EP1992898A2 - Heat exchanger for gaseous media - Google Patents

Abstract

The heat exchanger has a stack of first flow channels (5) extending in a first direction (3), second flow channels between them extending in a second direction (4) and inner and outer distance holders parallel to the first and second directions. It has corrugated profiles with lens-shaped nubs in flat sections and walls welded together in gas -tight manner to form a block (1) with the first and second flow channels.

Description

The invention relates to a heat exchanger of the type specified in the preamble of claim 1.

Known heat exchangers of this type are preferably used as condensers in tumble dryers (eg. EP 0 982 427 B1 . EP 1 106 729 B1 . DE 102 18 274 A1 . DE 103 56 417 A1 ). They are mainly characterized by the fact that the flow channels are limited by walls made of highly thermally conductive plastic or metal foils and z. B. by vacuum thermoforming, thermoforming or otherwise brought into their final form. A benefit obtained thereby is that the walls can be easily and in one piece provided with profiles that improve the heat exchange performance, as well as with spacers that keep the relatively flexible walls at a distance. However, the previously known heat exchangers of this type are not free from defects.

Due to the thin-walled, z. B. 0.2 mm thick walls or films arise despite the known profiles and spacers in particular problems in terms of the required compressive strength during operation of the heat exchanger. Higher temperatures can be mainly used for cost reasons, made of polypropylene or a copolymer such. B. ABS walls are soft with the result that they deform in the direction of the smallest pressure. In addition, high temperatures result in elongations resulting in distortions of the walls between their fixedly fixed in the frame ends. As a result, the structurally predetermined flow cross sections change during operation, which not only has an unfavorable influence on the performance of the heat exchangers, but can also cause the formation of depressions in the flow channels carrying the process air in the case of tumble dryer capacitors. In these wells, condensed water can accumulate in an undesired manner (puddling), which affects the condensation performance and should actually drain into a collecting container provided for this purpose.

Not desired are still the relatively high production costs, the u. a. caused by the cumbersome, gas-tight fastening of the individual tubular flow channels in the frame by gluing.

Finally, although good heat exchange performance can be achieved even with heat exchangers made of plastic films of the type mentioned, but these are still lower than with appropriately sized, soldered, glued or folded coolers od. Like. Metal.

Based on this prior art, the present invention seeks to provide the heat exchanger of the type described above in such a way that they have increased performance and greater compressive strength despite reduction of manufacturing costs.

This problem is solved by the characterizing features of claim 1.

Due to the fact that according to the invention the profilings are additionally provided with knobs known per se, a noticeable increase in performance also occurs when walls made of film material are used. The inventive design and arrangement of the spacers allows the use of a sufficiently large number of spacers, without thereby increasing the pressure losses during operation excessively. Finally, a significant cost reduction is made possible by not only the first flow channels at their lateral edges, but also the second flow channels are connected at their front and rear end faces by welding. This results in a coherent block which can be used as a whole in the frames, which only has to be connected to the frame at its periphery by gluing. This leads to the saving of glue and laborious steps in the production.

Further advantageous features of the invention will become apparent from the dependent claims.

• Fig. 1 eine perspektivische Ansicht eines Wärmeaustauschers;
• Fig. 2 eine perspektivische Ansicht eines erfindungsgemäßen, ersten Strömungskanals, bestehend aus zwei an ihren Längsseiten verbundenen Wänden;
• Fig. 3 und 4 in je einem Schnitt längs der Linie III - III der Fig. 2 je eine obere und untere, einen ersten Strömungskanal begrenzende Wand;
• Fig. 5 die Wände nach Fig. 3 und 4 in einem Schnitt längs der Linie III - III der Fig. 2, jedoch in einem Zustand, in dem die beiden Wände fest miteinander verbunden sind;
• Fig. 6 in einer perspektivischen, vom geschnittenen Vorderansicht mehrere übereinander angeordnete, erfindungsgemäß ausgebildete, erste und zweite Strömungskanäle;
• Fig. 7 eine perspektivische Ansicht eines erfindungsgemäß ausgebildeten Blocks des Wärmeaustauschers nach Fig. 1; und
• Fig. 8 eine der Fig. 6 entsprechende Ansicht eines zweiten Ausführungsbeispiels der erfindungsgemäßen Strömungskanäle.

The invention will be explained in more detail below in connection with the accompanying drawings of an embodiment. Show it:

• Fig. 1 a perspective view of a heat exchanger;
• Fig. 2 a perspective view of a first flow channel according to the invention, consisting of two connected at their longitudinal sides walls;
• 3 and 4 in each case a section along the line III - III of Fig. 2 a respective upper and lower, a first flow channel limiting wall;
• Fig. 5 the walls after 3 and 4 in a section along the line III - III of Fig. 2 but in a state in which the two walls are firmly joined together;
• Fig. 6 in a perspective, from the cut front view a plurality of superimposed, according to the invention formed, the first and second flow channels;
• Fig. 7 a perspective view of an inventively designed block of the heat exchanger according to Fig. 1 ; and
• Fig. 8 one of the Fig. 6 corresponding view of a second embodiment of the flow channels according to the invention.

To Fig. 1 a heat exchanger comprises a block 1 provided with first and second flow channels, which is fastened to two longitudinal ends in a respective frame 2. The first flow channels are in a first, indicated by arrows 3 direction, the second flow channels, however, in a second, indicated by arrows 4 direction, which is preferably perpendicular to the first direction in the manner of a cross-flow heat exchanger, flows through each of a gas.

In the preferred exemplary embodiment described below, a heat exchanger suitable in particular as a condenser for a tumble dryer is described, through which the process air flows in the direction of the arrows 3 and the cooling air flows through in the direction of the arrows 4.

Fig. 2 shows a inventively designed, first flow channel 5, of two accordingly 3 and 4 trained walls 6 and 7 is limited, as in particular also from Fig. 5 is apparent. Fig. 6 shows a plurality of superimposed, first flow channels 5, which are arranged at preselected intervals and therefore form between them second flow channels 8, which according to FIG Fig. 1 in the direction of the arrows 4 z. B. are flowed through by cooling air.

The first flow channels 5 limiting, alternately superimposed plates or walls 6 and 7 are made of a film material, for. For example, a polypropylene or aluminum foil, prepared and have a useful consistently constant wall thickness, which is preferably 0.2 mm to 0.5 mm. In the plan view, the walls 6 and 7 have a substantially rectangular shape. The two walls 6 and 7 have, in particular Fig. 3 to 5 can recognize, parallel to the first direction and in the exemplary embodiment also parallel to their longitudinal sides extended side strips 6a and 7a, which are connected in a gas-tight manner by welding ( Fig. 5 ). This creates flow channels 5 in the form of laterally closed, open at their front and rear ends of pipes.

The first flow channels 5 are further provided with inner, ie inwardly projecting spacers 9 which are connected to the in Fig. 4 . 5 and 6 bottom walls 7 are formed, substantially perpendicularly rise from these and rest with their free ends to the overlying upper walls 6. Thereby, the walls 6 and 7 of the flow channels 5 are kept at a preselected distance. In addition, the in Fig. 3 . 5 and 6 overhead walls 6 are provided with outer spacers 10. These do not protrude into the first flow channels 5, but stand from their walls 6 substantially perpendicular to the outside. In the stacked Condition of walls 6 and 7 ( Fig. 6 ) lie the free ends of these outer spacers 10 on the undersides of the overlying walls 7 and therefore set the distances between the stacked flow channels 5 and the heights of the second flow channels 8 located between them.

Continue to show above all 3 and 4 in that the walls 6 and 7 are transverse to the first flow direction (arrows 3 in FIG Fig. 2 ) extended, wavy profiles have, which are formed substantially identical in both walls 6 and 7 and arranged parallel to each other.

Heat exchangers of the type described are essentially known from the publications mentioned above and therefore need not be explained in more detail to the person skilled in the art.

Profiles 11 are provided with at least partially planar sections according to the invention. Trapezoidal profilings 11 which are in accordance with cross section are particularly advantageous Fig. 2 to 4 in the second direction (arrows 4 in FIG 2 to 4 and 6 ) rising portions 11a, sloping portions 11b and these connecting portions 11c have. The profiles 11 have according to Fig. 5 Wavelengths 1 and heights h, which are preferably in a ratio 1 / h to each other, which is at least five, and preferably less than twenty.

The sections 11a, 11b are particularly flat while the sections 11c are preferably flat and parallel to the second direction. In addition, the sections 11a, 11b and 11c according to the invention are provided with preferably lenticular nubs 12, which lead to increased heat exchange performance and in particular lead to no significant increase in pressure losses, especially in the second direction for the cooling air when its depth is approximately between 0.2 and 0.8 times the distance between the upper and lower walls 6 and 7 is. The other dimensions and also the shapes of the nubs 12 are dependent on the performance increases desired in the individual case or to accept the maximum purchase losses to be accepted. In particular, instead of lenticular knobs, it is also possible to provide those with oval or angular bases as well as diamond-shaped or pyramid-shaped or otherwise suitably shaped studs 12.

The nubs 12 can, in particular 3 and 4 show, are formed by forms that protrude from opposite broad sides of the walls 6, 7, therefore optionally in the first or in the second flow channels 5 and 8 protrude and lead on their backs to corresponding recesses. If the heat exchangers are arranged in use such that the walls 6 each form an upper boundary and the walls 7 respectively form a lower boundary of the flow channels 5, then in the case of tumble-dryer condensers, the lower walls 7 are to face the flow channels 5 Inner sides only with raised projecting, in the flow channels 5 projecting nubs to provide. This avoids that on these inner sides of the walls 7, ie at the bottoms of the flow channels 5 depressions are present, which lead to the formation of puddles when condensing water from the process air and impede the desired flow of condensate. Such puddles, in which condensate accumulates instead of draining, are undesirable because of the deteriorated heat transfer at these locations. On the upper walls, on the other hand, inwardly projecting nubs are less critical, as forming condensate can drip off of them.

From Fig. 2 to 6 apparent spacers 9 and 10 are preferably elongate and flat oval or biconvex in plan view. They extend with their longitudinal axes expedient in the first flow channels 5 parallel to the first direction and in the second flow channels 8 parallel to the second direction. In particular, the leading edges of the spacers 9, 10 are preferably provided with small radii of curvature, which has favorable flow conditions and small pressure losses result.

It is also particularly advantageous if the number of spacers 9 and 10 remains within certain limits. If the number of spacers is too large, on the one hand the pressure losses increase, while on the other hand the area remaining for the attachment of the studs 12 is reduced. On the other hand, if the number of spacers is too low, then there is the risk that the walls 6, 7 will become too deformed during operation due to the natural flexibility of the film material during operation because of the then prevailing pressure conditions, and if so will also lead to pressure losses. In the context of the present invention, it has been found that the number of spacers 9, 10 should not be less than four pieces per 100 cm ² wall surface with a uniform distribution, wherein under such a wall surface preferably a substantially square area piece of approximately 10 cm. 10 cm is understood. In this case, the surface areas located between two support points are so small that the deformations still possible there are largely harmless. The upper limit for the number of spacers 9, 10 per 100 cm ² or preferably 10 cm × 10 cm wall surface largely depends on which pressure losses are tolerable. The cross-sectional areas of the spacers 9, 10 should also be as small as possible, in particular transversely to the respective flow direction. Since they contribute to the heat exchange little or nothing, it is sufficient if they are just so large that the spacers 9, 10 by the coming to use manufacturing processes such. B. thermoforming just be produced with the required stability. In addition, the spacers 9, 10 should come to lie alternately one above the other in the finished stack, so that from top to bottom continuous, preferably perpendicular to the two directions 3 and 4 extending support lines are obtained, as can be seen in particular Fig. 6 results. If the spacers 9 and 10 are arranged with any lateral offset relative to one another, then there is a risk that pressure differences occurring during operation lead to moments, in particular in the area of individual support points, which could result in undesired deformations of the walls 6 and 7.

Further, it is considered advantageous for the purposes of the invention if the Walls 6 and 7 are arranged over the entire surface substantially parallel to each other and thus the flow channels 5 and 8 have a constant height, except of course, where the spacers 9, 10 arranged, provided in opposite directions nubs 12 and the walls , 7 are connected at their edges. As a result, almost uniform flow conditions are achieved throughout.

As wavy profilings 11 to achieve a good compressive strength has from Fig. 2 to 6 apparent trapezoidal shape with the preferably equally long, rising and falling sections 11a, 11b proved to be expedient. These have, inter alia, the advantage that the nubs 12 can be mounted in flat wall areas. However, it is recommended that the connection zones of the different regions 11a, 11b and 11c be slightly curved in order to obtain favorable flow conditions on the cooling air side, ie in the second flow channels 8, by rounded deflection zones. Alternatively, however, other, z. B. sinusoidal or zigzag waveforms applicable. Important in this context is a waveform that brings a high compressive strength without causing excessive pressure loss. To increase the performance of such waveforms contribute only slightly, which is why the nubs 12 are additionally provided according to the invention.

In particular Fig. 5 and 6 show, the two walls 6 and 7, each forming one of the first flow channels 5, each connected at their lateral edges firmly together. To make this possible, the trapezoidal walls 6 (see also Fig. 3 ) are provided at their sides with obliquely downwardly and outwardly curved or angled transition regions 6b, to which the side strips 6a adjoin outwardly. The walls 7, however, are provided at their edges with obliquely upwardly and outwardly curved or angled transition sections 7b, to which the side strips 7a connect. Both side strips 6a, 7a are preferably arranged substantially flat and both parallel to one another and parallel to imaginary center planes of the walls 6, 7. This preserves the walls 6, 7 a cup-shaped appearance, wherein in the embodiment, the walls 6, the ceilings and the walls 7, the bottoms of the flow channels 5 form. The position of the transition sections 6b, 7b is selected such that the walls 6, 7 automatically have the spacing also predetermined by the spacers 9 when the side strips 6a, 7a are placed one on top of the other.

Next, the invention provides, the walls 6, 7 also at their front and rear end faces by welding gas-tightly connected to each other, thereby sealing the second flow channels 8 laterally. In particular Fig. 2 and 7 For this purpose, the walls 6, 7 are provided at their front and rear ends with connecting strips 6c, 7c which, like the side strips 6a, 7a, are arranged substantially both parallel to each other and parallel to the imaginary center planes of the walls 6, 7 , Like the side strips 6a, 7a, the connecting strips 6c, 7c are also connected to the walls 6, 7 by means of short transition sections arranged at an angle to the middle planes. However, these non-illustrated transition sections are curved or angled in the opposite direction in each case compared to the attached to the same walls 6, 7 side strips 6a, 7a, ie, for example in the in Fig. 2 and 5 upper wall 6 upwards and at the in Fig. 2 and 5 bottom wall 7 down. Therefore, two flow channels 5, consisting of two walls 6 and 7, respectively Fig. 6 and 7 superimposed, then these two flow channels 5 are kept not only by the appropriately sized spacers 10, but also to form the lateral flow channels 8 through the coming to rest connection strips 6c, 7c at a distance. After the welding of the connecting strips 6c, 7c of all the flow channels 5 present in the stack, a coherent heat exchanger block 1 (FIG. Fig. 1 ), in which the first and second flow channels 5, 8 are already gas-tight and firmly connected to one another at their sides parallel to the respective flow directions 3, 4. For the completion of a heat exchanger, in particular a capacitor od. Like., It is then only necessary, the two end, provided with the connecting strips 6c, 7c ends of the block 1 according to Fig. 1 in the according to the outer circumference of the block 1 sized Insert frame 2 and connect with them by gluing.

A further advantage of the construction described is that the side and connecting strips 6a, 7a and 6c, 7c are connected to the walls 6, 7 by means of the additional transition sections 6b, 7b and therefore project beyond the actual flow channels 5, 8 , Thus, the side and connecting strips 6a, 7a and 6c, 7c for the welding tools are easily accessible, and there are no internal holders od. Like. Needed to perform the welding safely. This applies regardless of whether only the walls 6, 7 of the individual flow channels 5 laterally welded and the latter then stacked and welded to the front sides or conversely only all the walls 6, 7 stacked and then welded laterally and frontally.

Due to the described construction, the walls 6 and 7, which may also be referred to as plates or shells, not identical and arranged only rotated by 180 °. They differ rather by the position and direction of their side and connecting strips 6a, 6c and 7a and 7c, their spacers 9 and 10 and possibly their nubs 12th

Above and below the flow channels 5 are advantageously side parts 14 ( Fig. 1 ) arranged from a thick-walled, mechanically stable material. These preferably form at least with the end-side walls 6 a further flow channel 8 by resting on the spacers 10. On the opposite side, however, the side parts 14, for example, lie directly against the undersides of the walls 7. The front ends of the side parts 14 also project into the frame 2 and are firmly connected with these. As a result, the side parts 14 on the one hand serve the purpose of supporting the two frames 2 against each other and thereby relieving the stack formed by the walls 6, 7 of any occurring assembly and sealing forces. On the other hand, the side parts 14 serve to clamp the stack lying between them perpendicular to the directions 3 and 4 and thereby hold the spacers 9, 10 with the associated walls 6, 7 in abutment.

The example also a clothes dryer condenser illustrative embodiment Fig. 8 is different from that Fig. 2 to 7 especially in that the process air flows through the second flow channels 8 and the cooling air flows through the first flow channels 5 secured in the frame 2, as through the opposite Fig. 6 reversed arrows 3 and 4 is indicated. Therefore, the profilings 11 in this case are preferably extended in the direction of the first flow channels 5. Moreover, unlike Fig. 2 to 6 each of the inner spacers 9 and the outer spacers 10 is formed continuously, ie, over the entire length or at least approximately over the entire length of the first and second flow channels 5 and 8, respectively. Therefore, to achieve sufficient stability, not the number of spacers themselves, but the number of their crossing points should have a certain minimum value. The crossing points in this case are those areas (or rather their centers) at which the spacers 9, 10, which are perpendicular to each other and lie in different planes, intersect each other. It has proved to be expedient to provide at least four such crossing points per 100 cm ² or preferably per 10 cm × 10 cm wall surface. The location and arrangement of the remaining parts is opposite Fig. 2 to 7 unchanged.

Finally, in the case of Fig. 8 be expedient to embody the protruding into the flow channels 8 nubs 12 in the manner raised, as above with reference to 3 and 4 is explained in detail.

The invention is not limited to the described embodiment, which can be modified in many ways. This applies, as already mentioned, in particular for the waveform of the profilings 11 used in the individual case. Preference is given in particular to those waveforms which have the same wavelengths 1 throughout and in which the ascending and descending sections 11a, 11b are substantially the same length. Also, the size of the radii in the connecting zones between the sections 11a, 11b, 11c, and preferably also in the connecting zones between the transition sections 6b, 7b and the adjacent Wall parts or side and connecting strips 6a, 7a and 6c, 7c are provided, can be selected depending on the individual case. In addition, the spacers 9,10 other than the Fig. 6 and 8th have apparent lengths. Further, the heat exchangers described may be used for purposes other than those specified and gases other than air or steam. Depending on the purpose of use can also be contrary Fig. 1 the first flow channels 5 are shorter than the second flow channels 8. In addition, it is clear that the statements "above" and "below" with respect to the walls 6, 7 relate only to the described embodiment, in which the first flow channels 5 each bounded above by the walls 6 and below through the walls 7 while the reverse applies to the second flow channels 8. Instead, the heat exchanger can of course also z. B. in a slightly oblique position or in a rotated position by 90 ° are applied so that the flow channels 5 or 8 are arranged vertically. Finally, it is understood that the various features may be applied in combinations other than those described and illustrated.

Claims (16)

Heat exchanger for gaseous media, comprising: a plurality of first, in a first direction (3) extending flow channels (5), which are stacked in a stack and spaced above each other with their ends in a respective holding frame (2) protrude and between them second, in a second direction (4) extending flow channels (8) form, wherein the first flow channels (5) by alternately superposed, consisting of sheet material walls (6, 7) are limited by means of laterally and parallel to the first direction (3 Having arranged side strips (6a, 7a) are gas-tightly connected to each other by welding, and wave-shaped profilings (11) and formed on them inner, in the first flow channels (5) projecting spacers (9) and outer spacers (10) having the Stack of superimposed first flow channels (5) spaced from each other, characterized in that the wave-shaped profilings (11) with the Indented partially in planar portions (11a, 11b, 11c) arranged nubs (12), the walls (6, 7) front and rear, parallel to the second direction arranged connecting strips (6c, 7c), wherein the connecting strips (6c, 7c) of the walls (6, 7) of any first flow channel (5) respectively with the connecting strips of the walls (6, 7) of a stack above or below the first flow channel (5) to form a contiguous one with the first and second flow channels ( 5, 8) provided blocks (1) are interconnected by welding gas-tight, and the spacers (9, 10) of elongated shapes, wherein the inner spacers (9) with their longitudinal axes parallel to the first direction (3) and the outer spacers (10) are arranged with their longitudinal axes parallel to the second direction (4). Heat exchanger according to claim 1, characterized in that the block (1) is attached to the connecting strips (6c, 7c) having ends by gluing in the frame (2). Heat exchanger according to claim 1 or 2, characterized in that the profilings (11) are wave-shaped in the first or second direction. Heat exchanger according to one of claims 1 to 3, characterized in that the profilings (11) are trapezoidal and the walls (6, 7) are arranged parallel to each other such that the heights of the flow channels (5, 8) in the of the spacers ( 9, 10) and nubs (12) are substantially the same throughout free areas. Heat exchanger according to one of Claims 1 to 4, characterized in that the profilings (11) have a length (1) measured in the second direction (4) and a height (h) measured perpendicular to the walls (6, 7) and Ratio 20 ≥ 1 / h ≥ 5. Heat exchanger according to one of claims 1 to 5, characterized in that the inner and outer spacers (9, 10) distributed substantially uniformly over the walls (6, 7) and in area sections of the walls of 100 cm ² , preferably square area sections of 10 cm × 10 cm, in each case at least four spacers (9, 10) are present. Heat exchanger according to one of claims 1 to 6, characterized in that the inner and outer spacers (9, 10) are arranged so that they lie one above the other in the stack and form from top to bottom continuous support lines. Heat exchanger according to one of claims 1 to 7, characterized in that the walls (6, 7) have a substantially constant, 0.1 mm to 0.5 mm thickness. Heat exchanger according to one of claims 1 to 8, characterized in that the nubs (12) in the walls (6, 7) are raised and / or recessed formed. Heat exchanger according to claim 9, characterized in that the nubs (12) are at least on those walls (7) at which to arise in operation, liquid condensate flow, embossed are pronounced. Heat exchanger according to claim 10, characterized in that the nubs (12) are raised in operation during the lower walls (7) of the first flow channels (5) and are so pronounced that they protrude into the first flow channels (5). Heat exchanger according to one of claims 1 to 11, characterized in that the side strips (6a, 7a) and the connecting strips (6c, 7c) provided in over the flow channels (5, 8) outwardly projecting portions and curved by upward or downward Sections are connected to the walls (6, 7). Heat exchanger according to claim 12, characterized in that in each wall (6, 7) the sections leading to the side strips (6a, 7a) and the sections leading to the connecting strips (6c, 7c) are respectively curved towards opposite sides. Heat exchanger according to one of claims 1 to 13, characterized in that the side and connecting strips (6a, 7a and 6c, 7c) are arranged substantially parallel to each other. Heat exchanger according to one of claims 1 to 14, characterized in that the spacers (9, 10) extend approximately over the entire length of the associated flow channels (5, 8). Heat exchanger according to claim 15, characterized in that in surface portions of the walls (6, 7) of 100 cm ² , preferably square surface portions of 10 cm x 10 cm, at least four intersections between the inner and outer spacers (9, 10) are present ,

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