DE102013226153A1 - Pipe heat exchanger and arrangement - Google Patents

Abstract

The invention relates to a tubular heat exchanger (1) having a tubular element (3) which has an outer circumferential wall (5), wherein at least two chambers separated by a radially extending web (9) radially inside the outer circumferential wall (5) ( 7) are provided. It is provided that the web (9) extends - as seen in the radial direction - along a curve whose course deviates from the course of a straight line.

Description

The invention relates to a tube heat exchanger according to the preamble of claim 1 and an arrangement with an exhaust gas emitting internal combustion engine and a tube heat exchanger according to claim 9.

State of the art

Pipe heat exchangers of the type discussed here and corresponding arrangements are known. Such a tube heat exchanger has a tube element which has an outer circumferential wall. Radially within the outer circumferential wall at least two chambers are provided which are separated from one another by a web, wherein the web extends in the radial direction. Typically, it is provided that a first medium is arranged outside the outer peripheral wall, in particular flows around the outer circumferential wall, and that a second medium is arranged in the at least two chambers, in particular flows into the at least two chambers. In this case, heat is transferred through the outer circumferential wall from the first medium to the second medium or vice versa. As a result of the various temperatures acting on the component and, if appropriate, due to temperature changes in the media, stresses develop in the tube heat exchanger, which are critical especially in the region of the web where the tube element is designed to be weakest. In the worst case, the bridge can break.

Disclosure of the invention

The invention is therefore based on the object to provide a tube heat exchanger and an arrangement in which the disadvantages mentioned do not occur.

The object is achieved by providing a tube heat exchanger having the features of claim 1. This is characterized by the fact that the web extends - as seen in the radial direction - along a curve whose course deviates from the course of a straight line. While extending in the known tubular heat exchangers of the web along a straight line, so that these forces acting in the radial direction can easily lead to breakage of the web, which gives along a deviating from the course of a straight curve curve lends the pipe element increased elasticity, wherein In particular, a non-destructive, lateral buckling of the web is possible. The tube heat exchanger is thus designed to be more stable and durable, whereby it is not destroyed even at thermal stresses and / or rapid temperature changes.

The tube heat exchanger and in particular the tube element is / are preferably formed as an extrusion profile. The tube heat exchanger and in particular the tube element therefore has / have a cross-section which continues as seen along a longitudinal direction, wherein the longitudinal direction runs obliquely to the cross-sectional area, in particular is perpendicular thereto. A radial direction is a direction which lies in the cross-sectional plane and is preferably perpendicular to the longitudinal direction. The web thus extends in the cross-sectional plane from radially inward to radially outward, wherein it continues in the direction of the extrusion profile in the longitudinal direction. In the cross-sectional view results in the shape of the web, which describes a curve whose course deviates from the course of a straight line.

It is possible that an outer cross-section of the tube heat exchanger and in particular of the tubular element is round. In particular, it is possible that the tube heat exchanger and in particular the tube element is designed as a circular cylinder / are. Alternatively, it is also possible that a polygonal, in particular a hexagonal cross-section is provided.

In a preferred embodiment of the tube heat exchanger, the tube element has a plurality of chambers which are separated by a plurality of webs. In this case, preferably all webs extend - as seen in the radial direction - along curves whose course deviates from the course of a straight line. Particularly preferably, the curves of all webs are identical.

It is also preferred a tube heat exchanger, which is characterized in that the web extends along a curved curve. Alternatively, it is possible for the ridge to extend along a curve having a plurality of straight sections that enclose at least one angle with each other. Such a design of the web can ensure the described elasticity and allow a non-destructive lateral buckling of the web. However, a curved curve for the web has the advantage of increased stability and at the same time improved elasticity.

Particularly preferably, the web extends along a curve having a constant radius of curvature. In this case, the curvature of the curve does not change along its course. Such a bow shape is particularly stable and elastic. It allows in a particularly favorable manner, the lateral buckling of the web without the pipe element and thus the tube heat exchanger is damaged.

An embodiment of the tube heat exchanger is also preferred, which is characterized in that the tube element has an inner peripheral wall which separates the at least two chambers from a central chamber. In this case, the at least one web extends from the inner circumferential wall to the outer circumferential wall. The central chamber is provided, as it were, about the longitudinal axis of the tubular element and extends in the longitudinal direction. In a preferred embodiment of the tube heat exchanger, the central chamber is provided to guide a third medium, which serves in particular the re-cooling of the second medium arranged in the chambers. It is thus possible in particular to bring the second medium in the chambers in a first working phase of the tube heat exchanger through the arranged outside the outer circumferential wall, the first medium to a first, preferably higher temperature, preferably to heat, and in a second phase of work through the bring third medium to a second, preferably lower temperature, in particular to cool. In this way, the tube heat exchanger is exposed to changing temperatures, with the increased stability and elasticity of the tubular element has a favorable effect on the life of the Rohrwärmeübertragers.

An embodiment of the tube heat exchanger is also preferred, which is characterized in that the tube heat exchanger has a casing element encompassing the tube element. The tubular element has a first material with a first coefficient of thermal expansion, wherein the envelope element has a second material with a second thermal expansion coefficient. In this case, the first material is different from the second material. Due to the arrangement of the enveloping element around the tubular element, stresses in the tubular heat exchanger are formed in a special way, which are absorbed by the elastically configured web.

Preferably, the first thermal expansion coefficient is greater than the second thermal expansion coefficient. Thus, if the tube heat exchanger is heated in particular by the first medium, the tube element in the envelope element expands more strongly than the envelope element. This can lead to damage to the entire tube heat exchanger, because it can lead to voltage increases, the arrangement of the tubular element in the sheath element burst or at least can get cracks. The elastically designed web reduces this risk and thus protects the entire heat exchanger against stress damage. In particular, as a result of the fact that the web can buckle laterally, the tubular element expands to a lesser extent in the enveloping element, so that component overload is reliably avoided.

An embodiment of the tube heat exchanger is preferred in which the tube element comprises aluminum or an aluminum alloy, wherein it preferably consists of aluminum or an aluminum alloy. As a result, the tubular element is designed to be very light, so that it contributes to lightweight construction, especially when used in the automotive sector. On the other hand, aluminum or an aluminum alloy as a material is particularly suitable for applying a coating, which can be provided in particular in the use of the tube heat exchanger in an adsorption in the chambers of the tubular element.

An embodiment of the tubular heat exchanger is also preferred, which is characterized in that the enveloping element comprises steel, preferably stainless steel, wherein it preferably consists of steel, preferably of stainless steel. In this case, the enveloping element is very well suited to withstand even higher temperatures, which is not the case for aluminum or an aluminum alloy, for example.

Particularly preferred is an embodiment of the Rohrwärmeübertragers in which the tubular element comprises aluminum or an aluminum alloy, preferably made of aluminum or an aluminum alloy, wherein at the same time the sheath element steel, preferably stainless steel, or consists of steel, preferably made of stainless steel. This material combination is particularly suitable for the case that the tube heat exchanger is exposed by the first medium outside high temperatures, while he should be coated in the same time in the area of the chambers. This is the case in particular when the tube heat exchanger is used in an adsorption chiller. It turns out that aluminum or an aluminum alloy is a particularly suitable material for the coating to be provided in the chambers, while the cladding made of steel, in particular stainless steel, is excellently suited to withstand high temperatures, such as the exhaust gas temperatures of an internal combustion engine, non-destructive. Due to this combination for the use of the tubular heat exchanger favorable properties, a corresponding mixing construction of the tube heat exchanger is preferred, with a quasi-functional separation of the Hüllelements is realized by the pipe element in particular by the selection of different materials.

It turns out that aluminum or an aluminum alloy has a higher coefficient of heat recovery than steel or aluminum Stainless steel. Therefore, especially in such a combination there is a risk that the tubular element made of aluminum expands more strongly by heating than the enveloping element, which is designed as a steel pipe or stainless steel pipe. Due to the fact that the at least one web can buckle laterally, however, the tubular element made of aluminum-seen in the radial direction-expands to a lesser extent, so that overall a component overload is avoided.

An exemplary embodiment of the tube heat exchanger is also preferred, which is characterized in that a gap measured in the radial direction between an inner peripheral surface of the envelope element and an outer circumferential surface of the outer circumferential wall of the tubular element is made as small as technically possible. The enveloping element is preferably designed as a tube, in which the likewise tubular tube element is arranged. In this case, it is possible for a radial gap to remain between the inner circumferential surface of the enveloping element and the outer circumferential surface of the tubular element. This is favorable in view of the different expansion properties of the two parts, but unfavorable in terms of the most efficient heat transfer from the outside of the Hüllelements arranged first medium to the arranged in the chambers second medium. For the most efficient possible operation of the tube heat exchanger, thus the best possible heat transfer, it is important that the radial gap between the two elements is formed as small as technically possible. Particularly preferably, this radial gap disappears everywhere along the entire tube heat exchanger.

In this connection, an embodiment is preferred in which the outer circumferential surface of the outer circumferential wall of the tubular element rests on the inner circumferential surface of the enveloping element over the entire surface. The radial gap is closed everywhere, and the surfaces are directly adjacent to each other. In this way, a particularly efficient heat transfer is first possible from the first medium to the enveloping element and then from the enveloping element to the tubular element, so that the heat of the first medium can be transferred quickly and without loss to the second medium arranged in the chambers. With vanishing radial gap, however, there is again the problem that the enveloping element expands in particular less than the tubular element, so that there may be excessively high voltages which lead to a component damage of the tubular heat exchanger. However, this is in turn avoided by the fact that the web is elastic due to its special shape and can buckle sideways, so that the tubular element expands less than would be the case with a running along a straight web, the case of excess voltage, moreover, a high risk would be exposed to break.

Therefore, in particular, the shape of the web proposed here enables a minimization of the radial gap between the tubular element and the enveloping element and thus an improvement in the heat transfer properties of the tubular heat exchanger.

Also preferred is an adsorption refrigeration machine having a tube heat exchanger according to one of the embodiments described above. An adsorption chiller is a sorption chiller that works with a solid sorbent. It has an adsorber / desorber device and an evaporator / condenser device, which are either arranged in a common container or connected to each other by a pipe. In an adsorption phase of the adsorption chiller, a liquid refrigerant present in the evaporator / condenser device is vaporized there and adsorbed by the adsorber / desorber device, which has a very large surface area. In this case, the evaporator / condenser device operates as an evaporator, wherein it extracts heat of evaporation from the environment and thereby provides cooling capacity available. The adsorber / desorber device also works as an adsorber, in which case adsorption heat is released, which is preferably removed.

In a desorption phase of the absorption chiller, the adsorber / desorber device, which then acts as a desorber, is supplied with heat to drive the refrigerant out of the device and evaporate. In the evaporator / condenser device, which now acts as a condenser, the refrigerant is liquefied, in which case the released heat of condensation is dissipated.

In this connection, an embodiment of the adsorption chiller and also an embodiment of the tube heat exchanger is preferred in which the at least two chambers are coated with an adsorber / desorber material. Thus, the chambers are designed as adsorber / desorber device. In the desorption phase, the tube heat exchanger is heated by the first medium arranged outside the outer circumferential wall and in particular outside the enveloping element, the refrigerant being expelled from the adsorber / desorber material and flowing into the evaporator / condenser device. The second medium arranged or flowing in the chambers is designed as a refrigerant of the adsorption chiller. In the adsorption phase, this is removed from the evaporator / Capacitor means inflowing refrigerant adsorbed by the adsorber / desorber material, wherein the released heat of adsorption is preferably discharged through a third medium flowing in the central chamber.

The adsorption chiller is preferably designed such that no third medium flows in the central chamber in the desorption phase, while the outer peripheral wall or the enveloping element flows around the hot first medium. The adsorption chiller is further preferably designed such that preferably no first medium flows around the outer circumferential wall or the enveloping element in the adsorption phase, while at the same time the third medium flows in the central chamber in order to dissipate the heat of condensation.

As a second medium and thus as a refrigerant, water or methanol is preferably used. As adsorber / desorber material, the at least two chambers preferably comprise a material which is selected from a group consisting of activated carbon, aluminum oxide, aluminum phosphate, silica-aluminum phosphate, metal-silica-aluminum phosphate, mesostructured silicate, a metal-organic framework, a microporous material, especially a microporous polymer, a silica gel, and a zeolite. Due to their large inner surface, these materials have the property of absorbing the second medium, in particular water or methanol, very well.

The object is also achieved by providing an arrangement with the features of claim 9. This has an exhaust-emitting internal combustion engine and a tube heat exchanger according to one of the embodiments described above. The arrangement is preferably designed for use in a motor vehicle. It has a fluid path which is arranged and designed such that the outer circumferential wall of the tubular element can be acted upon by exhaust gas of the internal combustion engine from the radially outer side via the fluid path. Alternatively, it is possible that the enveloping element can be acted on radially outside with exhaust gas of the internal combustion engine. Alternatively or additionally, it is possible that the outer peripheral wall of the tubular element can be acted on radially outside with a coolant of a cooling circuit of the internal combustion engine. Finally, it is alternatively possible that the enveloping element can be acted upon radially from the outside with the coolant of the cooling circuit of the internal combustion engine.

Particularly preferred is an embodiment of the arrangement in which the tubular element is encompassed by the enveloping element, which can be acted upon radially from the outside with the exhaust gas of the internal combustion engine and / or with the coolant. Both the exhaust gas and the coolant may be used as the first medium to transfer heat from the first medium to the second medium disposed or flowing in the chambers.

Particularly preferred is an embodiment of the arrangement in which the tubular element is encompassed by the enveloping element, wherein the enveloping element is acted upon from the outside radially to the exhaust gas of the internal combustion engine. The exhaust gas is very hot, so that the tube element could possibly be destroyed by the high exhaust gas temperature without the envelope element. Therefore, the arrangement of the Hüllelements around the pipe element around here is particularly favorable. At the same time, the hot exhaust gas is a very efficient heat source for heating the second medium in the chambers.

Preferably, a valve device is arranged in the fluid path, by which the loading of the Hüllelements or the outer peripheral wall of the tubular element with the first medium, that is with the exhaust gas and / or with the coolant, is controllable. In particular, an operating phase of the arrangement is preferably feasible in which the application of the first medium is omitted, wherein a further operating phase can be realized, in which the application is carried out.

An arrangement is preferred which is characterized by an adsorption chiller, wherein the tube heat exchanger is part of the absorption chiller. In this case, the chambers of the tube heat exchanger are preferably coated with adsorber / desorber material, as has already been described in connection with the adsorption chiller. Agas or coolant is then supplied via the fluid path in a desorption phase to the outer circumferential wall of the tubular element or the enveloping element in order to expel the refrigerant from the adsorber / desorber material. In an adsorption phase, the admission of exhaust gas or coolant is omitted, but rather in this, preferably the adsorber / desorber material is recooled via the central chamber of the tubular element, so that the released heat of adsorption can be dissipated.

Finally, a motor vehicle is also preferred, which is characterized in that it has an arrangement according to one of the previously described embodiments. In this case, an adsorption refrigerator of the type described here represents a particularly efficient cooling device for a motor vehicle, because in this case only waste heat falling off in the form of the exhaust gas or of the coolant for the air conditioning of a vehicle interior can be used without having to divert drive power for a compressor of a conventional compression refrigeration machine. In this case, in a vehicle powered by fossil fuel consumption can be reduced, with an electric vehicle with a Adsorptionskältemaschine - compared to the same electric vehicle with a Kompressionskältemaschine - has a higher range.

The invention will be explained in more detail below with reference to the drawing. The single figure shows a cross-sectional view of an embodiment of a tube heat exchanger.

The single FIGURE shows an embodiment of a tube heat exchanger 1 in cross-sectional view, wherein the entire tube heat exchanger 1 extends in the sense of an extrusion profile along a longitudinal direction which is perpendicular to the image plane of the figure. In this case, the tube heat exchanger 1 here circular cylinder symmetry.

The tube heat exchanger 1 has a pipe element 3 with an outer circumferential wall 5 on. Within the outer peripheral wall 5 is arranged a plurality of chambers, of which the sake of clarity here only one with the reference numeral 7 is marked. The chambers are by a plurality of radially extending webs, of which for the sake of clarity, only one with the reference numeral 9 is marked, separated. It turns out that the bars 9 arcuate here, where they extend along a curved curve, in particular with a constant radius of curvature.

The pipe element 3 also has an inner circumferential wall 11 on which the majority of chambers 7 from a central chamber 13 divides. The bridges 9 extend from the inner peripheral wall 11 radially outward to the outer circumferential wall 5 out. They spring from the inner peripheral wall 11 and terminate in the outer circumferential wall 5 ,

The tube heat exchanger 1 also has a pipe element 3 encompassing enveloping element 15 which is tubular, wherein the tubular element 11 in the tubular enveloping element 15 is arranged.

The sheath element is preferred 15 designed as a stainless steel tube, wherein the tube element 3 made of aluminum or an aluminum alloy.

The wrapping element 15 lies with an inner peripheral surface 17 over its entire surface on an outer peripheral surface 19 the outer circumferential wall 5 at.

Due to the different thermal expansion coefficients of the tubular element 3 on the one hand and the wrapping element 15 On the other hand, it comes with a temperature increase of the tube heat exchanger 1 to a greater thermal expansion of the tubular element 3 as the envelope element 15 , which can cause tensions that lead to cracking or even bursting of the tube heat exchanger 1 being able to lead. Such damage to the Rohrwärmeübertragers 1 be in the illustrated embodiment by the arcuate webs 9 avoided in the expansion of the tubular element 3 can bend laterally, so that the pipe element 3 total in the enveloping element 15 extends to a lesser extent, thereby avoiding material overload.

The wrapping element 15 Preferably, a first medium flows around, from the heat to a in the chambers 7 arranged or flowing there, second medium is transmitted. In the central chamber 13 preferably flows through a third medium through which in the chambers 7 arranged, second medium can be recooled.

As the third medium, a water-glycol mixture is preferably used.

Particularly preferred are the chambers 7 coated with an adsorbent / desorber material so that they can be used as adsorber / desorber means of an adsorption chiller. In this case, the enveloping element 15 in a desorption phase of the adsorption chiller by the first medium, preferably exhaust gas of an internal combustion engine, heated, whereby also the adsorber / desorber material in the chambers 7 is heated, and whereby the refrigerant expelled from the adsorbent / desorber material, thus desorbed. In the desorption phase, preferably no third medium flows in the central chamber 13 ,

In an adsorption phase, refrigerant from the adsorber / desorber material in the chambers 7 adsorbed, with adsorption heat is released. In this case, the wrapping element 15 preferably does not flow around the first medium, but in the central chamber 13 the third medium flows, causing the adsorber / desorber material in the chambers 7 cooled back and the adsorption heat is dissipated.

It turns out that the envelope formed as a stainless steel tube element 15 is particularly suitable to withstand high exhaust gas temperatures of an internal combustion engine, while at the same time consisting of aluminum or an aluminum alloy material of the tubular element 3 is particularly suitable to with the adsorber / desorber material in the chambers 7 to be coated. Overall, it is found that by the tube heat exchanger and the arrangement increased reliability against temperature changes and thermal stresses is created, with the possibility of lateral buckling of the webs 9 Damage to the tube heat exchanger 1 be avoided.

Claims (10)

Tube heat exchangers ( 1 ) with a tubular element ( 3 ) having an outer peripheral wall ( 5 ), wherein radially inside the outer peripheral wall ( 5 ) at least two by a radially extending web ( 9 ) separate chambers ( 7 ) are provided, characterized in that the web ( 9 ) extends - as seen in the radial direction - along a curve whose course deviates from the course of a straight line. Tube heat exchangers ( 1 ) according to claim 1, characterized in that the web ( 9 ) along a curved curve, preferably along a curve of constant radius of curvature. Tube heat exchangers ( 1 ) according to one of the preceding claims, characterized in that the tubular element ( 3 ) an inner peripheral wall ( 11 ) having the at least two chambers ( 7 ) from a central chamber ( 13 ), wherein the at least one web ( 9 ) from the inner peripheral wall ( 11 ) to the outer peripheral wall ( 5 ). Tube heat exchangers ( 1 ) according to one of the preceding claims, characterized in that the tube heat exchanger ( 1 ) a pipe element ( 3 ) encompassing enveloping element ( 15 ), wherein the tubular element ( 3 ) has a first material with a first thermal expansion coefficient, wherein the sheath element ( 15 ) comprises a second material having a second coefficient of thermal expansion, wherein the first material is different from the second material, and wherein preferably the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion. Tube heat exchangers ( 1 ) according to one of the preceding claims, characterized in that the tubular element ( 3 ) Comprises aluminum or an aluminum alloy, preferably made of aluminum or an aluminum alloy. Tube heat exchangers ( 1 ) according to one of the preceding claims, characterized in that the enveloping element ( 15 ) Steel, preferably stainless steel, or made of steel, preferably made of stainless steel. Tube heat exchangers ( 1 ) according to one of the preceding claims, characterized in that a gap measured in the radial direction between an inner peripheral surface ( 17 ) of the envelope element ( 15 ) and an outer peripheral surface ( 19 ) of the outer peripheral wall ( 5 ) of the tubular element ( 3 ) is designed as small as technically possible. Tube heat exchangers ( 1 ) according to one of the preceding claims, characterized in that the outer peripheral surface ( 19 ) of the outer peripheral wall ( 5 ) of the tubular element ( 3 ) on the inner peripheral surface ( 17 ) of the envelope element ( 15 ) all over. Arrangement comprising an exhaust-emitting internal combustion engine and a tube heat exchanger ( 1 ) according to one of claims 1 to 8, preferably designed for use in a motor vehicle, the arrangement having a fluid path which is arranged and designed such that the outer peripheral wall ( 5 ) of the tubular element ( 3 ) or the envelope element ( 15 ) is acted upon radially from the outside with exhaust gas of the internal combustion engine or with a coolant of a coolant circuit of the internal combustion engine. Arrangement according to claim 9, characterized by an adsorption chiller, wherein the tube heat exchanger ( 1 ) Is part of the adsorption chiller.

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