cooling agent in the jacket compartment 8.

Owing to the flat plate-shaped construction of the cutting edges 17 it is additionally prevented that, during cooling, solidified particles will remain adhering at the heat exchange surface 9 or will dam up and collect in front of the scrapers l5. Quite to the contrary, they are continuously conveyed back into the fluent mass or medium as long as such particles are of small size.

The mass treated in this manner in one section, for instance the section 1c of the hollow cylinder 1, and with sufficient infeed pressure, will be gradually conveyed through the recesses 25 of the corresponding ring member 22 which closes that section and then into the next hollow cylinder section, for instance the section 1b, and so forth, until it reaches the non-illustrated opposite end of the hollow cylinder 1. At this location the mass, which is just still fluent and finally crystallized, will be removed at a conduit or pipe connected with the end cover member of the hollow cylinder 1 and conveyed for its further processing.

It has been found that masses treated in this manner crystallize in the form of very fine particles and in particular in a form possessing low thermal energy content so that they remain still relatively fluent or flowable even with pronounced heat withdrawal. They solidify during further removal of heat after leaving the equipment into products possessing hard crispy or cracking rupture characteristics and a pleasing luster, something which is desired for many chocolate products, but also or other foodstuffs.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced. Accordingly,

What is claimed is:

l. A heat exchanger for the pre-crystallization of fluent media, comprising: a hollow, substantially horizon tal cylinder having a heat-exchange surface; a cooling or heating jacket surrounding said cylinder; a substantially horizontal rotor arranged within, substantially coaxial with, and rotatable relative to said cylinder, and delimiting therewith a narrow gap; said rotor being provided at the region of said gap with scraper elements cooperating with said heat-exchange surface for preventing thereat deposits of particles of the media; said rotor having a substantially cylindrical configuration with the exception of flattened portions at the region of said scraper elements, said flattened portions allowing to provide said narrow gap, between said cylinder and said rotor, which ensures good crystallization of the media; said scraper elements including plate members arranged substantially parallel to tangential planes of said rotor, and being tapered at their lengthwise edges on the side confronting said rotor; means for radially displaceably guiding said scraper elements at said rotor; and elastic means for urging said plate members against said heat-exchange surface so that the former bear against the latter by means of two substantially parallel lengthwise edges of said plate members.

2. The heat exchanger as defined in claim 1, wherein said scraper elements only extend over a part of the length of said rotor which is separated from an axially neighboring part by means defining a zone at which extend ribs over a respective part of said periphery of said cylinder, radially towards said rotor.

3. The heat exchanger as defined in claim 2 wherein said ribs are separated from one another by intermediate recesses which are wider than associated neighboring ones of said scraper elements.

4. The heat exchanger as defined in claim 2, wherein said cylinder consists of a number of sections, and said ribs include projections formed by ring members inserted between neighboring ones of said sections.

5. The heat exchanger as defined in claim 1, further comprising radially extending plugs fixedly connected with said rotor for guiding said scraper elements.

6. The heat exchanger as defined in claim 5, further comprising helical pressure springs arranged coaxially with respect to said plugs between said rotor and said scraper elements. 7. The heat exchanger as defined in claim 1, wherein said rotor is provided with radial bores, and pin members with which said scraper elements are connected, said pin members being guided to be lengthwise displaceable in a radial bore of said rotor.

8. The heat exchanger as defined in claim 7, further comprising helical pressure springs cooperating with said pin members.

9. The heat exchanger as defined in claim 1, further comprising a blade spring arranged between said rotor and each one of said scraper elements, and which presses the associated one of said scraper elements towards the outside and against said heat-exchange surface.

Claims

1. A heat exchanger for the pre-crystallization of fluent media, comprising: a hollow, substantially horizontal cylinder having a heat-exchange surface; a cooling or heating jacket surrounding said cylinder; a substantially horizontal rotor arranged within, substantially coaxial with, and rotatable relative to said cylinder, and delimiting therewith a narrow gap; said rotor being provided at the region of said gap with scraper elements cooperating with said heat-exchange surface for preventing thereat deposits of particles of the media; said rotor having a substantially cylindrical configuration with the exception of flattened portions at the region of said scraper elements, said flattened portions allowing to provide said narrow gap, between said cylinder and said rotor, which ensures good crystallization of the media; said scraper elements including plate members arranged substantially parallel to tangential planes of said rotor, and being tapered at their lengthwise edges on the side confronting said rotor; means for radially displaceably guiding said scraper elements at said rotor; and elastic means for urging said plate members against said heat-exchange surface so that the former bear against the latter by means of two substantially parallel lengthwise edges of said plate members.

6. The heat exchanger as defined in claim 5, further comprising helical pressure springs arranged coaxially with respect to said plugs between said rotor and said scraper elements.

7. The heat exchanger as defined in claim 1, wherein said rotor is provided with radial bores, and pin members with which said scraper elements are connected, said pin members being guided to be lengthwise displaceable in a radial bore of said rotor.