EP3578911B1 - Pipe heat exchanger for a baking oven - Google Patents

Description

The invention relates to a tubular heat exchanger for an oven. The invention also relates to a method for producing a coil tubular heat exchanger and an oven module and an oven with at least one such tubular heat exchanger.

Tube heat exchangers of the type mentioned at the beginning are known from the market, for example, as flat tube coils or as pillow radiators. A tubular heat exchanger is known from AT 27 736 B . An oven is known from the DE-PS 927 861 . A heat exchanger for a shower or bathtub is known from the CH 709 194 A2 . The EP 0 144 040 discloses a tubular heat exchanger according to the preamble of claim 1 and describes a loop heat exchanger. The AU 524 322 B2 discloses an air cooled heat exchanger. The US 2004/0 069 470 A1 and the GB 16,746 describe different variants of heat exchangers.

It is an object of the present invention to develop a tubular heat exchanger of the type mentioned at the beginning in such a way that a baking chamber can be heated efficiently and variably via it.

This object is achieved according to the invention by a tubular heat exchanger with the features specified in claim 1.

According to the invention, it was recognized that a defined small distance between adjacent pipe sections of the pipe heat exchanger, which is smaller than a pipe diameter, leads to an efficient heat transfer from the pipe sections leads to a fluid flowing through between adjacent pipe sections, for example by flowing air. The advantages of heating the baking space by emitting radiation from the tubular heat exchanger can thus be combined with the advantages of convective heat transfer, in particular in a baking space heated by circulating air. Depending on the design of the tubular heat exchanger and depending on the circulating air control, one of the heat transfer mechanisms “radiant heat” or “heat transfer to fluid flowing through” can then be dominant. Thermal oil can be used as the heat transfer fluid. The distance between adjacent pipe sections can be greater than 2% of the pipe diameter, can be greater than 3% and can, for example, be in the range of 5% of the pipe diameter. The distance between adjacent pipe sections can be smaller than 20% of the pipe diameter, can be smaller than 15% and can be smaller than 10% of the pipe diameter. An absolute distance between adjacent pipe sections of the pipe heat exchanger can be 2 mm. The design as a coiled pipe heat exchanger simplifies the supply and discharge of the heat transfer fluid carried in the pipe sections. The design of the serpentine tube heat exchanger with two serpentine conduit paths increases the flexibility of a conduit routing through the tube heat exchanger, which can then be adapted to production-related requirements and / or structural requirements, for example installation space requirements. 180 ° deflection sections between two pipe sections of the same serpentine conduction path are led out of the arrangement plane for exactly one of the serpentine conduction paths. 180 ° deflection sections leading out of the arrangement plane in this way avoid a space conflict between the deflection sections of the various snake conduction paths.

In the case of the tubular heat exchanger according to claim 2, a passage extends between the tubular sections, which at most can be interrupted by mounting components along negligible extension sections, along the entire tubular section. This increases the effectiveness the heat transfer from the pipe sections to the fluid flowing between them is optimized.

According to claim 3, the tubular heat exchanger can also have more than two serpentine conduction paths.

An arrangement of the pipe sections according to claim 4 can enlarge a minimum bending radius of the pipe forming the pipe sections within a respective serpentine conduction path. This simplifies the manufacture of the tubular heat exchanger.

An inlet-side Y-pipe piece according to claim 5 enables a common heat transfer fluid supply for the various coil line inlets.

Alternatively or additionally, according to claim 6, a corresponding Y-pipe section can also be provided on the outlet side.

A further object of the invention is to provide a manufacturing method for a coiled pipe heat exchanger which has at least two coiled conduction paths.

According to the invention, this object is achieved by a production method with the steps specified in claim 7.

The advantages of the manufacturing process correspond to those which have already been explained above with reference to the coil pipe heat exchanger with the at least two coil line paths. The snake tube heat exchanger can be manufactured from exactly one type of pipe by corresponding sequential bending and, if necessary, adding further pipes to pieces.

A method according to claim 8 enables the production of a snake tube heat exchanger according to claim 6. The bending out of the bent out 180 ° deflection sections can take place with the aid of a corresponding tube bending device in the course of the production of the snake line paths.

Simultaneous bending out of the bent-out 180 ° deflection sections according to claim 9 simplifies the manufacture of the coil-type tubular heat exchanger. A resulting bending angle can be in the range of 150 °, for example.

The advantages of an oven module according to claim 10 and an oven according to claim 11 correspond to those which have already been explained above with reference to the tubular heat exchanger.

The pipe sections of the pipe heat exchanger can extend horizontally in the oven module or in the oven. The pipe sections of the pipe heat exchanger can extend transversely to a conveying direction of the baked good through the oven module or the oven. This transverse extension can take place over a width of the entire baking chamber. Alternatively, the pipe sections of the pipe heat exchanger can also extend in the conveying direction of the baked good.

The oven can be a continuous oven, in particular a tunnel oven. The oven can consist of several oven modules be made, which can be constructed in particular in the same way.

Fig. 1

eine Seitenansicht eines modular aufgebauten Backenofens;

Fig. 2

einen Schnitt gemäß Linie II-II in Fig. 1;

Fig. 3

eine perspektivische Ansicht auf einen SchlangenRohrwärmetauscher für ein Backofenmodul des Backenofens nach Fig. 1;

Fig. 4

eine Ausschnittsvergrößerung einer perspektivischen Ansicht des Rohrwärmetauschers nach Fig. 3 im Bereich von 180°-Umlenkabschnitten zweier SchlangenLeitungswege;

Fig. 5

in einer zu Fig. 4 ähnlichen Darstellung wiederum eine perspektivische Ansicht der 180°-Umlenkabschnitte, in etwa aus der entgegengesetzten Blickrichtung wie in Fig. 4;

Fig. 6

in einer zu den Fig. und 5 ähnlichen Darstellung eine Aufsicht auf einen Abschnitt des Rohrwärmetauschers, die einen Abstand zwischen jeweils zwei benachbarten Rohrabschnitten verdeutlicht;

Fig. 7

schematisch Strömungsverhältnisse beim Durchtritt eines Gases, an welches der Rohrwärmetauscher Wärme abgibt, durch Durchgänge zwischen zwei im Querschnitt dargestellten, benachbarten Rohrabschnitten des Rohrwärmetauschers;

Fig. 8

eine perspektivische Ansicht eines Bandgliedes eines Endlos-Förderbandes des Backofens; und

Fig. 9

eine Aufsicht auf das Bandglied nach Fig. 8.

An embodiment of the invention is explained in more detail below with reference to the drawing. In this show:

Fig. 1

a side view of a modular oven;

Fig. 2

a section along line II-II in Fig. 1 ;

Fig. 3

a perspective view of a coil tube heat exchanger for an oven module of the oven according to Fig. 1 ;

Fig. 4

an enlarged detail of a perspective view of the tubular heat exchanger Fig. 3 in the area of 180 ° deflection sections of two serpentine pipeline routes;

Fig. 5

in one too Fig. 4 In a similar illustration, in turn, a perspective view of the 180 ° deflection sections, approximately from the opposite viewing direction as in FIG Fig. 4 ;

Fig. 6

In a representation similar to FIGS. 1 and 5, a plan view of a section of the tubular heat exchanger, which illustrates a distance between each two adjacent tube sections;

Fig. 7

schematic flow conditions when a gas, to which the tubular heat exchanger gives off heat, passes through passages between two adjacent tubular sections of the tubular heat exchanger shown in cross section;

Fig. 8

a perspective view of a belt link of an endless conveyor belt of the oven; and

Fig. 9

a plan view of the link Fig. 8 .

Fig. 1 shows an overall side view of a tunnel oven 1 designed as a tunnel oven, with which, for example, long-life baked goods in the form of soft biscuits, hard biscuits or lye biscuits can be produced. Other baked goods, such as toast, can also be processed in the oven. The oven 1 can also be used for roasting and, as a special application, drying or sterilization. The oven 1 is shown interrupted in the embodiment shown and has a plurality of oven modules 2 _i , 3 _i with baking chambers, which together have two stacked continuous baking chambers between an initial oven module 2 ₁ , 3 ₁ and one each leading in the direction of baked goods conveyance Form the last final oven module 2 _N , 3 _N (i = 1, ..., N, N: number of oven modules) in the direction of baked goods conveyance. In the Fig. 1 a total of eight oven modules 2 ₁ to 2 ₈ , which belong to an upper continuous baking chamber, and eight oven modules 3 ₁ to 3 ₈ underneath, which belong to a lower continuous baking chamber of the continuous oven 1. In the case of the continuous oven 1, the oven modules are thus arranged on two levels.

The furnace modules 2 ₁ to 2 ₈ and 3 ₁ to 3 ₈ each have the same basic structure, in particular with regard to a support frame design and receptacles for add-on and built-in parts. In this respect, the furnace modules 2 ₁ to 2 ₈ and 3 ₁ to 3 _{8 have} the same dimensions, that is, in terms of height, width and depth, each basically have the same space requirements.

The oven modules 2 ₁ to 2 ₈ and 3 ₁ to 3 ₈ are initially available as separate modules and are connected to one another when the oven 1 is assembled. In each of the oven modules 2 ₁ to 2 ₈ and 3 ₁ to 3 ₈ , heated circulating air is in each case conducted in a circuit via the heat exchangers described below. The upper oven modules 2 ₁ to 2 ₈ are supported by the lower oven modules 3 ₁ to 3 ₈ . The lower furnace modules 3 ₁ to 3 ₈ are supported by a machine floor.

In front of an initial baking oven module 2 ₁ or 3 ₁ leading in the direction of baked goods, a loading module 4 for the baked goods is arranged in the conveying direction, which in turn has two floors and communicates with the two continuous baking rooms. Behind a final oven module 2 _i and 3 _i in the direction of baked goods is an output module 5 of the continuous oven 1 for taking over the baked goods from the continuous baking rooms and for dispensing them, which is also designed in two floors and again with communicates with the two continuous baking rooms. The loading module 4 on the one hand and the output module 5 on the other hand close the circulating air circuit at the beginning and at the end of the continuous baking rooms.

Between the oven modules 2 ₈ , 3 ₈ and the output module 5, the conveyor oven 1 is in the Fig. 1 shown interrupted to indicate that the number of furnace modules 2 _i , 3 _i can be greater than in the Fig. 1 shown. The number N of furnace modules 2 _i , 3 _i can vary in practice, for example, between 5 and 20.

Baked goods to be baked enter the respective continuous baking chamber 7, 8 via the loading module 4, i.e. into the respective leading initial oven module 2 ₁ , 3 ₁ , pass through the respective continuous baking chamber 7, 8 along the baked good conveying direction 9 and enter via the output module 5 after having passed through the last final oven modules 2 _i , 3 _i from the continuous baking chambers 7, 8, completely baked again.

In the side view of the conveyor oven after Fig. 1 For some or all of the furnace modules 2 _i , 3 _i , a cleaning opening 6a, an inspection opening 6b and a steam opening 6c are also provided. Steaming / unloading of the respective baking chamber of the oven module 2 _i , 3 _{i is} possible via the respective damage opening 6c.

Fig. 2 shows a section through one of the oven modules using the oven module 2 ₁ as an example. The conveying direction 9 is perpendicular to the cutting plane or plane of the drawing Fig. 2 . Fig. 3 shows this in greater detail using the example of one of the furnace modules 2 _i. The furnace modules 3 _i are constructed in the same way, so that it is sufficient to follow the detailed illustration Fig. 3 to show an example of one of the furnace modules 2 _i. As far as details are concerned, the Fig. 2 are not to be found, is in this respect to the Fig. 3 referenced.

The oven modules 2 _i , 3 _i each have an oven 10, which is heated on the one hand directly via the circulating air and on the other hand via radiant heat, which is generated by heat exchangers in the form of two coil tube heat exchangers 11, 12. The baking rooms 10 are each part of the two stacked through-going baking rooms 7, 8, which are formed on the one hand by the upper oven modules 2 _i and on the other hand by the lower oven modules 3 _i . The tubular heat exchanger 11 arranged above the baking space generates top heat for the baking space 10. The tubular heat exchanger 12 arranged below the baking space generates bottom heat for the baking space 10.

Thermal oil is used as the heat transfer fluid that flows through the tube heat exchangers 11, 12. The two heat exchangers 11, 12 together with a thermal oil source (not shown) form a thermal oil heating device.

The upper tubular heat exchanger 11 is carried by a holding frame 13 which is mounted on the side frame cheeks 14, 15 of the oven module 6. Together with an upper retaining plate 16 and a lower retaining plate 17, the two frame cheeks 14, 15 form a baking room module 18 in which, among other things, the two tubular heat exchangers 11, 12 of the baking oven _{module 2 i are} accommodated. An air guide plate 18a is arranged between the upper retaining plate 16 and the upper tubular heat exchanger 11. The latter serves to equalize a circulating air flow in the baking chamber 10. The air guide plate 18a can also absorb heat energy from the tubular heat exchanger 11 and release it to the circulating air, so it can serve as an additional indirect heat exchanger component. A corresponding air guide plate 18a is arranged between the lower tubular heat exchanger 12 and the lower holding plate 17.

An upper conveyor strand 19 of an endless conveyor belt 20 runs between the two tubular heat exchangers 11, 12 and is used to transport the baked goods through the respective continuous baking chamber 7, 8 between the loading module 4 and the output module 5. The continuous oven 1 has two endless conveyor belts 20, namely an upper endless conveyor belt 20 for the oven modules 2 _i and a similarly constructed lower endless conveyor belt for the lower oven modules 3 _i . It is therefore sufficient to describe one of these conveyor belts below.

The conveyor belt 20 has a plurality of belt links 21, of which in the Fig. 2 an upper belt link 21 _o and a lower belt link 21 _u can be seen. In its current operating position, the upper belt link 210 is part of the upper conveyor strand 19 and is arranged in the baking chamber 10. The _{lower belt link 21 u} is part of a lower belt run 22 which runs beneath the baking chamber 10 and the lower tubular heat exchanger 11 through a return conveyor belt chamber 23 counter to the conveying direction 9 as part of the endless conveyor belt 20.

An upper air circulation duct 24 is arranged between the upper holding plate 16 of the baking room module 18 and an upper module plate 23a of the oven module 2 _i , 3 _i. A lower circulating air duct 26 is arranged between the lower holding plate 17 of the baking room module 18 and a lower module plate 25. The two circulating air ducts 24, 26 extend over the entire width of the oven module 2 _i , 3 _i .

The two circulating air ducts 24, 26 are in fluid connection with two axial / radial fans 31, 32 via supply and exhaust air ducts 27, 28, 29, 30. Overall, this results in a circulating air circuit of the respective oven module 2 _i , 3 _i . The baking chamber 10 of the respective oven module 2 _i , 3 _i is part of this circulating air circuit. The fans 31 and 32, together with the respective circulating air circuit, are components of a circulating air device of the continuous oven 1.

The two fans 31, 32 and the supply air and exhaust air ducts 27 to 30 are mounted on lateral, vertically extending frame plates 33, 34 of the oven module 2 _i , 3 _i .

Fig. 3 shows one of the two tube heat exchangers that are used in the oven module 2 ₁ using the example of the upper coil tube heat exchanger 11. All tubular heat exchangers 11, 12 of the oven modules 2 _i , 3 _{i of} the oven 1 are constructed in the same way, so that it is sufficient to describe this upper tubular heat exchanger 11 below.

The tubular heat exchanger 11 has a plurality, namely thirty-six in the illustrated embodiment, in an arrangement level (cf. level 35 in FIG Fig. 2 ) juxtaposed heat exchanger pipe sections 36 for guiding a heat transfer fluid. Thermal oil, in particular, can be used as the heat transfer fluid.

The arrangement of the heat exchanger tube sections 36 next to one another in the arrangement plane 35 can be such that actually in a side view as in FIG Fig. 2 all heat exchanger pipe sections 36 are completely aligned with one another. Alternatively, longitudinal axes, in particular of adjacent pipe sections 36, can have different distances from the arrangement plane 35. A bandwidth of the distances between the longitudinal axes of the pipe sections 36 and the arrangement plane 35 is, however, also in this case smaller than a diameter of the individual pipe sections 36 and is in particular smaller than a fraction of this diameter, for example less than 80%, less than 70%, less than 60%, less than 50%, less than 40%, less than 30%, less than 20% and in particular can be less than 10% of the The diameter of the pipe sections 36. The pipe diameter of the pipe sections 36 can be in the range between 10 mm and 150 mm and, for example, in the range between 25 mm and 50 mm, for example 35 mm, 38 mm or 40 mm. Unless the pipe sections 36 in side view, as for example in the Fig. 2 are completely aligned with one another, the longitudinal axes of the pipe sections 36 can in this case have a distance from the arrangement plane 35 that is in the range between 0 mm and +/- 20 mm.

A distance A between two adjacent pipe sections 36 is on the one hand smaller than the pipe diameter and on the other hand greater than 1% of the pipe diameter. This distance A is in the Fig. 6 , which shows a section of the tube heat exchanger 11 in a plan view, exemplifies two adjacent tube sections 36.

An absolute distance between two adjacent pipe sections 36 can be in the range between 1 mm and 50 mm, in particular in the range between 1 mm and 10 mm, in the range between 1 mm and 5 mm and can be, for example, 2 mm.

This distance between the adjacent pipe sections 36 enables a passage between these pipe sections. Such a passage runs along an entire extension of the pipe sections 36 through the baking chamber 10 transversely to the conveying direction 9 and is at most interrupted by mounting components. Such interruptions are very small compared to the overall extent of the pipe sections 36 and Usually less than 5% of the total extension of the pipe sections 36. Because of these passages resulting from the distance between adjacent pipe sections 36, an effective heat transfer results from the pipe sections 36 to fluid flowing through between adjacent pipe sections 36.

Corresponding heat transfer conditions are very schematically shown in FIG Fig. 7 for two adjacent pipe sections 36 of the pipe heat exchanger 12. The Fig. 7 shows the flow conditions at the lower coil pipe heat exchanger 12. The heat transfer fluid 37 flows through the pipe sections 36. The jacket walls 38 of the pipe sections 36 have a further heat-absorbing fluid, in the embodiment described, air 39 flowing around them, as shown schematically by some flow arrows reproduced. Due to the distance A between the adjacent pipe sections 36, which is in the range between 1% and 100% of the pipe diameter D, the inflowing air 39 flows through between the adjacent pipe sections after it has come into contact with peripheral sections U of the jacket walls 38. After passing through the narrowest point of the passage between the adjacent pipe sections 36 at which the distance A is present, the air 39 breaks off from the jacket wall 37 in the further course of the flow and the air 39 continues to flow turbulently upwards, where the Air which has flowed through the passage under consideration between the adjacent pipe sections 36 is effectively mixed with the air 39 which has flowed through adjacent passages between the pipe sections 36 shown and adjacent pipe sections not shown on the left and right. Above the arrangement plane 35, with the illustrated air flow from bottom to top, a closed and essentially uninterrupted flow occurs very quickly Volume air flow upwards to the baking chamber 10, which is in the Fig. 2 is shown by flow arrows 40. The turbulence ensures that the pipe sections 36 themselves do not serve as screens for the further air flow, that is, the air flow above the pipe heat exchanger 12 results in a closed air curtain without gaps through the baking chamber 10.

The tube heat exchanger 11 is designed as a coil tube heat exchanger. A first serpentine conduit path 41 runs between a first serpentine conduit inlet 42 and a first serpentine conduit outlet 43. A second serpentine conduit path 44 runs between a second serpentine conduit inlet 45 and a second serpentine conduit outlet 46 Fig. 3 The tubular heat exchanger 11 shown has exactly two serpentine line paths 41 and 44. In principle, a larger number of corresponding serpentine line paths is also possible.

In each case two pipe sections 36 adjacent to one another in the arrangement plane 35 belong to different serpentine conduction paths. In the representation according to Fig. 3 the pipe section 36 shown at the bottom left belongs to the first serpentine conduction path 41. The pipe section 36 directly adjacent to it to the top right belongs to the second serpentine conduction path 44. The pipe section directly adjacent to this in turn at the top right then belongs to the first serpentine conduction path 41. The further adjacent pipe sections 36 belong alternately to the second serpentine conduit path 44 and to the first serpentine conduit path 41. The tube section 36 shown at the top right on the far outside then belongs to the second serpentine conduit path 44 and opens into the second serpentine conduit outlet 46.

This alternating affiliation of the pipe sections 36 to the two serpentine conduction paths 41 and 44 increases a minimum bending radius of the pipe, from which the pipe sections 36 are made, within one of the two serpentine conduction paths 41, 44 180 ° deflection sections 47, 48 of the two serpentine conduction paths 41, 44 clearly, which is particularly evident from the Figures 4 to 6 results, which show correspondingly enlarged representations of the serpentine conduction paths 41, 44 of the tubular heat exchanger 11. An inner bending radius of the 180 ° deflecting sections 47, 48 is greater than the pipe radius, i.e. is greater than half the pipe diameter D. This inner bending radius of the 180 ° deflecting sections 47, 48 is, on the other hand, smaller than the pipe diameter D.

The two serpentine line inlets 42, 45 on the one hand and the two serpentine line outlets 43 and 46 on the other hand are each in fluid connection via a Y-pipe section 49, 50 with one another and with a collecting inlet 49a on the one hand and with a collecting outlet 50a on the other hand.

The two serpentine line inlets 42, 45 are in fluid connection with the collecting line inlet 49a via the Y-pipe section 49. The collecting line inlet 49a is in turn in fluid connection with a heat transfer fluid source not shown in the drawing. The two collecting line outlets 43, 46 are in fluid connection with the collecting line outlet 50a via the further Y-pipe section 50. The collecting line outlet 50a can be in fluid connection with the collecting line inlet 49a to form a heat transfer medium-fluid circuit. A pump for the heat transfer fluid 37, which is likewise not shown in the drawing, can be part of this circuit.

For the serpentine conduction path 41, the 180 ° deflection sections 47 are led out of the arrangement plane 35 between the two pipe sections 36 connected via this, namely bent out at an obtuse angle. A bending angle β between the plane of arrangement 35 and a plane of arrangement of the 180 ° deflection sections 47 (cf. Fig. 2 , shown there in the tubular heat exchanger 12) is about 150 ° in the embodiment shown. This bending angle can be in the range between 120 ° and 165 °.

This routing of the 180 ° deflection sections 47 out of the arrangement plane 35 means that no installation space conflict occurs between the 180 ° deflection sections 47, 48 of the various hose line paths 41, 44.

A hose-pipe heat exchanger in the manner of hose-pipe heat exchangers 11 and 12 of the oven module 6 is produced as follows:
First, a tube is provided which is a multiple of the length of one of the tube sections 36 between the respective deflection sections 47, 48. A first hose line path, for example the hose line path 41, is then produced by bending the pipe in the area of the deflection sections 47 between the pipe sections 36. A second hose line path, in this case the hose line path 44, is then produced by bending the pipe of the deflection sections 48 between the pipe sections 36. As soon as these manufacturing bending steps If the end of the tube is reached, a further tube with the same diameter is optionally pieced together, that is to say connected to the tube that has just been machined, for example welded to the end face.

After the two hose line paths 41, 44 have been produced, the two hose line paths 41, 44 are inserted into one another in the arrangement plane 35. The Y-pipe pieces 49, 50 can then be connected to the serpentine line inlets 42, 45 and the serpentine line outlets 43, 46, for example welded to them and optionally a fluid passage between the respective Y-pipe piece 49, 50 and the respective line inlets 42, 45 on the one hand and Outlets 43, 46 on the other hand are created.

In a variant of the production method, before the two hose line paths 41, 44 are inserted into one another, the 180 ° deflection sections 47 between the pipe sections 36 of the same hose line path 41 are bent out of the arrangement plane 35. This bending out can take place at the same time when producing this serpentine conduction path 41 by using a corresponding, in particular flat, bending tool.

When baking with the tunnel oven 1, the baked goods carried on the conveyor belt 19 through the oven modules 2 to 6 are heated on the one hand by radiant heat from the tube heat exchangers 11, 12, which are housed in the respective oven modules 2 to 6, and on the other hand via the circulating air , which flows through the respective baking chamber 10 of the oven module 2 to 6, heated. The heat contributions "radiant heat" on the one hand and "circulating air heat" (heat transfer to fluid flowing through) on the other can be specified by appropriate design of the tubular heat exchangers 11, 12 and by the temperature and flow of the heat transfer fluid 37 through the tubular heat exchangers 11, 12 and on the other hand by the amount of air flowing through the baking chambers 10.

An air flow through the baking chamber 10 (cf., for example, the air flow 40 in FIG Fig. 2 ) can be directed from bottom to top or from top to bottom, depending on the design of the furnace module 2 to 6.

In the flow example according to Fig. 2 takes care of in the Fig. 2 Left fan 31 ensures that the circulating air first flows through the supply air duct 27 into the lower circulating air duct 26. At the same time, the Fig. 2 Right fan 32 ensures that the circulating air flows through the right supply air duct 28 into the lower circulating air duct 26. As a result of the overpressure then occurring in the lower circulating air duct 26, the circulating air flows out of the lower circulating air duct 26 upwards and between the adjacent pipe sections 36 of the lower pipe heat exchanger 12, as above in connection with FIG Fig. 6 already described. The circulating air then flows through the upper conveyor strand 19 of the endless conveyor belt 20 and then flows around the dough pieces conveyed thereon through the baking chamber 10. The circulating air then flows through the passages between the pipe sections 36 of the upper tubular heat exchanger 11 and then flows into the upper circulating air duct 24, from where the circulating air is then sucked out again via the fans 31, 32 and the exhaust air ducts 29, 30 to complete the respective circulating air circuit. An overpressure in the circulating air circuit can be achieved via a flap-controlled exhaust pipe 51 (cf. Fig. 2 ) escape.

Depending on the structure of the oven module 2 to 6, the oven module can have 2 fans as in the version Fig. 2 or just an axial-radial fan have, which can then be attached to one or the other side of the furnace module. If several oven modules are equipped with exactly one fan of this type one behind the other in the conveying direction 9, the arrangement of this fan can alternate between the two sides of the continuous oven 1, for example, so that, for example, in oven module 3, the fan is arranged on the right in the manner of fan 32 following furnace module 4 on the left and in the following furnace module 5 again on the right. As an alternative or in addition, the direction of flow of the circulating air through the baking chamber 10 can be specified by appropriately activating the respective fan 31, 32 from bottom to top or from top to bottom.

Different temperature zones can be specified in the furnace modules 2 to 6. This can be specified by specifying the temperature and / or the flow rate of the thermal oil and / or the amount of circulating air and the direction of the air circulation from bottom to top / from top to bottom. A central control device of the oven 1 is used for this.

Based on Fig. 8 and 9 one of the belt links 21 of the endless conveyor belt 20 is explained in more detail below. Since all the belt links 21 of the endless conveyor belt 20 are constructed in the same way, the description of one of the belt links 21 is sufficient.

The belt link 21 extends transversely to the conveying direction 9 between lateral guides 53, 54 for the endless conveyor belt 20, which are accommodated in the baking room module 18 for the upper conveyor strand 19. The respective belt link 21 is connected to these guides 53, 54 via suspension mounting plates 55.

The upper conveying strand 19 extends in a conveying plane 56 which runs parallel to the planes of arrangement of the tubular heat exchangers 11, 12 (cf. plane of arrangement 35).

In projection in a direction perpendicular to the conveying plane 56, that is, seen in the viewing direction of FIG Fig. 9 , the band member 21 has gas passage openings 57, 58. These gas passage openings 57, 58 have a total opening area which is at least 30% of a total area of the projection of the band member 21.

The belt link 21 has between the lateral guides, that is, between the two suspension mounting plates 55, several link planes 59, 60 which, in the embodiment 2 shown, are spaced apart from one another perpendicular to the conveying plane 56.

The first, upper link level 59 coincides with the conveying level 56 and is defined by a plurality of double link brackets 63 extending along the conveying direction 9 between lateral link cheeks 61, 62. The gas passage openings 58 are between the brackets of the respective double Link bracket 63 executed. Further gas passage openings in the upper link level 59 are made between two adjacent double link brackets 63.

The second, lower link level 60 is formed below the first link level 59 in the case of the belt links 21 currently forming the upper conveyor strand 19. There runs between the link cheeks 61, 62 a stiffening plate 64 in which the gas passage openings 57 are made. The gas passage openings 57 in the stiffening plate 64 run in the manner of elongated holes. The gas passage openings 57 have a longitudinal extension in the direction of the longitudinal extension of the belt link 21.

The gas passage openings 58 between the brackets of the respective double link bracket 63 are designed in the manner of elongated holes. The gas passage openings 58 have a longitudinal extension transverse to the longitudinal extension of the belt link 21, that is, as long as the belt link 21 is part of the upper conveying strand 19, parallel to the conveying direction 9.

Between the suspension mounting plates 55, the belt link 21 is designed to be self-supporting.

When the tunnel oven 1 is in operation, the belt links 21 revolve endlessly in the manner of chain links between the guides 53, 54, the upper conveyor strand 19 running in the conveying direction 9 and the lower belt strand 22 opposite to the conveying direction 9 Oven module 2 ₁ and the final oven module 2 _N , a 180 ° deflection takes place via the correspondingly designed guides 53, 54 between the upper conveyor run 19 and the lower belt run 22.

Claims (11)

1. Pipe heat exchanger (11, 12) for a baking oven (1),

   - with a plurality of heat exchanger pipe sections (36) configured to guide a heat carrier fluid (37), the heat exchanger pipe sections (36) being arranged adjacent to each other in an arrangement plane (35),

   - wherein a distance (A) of adjacent pipe sections (36) is smaller than a pipe diameter (D) and greater than 1% of the pipe diameter (D),

   - wherein the pipe heat exchanger (11, 12) is configured as a pipe coil heat exchanger, which has:

   - a first coil line path (41), formed between a first coil line inlet (42) and a first coil line outlet (43), and

   - a second coil line path (44), formed between a second coil line inlet (45) and a second coil line outlet (46),

   - characterized in that
   180° deflection sections (47) between two pipe sections (36) of the same coil line path (41) are guided out of the arrangement plane (35) for exactly one of the coil line paths (41).
2. Pipe heat exchanger as claimed in claim 1, characterized in that a passage between the pipe sections (36), with the exception of interruptions due to mounting components, extends along all of the pipe sections (36).
3. Pipe heat exchanger as claimed in claim 1 or 2, characterized in that it has more than two coil line paths.
4. Pipe heat exchanger as claimed in any one of claims 1 to 3, characterized in that in each case two pipe sections (36) arranged adjacent to one another in the arrangement plane (35) belong to different coil line paths (41, 44).
5. Pipe heat exchanger as claimed in any one of claims 1 to 4, characterized in that the two coil line inlets (42, 45) are in a fluidic connection, via a Y-pipe section (49), with a collective line inlet (49a).
6. Pipe heat exchanger as claimed in any one of claims 1 to 5, characterized in that the two coil line outlets (43, 46) are in a fluidic connection, via a Y-pipe section (5), with a collective line outlet (50a).
7. Method of producing a pipe coil heat exchanger as claimed in any one of claims 1 to 6, characterized by the following steps:

   - providing a pipe, which has a multiple of the length of one of the pipe sections (36),

   - producing a first coil line path (41) by bending the pipe in the region of deflection sections (47) between the pipe sections (36),

   - producing a second coil line path (44) by bending the pipe in the region of deflection sections (48) between the pipe sections (36),

   - inserting the two coil line paths (41, 44) into one another in the arrangement plane (35).
8. Method as claimed in claim 7, characterized in that prior to inserting, 180° deflection sections (47) are bent out of the arrangement plane (35) between two pipe sections (36) of the same coil line path (41) for at least one of the coil line paths (41).
9. Method as claimed in claim 8, characterized in that the 180° deflection sections (47) of the coil line path (41), which are arranged at an end of the pipe coil heat exchanger (11, 12), are bent out of the arrangement plane (35) simultaneously.
10. Baking oven module (2_i, 3_i) with at least one pipe heat exchanger (11, 12) as claimed in any one of claims 1 to 6, and with a baking space (10), which is heated by means of the pipe heat exchanger (11, 12).
11. Baking oven (1) with at least one pipe heat exchanger (11, 12) as claimed in any one of claims 1 to 6, and with a baking space (10), which is heated by means of the pipe heat exchanger (11, 12).

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