Patent Application
20090126919
The right of foreign priority is claimed under 35 U.S.C. ยง 119(a) based on Federal Republic of Germany Application No. 10 2007 047 294.5, filed Oct. 2, 2007, the entire contents of which, including the specification, drawings, claims and abstract, are incorporated herein by reference.
The invention relates to a heat exchanger, in particular for cooling a coolant, preferably in a motor vehicle, which heat exchanger has a multiplicity of heat-exchanger tubes in which coolant can flow, and whose ends are held in collecting tanks. At least two collecting volumes which are separated from one another by an insert are arranged in at least one collecting tank.
A heat exchanger of the stated type is known for example from EP 1 410 929. Hot water is conducted from an engine into a first collecting volume of a collecting tank, flows through the heat-exchanging tubes, changes its flow direction in a second collecting tank and is conducted through heat-exchanging tubes into a second collecting volume of the first collecting tank. As it flows through the heat-exchanger tubes, the hot water heats the air which flows transversely through the heat exchanger. Situated between the two collecting volumes of the first collecting tank is a partition which separates the two collecting volumes.
The water at the two sides of the partition has a different temperature as a result of the cooling as it passes through the heat-exchanger tubes, with the difference between the two temperatures varying with the heating temperature set by the motor vehicle occupants.
If use is made, for example, of coolant coolers with relatively long tubes and a partition in one collecting tank, then thermal loading which is generated on account of a temperature difference can generate stresses in the region of the partition of the heat exchanger. Said stresses may cause damage, such as for example fracture points in the collecting tank wall in the region of the partitions, and thereby lead to a limited durability of collecting tanks of said type or of the heat exchanger.
To prevent damage by thermal loading, it is proposed in DE 3 927 955 to produce water tanks from plastic in order to obtain thermal decoupling. In DE 3 540 415, to prevent an exchange of heat between two collecting volumes, it is proposed to join together two in each case complete, separate heat exchangers to form a double heat exchanger. Here, the two heat exchangers bear against one another at the fluid inlet, such as coolant inlet. The two collecting tanks between which there is a temperature difference are arranged spaced apart from one another.
DE 44 01 859 discloses a double cross-flow heat exchanger in which the coolant is supplied and discharged at the two sides of the heat exchanger. After passing in each case once through the heat-exchanger tubes, the two coolant flows converge, with a small temperature difference, at the partition which is arranged centrally in the heat exchanger, resulting in relatively low stresses in the partition region. The required tube arrangement for the two sides of the heat exchanger, however, requires increased expenditure in the heat exchanger and during installation into a motor vehicle.
It is also known to provide additional reinforcement elements such as for example metal sheets in the partition region of the collecting tank in order to absorb the stresses generated by the temperature difference. The insertion of such metal sheets has proven firstly to be complex and secondly to be insufficient with regard to relatively high thermal-cycle loading.
It is the object of the present invention to create a heat exchanger which has a simple design with thermal decoupling of adjacent collecting tanks. Furthermore, it is intended to specify a method which permits simple and cost-effective production of said heat exchanger.
Said object is achieved according to the invention by means of the subject matter of Claim 1. The method according to the invention for producing the heat exchanger is the subject matter of Claim 13. Advantageous refinements are the subject matter of the subclaims.
To achieve said object, a heat exchanger is proposed which has a multiplicity of heat-exchanger tubes in which coolant can flow, and whose ends at the two sides are held in collecting tanks. At least two collecting volumes which are separated from one another by an insert are arranged at least in one collecting tank. The insert is separated into two parts by a continuous separating cut which separates the collecting tank.
In one preferred embodiment of the present invention, the heat exchanger has a multiplicity of preferably rectangular heat-exchanging tubes, between which are preferably arranged heat-exchanging devices such as lamellae which preferably bear at both sides in a heat-conducting manner against in each case one heat-exchanging tube in order to ensure a good exchange of heat between the heat-exchanging tubes and the lamellae, and thereby to obtain a high cooling capacity. The two axial ends of the heat-exchanging tubes open out into collecting tanks which are arranged there and in which the heat-exchanging tubes are held in an individually sealingly enclosed fashion.
At least one of the collecting tanks has a partition which, according to the invention, is formed by the insert in the collecting tank, which insert is fixedly connected to the collecting tank. As a result of a separating process, the insert according to the invention and therefore the collecting tank is separated into two parts, such that the parts of the insert form in each case one outer wall of two independent collecting volumes.
For the separation, the insert according to the invention is preferably inserted into the collecting tank in such a way that said insert is sealingly connected along its periphery at both opposite sides to the collecting tank. Here, the insert may be composed of a solid separating element. The insert preferably has a recess in the region of the intended separating process, which recess serves to control and shorten the separating process.
The insert is preferably designed so as to hold a heat-exchanging tube which is separated along its longitudinal axis by the separating process. In this case, it is possible to maintain the construction of the heat-exchanging unit of the heat exchanger from alternately arranged heat-exchanging tubes and lamellae. In this design, it is also advantageous that the lamellae at both sides of the separating cut are still supported. Furthermore, on account of the small wall thickness, only a low level of separating energy is required for separating a heat-exchanging tube along its longitudinal axis. Furthermore, by using the same heat-exchanging tubes in the insert and for exchanging heat, the construction of the heat exchanger can be substantially maintained, and the preparation for production can be simplified.
It is however also possible for two metal sheets, which preferably correspond to the shape of a heat-exchanging tube, to be provided in the insert instead of a heat-exchanging tube. In this embodiment, the separating process is complete after the process of cutting through the insert with the collecting tank. The separation of the two heat-exchanging units of the heat exchanger extends here up to the point at which the metal sheets are held in the collecting tank on the opposite side of the heat exchanger.
As a result of the separation of a first collecting tank in the region of the insert, a first heat-exchanging unit is generated which is preferably connected at one side to a first separate collecting tank, which forms a first collecting volume, and a second heat-exchanging unit, which is preferably connected at one side to a second separate collecting tank, which forms a second collecting volume. Now, in a heat exchanger which is designed in this way, if a coolant at a high temperature is conducted into the first collecting tank, said coolant flows through the heat-exchanging tubes of the first heat-exchanging unit, changes its direction in the second collecting tank on the opposite side of the heat-exchanging tubes, and flows through the heat-exchanging tubes of the second heat-exchanging unit, which heat-exchanging tubes are connected to the second separate collecting tank, into said second separate collecting tank.
While the coolant flows through the heat-exchanging tubes, it heats said tubes and also the interposed lamellae. The heat energy is dissipated from there to the air flowing through the heat exchanger. Here, the coolant in the heat-exchanging tubes is cooled. A temperature difference is thus generated between the coolant in the first and second separate collecting tanks. The separation of the two adjacent collecting tanks allows the two heat-exchanging units to expand and move independently. As a result of the temperature difference, therefore, no stresses arising from the heat-exchanging units are generated either which could lead to damage of the collecting tanks.
The depth of the separating cut in the heat-exchanging region also influences the stability of the heat exchanger. In one preferred embodiment, it is therefore provided that the insert comprises a connecting element, for example a heat-exchanging tube which is not traversed by coolant. Depending on the expected temperature difference, the separating cut, preferably in the connecting element, preferably does not extend as far as the opposite collecting tank, such that a high level of stiffness of the heat exchanger is maintained. Here, an independent movement of the two collecting tanks generated by the separation, and a prevention of the exchange of heat between the two partition surfaces, is restricted only to the extent required on account of the thermal loading of the heat exchanger. Here, a separation length of the heat-exchanging unit in the range from 10 to 75%, in particular in the range from 10 to 50% and very particularly in the range from 10 to 25% has proven to be particularly expedient. This constitutes an optimum compromise between sufficient thermal independence of the two regions and the stability of the heat exchanger.
In a further embodiment of the heat exchanger according to the invention, a separation according to the invention is also formed in a second collecting tank which, as a result of the coolant guidance, comprises two collecting volumes. In this embodiment, too, the stability of the heat exchanger is dependent on the length of the separation of the heat-exchanging units in the direction of the opposite collecting tank. On account of the possibility for separating the collecting tanks between two collecting volumes, it is also made possible to provide a simplified configuration of the flow of coolant through a heat exchanger.
A method according to the invention for producing a heat exchanger of the above-described type comprises substantially three method steps: arranging elements of the heat exchanger, joining said elements, and separating at least one collecting tank in the region of an insert. It is likewise possible to separate the water tank(s) in the region of inserts before the joining of the heat exchanger, and to subsequently join the water tanks produced to the further elements of the heat exchanger, or preferably, to join the elements of the heat exchanger and subsequently separate the water tanks.
The method according to the invention for producing the heat exchanger is described by way of example using an insert which comprises a heat-exchanging tube which is not traversed by coolant. When using other inserts according to the invention, a method is used which corresponds to the production steps described. Furthermore, the method for producing a heat exchanger is described with only one separation of a collecting tank. Further separating processes may take place corresponding to the approach for carrying out the described separating process.
In a first step, a grouping of a heat-exchanging unit, which is in one piece at this time, preferably takes place. At the position of the later separation of the collecting tank, the heat-exchanging unit comprises a heat-exchanging tube with a substantially equal or greater length. A tube of said type may for example be offset or displaced with respect to the partition. The receptacle of the tube may be omitted in a base without a partition or in a region of the base without a partition, such that said tube is not traversed by coolant. The grouped heat-exchanging unit preferably comprises the heat-exchanging tubes, the side parts and lamellae which are inserted between said elements. In a compressed, aligned state of said heat-exchanging unit, a heat-exchanging tube which is to be held in the insert projects beyond the other parts of the heat-exchanging unit. The heat-exchanging unit is joined at both sides to the corresponding elements of the water tanks. Here, the heat-exchanging tube of greater length is preferably held in the insert according to the invention, which later forms the two side walls of the separated collecting volumes. It is also possible to retroactively place the insert onto the respective heat-exchanging tubes. Depending on the assembly sequence, further elements of the collecting tanks including the heat-exchanger connections are now arranged.
The joining of the individual elements of the heat exchanger preferably follows in the next step. Soldering is used as the preferred joining process. It is however also possible to connect the elements of the heat exchanger by means of some other suitable joining process, such as for example by adhesive bonding or welding.
The separation of the collecting tank into two independent collecting volumes in the plane defined by the position of the insert, which is fixedly connected to the collecting tube, preferably takes place after the joining process. The length of the formed separating cut, which is preferably formed by sawing, is dependent on the requirement for preventing the exchange of heat between the separated collecting tanks and on the required strength of the heat exchanger or the required mobility of the collecting tanks with respect to one another.
Depending on the joining process which is used and the desired depth of the separating cut, it is also possible for the water tanks to be separated, according to the invention, before the joining of the heat exchanger.
An advantage of an insert which comprises a separating tube or metal sheets is that said elements support the two heat-exchanging units, and in particular lamellae which bear against these, both during the separating process and also in the heat exchanger produced in this way, and thus reinforce said heat exchanger and enlarge the heat-exchanging surface. When using a heat-exchanging tube, it is possible, as already described, to use the same semifinished part as for the heat-exchanging tubes which are traversed by coolant. In this way, the bundling process is advantageously virtually unchanged in relation to that of a heat exchanger from the prior art. The mechanical separation of the collecting tank results in thermal decoupling which leads to a considerably increased level of durability, in particular under alternating or varying thermal loading.
Further objects, features and advantages of the present invention will become apparent from the detailed description of preferred embodiments that follows, when considered together with the accompanying figures of drawing.
Further advantages, features and possible applications of the present invention can be gathered from the following description in connection with the figures, in which:
The collecting tanks 12 and 13 and the two heat-exchanging units 31 and 32 have been formed by a separating cut 40 which divides elements of the previously unseparated heat exchanger.
The heat exchanger 10 illustrated in
The heat-exchanging tubes 33 of the heat-exchanging unit 32 have only a small temperature difference with respect to the heat-exchanging tubes 33 of the heat-exchanging unit 31 in the region of the collecting tank 11, but have a considerably greater temperature difference with respect to the heat-exchanging tubes 33 of the heat-exchanging unit 31 in the region of the collecting tanks 12 and 13. The two collecting tanks 12 and 13 and the adjoining heat-exchanging units 31 and 32 are thermally decoupled by the separating cut 40 in the heat exchanger 10 and can move substantially independently of one another.
The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description only. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible and/or would be apparent in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and that the claims encompass all embodiments of the invention, including the disclosed embodiments and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 047 294.5 | Oct 2007 | DE | national |
