Patent Application
20050103486
The invention relates to a heat exchanger with tubes which, along a plurality of hydraulically parallel flow paths, can have a first medium flowing through them and a second medium flowing around them.
A heat exchanger of this type is described, for example, in EP 0 563 471 A1. The heat exchanger disclosed by that document is designed as a two-row flat-tube evaporator which has two flows of medium passing through it. Corrugated fins which have ambient air flowing over them are located between the flat tubes. The refrigerant first of all flows through the rear row of flat tubes, as seen in the main direction of flow of the air, from the top downward and is then collected and diverted, by means of a diverter device, in the opposite direction to the direction of flow of the air, entering the first, i.e. front row of flat tubes, through which it flows from the bottom upward. With this design, therefore, the refrigerant is diverted over the depth, i.e. counter to the direction of flow of the air. As a result, the flow paths for the refrigerant in each case comprise two sections, with each section corresponding to a tube length. The refrigerant is distributed and collected by a collection and distribution device, which is formed by a multiplicity of plates which are layered on top of one another and are soldered together. These plates substantially, comprise a base plate, a distributor plate above it, with a partition running in the longitudinal direction, and a cover plate with feed and discharge openings for the refrigerant. In a similar way, the diverter device arranged on the opposite side is composed of individual plates. This results in a low overall height of this evaporator. In addition, there is optionally what is known as a stop plate, which is in each case laid onto the base plate and forms a stop for the tube ends. One drawback of this type of evaporator is that the refrigerant, on account of the distribution or collection chamber extending over the entire width of the evaporator, is distributed unevenly to the individual tubes. Furthermore, the two-row design requires increased assembly outlay.
What is known as a divider plate with individual openings for distributing the refrigerant between the individual tubes has been proposed for a similar evaporator in EP 0 634 615 A1. This results in more uniform distribution of the refrigerant to the tubes, but this is at the expense of an increased number of plates and therefore higher outlay on materials and assembly.
U.S. Pat. No. 5,242,016 describes an evaporator with refrigerant distribution through passages in a large number of plates, which likewise contribute to a more uniform distribution of the refrigerant between heat-exchanger tubes. However, this requires a very large number of plates and high manufacturing costs.
DE 100 20 763 A1 has disclosed a further design of evaporator, which is intended for operation with CO2 as refrigerant and in which a pressure-resistant collector housing is to be achieved by virtue of the fact that a multiplicity of plates provided with apertures are stacked on top of one another and soldered together. This evaporator is of one-row design, specifically with multi-chamber flat tubes through which medium flows both upward and downward, which is made possible by a diverter device located at the lower end of the tubes. One drawback of this design of evaporator is the large number of plates with relatively narrow passages, which firstly entails additional weight and secondly involves the risk of the passages in the collector housing being closed up during soldering, i.e. becoming blocked by solder.
EP 1 221 580 A2 has described an evaporator for a fuel cell system, which comprises a header piece which includes a base plate and a cover plate secured to it. Fuel passes via a connection part into a fuel distributor chamber, and from there into guide passages and via apertures in the base plate into heat-uptake passages of the evaporator. In this fuel evaporator, there is a small number of plates in the header piece, but these plates are highly complex to manufacture. Moreover, supply of fuel to the heat-uptake passages is very uneven depending on the pressure distribution in the fuel distributor chamber and in the guide passages.
WO 01/06193 A1 shows a serpentine heat exchanger with an inlet header piece, a serpentine tube and an outlet header piece. On account of the long distance which a medium flowing through the tube has to cover inside the heat exchanger, a heat exchanger of this type involves an undesirably high pressure drop for this medium. The tube bends, the overall length of which, on account of the fact that the inlet header piece and the outlet header piece are arranged on different sides of the heat exchanger, is at least equal to a width of the heat exchanger, do not adjoin the fins and therefore make scarcely any contribution to heat transfer. As a result, the pressure loss is unnecessarily increased to an additional extent.
The object of the invention is to provide a heat exchanger and/or an air-conditioning device in which it is possible to realize a plurality of hydraulically parallel flow paths with a simple design and/or a uniform distribution of a medium to the flow paths.
This object is achieved by a heat exchanger having the features of claim 1 and by an air-conditioning device having the features of claim 24.
According to claim 1, a heat exchanger has tubes which, along a plurality of hydraulically parallel flow paths, can have a first medium flowing through them and a second medium flowing around them. The object of the invention is advantageously achieved by virtue of the fact that two sections of a flow path, through which medium can flow in opposite directions, are arranged next to one another in the main direction of flow of the second medium.
The basic concept of the invention is for a plurality of hydraulically parallel flow paths each themselves to be constructed in serpentine form from a plurality of sections. Arranging the flow-path sections, through which medium can flow in particular in succession, next to one another means that the number of mutually parallel flow paths is reduced for a predetermined surface area of the heat exchanger onto which the second medium can flow. This firstly facilitates more uniform application of medium to the flow paths of the heat exchanger, and secondly if each flow path comprises an even number of serpentine sections, allows what is known as a single-tank construction, in which all the distribution and/or collection devices which may be present are arranged on the same side of the heat exchanger and in particular form a structural unit.
To avoid an excessive loss of pressure in the first medium along the heat exchanger, the number of parallel flow paths should not be selected to be too small, since otherwise the paths, on account of their length, may under certain circumstances form an excessive flow resistance for the first medium.
According to a preferred configuration of the invention, the flow paths which are parallel to one another are likewise arranged next to one another in the main direction of flow of the second medium. It is particularly preferable for the flow paths not to overlap in this arrangement, when seen in the main direction of flow of the second medium. This ensures uniform application of the second medium to the paths, with the result that the heat transfer from the first medium to the second medium or vice versa becomes even more uniform and therefore more effective, i.e. the performance of the heat exchanger is improved.
According to an advantageous embodiment, the heat exchanger has an end face which the flow of second medium can reach and which can be divided into a plurality of continuous sub-surfaces, with the parallel flow paths each being assigned to one of these continuous subregions. This brings with it the advantage that, under certain circumstances, only a very small proportion of the flow paths is arranged outside a heat-transfer region, and therefore unnecessary pressure loss is reduced.
By way of example, a rectangular end face of the heat exchanger can be divided into adjacent, likewise rectangular strips, in which case the flow paths are, as it were, arranged stacked on top of one another. A modular structure of this type allows standardization, with the aid of which it is possible to produce heat exchangers for different applications, capacity demands or dimensions by assembling them from simple modules, which are in this case provided by the flow paths.
According to one preferred embodiment, a heat exchanger includes tubes through which a first medium can flow and around which a second medium can flow, so that heat can be transferred from the first medium to the second or vice versa through walls of the tubes. For this purpose, heat-exchange passages, through which the first medium can be passed, are located in the tubes, with an individual tube having either one heat-exchange passage or, as what is known as a multi-chamber tube, having a plurality of heat-exchange passages located next to one another. The tubes may in this case have a circular, oval, substantially rectangular or any other desired cross section. By way of example, the tubes are designed as flat tubes. To increase the heat transfer, it is if appropriate possible to arrange fins, in particular corrugated fins, between the tubes, in which case the tubes and the fins can in particular be soldered to one another.
There are various conceivable uses for the heat exchanger, for example as an evaporator of a refrigerant circuit, in particular of a motor vehicle air-conditioning system. In this case, the first medium is a refrigerant, for example R134a or R744, and the second medium is air, with heat being transferred from the air to the refrigerant. However, the heat exchanger is also suitable for other media, in which case the heat can if appropriate also be transferred from the first medium to the second.
If appropriate, there are at least two collection chambers, it being possible for the first medium to be passed from a first collection chamber to a second collection chamber. In the context of the invention, the term flow-path section is to be understood as meaning one or more heat-exchange passages which run from one side of the heat exchanger to an opposite side and are hydraulically connected in parallel with one another. The heat-exchange passages of a flow-path section are, for example, arranged in a single tube, although an arrangement of the heat-exchange passages of a flow-path section which is distributed between a plurality of tubes is also conceivable.
According to an advantageous embodiment, the heat exchanger has a distribution and/or collection device with a tube plate which actually comprises a number of plates bearing against one another, namely a base plate, a diverter plate and a cover plate. The base plate can be connected to ends of the tubes by virtue of the base plate having, for example, cutouts, in which the tube ends can be received. Within the context of the invention, it is also conceivable to use other types of connection between tubes and the base plate, for example connections produced by extensions at the edges of cutouts in the base plate, so that the tubes can be plug-fitted onto the extensions. Cutouts in the diverter plate serve to form through-passages and/or diverter passages, which can be closed off in a fluid-tight manner with respect to an environment surrounding the heat exchanger by means of a cover plate. The plate structure of the tube plate allows the distribution and/or collection device and the entire heat exchanger to be of very pressure-stable construction.
According to one preferred embodiment, a collection box which may if appropriate be integrated into the distribution and/or collection device is soldered or welded to the cover plate in a fluid-tight manner. According to another advantageous embodiment, the collection box is formed integrally with the cover plate, thereby simplifying production. A particularly lightweight construction is achieved by designing the collection box in the form of a tube in accordance with a further configuration of the invention. It is particularly preferable for the cover plate, at edges of apertures, to have extensions which engage into apertures in a housing of the collection box. Conversely, according to another embodiment it is possible to provide apertures in the collection-box housing with extensions which engage in apertures in the cover plate. In both cases, manufacturing reliability is increased by aligning the apertures which are to be flush with one another in the cover plate and in the collection-box housing.
According to a preferred embodiment, the passage openings which are formed by the flush apertures in the cover plate and in the collection-box housing have different cross sections of flow. This makes it easy to adapt the distribution of the first medium to the flow conditions in the associated collection chamber. In particular, a uniform distribution between a plurality of flow paths is desirable in this context, although a deliberately uneven distribution is conceivable, for example, in the case of a non-uniform mass flow of the second medium over an end face of the heat exchanger.
It is advantageous for the passage openings with different cross sections of flow to be arranged upstream of the heat-exchange passages, so that it is particularly easy to balance out the flow in the flow paths. If through-flow quantities through the flow paths are controlled on an inlet side for the first medium, the passage openings on the outlet side can be made larger, for example with a cross section of flow which corresponds to the cross section of flow of the corresponding flow path. If the heat exchanger is used, for example, as an evaporator in a refrigerant circuit, the pressure ratios along the circuit are more advantageous for the performance of the heat exchanger if cross sections of flow are narrowed prior to heating of the refrigerant than if the cross sections of flow are narrowed after this heating.
According to one configuration, the cross sections of flow of the passage openings can be adapted to a pressure distribution of the first medium within the corresponding collection chamber. In another configuration, the cross sections of flow can be adapted to a density distribution of the first medium within the collection chamber in question. In the context of the invention, the term density of a medium is, in the case of single-phase media, to be understood as meaning the physical density, whereas, in the case of multiphase media, for example in the case of media which are partially in liquid form and partially in gas form, it is to be understood as meaning a mean density across the volume in question.
In one preferred embodiment, and for similar reasons, the cross-sectional areas of the first and second collection chambers are different from one another. It is particularly preferable for it to be possible to match the cross-sectional areas of the collection chambers to the density ratios of the first medium in the chambers.
According to one preferred embodiment, the distribution and/or collection device comprises a housing and at least one collection chamber. It is particularly preferable for the distribution and/or collection device also to comprise a tube plate with cutouts into which the tubes can be received.
According to a further configuration, the heat exchanger has at least one refrigerant inlet and at least one refrigerant outlet, which according to a preferred embodiment open out in at least one header tube. According to a preferred embodiment, the header tube itself is divided into at least one inlet section and at least one outlet section by at least one separating element, these sections preferably respectively being assigned to a refrigerant inlet and a refrigerant outlet. The inlet and outlet sections, which are separated from one another in a liquid-tight and/or gastight manner by at least one separating element, of the header tube are fluid-connected by means of a plurality of flow-path sections and preferably at least one transverse distributor.
According to a particularly preferred embodiment, the refrigerant inlets or refrigerant outlets are tubes with a defined cross section, in the periphery of which there are bores which are arranged substantially perpendicular to the longitudinal center axis of the refrigerant inlet tube or refrigerant outlet tube and which, according to a particularly preferred embodiment, on their center line intercept the longitudinal center axis of the refrigerant inlet tubes or refrigerant outlet tubes or are arranged at a predetermined distance therefrom. According to a particularly preferred embodiment, the center line of the bore is offset with respect to the longitudinal center axis of the header tube, so as to form a tangent on the outer periphery of the refrigerant inlet tube or refrigerant outlet tube.
According to a refinement, the refrigerant inlets or refrigerant outlets of a plurality of interconnected assemblies are of single-piece design.
According to one preferred embodiment of the present invention, the separating element which divides the header tube into an inlet section and an outlet section is connected to the header tube in such a way that the exchange of gaseous or liquid media between the sections is prevented.
According to a preferred embodiment, the header tube has a substantially cylindrical basic shape, with a predetermined number of leadthroughs arranged in its circumference, through which the refrigerant inlets and refrigerant outlets and at least one tube, in particular a flat tube, extend into the interior of the header tube. According to a particularly preferred embodiment, the leadthroughs for the flat tubes to pass into the interior of the header tube are configured in such a manner that the flat tubes are not only connected to the header tube by means of a cohesive bond, but also, as a result of additional pressing of the header tube, a flat tube or flat tubes which has/have been introduced is/are connected nonpositively to the walls of the header tube. According to a particularly preferred embodiment, a header tube for this joining method has a basically Q-shaped cross section, in the narrowest region of which the leadthroughs for the through-flow devices, in particular for a flat tube, are provided. According to a further embodiment, it is even possible for a plurality of flat tubes to be received in one or more leadthroughs.
According to a particularly preferred embodiment, the leadthroughs have an outer contour which corresponds to that of the object which is to pass through them, in particular that of the refrigerant inlet or refrigerant outlet tube and that of the flat tube, or are at a predetermined distance from one another. Furthermore, the apertures, with respect to their center line, are arranged offset by a predetermined distance from the center line of the header tube or of the transverse distributor.
According to one advantageous configuration, the header tube has, at an edge of at least one leadthrough, an extension which engages into a leadthrough of the refrigerant inlet or outlet. As a result, the header tube is fixed with respect to the refrigerant inlet or outlet during assembly of the apparatus, which facilitates manufacture of the apparatus for exchanging heat.
According to a further particularly preferred embodiment of the heat exchanger, a tube, in the region of the leadthroughs which project into the header tube, has at least one recess into which, for example, the separating element which divides the header tube into an inlet section and an outlet section engages. In a further embodiment, the heat exchanger has a separating element with a recess into which a tube, in particular a flat tube, engages into the header tube in the region of the leadthrough. This arrangement ensures that the regions of the inlet section and of the outlet section are sealed in a liquid-tight and gastight manner with respect to one another in the header tube, and defined positioning and fixing of the tubes is ensured.
According to a further embodiment, the header tubes and/or the refrigerant inlet and/or outlet are configured in such a way that the pressure of the first medium across the inlet and outlet sections is substantially equal or adopts a predetermined value. For the refrigerant inlet, this may preferably, under certain circumstances, be achieved by virtue of the cross section of flow of the refrigerant inlet tapering over the number of header tubes fluid-connected to it, so that the pressure drop at each “removal point” is as far as possible compensated for. In this case, the refrigerant outlet particularly preferably has the largest possible cross section of flow.
Alternative embodiments are also within the scope of the present invention, in which context the configuration of the opening or of the refrigerant leadthrough of the header tube and/or its size can likewise be used to even out the pressure or density level of the header tubes arranged at the refrigerant inlet.
According to one particularly preferred embodiment, it is also possible for the various removal points from the refrigerant inlet or outlet to be divided into flow regions by using a pushed-in profiled section which is cohesively joined to the surrounding tube. By way of example, the tube is divided into 2, 3 or 4 or further flow regions. Predetermined rotation of the profile section in the tube connects the flow regions of the refrigerant inlet or refrigerant outlet to the corresponding removal regions, for example the bore which opens out into the header tube.
According to a further preferred embodiment, the volumes of the inlet and outlet sections of a header tube have a predetermined ratio to one another, and this ratio may in particular be 1:1, 1:2, 1:4, 1:10 and any desired values in between. This in particular takes account of the changing density of the coolant during evaporation or cooling. If the heat exchanger is used as an evaporator, this arrangement makes it possible, for example, to take into account the fact that the volume of the refrigerant increases significantly as a result of its evaporation, and therefore a larger cross section of flow is required to transport the refrigerant mass flow. For example, the density ratio for CO2 between refrigerant inlet and refrigerant outlet is between 1:2 and 1:10, preferably between 1:3 and 1:7, and is particularly preferably approx. 1:5.
According to a preferred embodiment, the openings in the tubes open out into an interior space of a header tube or of a transverse distributor. Furthermore, the components are connected to one another cohesively, nonpositively and/or positively, in such a way that the interior of the components is gastight and/or liquid-tight with respect to the surrounding environment of the heat exchanger even in particular at high pressures of up to approx. 300 bar.
According to a further preferred embodiment, at least one transverse distributor has a second separating element, which divides the transverse distributor into at least two flow sections. Furthermore, a heat exchanger according to a preferred embodiment has at least one tube which extends into the interior of a transverse distributor.
According to a further preferred embodiment, the heat exchanger has, as a further component, cooling fins which in particular are connected to a region of the outer surface of the tubes in such a way that the transfer of thermal energy is promoted. According to one particularly preferred embodiment, the cooling fins are cohesively joined to the surface of the tubes, with soldering processes, welding processes and adhesive-bonding processes in particular being used to produce the cohesive bond. It is preferable for the cooling fins to be joined to the surfaces of the tubes in such a manner that the cohesive bond is effected in particular at the turning points of the cooling fins. According to a particularly preferred embodiment, the cooling fins have a serpentine-like basic structure in the direction of flow, the depth of which structure substantially corresponds to the overall depth of the assembly or the width of the tubes.
Furthermore, the cooling fins include slots which extend substantially between the two connecting points or turning points of the cooling fins. According to a particularly preferred embodiment, these slots in the cooling fins are between 1 and 15 mm long, preferably between 2 and 13 mm long and particularly preferably between 3.7 and 11.7 mm long. Furthermore, the width of these slots is between 0.1 and 0.6 mm, preferably between 0.1 and 0.5 mm and particularly preferably between 0.2 and 0.3 mm. These so-called “gills” of the coolant fins allow improved heat transfer between the gas flowing through and the cooling fins or walls of the tubes. Furthermore, the cooling fins are characterized by a wall thickness which is between 0.01 and 0.5 mm, preferably between 0.02 and 0.07 mm and particularly preferably between 0.07 and 0.15 mm. The fin density of the cooling fins is 10 to 150 fins per dm, preferably 25 to 100 fins per dm and particularly preferably 50 to 80 fins per dm. In a particularly preferred embodiment, the fin height is 1 to 20 mm, preferably 2 to 15 mm and particularly preferably 3 to 12 mm.
In one preferred embodiment, the heat exchanger uses a refrigerant which includes at least one component selected from a group consisting of gases, in particular carbon dioxide, nitrogen, oxygen, air, ammonia, hydrocarbons, in particular methane, propane, n-butane, and liquids, in particular water, floe ice, brine, etc. According to a particularly preferred embodiment, the refrigerant used is carbon dioxide, the physical properties of which can be used as a colorless, incombustible gas in order to increase the refrigeration capacity, possibly reduce the size of the unit and/or to reduce losses of capacity.
According to one preferred embodiment, the heat exchanger, but at least the tubes and in particular the cooling fins, has/have a preferably gaseous medium, in particular air, flowing around it/them.
According to a particularly preferred embodiment, the heat transfer between the first medium and the second medium is substantially effected by convection and heat conduction. For example, the air flowing around the heat exchanger releases thermal energy to the cooling fins, from which the heat can be transferred to the refrigerant via the cooling fins and the walls of the tubes. For heat conduction, the components are connected to one another in such a way that the transfer of thermal energy is promoted. This is effected in particular by cohesive, nonpositive and positive connection, such as for example by soldering, welding, flanging or adhesive bonding.
Furthermore, the transition regions of the components of the heat exchanger through which fluids flow are connected to one another in a gastight and liquid-tight manner, so that exchange of the first medium with the second medium is prevented. In particular if low-molecular-weight refrigerant, such as for example carbon dioxide, is used, it is particularly important to achieve a connection between the components which prevents the refrigerant or its components from escaping.
In one preferred embodiment, the heat exchanger has frame elements at two opposite sides, these frame elements extending at least over part of the side face of the heat exchanger. These frame elements are preferably profiled-section elements which, inter alia, may have a U-shaped, V-shaped, L-shaped or other typical profiled-section structure. Furthermore, these frame elements are nonpositively and/or positively connected to at least one component of the heat exchanger. Cohesive joining, such as for example by soldering, welding and adhesive bonding, is also within the scope of the present invention.
Furthermore, it should be noted that the substantially cylindrical header tubes, refrigerant inlets and refrigerant outlets and the transverse distributor, as well as an exactly cylindrical or tubular configuration, may also take different shapes, such as for example deformed cylindrical or elliptical, polygonal or rectangular cross sections.
According to one preferred embodiment, the refrigerant inlets or outlets, the header tube and the transverse distributor are arranged on one side of the heat exchanger. In this case, the heat exchanger has in particular a cuboidal basic shape, which preferably has a front surface and a rear surface, which according to one particular embodiment represents the sides of the heat exchanger through which substantially the gaseous medium, for example air flows in order to release or take up energy, in particular thermal energy.
The front and rear surfaces of the assembly are delimited by four side faces which are substantially defined by a width or diameter of the heat-exchange tubes used and the adjoining cooling fins, as well as the shape thereof. However, it is also possible to select alternative embodiments of this preferred rectangular basic shape, which correspond in particular to the requirements relating to arrangement in an air-conditioning installation or a ventilation device.
Further embodiments of the heat exchanger according to the invention relate to the connection of the flow-path sections by means of diverter passages, which may be arranged in particular in a diverter plate or in transverse distributors.
According to one advantageous configuration, flow-path sections which are arranged next to one another in the main direction of flow of the second medium are connected to one another by a diverter passage. This is then referred to as a diversion over the width. This makes it possible for a plurality of flow-path sections within a row or within a tube row to be connected to one another to form a flow path. This leads to a local serpentine design of the heat exchanger. In another configuration, the interconnected flow-path sections are arranged one behind the other in the main direction of flow of the second medium. This is then known as a diversion over the depth. This makes it possible for flow paths for the first medium to be connected in parallel or antiparallel with the main direction of flow of the second medium. This leads to a local countercurrent design of the heat exchanger.
According to a further embodiment, two flow-path sections within a tube are connected to one another by a diverter passage. This means that the first medium flows through the tube in one direction and flows back through the same tube but in different heat-exchange passages in the opposite direction. The use of tubes with a large number of heat-exchange passages therefore reduces the total number of tubes and therefore the manufacturing costs.
According to one preferred configuration, the number of sections of at least one flow path can be divided by two. This means that it is easy to connect up a two-row arrangement of the flow-path sections, by virtue of the first half of the sections of a flow path being arranged in a first row and being connected to one another by diversions over the width, whereas the second half of the sections are arranged in a second row and are likewise connected to one another by diversions over the width, with the two halves of the flow path being connected by a diversion over the depth. This diversion over the depth takes place, for example, in a diverter passage on the opposite side of the heat exchanger from the collection chambers. It is particularly preferable for the number of sections of the flow path to be divisible by four. This means that with a two-row arrangement of the flow-path sections connected up as described above, the diversion over the depth takes place on that side of the heat exchanger on which the collection chambers are located as well. As a result, if appropriate it may be possible to configure just one diverter plate of the heat exchanger if the heat exchanger is designed for predetermined requirements, whereas other components are left unchanged.
In one configuration, the first and last flow-path sections within one or more tube rows are not acted on as hydraulically the first sections of flow paths, since the flow and/or pressure conditions of the first medium are unfavorable for application to flow paths in the edge region of collection chambers, which are usually arranged along tube rows.
According to an advantageous embodiment, two adjacent flow paths run mirror-symmetrically with respect to one another. It is particularly preferable for diverter passages of at least two flow paths to communicate. This results in additional compensation of the through-flow within the flow paths. With a mirror-symmetrical profile of the flow paths communicating with one another, communication between the then optionally adjacent diverter passages is particularly simple to realize, for example by omitting a web which may under certain circumstances otherwise be present between two diverter passages.
In a further preferred embodiment, a cross section of flow of a flow path changes over the course of its profile. This is very simple to realize, for example by flow-path sections with a small number of heat-exchange passages being connected, via correspondingly configured diverter passages, to flow-path sections with a large number of heat-exchange passages. It is particularly preferable to match the cross section of flow of one flow path to a density of the first medium which changes along the flow path.
According to one advantageous embodiment of the invention, a simplified structure is also made possible by tubes which have been deformed in a U-shape, with the tubes being deformed once or, to provide a structure which may under certain circumstances be even simpler, a number of times. As a result, two tube-plate connections and possibly one diverter passage are eliminated in the region of the U-shaped deformation. If exclusively U-tubes are used, it is even possible to eliminate an end piece, if all the diversions on one side of the heat exchanger are realized by deformations of tubes. In this case, the ends of in each case one tube can under certain circumstances be connected to the same base plate or the same tube plate.
According to a preferred embodiment, all the tubes have precisely one tube bend. This results in a modular construction with a large number of structurally identical parts.
In the case of a flat tube, a tube bend is particularly preferably curved in the direction of a short side of the flat tube, since as a result reduced stresses occur in the tube material during the deformation.
According to a particularly preferred embodiment, the tubes each have between 1 and 10 tube bends, with the diverter passages being arranged, if appropriate, on the same side or on opposite sides of the heat exchanger depending on whether the number of tube bends is odd or even, as a distribution and/or collection device. For example, if there are 2, 4, 6, 8 or 10 tube bends, the diverter passages are arranged on the opposite side from the distribution and/or collection device. If there are 1, 3, 5, 7 or 9 tube bends, the diverter passages and the distribution and/or collection device are, by contrast, arranged on the same side of the heat exchanger.
According to one preferred embodiment, the sections of a flow path are of substantially equal length. According to a particularly preferred embodiment of the present invention, there is provision for the length of a flow-path section between two tube bends to possibly differ from the length of other sections of the same or other flow paths.
Furthermore, a tube designed as a flat tube is characterized, in cross section, by a width of between 10 mm and 200 mm, preferably between 30 mm and 70 mm, and by a height of between 1.0 mm and 3 mm, preferably between 1.4 mm and 2.4 mm, and an outer wall thickness of between 0.2 mm and 0.8 mm, preferably between 0.35 mm and 0.5 mm. Furthermore, heat-exchange passages in the interior of the tubes are circular or elliptical in cross section, but in particular in the edge region of the flat tube are matched to the outer contours of the flat tube in such a way that the thickness is never less than a minimum wall thickness.
According to one particularly preferred embodiment, the components, such as for example the flat tubes, are produced at least from a material which is selected from the group of materials consisting of metals, in particular aluminum, manganese, magnesium, silicon, iron, brass, copper, tin, zinc, titanium, chromium, molybdenum, vanadium and alloys thereof, in particular wrought aluminum alloys with a silicon content of from 0 to 0.7% and a magnesium content of between 0.0-1%, preferably between 0.0-0.5%, and particularly preferably between 0.1 and 0.4%, preferably EN-AW 3003, EN-AW 3102, EN-AW 6060 and EN-AW 1110, plastics, fiber-reinforced plastics, composite materials, etc.
In a further embodiment, the heat exchanger comprises flat tubes which have a refrigerant in liquid and/or vapor form flowing through them, corrugated fins arranged between the flat tubes and acted on by ambient air, a collection and distribution device for supplying and discharging the refrigerant, the collection and distribution device comprising a plurality of interrupted plates which are layered on top of one another, so as to form refrigerant passages, with the ends of the flat tubes being held in receiving openings in a base plate, and a diverter device for diverting the refrigerant in the direction of flow of the ambient air, the heat exchanger comprising a series of flat tubes, with in each case one flat tube having two flow sections running parallel, through which medium flows in succession, these flow sections being connected by the diverter device, each flat tube, at the end side, having a groove between the two flow sections in the center of the flat-tube end, and the base plate, between the receiving openings, having webs, the dimensions of which, in terms of height and width, corresponding to the grooves, so as in each case to form a joined connection to the grooves.
It is particularly preferable for the diverter device to be formed by a further base plate with receiving openings and webs which form a joined connection to the end-side groove of the flat tubes.
It is particularly preferable for the diverter device additionally to have a passage plate with continuous slots and a closed cover plate.
It is particularly preferable for the collection and distribution device to have a passage plate with passage openings and webs between the passage openings, a cover plate with refrigerant inlet and outlet openings and a refrigerant feed and refrigerant discharge passage, which are arranged parallel to one another and in the longitudinal direction of the heat exchanger, with the base plate, the passage plate and the cover plate being arranged above one another in such a manner that the openings in the plates are aligned with the flat-tube ends.
It is particularly preferable for the refrigerant inlet openings to be designed as calibrated bores, with the diameter of the bores in particular being variable. It is also preferable for the cover plate and the refrigerant feed and discharge passages to be of single-part design.
According to a further configuration, the heat exchanger, which can be used in particular as an evaporator for motor vehicle air-conditioning systems, comprises flat tubes which have a refrigerant in liquid and/or vapor form flowing through them, corrugated fins arranged between the flat tubes and acted on by ambient air, a collection and distribution device for supplying and discharging the refrigerant, the collection and distribution device comprising a plurality of interrupted plates layered on top of one another, so as to form refrigerant passages, with the ends of the flat tubes being held in receiving openings in a base plate, and a diverter device for diverting the refrigerant in the direction of flow of the ambient air. The heat exchanger in this case comprises a row of flat tubes, with in each case one flat tube having two flow sections which run parallel, through which medium can flow in succession and which are connected via the diverter device, and the collection and distribution device having a calibration device which is arranged between refrigerant inlet and refrigerant outlet and is designed as a cover plate with calibration openings for the refrigerant distribution. It is preferable for the calibration openings to be arranged on the refrigerant inlet side.
According to an advantageous refinement, the calibration openings have different cross sections of flow. The cross sections of flow of the calibration openings preferably increase in size in the direction of the pressure drop of the refrigerant in the feed passage. It is particularly preferable for the cross sections of flow of the calibration openings to be variable as a function of the specific volume of the refrigerant and/or its vapor content.
In another embodiment of the heat exchanger, the flat tubes are designed as serpentine segments, and the diverter device is arranged in the collection and distribution device.
According to a further configuration, the collection and distribution device has a passage plate with continuous passage openings for diverting the refrigerant, and passage openings with webs, a cover plate with refrigerant inlet and outlet openings and a refrigerant feed passage and a refrigerant discharge passage. The passage openings with webs are in this case each arranged flush with the first flat-tube end of the serpentine segment, whereas the continuous passage openings are arranged flush with the second flat-tube end of the serpentine segment, the refrigerant inlet and outlet openings being flush with the passage openings, and the continuous passage openings being covered by the cover plate. It is preferable for the serpentine segments to have two or three diversions over the width.
According to an advantageous embodiment of the heat exchanger, the flat tubes are designed as U-tubes, i.e. with in each case one diversion (over the width). It is preferable for in each case two U-tubes to be connected in series on the refrigerant side, and for in each case two adjacent passage openings, which are assigned to a U-tube outlet and a U-tube inlet, to be in refrigerant communication with one another through a transverse passage in the passage plate.
It is preferable for the width b of the passage openings in the passage plate to be greater than the width a of the receiving openings in the base plate. It is also advantageous for the depth of the groove in the flat-tube ends to be greater than the thickness of the base plate.
It is advantageous for one or more of the following dimensional stipulations to apply to the heat exchanger:
According to a preferred refinement, the heat exchanger according to the invention is used in an air-conditioning device with at least one air feed element and at least one air passage, which is in particular provided with at least one airflow-control element, in order to transfer heat from air flowing through the air passage to a refrigerant or vice versa. The refrigerant then represents the first medium, while the second medium is formed by the air.
Moreover, there is the possibility of using the heat exchanger according to the invention in any desired air-conditioning device, alone or in combination with at least one further heat exchanger, in which case the at least one further heat exchanger may likewise be a heat exchanger according to the invention or may be a heat exchanger of the prior art.
The invention is explained in more detail below on the basis of exemplary embodiments and with reference to the drawings, in which:
In the drawing, a base plate 8, in which a first row of slot-like apertures 9a-9f and a second row of similar apertures 10a-10f are arranged, is illustrated above the flat tubes 2, 3. The openings 9a and 10a, 9b and 10b, etc. are located one behind the other in the depth direction (airflow direction L) and in each case leave between them webs 11a, 11b-11f. In terms of their width in the depth direction, these webs 11a-11f correspond to the width of the cutout 5 of the tube ends 2a. The number of openings 9a-9f and 10a-10f corresponds to the number of flat tubes 2, 3.
What is known as a diverter plate 12, in which two rows of apertures 13a-13f and 14a-14f (partially covered) are arranged, is illustrated above the base plate 8 in the drawing. The arrangement of the apertures 13a-f and 14a-f corresponds to the arrangement of the apertures 9a-9f and 10a-10f, respectively, but the width b and depth of the apertures 13a-f and 14a-f are greater than the corresponding dimensions of the apertures 9a-9f and 10a-10f, respectively, which in each case only have a width a corresponding to the thickness of the flat tubes 2, 3. Webs 15a, 15f are partially left between the apertures 13a, 14a, 13b, 14b-13f and 14f. The dimensions of these webs 15a-15f in the depth direction are smaller than the corresponding dimensions of the webs 11a-11f of the base plate 8.
What is referred to as a cover plate 16, which includes a first row of refrigerant inlet apertures 17a, 17d and a second row of refrigerant outlet apertures 18c, 18f, is illustrated in the drawing above the diverter plate 12. These apertures 17a, 17f and 18a, 18f are preferably designed as circular bores with a diameter matched to the desired refrigerant distribution and quantitative flow.
Finally, a collection box 19 with a housing and in each case one collection chamber 20, 21 for supplying and discharging the refrigerant is located above the cover plate 16 in the drawing. The collection box has apertures 22a, d and 23c, f, illustrated by dashed lines, the position and size of which correspond to the apertures 17a, d and 18c, f, at the underside of both collection chambers.
In the drawing, a further base plate 24, which analogously to the first base plate 8 has two rows of slot-like apertures 25a-f and 26a-f, is illustrated beneath the flat tubes 2, 3 in the drawing. Between the apertures 25a and 26a to 25f and 26f there are likewise webs 27a-f (partially covered), the width of these webs in the depth direction corresponding to the width of the cutout 6 in the end of the flat tube 2. A further diverter plate 28, which has continuous diverter passages 29a-29f, is illustrated in the drawing below the second base plate 24. These diverter passages 29a-f extend over the entire depth t of the flat tubes 2, 3.
Finally, a cover plate 30, which does not have any apertures, but rather closes off the diverter passages 29a-29f with respect to the environment surrounding the heat exchanger, is illustrated at the bottom of the drawing.
The above-described individual parts of the evaporator 1 are assembled in the following way: the base plate 8 is fitted onto the flat-tube ends 2a, etc., so that the webs 11a-11f come to lie in the cutouts 5 in the flat-tube ends. Then, the diverter plate 12, the cover plate 16 and the collection box 19 with the collection chambers 20, 21 are stacked on top of the base plate 8. In a similar way, the lower base plate 24 is pushed onto the flat-tube ends 2b, so that the webs 27a-27f come to lie in the cutouts 6; then, the passage plate 28 and the cover plate 29 are attached. After the evaporator 1 has therefore been assembled, it is soldered to form a fixed block in a soldering furnace. During the soldering process, the plates are held in position with respect to one another by a positive or nonpositive clamping action. However, it is also possible firstly to assemble the end piece comprising base plate, diverter plate and cover plate, and then to connect it to flat tubes.
The profile of the refrigerant flow is illustrated by way of example on the basis of a row of arrows V1-V4 on the front side of the evaporator, by diverter arrows U1-U5 in the diverter passages 29a, 14a-b, 29b, 13b-c, 29c and the arrows R1, R2 and R3 on the rear side of the evaporator 1. The refrigerant, in this case therefore CO2, flows through the evaporator, starting from the distribution chamber 20, for example initially on the front side from the top downward, as indicated by V1, V2, V3 and V4, is then diverted in the diverter passage 29a, as indicated by U1, onto the rear side of the evaporator 1, where it flows from the bottom upward. The two first flow sections of this flow path are therefore arranged one behind the other in the main direction of flow of the air. Then, the refrigerant is diverted in the direction indicated by U2 to the adjacent flat tube, through which the refrigerant likewise initially flows from the top downward and then, after diversion indicated by U3, from the bottom upward. The two flow-path sections in this tube lie next to the first two flow-path sections in the main direction of flow of the air. After a diversion as indicated by U4, the refrigerant flows through the flat tube 2 in its sections 2d, 2e with an intervening diversion indicated by U5 and finally flow into the collection chamber 21 as indicated by arrows R1, R2 and R3. The arrangement of sections of the flow path which has just been described adjacent to one another in the main direction of flow of the air produces a small number of hydraulically parallel flow paths—in this exemplary embodiment two flow paths—which facilitates more uniform application of medium to the flow paths of the heat exchanger, since an identical or at least similar refrigerant pressure for this purpose is required in particular only at two locations of the distribution chamber 20.
The refrigerant flow route is illustrated by arrows: first of all the refrigerant leaves the collection chamber 53 as indicated by the arrow E1, then follows the direction of the arrows E2, E3, E4 and passes into the front flow section of the flat-tube limb 42 and then flows through the entire serpentine segment 41 on its front side and emerges from the final limb 45 at E6, passes into the diverter passage 61, where it is diverted over the depth in accordance with arrow U, before then flowing through the rear side of the serpentine segment, as indicated by arrow R1, i.e. in the opposite direction to on the front side. Finally, this stream of refrigerant passes into the collection chamber 54 as indicated by the arrow R2, i.e. through the aperture 64.
This construction therefore diverts the refrigerant over the width of the evaporator, i.e. transversely to the main direction of flow of the air, specifically initially from the right to the left on the front side in the drawing, and then from the left to the right on the rear side. As has already been mentioned above, one or more serpentine segment sections which are not illustrated follow the serpentine segment section 41 illustrated in the drawing.
The flow of the refrigerant then follows the direction of the arrows, i.e. the refrigerant enters the front flow section of the U-tube 71a at E, initially flows downward, is diverted at the bottom, then flows upward and passes into the diverter passage 79, where it is diverted as indicated by arrow U before then flowing downward on the rear side, where it is diverted and then flows upward again in order to pass through the aperture 77 as indicated by arrow A. The supply and discharge of the refrigerant is described on the basis of the following figure, corresponding to sections IV-IV and V-V.
This mode of design of the evaporator shown in
To summarize, the invention allows the production of a heat exchanger which comprises a row of tubes (to realize heat-exchange passages), two plates (the tube plates) and two tubes (the collection boxes). This makes it possible to realize an extremely simple and, moreover, pressure-stable structure of the heat exchanger.
FIGS. 21 to 24 show exemplary embodiments of a tube plate which involves little outlay on material and, for this reason, low materials costs and a low weight.
The tube plate 2010 in
According to a particularly preferred embodiment, the header tubes 2407, 2408 and 2409 have at least one separating element (not shown), which is arranged, for example, in the center of the header tube. As a result, the header tubes are divided into at least two sections, from which the coolant is introduced into the tube 2419 and passed via the heat-exchange passages of the tube 2419 into the transverse distributor 2410′, 2410″, 2411′, 2411″ and 2412. From there, the refrigerant, which has already to a certain degree taken up heat from the medium flowing around it, flows, for example, into the rear region of the transverse distributor, from which it is in turn passed into the rear heat-exchange passages of the tube 2419. At the end, these flow routes open out into the outlet section of the header tube 2407, 2408 and 2409 and are returned via the refrigerant outlet tube 2404 into the pipeline system of the air-conditioning system. In this case too, by way of example, the refrigerant return tube has a seal 2406 and, for example, a coupling system 2405 for connection to the pipeline system. In addition to the refrigerant-carrying constituents of the heat exchanger, this embodiment also has frame elements 2416 and 2417. Reference numeral 2418 denotes the position of the cooling fins for the apparatus.
Corresponding to the plan view shown in
According to a particularly preferred embodiment, the cooling fins are configured in such a manner that they likewise extend in serpentine form between the serpentine sections of the tubes and, over the depth of the heat exchanger, are additionally provided with what are known as gills, i.e. with slots, which serve in particular to generate turbulence and therefore to improve the heat transfer between the medium flowing around and the heat-dissipating cooling fins.
In accordance with the illustration presented in
According to a particularly preferred embodiment, the transverse distributors and the header tubes are closed off in a fluid-tight manner at their outer boundaries by means of additional separating elements. These separating elements are preferably connected to the header tube, transverse-distribution tube or the coolant inlet or coolant outlet tube in a cohesive, positive and/or nonpositive manner.
According to a particularly preferred embodiment, these tubes have a Ω-shaped cross section, in the narrowed region of which there are recesses which receive, for example, the heat-exchange tubes. In this case, it should be noted in particular that the heat-exchange tubes have a predetermined depth of penetration into the header tube or the transverse-distribution tube, and that to assemble the components during production of the heat exchanger, it is possible to clamp the through-flow device using the header tubes or transverse distributors. According to a particularly preferred embodiment, the depth of penetration is 0.01 to 10 mm, preferably 0.1 to 5 mm and particularly preferably 0.15 to 1 mm. Furthermore, the header tubes 2645 and 2647 or the transverse distributors 2644 and 2646 have embodiments in which two through-flow devices open out into the interior of the header tubes or transverse distributors. In this case, the outlet limbs of the header tubes or the transverse distributors are matched to the inlet angle of the tubes, so that they extend parallel to the transverse distributor at least in a section.
According to a particularly preferred embodiment,
The tube 2870 in
In accordance with 3102, thermal energy is also withdrawn from the second medium, such as for example the air, in section 3105 and transferred to the refrigerant. This refrigerant is combined as a liquid-gas mixture in the outlet section of the header tube 3106 and returned via the refrigerant discharge line 3107 into the adjoining pipeline system, for example of an air-conditioning system.
According to a further particularly preferred embodiment, it is also possible for two or more tubes to open out in a header tube of the configuration shown in
The first medium flows from the inlet 3207 via the heat-exchange passages 3209 of the tubes into the transverse distributor 3212, which is likewise closed off from the surrounding environment by two separating elements 3211 and 3212. In the transverse distributor 3212, the first medium is then diverted onto the returning heat-exchange passages 3210, which then open out via the header tube 3201 into the outlet section 3208, from which the first medium is discharged via the outlet 3200″.
The present invention has been described in part on the basis of the example of an evaporator. However, it should be noted that the heat exchanger according to the invention is also suitable for other uses.
| Number | Date | Country | Kind |
|---|---|---|---|
| 101 63 202.9 | Dec 2001 | DE | national |
| 102 34 118.4 | Jul 2002 | DE | national |
| 102 40 556.5 | Aug 2002 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP02/14582 | 12/19/2002 | WO |
