Patent Application
20180058765
The present application claims priority to German patent application DE 20 2016 104 702.1, filed Aug. 26, 2016, the entire disclosure of which is herein expressly incorporated by reference.
Exemplary embodiment of the present invention relate to a heat exchanger.
Heat exchangers used for high-temperature applications, for example, in charge air coolers, radiators, and oil coolers of motor vehicles and construction machines, are subjected to substantial cyclic thermal tensions as a result of cyclic changes of the temperature and flow rate of process media guided through the heat exchanger.
The cyclic change of temperature and flow rate of the process medium correspondingly results in a cyclic change of the temperature of the individual components of the heat exchanger, in particular the components of a heat exchanger block, which consists of process channels, coolant medium channels, end plates, lateral parts, and the like, and the collector boxes adjoining thereon, and a cyclically occurring material expansion or compression of the various heat exchanger components which accompanies this.
These components are fixedly connected to one another by soldering or in another manner to form a rigid block, so that high thermal tensions occur in and between the individual components, which has a negative effect on the service life of the radiator.
To lengthen the service life of such a heat exchanger, it is important to reduce the occurring thermal tensions as a result of the above-described cyclic thermal expansions, primarily in the block length and block width directions.
A reduction of the thermal tensions can be achieved by the use of flexible components in the heat exchanger block. Such heat exchangers are known, for example, from German patent documents DE 202 08 748 U1 and 20 2011 052 186 U1, in which flexible block profiles are used in an edge region of the heat exchanger block, adjoining a collector box, which hold the process channels of the heat exchanger block arranged parallel to one another spaced apart and form the flow channels of the coolant medium together with the fins arranged between the process channels.
These heat exchangers achieve a reduction of the tensions induced by cyclic thermal expansions in the block width direction of approximately 50% compared to heat exchangers having nonflexible block profiles.
However, it has been shown that the maximum tensions occurring in the block longitudinal direction are reduced only slightly in spite of the flexibly designed block profile.
To reduce the maximum tensions in edge-side process channels of a heat exchanger block, in particular in the block length direction, providing slots in end or terminal plates of the heat exchanger block, which close the heat exchanger block on an upper side and a lower side, is known from European patent document EP 0 748 995 B1. The tension in the edge process channels is only reducible by 1.1 to 1.3 times in this way, however.
For stiffening the edge process channels in the block length direction, manufacturing them from thicker partition plates than the further partition plates used in the interior of the heat exchanger block is also known. However, the maximum material temperature difference between the edge process channels and the process channels arranged adjacent thereto further into the interior of the heat exchanger block does not thus change. A further tension reduction is therefore not achievable by this measure.
The maximum material temperature difference between two adjoining process channels can reach up to 20 K or even up to 40 K in running operation in critical block regions in the heat exchangers considered here.
Exemplary embodiments of the present invention are directed to a heat exchanger having lengthened service life and lower risk of cracks.
A heat exchanger according to the invention has a heat exchanger block, a first collector box, which is arranged on a first end face of the heat exchanger block, and a second collector box, which is arranged on a second end face of the heat exchanger block opposite to the first end face of the heat exchanger block.
The heat exchanger block has multiple process channels, which are arranged in parallel to one another and connect the first collector box to the second collector box, for through flow of a process medium, and also multiple coolant medium channels for through flow of a coolant medium, wherein the coolant medium channels are arranged between the process channels, wherein adjacent process channels are formed having different material masses and/or heat-transferring areas of different sizes and/or structural flow resistances of different sizes and/or coolant medium channels are formed having different material masses and/or heat-transferring areas of different sizes, so that in operation, in the event of a cyclic temperature change of the process medium, an equal or nearly equal material temperature gradient results between adjacent process channels and lateral parts in the heat exchanger block.
Due to the combinations of different material masses, heat-transferring areas, and/or structural flow resistances, the process channels, coolant medium channels, and lateral parts are formed so that an equal or nearly equal cyclic change of the material temperatures of adjacent process channels is reached, whereby the maximum temperature difference between the process channels, in particular in the critical block regions, is reduced by at least two or three times in relation to the construction of heat exchangers known from the prior art.
A reduction of the thermally-related tensions in the heat exchanger block by up to two times is thus enabled in the block length direction.
According to one preferred embodiment variant, the process channels having higher heat-transfer rate than the process channels adjoining them are formed having an up to three times greater material mass and/or having an up to three times smaller heat-transferring area and/or having an up to five times greater structural flow resistance than the adjoining process channels.
Such different material masses are achieved, for example, by the use of similar passage components such as partition plates, turbulators, or longitudinal profiles having different structural dimensions and also optional additional components, for example, intermediate profiles or the use of pipes having different pipe dimensions, for example, different pipe thicknesses or pipe heights in one process channel in relation to two adjoining process channels.
A reduction of the maximum difference between the material temperatures of adjacent process channels in the event of a thermal cyclic stress by up to 2.5 times is thus enabled.
According to a further preferred embodiment variant, the process channels adjoining a process channel having a higher heat transfer rate than the process channels adjacent thereto are formed having an up to three times smaller heat-transferring area than the adjacent, adjoining process channels in the heat exchanger block.
Such a heat-transferring area, which is up to three times smaller, can be achieved, for example, by corresponding different structural dimensions, in particular lobe parts of the turbulators or different rib divisions.
Heat transfers of different sizes from the process medium to the coolant medium channels thus occur in adjacent process channels, which has the result that the maximum difference between the cyclic material temperatures of the adjoining process channels is reduced in the event of a thermal cyclic stress.
According to a further preferred embodiment variant, the coolant medium channels adjoining a process channel having a higher heat transfer are formed having an up to three times smaller heat-transferring area.
The reduction of the heat-transferring area in the above-mentioned coolant medium channels is achieved, for example, by up to three times reduction of the height of the coolant medium channels and/or the use of fins or guide plates in the coolant medium channels having an up to five times greater fin lobe or guide plate division.
The difference between the heat transfers in two adjoining process channels is thus reduced, which has the result that the maximum difference between the cyclic material temperatures of the adjoining process channels is reduced by up to two times.
According to still another preferred embodiment variant, the process channels enabling a higher heat transfer than the adjoining process channels are formed having up to five times higher structural flow resistances for process medium in comparison to these above-mentioned adjoining process channels.
This is achieved, for example, by the use of the different turbulators, longitudinal profiles, or additional components, for example, intermediate profiles, and also pipes having a smaller flow cross section for the flow of the process medium.
A ratio is thus increased between the flow rates of the process medium in the adjoining process channels. As a result, the maximum difference between the cyclic material temperatures in the adjoining process channels is decreased by up to three times, which results in a substantial reduction of the thermal tensions.
According to still another preferred embodiment variant, the end plates/lateral parts are formed having an up to five times smaller material mass than the material mass of the edge process channels. The negative influence of the end plate/lateral part on the cyclic change of the material temperature of the edge process channels is thus reduced, which results in a reduction of the maximum material temperature difference between the edge process channels and adjoining process channels in the heat exchanger block.
Exemplary embodiments of the invention will be explained in greater detail hereafter on the basis of the appended drawings.
In the figures:
In the following description of the figures, terms such as above, below, left, right, front, rear, etc. relate exclusively to the illustration and position selected by way of example in the respective figures of the heat exchanger, the process channels, coolant medium channels, lateral parts, and the like. These terms are not to be understood as restrictive, this means that these references can change due to different operating positions or mirror-symmetrical design or the like.
In
The heat exchanger block 1 furthermore has multiple coolant medium channels 5 for the through flow of a coolant medium. The coolant medium channels 5 are arranged between inner process channels 2 and between edge process channels 6 arranged on an outer edge of the heat exchanger block 1 and also lateral parts 7, preferably embodied as end plates, in the heat exchanger block 1.
The coolant medium channels 5 are arranged in the heat exchanger block 1 so that a through flow of the coolant medium between the process channels 2 occurs in a transverse direction or a direction parallel to the directional flow Y of the process medium.
As is further illustrated in
An outlet nozzle 9 is accordingly provided on a head side of the exit box 4, through which the process medium can be guided out of the exit box 4.
The inlet nozzle 8 and the outlet nozzle can also be arranged on one of the other sides of the entry box 3 or exit box 4, respectively.
The inlet nozzle 8 and outlet nozzle 9 are accommodated in this case in a receptacle opening, which corresponds to the cross section of the inlet nozzle 8 or the outlet nozzle 9, respectively, in the head side of the entry box 3 or the exit box 4, respectively.
As shown in
In the embodiment variant shown in
In the embodiment variant shown in
As can furthermore be seen in
For all embodiment variants shown in
Thus, according to one embodiment variant of a heat exchanger according to the invention, the material mass of process channels 2, 6 having higher heat transfer rate than the process channels 2, 6 adjoining them is formed having an up to three times greater material mass than these adjoining process channels.
Alternatively or additionally, the heat-transferring area of the process channels 2, 6 having higher heat transfer rate than the process channels 2, 6 adjoining them is up to three times smaller than the heat-transferring area of adjoining process channels 2, 6. This is achieved, for example, by enlarging the lobe division of turbulators or the use of fewer heat-transferring ribs 14 in the process channels 2, 6, into which the hottest component of process medium flows, in relation to the process channels through which a component of the process medium flows which is already partially cooled.
Alternatively or additionally, respective coolant medium channels 5, which adjoin a process channel 2, 6 having a higher heat transfer rate than the process channels 2, 6 adjacent to them, are formed having an up to three times smaller heat-transferring area than adjacent coolant medium channels 5 in the heat exchanger block 1.
Thus, in particular the coolant medium channels 5 between edge process channels 6 and lateral parts 7 are formed having an up to three times smaller heat-transferring area than other coolant medium channels 5 in the heat exchanger block 1.
Furthermore, the lateral parts 7 are preferably formed having an up to five times smaller material mass than the material mass of the edge process channels 6.
In each case, due to the formation of the process channels and coolant medium channels having different material masses or heat-transferring areas of different sizes, the material temperature gradient between adjacent process channels 2, 6 and lateral parts 7 in the heat exchanger block 1 upon the through flow of the process channels with the process medium and the through flow of the coolant medium channels with a coolant medium can be kept constant or nearly constant and as small as possible, whereby thermally-related tensions in the heat exchanger block are significantly reduced and therefore the service life of such heat exchangers is lengthened.
Although the invention has been illustrated and described in detail by way of preferred embodiments, the invention is not limited by the examples disclosed, and other variations can be derived from these by the person skilled in the art without leaving the scope of the invention. It is therefore clear that there is a plurality of possible variations. It is also clear that embodiments stated by way of example are only really examples that are not to be seen as limiting the scope, application possibilities or configuration of the invention in any way. In fact, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete manner, wherein, with the knowledge of the disclosed inventive concept, the person skilled in the art is able to undertake various changes, for example, with regard to the functioning or arrangement of individual elements stated in an exemplary embodiment without leaving the scope of the invention, which is defined by the claims and their legal equivalents, such as further explanations in the description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2016 104 702.1 | Aug 2016 | DE | national |
