FI102412B - Heat exchanger - Google Patents

Abstract

Heat exchangers of high performance and high hygiene levels are produced from steel and galvanised. It has been found that a more stable and resistant structure is achieved by constructing the heat-transferring ribs by means not of plates, but of sheets 19 to 21, 23 to 25 arranged in a multiplicity of rows. The alternating use of sheets of different width permits different dividing spacings of the sheets to be achieved in the direction of passage of the air to be cooled, without the need arising for a corresponding number of gaps acting as balancing zones. Due to the elimination or substantial reduction of the number of gaps, the latter can be held so wide without essential impairment of the thermal performance that metal bridges are avoided in the case of galvanisation and the settling of foreign bodies which impair hygiene is suppressed during operation. <IMAGE>

Description

102412 Heat exchanger Värmeväxlare 5

The present invention relates to a high-efficiency steel heat exchanger, in particular for the immediate freezing of foodstuffs, by means of a plurality of S-shaped tubes connected to each other by means of tubular arches , provided with recesses formed in a row, the edge regions of which project laterally in a collar-like manner.

The following reference publications are known from the prior art: GB patent 783,925, FR patent 15,180,908, DE patent 22 39,086 and JP application publication 58-136992. From these publications, heat exchanger structures comprising lamellae are generally known.

For example, the immediate freezing of foodstuffs in connection with continuous production requires hygienically sound heat exchangers, the use of which requires correspondingly large heat-exchanging surfaces. Usually, the groups formed by tortuous parallel tube coils are formed together and provided with lamellae that improve heat transfer through large surfaces. Also, in order to obtain a structure 25 which is mechanically resistant and chemically resistant to effective cleaning agents and thus meets the highest hygiene requirements, the pipe coils and the lamellae passing through them must be made of steel and stabilized by hot-dip galvanizing connecting and protecting the pipe and lamellae.

Since the flowing air is passed through in a periodic manner as it absorbs considerable moisture from the material to be frozen, the lamellae associated with the cooling coils are placed on the intake side at relatively large distribution intervals and only the following parts in the air flow direction at narrower distribution intervals. This arrangement has the advantage that the latter parts result in considerably large heat transfer surfaces, while the intake air is dehumidified at the intake side, thus avoiding frost crystals deposited on the lamellae due to separated water, which may prematurely increase the distance between the lamellae. premature defrosting period is necessary.

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Generally, in the case of steel heat exchangers, each tubular coil is provided with a strip-like lamella extending over it, but strip-like lamellae are also used which contain two, or in some cases three, recess rows and can thus be used for two or up to three tubular coils. Unfortunately, however, it has been found that these lamellae, arranged one after the other in the direction of air flow, are not at the same levels, even with predetermined regular pitches, but are statistically displaced relative to each other due to the inevitable tolerances during manufacture. In order to avoid shrinkage of the passage between the two lamella strips due to the next lamella strip 15, it is required that the lamella strips be made with smaller widths so that there are change zones between them, which also detrimentally limit the total number of lamella surfaces for heat exchanger operation. Usually, in the case of heat exchangers, the inlet zone also causes difficulties, in connection with which, due to the accumulation of frost, it is necessary to select such large distribution lines that they can no longer be implemented in practice in the case of collar-shaped recess locks. In general, the lamellae, the dividing points of which exceed the maximum height of these collar-like shoulders, are provided with wooden strips which secure the distribution distance when the lamellae are placed. However, after the removal of these strips, embarrassing and detrimental shifts can occur during transport and additional work steps, such as hot-dip galvanizing.

It is therefore an object of the present invention to further develop lamellas of the kind described for steel heat exchangers, so that the required number of heat transfer surface-reducing exchange zones is reduced to a minimum value and at the same time lamella distances exceeding possible collar height are ensured.

This object is achieved by placing a larger number of parallel tube coils 3 102412 through their common waves in the form of a thin metal plate. • In this case, it has proved expedient to place the lamellae at short intervals in at least one common width range with this division interval. On the other hand, it is also possible to use lamellas of different widths, which are arranged periodically in alternating ways to form several width ranges with different pitches. In either case, however, thin metal plates containing more than six rows, each with at least fifteen recesses, are used.

The heat exchanger according to the invention is characterized by what is stated in the claims.

The individual characteristic features of the invention will become apparent from the following description of an exemplary embodiment thereof with reference to the accompanying drawings, in which: Figure 1 is a partial view of a tubular coil with lamellae;

Figure 2 shows a fragmentary cross-section of a lamella with a recess;

Figure 3 shows a lamella formed by a thin metal plate; 20

Figure 4 shows a schematic perspective view of a heat exchanger;

Figure 5 shows a schematic perspective view of another heat exchanger; Fig. 6 shows a similar view for comparing the lamella arrangement included in the heat exchanger; . · A

Figure 7 shows the lamella arrangement in an enlarged section taken from Figure 6.

Fig. 1 shows a schematic, broken and mid-sectional view of a single sintered tube coil 1. It comprises tubes bent like a hairpin, the straight branches of which are called inner tubes, the free ends of the two inner tubes being 4 102412 always connected The inner tubes can receive heat transfer lamellae 4. Figure 2 shows a section of an enlarged, cut and cut on both sides of the lamella. For the placement of the inner tubes, recesses 5 are formed, the edge areas of which are stamped, pressed or in some other way formed into collar-like surrounding shoulders 6, which define the distance between adjacent lamellae rows in length and thus their spacing. The slightly conical constriction of the free end of the shoulder 6 helps to push the lamella 5 into the inner tube 2 by means of a somewhat funnel-shaped open recess 5. At the same time, this taper of the shoulder 6, in connection with the corresponding compression fitting of its free end, also allows installation at distances exceeding the maximum length of the shoulder 6, so that the lamella setting positions can be ensured without the need for wooden strips or the like. The slight additional annular expansion in the region of the recess 5 provides secure grip with the free end of the shoulder 6 of the previous lamella 4 15 without the risk of cracking of these free ends due to their deformation cracks, and in any case fixed expanded abutment surfaces for hot dip galvanizing.

In the case of large heat exchangers, strip-like lamellae are usually used, which are only sometimes provided with a row of recesses 5 and which extend, for example, over a single coil of tubes. However, when in the case of adjacent rows of lamellae 4 in the inner tubes 2, the shoulders 6 of which define the distances between the lamellae and thus their spacing, these distances can only be maintained within the additional tolerances 25, the heat exchanger is not normally located in one successive air or less in relation to each other in succession. In this case, however, the free flow space for air becomes divided and separated, and the successive lamellae at the opposite ends of the air flow are provided with narrow distances which retain locally so that the separated water deposited as frost can block the flow channels prematurely. The strip-like lamellae of the tubular coils are thus formed so narrow that there is a free space between them which acts as a change zone, which is preferably a multiple of the distribution interval and ensures an air flow 5 and a new distribution through the lamellae. In this case, however, the surfaces defining the heat transfer become harmfully limited.

In the case of heat exchangers made of steel, strip-like lamellae are also used, which are provided with two rows of recesses and, in exceptional cases, also with three rows of recesses, whereby they connect two or three pipe coils, respectively. In this case, however, the heat transfer surfaces only increase gradually as the free exchange zones between some of the strip lamella groups are frozen.

According to the invention, however, plate-like lamellae made of thin steel sheet are used instead, which contain at least as many rows 8 according to the recesses 5 as the heat exchanger part of the heat exchanger with the same lamellar division, while the rows 8 have as many recesses 5 In Figure 3, these thin metal plates 7 are shown in discontinuous form and contain only six rows 8, while only seven recesses 5 are shown in one row.

Figure 4 shows a heat exchanger made according to the invention, the thin metal plates being shown, however, only in part for the sake of clarity. The heat exchanger according to this figure 25 comprises a plurality of three-screw coils arranged in series, three connections 11 being connected to each of the refrigerant supply and discharge devices 9 and 10, only partially and symbolically shown by the inner tubes 2 connected to one tube 3,12 and 13, connecting different distances. The tube coils are held together 30 by means of end plate plates 14 tightened on both sides thereof.

The lamellae contained in the heat exchanger are arranged along the entire length of the inner tubes at the same 6 102412 pitch intervals, however, as already mentioned above, the figure shows, for the sake of clarity, only two groups formed by these lamellae. In the direction of air flow indicated by the arrow 15, three parts 16, 17 and 18 follow each other in succession, within which different spacing intervals of thin metal plates are used.

5, the foremost part in the direction of arrow 15 of 16 is provided in this exemplary embodiment jakoväliltään 18 mm in four coiled pipe, the next part 17 comprises seven jakoväliltään 9 mm in a pipe, the last section 18 comprising twelve o'clock jakoväliltään 7 mm in a pipe. This stepwise tapering of the air flow direction takes into account the rather strong separation of water during the first cooling, which then weakens during the subsequent cooling of the air flow.

Part 17 includes alternating thin metal plates 19 and 20 extending over the entire area of part 17 as well as part 16. In this way, the advantage is obtained that within part 17 15 mm spacing is determined by the collar-shaped shoulders 19 and 20 receiving the inner tubes 2 of the metal plates 19 and 20. 6, and since every other metal plate 20 further extends into the region of the part 16, a double pitch is maintained in this connection. This 18 mm pitch could no longer be achieved by means of the collar-shaped shoulders 6, since they cannot be formed so strongly as the collar-shaped shoulders. If separate metal plates are desired, aids to ensure this distance should therefore be used. According to the invention, this operation is avoided by ensuring the lamella spacing by means of the collar-shaped shoulders 6 of the alternating metal plates 19 and 20, whereby the metal plates 20 further extend to the part 16 and thus maintain a double spacing therein as well. Further stabilization is achieved by a light compression fit of the end regions of the conical shoulder 6.

"The part 18 includes narrow partitions and thus substantially heat-transmitting surfaces. In this exemplary embodiment, the metal plates 21 placed therein are provided with twelve rows 8, each having five recesses 5 for the inner tubes 2, the collar-shaped shoulders 6 surrounding the recesses 5 projecting 7 mm and thus ensuring the spacing of the lamellae in place.

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When moving from the part 16 to the part 17, no special measures are required, because the metal plates 12 extend in one piece and thus in a straight line in the area of both parts. Between the parts 17 and 18, between the opposite ends of the metal plates 19 and 20 on the one hand and the metal plate 21 on the other hand, a free gap 22 is kept as a change zone 5 to allow air to flow from the part 16 to the part 17 without bottlenecks. Because the heat exchanger is provided with only one such gap 22 between the metal plates, it can be fabricated to a width that reliably prevents bridge formations caused by blown food waste or frozen accumulated water during galvanizing or operation. When other exchange zones between the parts are omitted, in addition to facilitating the setting of the metal plates, the spaces available for heat transfer surfaces can be used in the best possible way during manufacture.

After the lamellae have been placed in place, the heat exchanger is made ready for use in a manner known per se: the second end plate 14 is pushed and fastened in place and the pipe arches 3, 12 and 13 are welded in this connection to three rings, i.e. for pipe coils with three separate conduits. In the case of such heat exchangers, especially due to the hygienic requirements, generally steel pipe coils, assemblies and lamellae or thin metal plates, respectively, are then protected against corrosion, for example by galvanizing, whereby suitable galvanizing and, for example, hot-dip galvanizing . Harmful zinc bridge formation is virtually avoided or reduced to a minimum by a single gap 22.

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Fig. 5 shows a heat exchanger application corresponding to Fig. 4, in which the slots 22 contained in the heat exchanger according to Fig. 4 can be completely omitted. In this case, the metal plates 23 extend over the entire depth of the heat exchanger, the metal plates 24 are made shorter, and the metal plates 25 are even lower. In this case, the widest spacing of the metal plates 23 is reached on the inlet side 30 from the air flow arrow 15, while in the following areas the metal plates 23 and 24 have alternating half-spacing, and on the outlet side the metal plates 23, 24 and 25 have the smallest spacing and the number of heat transfer surfaces.

Fig. 6 shows, for comparison, a heat exchanger comprising, in a known manner, one vertical lamella 26 for each of the two planes of tubular coils.

5 These lamellae are arranged in individual or successive rows with different pitches and separated from each other by slots 27 to form a plurality of smoothing zones. Since nine sequentially arranged lamella groups are used in connection with this exemplary embodiment of the usual construction, this embodiment includes eight slits which are kept narrow to reduce the reduction of heat transfer surfaces. In this case, as can be seen from the enlarged part shown in Fig. 7, there is already a risk of zinc bridges 28 being formed during galvanizing and the risk of stratification of foreign objects brought by cooling air during use, which is further increased by zinc bridges already formed.

A characteristic feature of the heat exchanger according to the invention is that the space is used efficiently and also that the response surface of the water separated during cooling is distributed in an advantageous manner, the downtimes caused by remelting and cleaning the heat exchanger occurring only after longer operating periods. increases. The required cleaning operations can also be carried out more easily and completely than in currently known heat exchangers, mainly due to smooth surfaces and the avoidance of additional front surfaces, as well as mechanically stable construction and corrosion-resistant construction, thus improving the hygiene required for food freezing or pressure freezing. By avoiding conventional cross-sectional reductions and associated zinc bridges forming cavities and cavities, the structure of the invention prevents permanent deposition of organic waste and removal of nutrient bases, as well as bacterial fouling often associated with such heat exchangers through improved cleaning capabilities.

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Claims (7)

9 102412 1. A highly efficient and hygienic steel heat exchanger, in particular for the immediate freezing of foodstuffs, comprising Heat exchanger according to Claim 1, characterized in that plates (19, 20) with periodically alternating widths are arranged in the width ranges (sections 16 and 17). Heat exchanger according to Claim 1 or 2, characterized in that the plates (18) with a narrow pitch extend into the width range (portion 18) of this pitch, and that there is a gap between the plates (16, 17) of this and the adjacent width range (portion 17). (22), the width of which is at least equal to the width of their spacing. Heat exchanger according to one of Claims 1 to 3, characterized in that the shoulders (6) extruded from the recesses (5) of the plates (7) taper slightly conically towards their free end. Heat exchanger according to one of Claims 1 to 4, characterized in that the shoulders (6) extruded from the recesses (5) of the plate (7) have an annular extension corresponding to the outer diameter of the free end of the annular shoulder at their end connected to the plate (7). 10 102412 S-shaped tube coils (3,12,13) formed at each end by an S-shaped tube connected to each other by means of tube arcs, the inner tubes (2) of which pass at predetermined distribution distances through predetermined lamellae (4) arranged in a row (8) formed recesses (5) with edge regions projecting collarically to the side, characterized in that the lamellae are formed as wide plates (7,19-21,23-25) comprising more than six rows (8) formed by the recesses (5) and that each of the rows (8) comprises at least fifteen recesses (5) through which the recesses (5) pass a single or multi-drive tubular coil (1), and that the distribution distances of the plates decrease stepwise in the air flow direction (15). 15 Heat exchanger according to Claim 4 or 5, characterized in that the free ends of the shoulders (6) of the recesses (5) or their annular extensions are securely attached to the metal plates (7) in front of them. 5 Heat exchanger according to one of Claims 1 to 6, characterized in that the tube coils and the plates are coated and joined together by means of hot-dip galvanizing. 10 and 102412