DE102011077154A1 - Vaporizer for use as plate heat exchanger in waste heat utilization device of combustion engine for vaporizing liquid, has channel whose flow conducting cross-section increases in direction of flow of vaporizing liquid in vaporization zone - Google Patents

Abstract

The vaporizer (1) has gas paths (6) formed between respective neighboring channel plate arrangements (2) for conducting gas (7), over which the heat required to vaporize liquid (4) is supplied. Each plate arrangement has a channel for connecting a liquid inlet with a vapor outlet and forming a multiply-deflected vaporization path for the liquid to be vaporized. The channel comprises a flow conducting cross-section that increases in the direction of flow of the vaporizing liquid in a vaporization zone of the vaporization path.

Description

The present invention relates to an evaporator for evaporating a liquid, in particular for a waste heat utilization device of an internal combustion engine.

In waste heat recovery devices, which are based on the principle of a Rankine cycle process or a Rankine-Clausius cycle, evaporators are used, with the aid of the working medium of the cycle can be evaporated, the heat required for this is taken from the exhaust gas of an internal combustion engine. Accordingly, such an evaporator contains on the one hand a gas path for the exhaust gas and on the other hand an evaporation path for the working medium to be evaporated.

Such an evaporator may for example be designed as a plate heat exchanger and accordingly have a plurality of channel plate assemblies which are stacked in a stacking direction, wherein in each case between two adjacent channel plate assemblies, a gas path is formed through which a gas is feasible, via which the heat required for the evaporation of the liquid supplied is. The respective channel plate arrangement may expediently contain a liquid inlet, a steam outlet and a channel connecting the liquid inlet to the steam outlet, which channel forms for example a multiply deflected evaporation path for the liquid to be evaporated.

The present invention addresses the problem of providing for an evaporator of the type mentioned an improved or at least another embodiment, which is characterized by a high efficiency and low cost manufacturability.

This problem is solved by the present invention, in particular by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea of designing the respective channel in which the evaporation of the liquid takes place, at least in an evaporation zone of the evaporation path, in such a way that the flow-through cross section in the direction of flow of the evaporating liquid increases. The increasing in the flow direction through-flowable cross section of the evaporation path takes into account to some extent the increase in volume of the liquid to be evaporated by the evaporation. As a result, for example, an excessive increase in pressure in the evaporation path can be avoided. Furthermore, the flow velocity in the gas phase can be reduced, which increases the residence time of the liquid to be evaporated in the evaporator. Overall, the efficiency of the evaporator can be increased thereby.

In conjunction with the plate design of the evaporator, the evaporator can be realized comparatively inexpensive. The individual channel plate arrangements can be realized identical, which reduces the manufacturing costs.

The increase of the flow-through cross-section of the evaporation path at least within the evaporation zone in the flow direction of the liquid to be evaporated can be unrestrained or continuous, for example linear or progressive. It is also possible to realize the cross-sectional increase in a stepped manner.

The vaporization zone of the vaporization path substantially extends from a region of the vaporization path in which vaporization begins to a region of the vaporization path in which the fluid is substantially completely vaporized.

According to an advantageous embodiment, the respective channel in a preheating zone may have a flow-through cross-section which remains constant in the direction of flow of the liquid. This takes into account that no significant volume change occurs in the preheating zone. The preheat zone extends substantially from the liquid inlet to a portion of the evaporation path where evaporation begins.

In addition or as an alternative, it can be provided that the respective channel in an overheating zone has a flow-through cross-section which remains constant in the direction of flow of the liquid. This is based on the consideration that in the overheating zone primarily an increase in pressure in the steam should be achieved. In this case, the overheating zone essentially extends from a region of the evaporation path in which the liquid has essentially completely evaporated to the vapor outlet.

If constant flow cross-sections remain both in the preheating zone and in the superheating zone, this means that the evaporation path has an air flow-through cross-section increasing only in the evaporation zone, ie only in the evaporation zone. Furthermore, this means that the flow-through cross section in the overheating zone is greater than in the preheating zone.

In another embodiment, the respective channel may be formed by a plurality of juxtaposed channel sections, wherein the evaporation path at the transition between two adjacent channel sections each having a 180 ° deflection. This gives the channel or the evaporation path a meandering course, which realizes a relatively large path length or channel length over a comparatively narrow space.

In another embodiment, the respective channel plate assembly may comprise two plates, wherein the respective channel is formed by indentations which are either formed only in one of the two plates or are formed mirror-symmetrically in both plates. The impressions may be configured in particular according to the channel sections in order to realize the meandering course for the channel or the evaporation path. The indentations can be realized for example by deep drawing or by high-pressure forming. If the indentations are formed only in one of the two plates, the other plate can be configured just.

According to an advantageous development, the respective plate provided with embossings may have convexly curved or flat contact surfaces in the region of the impressions on an outer side facing the gas path. The curved contact surfaces are particularly easy to produce. The flat contact surfaces favor the flow in the gas path and can simplify the connection of the heat transfer enhancing elements.

According to an expedient development, a fin structure can be arranged in the respective gas path, which is arranged on the contact surfaces, in particular attached thereto. Such a fin structure can improve the heat transfer between the gas of the gas path and the respective plate, which improves the heat transfer coupling between the gas path and the evaporation path. The fin structure can be soldered or welded, for example, in the region of the contact surfaces with the respective plate.

Particularly expediently, the two plates of the respective channel plate arrangement can be fastened to one another. As a result, the stack of plates formed by the stacked channel plate arrangements can be stabilized and, in particular, configured to be self-supporting. The two plates of the respective channel plate arrangement may expediently be fastened to the respective channel laterally enclosing one another along the evaporation path. This makes the channels particularly easy to implement. At the same time an efficient sealing of the respective channel can be realized thereby. The attachment can in this case be realized for example by means of a soldering process or a welding process. Suitable welding methods are, for example, laser welding, micro-plasma welding, micro-TIG welding, roll seam welding and resistance welding.

In another advantageous embodiment, two lateral boundary walls may be provided, which bound the gas paths on opposite sides in each case from a gas inlet to a gas outlet. The boundary walls can in particular connect or fasten together the adjacent channel plate arrangements. Thus, the boundary walls increase the stability of the plate stack. The one boundary wall may have inlet openings each fluidly connected to a fluid inlet of one of the channel plate assemblies. This simplifies the supply of the liquid to be evaporated through the boundary wall. The other boundary wall may have outlet openings each fluidly connected to a vapor outlet of one of the channel plate assemblies. Thus, a common discharge of the evaporated liquid through the other boundary wall can be simplified.

According to an advantageous development, the boundary walls can each be formed by a plurality of wall elements, each of which limits only one of the gas paths laterally. This simplifies the modular design of the evaporator, wherein in particular the number of wall elements of the respective boundary wall of the number of channel plate arrangements largely corresponds. Conveniently, the wall elements may either be attached to both channel plate arrangements delimiting this gas path or may be integrally formed on one of the plates of one of the channel plate arrangements delimiting this gas path and then be attached to the adjacent channel plate arrangement. In particular, the integrated design, in which the respective wall element is integrally formed on at least one plate, simplifies a cost-effective production of the evaporator. The attachment of the wall elements is expedient again via welded joints or solder joints. By means of welded joints can be realized, for example, multi-sheet seams, which simultaneously several components can be fixed together. If the components to be fixed to each other lie flat against each other, solder joints are preferred.

In another advantageous development, an inlet cover which covers several or all inlet openings and forms a feed channel can be attached to the one boundary wall fluidly connects a common fluid port to the fluid inlets. Additionally or alternatively, an outlet cover may be attached to the other boundary wall, covering a plurality or all of the outlet openings and forming a discharge channel that fluidly connects a common steam connection to the steam outlets. These measures simplify the assembly of the evaporator or the installation of the evaporator in the waste heat recovery device.

Conveniently, the stacked channel plate assemblies may form a stack having two mutually remote end plates with respect to the stacking direction, each forming or defining a gas path together with a channel plate assembly adjacent thereto. The end plates thus contain no evaporation path, but serve only to limit the gas path. This construction results in that all evaporation paths are arranged in the stacking direction between two gas paths, which increases the effectiveness of the evaporator.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Show, in each case schematically,

1 an isometric view of an evaporator,

2 a longitudinal section through a channel plate assembly of the evaporator according to section lines II in 1 .

3 and 4 in each case a different longitudinal section of the channel plate arrangement according to section lines III in 2 in various embodiments,

5 a longitudinal section of the evaporator in the range of several channel plate assemblies,

6 a partially sectioned isometric view of a channel plate assembly,

7 an isometric view of an area of the evaporator,

8th - 11 in each case a sectional view through a region of the evaporator according to section lines VIII in FIG 7 in various embodiments,

12 an isometric partial view of a channel plate assembly with fin structure,

13 and 14 Isometric partial views of the evaporator, in various embodiments.

Corresponding 1 includes an evaporator 1 several channel plate arrangements 2 in a stacking direction 3 are stacked. The evaporator 1 serves to evaporate a liquid 4 that the evaporator 1 can be supplied according to an arrow. Preferably, the evaporator comes 1 in a waste heat utilization device of an internal combustion engine for use in order to extract heat from exhaust gases of the internal combustion engine in order to evaporate a liquid, namely a working medium of the waste heat utilization device. Such a waste heat utilization device operates according to the Rankine cycle process or the Rankine-Clausius cycle process. An essential component of such a waste heat utilization device is the evaporator 1 which provides a heat transfer coupling between an exhaust system of the internal combustion engine and a waste heat utilization circuit of the waste heat utilization device.

The stacked channel plate assemblies 2 form a plate stack 5 or evaporator block 5 , Inside the stack 2 or within the block 5 is between each two adjacent channel plate assemblies 2 a gas path 6 formed by a gas 7 according to arrows can be passed. About this gas 7 is used to evaporate the liquid 4 required heat supplied. In particular, it is the gas 7 to exhaust gas of an internal combustion engine whose waste heat is to be used for example in a waste heat recovery device.

According to 2 has each channel plate assembly 2 a liquid inlet 8th and a steam outlet 9 up, through the steam 10 or vaporized liquid can escape. Furthermore, the respective channel plate arrangement contains 2 a channel 11 that the fluid inlet 8th fluidic with the steam outlet 9 combines. The channel 11 forms a broken line, repeatedly deflected evaporation path 12 for the too vaporizing liquid 4 , The channel 12 comprises in the flow direction of the liquid to be evaporated 4 first a preheating zone 13 to which there is an evaporation zone 14 connects, and to an overheating zone 15 followed. The preheating zone 13 essentially extends from the liquid inlet 8th up to one area 16 the evaporation path 12 in which the evaporation of the liquid 4 starts. Within the preheating zone 13 Thus, the liquid heats up 4 on their boiling temperature. The evaporation zone 14 essentially extends from this area 16 in which the evaporation of the liquid 4 starts, up to an area 17 the evaporation path, in which the liquid 4 essentially completely evaporated. Within the evaporation zone 14 the fluid stays 4 essentially at its boiling point and is within the evaporation zone 14 completely evaporated. The overheating zone 15 essentially extends from the area 17 in which the liquid 4 is essentially completely vaporized, to the steam outlet 9 , Within the overheating zone 15 the temperature of the steam increases 9 about the boiling temperature of the liquid 4 out.

The here presented evaporator 1 is characterized in that within the respective channel plate assembly 2 the respective channel 11 a flow-through cross-section 18 which, at least in the evaporation zone 14 in the flow direction of the evaporating liquid 4 increases. In the embodiment shown the 2 takes the flow-through cross-section 18 doing so in several stages leaps and bounds. In another embodiment, there is also an un-graded or continuous increase in the flow-through cross-section 18 realizable.

At the in 2 the embodiment shown is the durchströmbare cross section 18 within the preheating zone 13 kept constant. Furthermore, at the in 2 The embodiment shown by the flow-through cross-section 18 within the overheating zone 15 kept constant. Thus, here an increase of the cross section takes place 18 only within the evaporation zone 14 , The flow-through cross section 18 is therefore in the preheating zone 13 smaller than in the overheating zone 15 ,

The respective channel is expedient 11 configured meandering around the multiply deflected evaporation path 12 To realize as compact as possible. According to 2 may be the respective channel 11 by several juxtaposed, by common channel walls 43 separate channel sections 19 be formed, which are arranged together 19 that the evaporation path 12 at the transition between two adjacent channel sections 19 each undergoes a 180 ° deflection. For example, the liquid flows through 4 or the steam 10 the individual channel sections 19 starting from the liquid inlet 4 to the steam outlet 9 alternately from bottom to top and from top to bottom.

According to the 3 - 14 can the respective channel plate assembly 2 two plates each 20 . 21 have, wherein the respective channel 11 or the channel sections 19 through imprints 22 are formed. These impressions 22 can according to 3 in both plates 20 . 21 be formed mirror-symmetrically or according to 4 in only one of the two plates 20 . 21 be educated. In the example of 4 is the one plate 20 with the imprints 22 equipped while the other plate 21 just configured.

The two plates 20 . 21 between them the channel 11 or the channel sections 19 training, are purposefully fixed to each other. Corresponding attachment points are in the 3 and 4 With 23 designated. These attachment points 23 may be solder joints or welded joints. The attachment points 23 are expediently tight and realized so that they the respective channel 11 or the respective channel section 19 border laterally and in particular the channel walls 43 form, so that ultimately the two plates 20 . 21 along the evaporation path 12 attached to each other.

The with the imprints 22 provided plates 20 . 21 can on their outside, inside the block 5 the gas path 6 facing, in the area of imprints 22 according to the 3 - 5 be convex or according to the 6 - 14 just be designed. For arched imprints 22 arise vaulted contact surfaces 24 , At the flat impressions 22 Accordingly, flat contact surfaces arise 24 ,

According to the 1 . 5 and 7 - 14 can be within the respective gas path 6 a fin structure 25 be arranged to transfer heat from the gas flow 7 on the channel plate arrangements 2 and thus on the liquid to be evaporated 4 to improve. The respective fin structure 25 contacts the plate facing the gas path 20 . 21 the respective channel plate assembly 2 , Appropriately, this contacting takes place in the aforementioned contact surfaces 24 , Advantageously, according to 5 also a fixation of the fin structure 5 at the channel plate arrangements 2 in the area of contact surfaces 24 will be realized. Corresponding attachment points are in 5 with it 26 designated. These may again be solder joints or welds.

To connect the fin structure 25 to the channel plate assemblies 2 To improve, the flat contact surfaces 24 prefers. In particular, the fin structures 25 this according to the 7 - 14 across the gas path 6 have a rectangular profile or a diamond profile and accordingly also have flat contact surfaces, the area with the contact surfaces 24 the channel plate arrangements 2 stay in contact.

According to the 1 and 7 - 14 points the evaporator 1 two lateral boundary walls 27 . 28 on which the gas paths 6 limit on opposite sides, and thereby of a gas inlet 29 up to a gas outlet 30 extend. According to the 7 and 13 can the respective, the viewer facing boundary wall 27 inlets 31 each having a liquid inlet 8th the respective channel plate assembly 2 are fluidically connected. The respective opposite boundary wall 28 contains accordingly unrecognizable outlet openings here, each with a steam outlet 9 the respective channel plate assembly 2 are fluidically connected.

In the embodiments shown here the 7 - 14 are the two boundary walls 27 . 28 each by several wall elements 32 formed, with the individual wall elements 32 only one of the gas paths 6 limit laterally. At the in 8th shown embodiment, these wall elements 32 as separate components with respect to the channel plate assemblies 2 designed to the the respective gas path 6 delimiting channel plate arrangements 2 are grown. In contrast, in the embodiments of the 7 and 9 - 14 the wall elements 32 on one of the plates 20 . 21 integrally formed and to the adjacent channel plate assembly 2 grown. The assembly takes place in each case again via various attachment points 33 or 34 , which may be designed as solder joints or welded joints. By way of example, several attachment points 33 as Mehrblechnähte, z. B. as 3-sheet seams or 4-sheet seams, designed while several other attachment points 34 are designed as flat solder joints. In the embodiments of the 1 and 9 - 14 is the respective wall element 32 integral to the respective plate 21 formed, which is just laid out and no impressions 22 having. In principle, however, another embodiment is conceivable. For example, two embossed plates 20 . 21 be provided. Alternatively, the wall elements 32 integral with the imprints 22 provided plate 20 be formed.

At the in 14 embodiment shown is facing the observer facing boundary wall 27 an inlet cover 35 grown, the more or preferably all the inlet openings 31 the respective boundary wall 27 covers and a feed channel 36 forms, which has a common liquid connection 37 with the fluid inlets 8th the various channel plate arrangements 2 fluidly connects. Similarly, according to 1 also the other boundary wall 28 with an outlet cover 38 be equipped, the more or preferably all the outlet openings of the respective outlet-side boundary wall 28 covers while a discharge channel 39 forms a common steam connection 40 with the steam outlets 9 the respective channel plate assemblies 2 fluidly connects.

Like yourself 14 furthermore, the stack comprises 5 or the block 5 with respect to the stacking direction 3 at two opposite ends each have an end plate 41 respectively. 42 , The respective end plate 41 . 42 limited in the stacking direction 3 together with a channel plate arrangement adjacent thereto 2 each a gas path 6 , In said gas path 6 can also have a fin structure 25 be arranged. In the example of 14 is the upper end plate 41 also integral with two wall elements 32 shaped, which together with the wall elements 32 the channel plate arrangements 2 the two boundary walls 27 . 28 form.

In the 14 shown lower end plate 42 is from the wall elements 32 the adjacent channel plate assembly 2 overlaps laterally, creating a sealed end for the stack 5 or the block 5 easy to implement.

Claims (11)

Evaporator for evaporating a liquid ( 4 ), in particular for a waste heat utilization device of an internal combustion engine, - with a plurality of channel plate arrangement ( 2 ) in a stacking direction ( 3 ) are stacked, each between two adjacent channel plate assemblies ( 2 ) a gas path ( 6 ) is formed, through which a gas ( 7 ) is feasible over which the evaporation of the liquid ( 4 ) heat can be supplied, - wherein each channel plate arrangement ( 2 ) a liquid inlet ( 8th ), a steam outlet ( 9 ) and a liquid inlet ( 8th ) with the steam outlet ( 9 ) connecting channel ( 11 ) containing a multiply deflected evaporation path ( 12 ) for the liquid to be evaporated ( 4 ), whereby the respective channel ( 11 ) at least in an evaporation zone ( 14 ) of the evaporation path ( 12 ) one in the flow direction of the evaporating liquid ( 4 ) increasing flow-through cross section ( 18 ) having. Evaporator according to claim 1, characterized in that - the respective channel ( 11 ) in a preheating zone ( 13 ) of the evaporation path ( 12 ) one in the flow direction of the liquid ( 4 ) constant flow cross-section ( 18 ), and / or - that the respective channel ( 11 ) in an overheating zone ( 15 ) of the evaporation path ( 12 ) one in the flow direction of the evaporated liquid ( 4 ) constant flow cross-section ( 18 ), and / or - that the respective channel ( 11 ) in a preheating zone ( 13 ) of the evaporation path ( 12 ) a smaller flow-through cross section ( 18 ) than in an overheating zone ( 15 ) of the evaporation path ( 12 ). Evaporator according to claim 1 or 2, characterized in that the respective channel ( 11 ) by a plurality of juxtaposed channel sections ( 19 ), wherein the evaporation path ( 12 ) at the transition between two channel sections ( 19 ) each having a 180 ° deflection. Vaporizer according to one of claims 1 to 3, characterized in that the respective channel plate arrangement ( 2 ) two plates ( 20 . 21 ), wherein the respective channel ( 11 ) by impressions ( 22 ) formed either only in one of the two plates ( 20 . 21 ) or in both plates ( 20 . 21 ) are mirror-symmetrical. Evaporator according to claim 4, characterized in that the respective impressions ( 22 ) provided plate ( 20 . 21 ) at a gas path ( 6 ) facing outside in the region of the indentations ( 22 ) convexly curved or flat contact surfaces ( 24 ) having. Evaporator according to claim 5, characterized in that in the respective gas path ( 6 ) a fin structure ( 25 ) arranged at the contact surfaces ( 24 ), in particular fastened, is. Evaporator according to one of claims 4 to 6, characterized in that the two plates ( 20 . 21 ) of the respective channel plate arrangement ( 2 ) are attached to each other, wherein it can be provided in particular that the two plates ( 20 . 21 ) of the respective channel plate arrangement ( 2 ) the respective channel ( 11 ) laterally bordering along the evaporation path ( 12 ) are attached to each other. Evaporator according to one of claims 4 to 7, characterized in that - two lateral boundary walls ( 27 . 28 ) are provided which the gas paths ( 6 ) on opposite sides of each of a gas inlet ( 29 ) to a gas outlet ( 30 ), - that the one boundary wall ( 27 ) Inlet openings ( 31 ), each with a liquid inlet ( 8th ) one of the channel plate assemblies ( 2 ) is fluidically connected, - that the other boundary wall ( 28 ) Has outlet openings, which with a steam outlet ( 9 ) one of the channel plate assemblies ( 2 ) is fluidly connected. Evaporator according to claim 8, characterized in that the boundary walls ( 27 . 28 ) each by a plurality of wall elements ( 32 ) are formed, each only one of the gas paths ( 6 ), in particular, it may be provided that the wall elements ( 32 ) either to both, this gas path ( 6 ) limiting channel plate arrangements ( 2 ) or on one of the plates ( 20 . 21 ) one of this gas path ( 6 ) limiting channel plate arrangements ( 2 ) are integrally formed and to the adjacent channel plate assembly ( 2 ) are grown. Evaporator according to claim 8 or 9, characterized in that - to the one boundary wall ( 27 ) an inlet cover ( 35 ), which has several or all inlet openings ( 31 ) and a feed channel ( 36 ) forming a common liquid connection ( 37 ) with the liquid inlets ( 8th ) fluidly connects, and / or - that to the other boundary wall ( 28 ) an outlet cover ( 38 ), which covers several or all outlet openings and a discharge channel ( 39 ) forming a common vapor connection ( 40 ) with the steam outlets ( 9 ) fluidly connects. Vaporizer according to one of claims 1 to 10, characterized in that the stacked channel plate arrangements ( 2 ) a stack ( 5 ), which with respect to the stacking direction ( 3 ) two mutually remote end plates ( 41 . 42 ), which in each case together with a thereto adjacent channel plate arrangement ( 2 ) a gas path ( 6 ) train.

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