EP2901096A1 - Tube for a motor vehicle heat exchanger - Google Patents

Abstract

This tube (10) for a motor vehicle heat exchanger extends in a longitudinal direction and has a transverse cross-section. The tube (10) comprises, on the inside, a plurality of longitudinal channels (12) for the circulation of a fluid and at least a portion of the channels is distributed in the transverse cross-section of the tube (10) in such a way as to define two rows (15) of channels (12).

Description

 Tube for a motor vehicle heat exchanger

The present invention relates to the technical field of heat exchangers for motor vehicles, and relates more specifically to a tube for such an exchanger.

The heat exchanger tubes concerned are intended to be used for example in cooling radiators, especially low temperature cooling radiators, or condensers of air conditioning circuits of vehicles.

There is already known a cooling radiator comprising a multiplicity of parallel tubes in which a refrigerant circulates and allowing, thanks to an air flow between the tubes, to cool the bodies of the vehicle. Generally, such a tube extends in a longitudinal direction and has a cross section, the tube having in its interior a plurality of longitudinal channels of fluid flow. Usually, these channels are aligned to form a row of channels according to the cross section of the tube. It is interesting to design these tubes so as to reduce as much as possible their hydraulic diameter, so the diameter of the fluid circulation channels, because this allows to obtain good heat exchange performance of the exchanger. However, the diameter of the channels can not be reduced too much because in this case, the energy dissipated by the friction of the liquid, and therefore the loss of charge during the flow of the fluid, is considerably increased.

Thus, it is difficult to combine a good thermal performance and a reduction in pressure losses of the tubes. The present invention is intended to provide a heat exchanger tube whose thermal efficiency is improved.

For this purpose, the subject of the invention is a tube for a motor vehicle heat exchanger, extending in a longitudinal direction and presenting a cross section, the tube having in its interior a plurality of longitudinal channels for circulating a fluid in which at least a portion of the channels is distributed in the cross section of the tube so as to define two distinct rows of channels.

Thus there is provided an exchanger tube which has in its cross section, not a single row of channels, but at least two rows, preferably arranged one in parallel with the other. This is particularly advantageous insofar as this makes it possible to have more channels in the tube, thus to improve the thermal performance of the tube, without producing channels of too small diameter, which can increase the pressure drops. Thus to increase the thermal performance, it is proposed to increase the exchange surface by increasing the number of channels with this particular provision, rather than decreasing the diameter of these channels. This good compromise between the hydraulic diameter and the losses of charges improves the thermal efficiency of the exchanger. In the tubes of the state of the art, the number of channels per tube is relatively limited since each tube accommodates a single row of channels. The term "row of channels" is preferably understood to mean an imaginary straight line lying in a cross section of the tube and passing through axes of longitudinal symmetry of several channels. It is of course understood that the tube may possibly comprise more than two distinct rows. It will further be understood that preferably one channel forming a row of the tube is only part of this row and not the other. In other words, the channels of one row do not "bite" on the other row.

The tube proposed above is advantageously used in a heat exchanger such as a cooling radiator or an air conditioning circuit condenser. It will be noted that the heat exchanger may comprise between 20 and 150 tubes.

Generally, in the case of a radiator, a tube comprises between 3 and 7 channels per row, preferably between 4 and 5 channels per row. The pressure of the fluid flowing inside the channels is between 1 and 10 bar, preferably of the order of 2 to 3 bar. In this case, because of this number of channels per tube, can have channels of diameter large enough not to have too much resistance to pressure and thus generate too much pressure loss. The radiator is for example used to cool an engine, a so-called "low temperature" loop for cooling electronic components, a battery, an air / water heat exchanger, and / or a hybrid engine for hybrid vehicles.

 Moreover, in the case of an air conditioning circuit condenser, a tube generally comprises between 8 and 20 channels per row, preferably between 10 and 16 channels per row. The pressure of the fluid flowing inside the channels is often between 10 and 150 bar, preferably of the order of 80 to 120 bar. In this case, because of the high pressure, this relatively large number of channels is interesting in that it allows for small channels, capable of providing better resistance to this high pressure, where larger channels might 'explode. It will be noted that the tube is generally manufactured by extrusion or by folding and sometimes has internal fins intended to increase the thermal performance.

The heat exchanger tube as defined above may further include one or more of the following features, taken alone or in combination.

- The tube comprises a continuous strip of material between the two rows. Thus, the two rows are distinctly separated by this band. This configuration allows each row to optimize its thermal performance and also improves the mechanical strength of the tube.

 - The channels of one of the rows are mainly staggered with respect to the channels of the second row. This case is particularly interesting in that it improves the mechanical strength of the tube and the heat gain, because it can better distribute the heat in the tube.

 - The channels of one of the rows are aligned in pairs with the channels of the second row.

The tube has, according to the cross section of the tube, a length L _iute and a thickness e _tU be, each of the rows being substantially parallel to the length of the tube L _iute . According to the cross-section of the tube, each channel of a row has a length L _{ca (ia} , taken in the direction of this row, the row of channels having a length L _{ra (ig,} the sum of the lengths L _{ca (ia} , channels of the row, divided by the length of the row L _{ra (igated!} being greater than or equal to 0.75, preferably greater than 0.8, more preferably greater than 0.85.

- The tube has a thickness e _tU be between 1 and 2 millimeters.

- The channels arranged in a row have a width l _{cana /} , taken in the perpendicular direction of the row, between 0.3 and 0.7 millimeters.

- The channels arranged in a row have a length L _{ca (ia} , taken in the direction of the row between 0.5 and 5 millimeters.

Two consecutive channels of a row are separated by a distance of _{ca / ia // ca / ia /} from 0.2 to 0.4 millimeters.

- The tube comprises an outer skin and the channels of one row have a wall adjacent to the outer skin, the distance d be _tU / canai between the outer skin of the pipe and the adjacent wall of a channel being between 0.2 and 0.4 millimeters.

The various characteristics described above have the advantage of improving the efficiency of the heat exchange of the proposed tube, taking care not to increase the pressure drop too much and to improve the mechanical strength of the tube.

The invention also relates to a heat exchanger for a motor vehicle comprising a plurality of tubes as presented above, the tubes extending substantially parallel to each other, the distance of the axes of two consecutive tubes, called "no ", Being between 6 and 10 millimeters, preferably between 6 and 8 millimeters. Thus, the efficiency of a heat exchanger comprising such tubes is improved. Note that the smaller the pitch, the better the heat exchange.

The invention will be better understood on reading the appended figures, which are provided by way of examples and are in no way limiting, in which:

FIG. 1 is a schematic cross-sectional view of a tube according to one embodiment, and - Figure 2 is a schematic cross-sectional view of a tube according to another embodiment.

FIG. 1 shows a tube 10 for a heat exchanger, intended more specifically for use on an air conditioning circuit condenser.

In the present description, the longitudinal direction L is defined as the direction which extends parallel to the longitudinal axis of the tube 10, the longitudinal axis of the tube generally corresponding to the direction of flow of the fluid inside the tube. . The cross section of the tube is defined by the intersection of the tube with a plane perpendicular to the longitudinal direction L. The cross section is defined by a first direction T and a second direction perpendicular to the direction T in the plane perpendicular to the longitudinal direction L. The external cross section of the tube is delimited by a length L _iute and a thickness e _tU be, which is between 1 and 2 millimeters.

The heat exchanger comprises a plurality of tubes 10 as shown in this example, generally between 20 and 150 tubes such as tube 10. These are arranged parallel to each other and so as to form spaces, called spaces inter-tubes, in which circulates a flow of air. In the example, the distance between the longitudinal axes of two consecutive tubes 10 is 6 millimeters. This distance may in certain cases be different, and have a value of between 6 and 10 millimeters, preferably between 6 and 8 millimeters. Each tube 10 is provided with an outer skin 11 which allows heat exchange and comprises inside a plurality of longitudinal channels 12 for circulating a refrigerant fluid whose function is to exchange heat with the flow of heat. air circulating between the tubes 10, so as to cool. According to the cross section, the tube substantially forms an elongated rectangle, of oblong shape, having two long straight parallel edges 13, and two rounded lateral edges 14. The tube is for example made from an alloy sheet metal strip. aluminum. This strip is subjected to metallurgical processes which make it easier to shape the tubes by folding and their assembly by brazing in the exchanger. However, it is also possible to realize these tubes by other manufacturing processes, for example by extrusion.

According to the cross section, a majority of the channels 12 are distributed so as to define two distinct rows of channels 12. The rows 15 are separated by a continuous strip of material 16. Each row 15 is substantially parallel to the length of the tube L _Iute and a row 15 of channels 12 has a length L _{ra (igée} - The two rows 15 are parallel to each other and the channels 12 of one of the rows are aligned in pairs with the channels of the second Two consecutive channels 12 of the same row 15 are separated by a bridge of material 18 which has a width corresponding to a distance ù _cana i / _cana i between 0.2 and 0.4 millimeters.

In the cross section of the tubes 10, the channels 12 of a row 15 have a generally rectangular shape. Each channel of a row has a long side corresponding to a length L _{ca (ia} , taken in the direction of the row and between 0.5 and 5 millimeters, and a small side corresponding to a width l _{cana /} taken in the perpendicular direction of the row between 0.3 and 0.7 millimeters.

The tube 10 has two end channels 20, which are adjacent to the lateral edges 14. These end channels 20 have a rounded wall 21 whose profile corresponds to the profile of the lateral edges 14 of the tube, their section forming a D. note that the end channels 20 intersect each of the two rows. It is considered that these end channels 20, which bite each on the two rows 15, are not part of the channels defining the rows 15 defined above. In other words, the rows 15 are imaginary lines composed solely of the juxtaposition of channels similar to the channels 12, without including the biting channels on the two rows.

In the example, the sum of the lengths L _{ca (ia} , of the channels 12 of a row, divided by the length of this row is greater than or equal to 0.75. However, in other cases the sum of the lengths L _{ca (ia} , of the channels of a row, divided by the length of this row could be greater than 0.8 or even greater than 0.85. The channels 12 of a row 15 comprise a wall 22 adjacent to the skin external 11, which corresponds to the distance closest to a channel 12 of the outer skin 11 of a tube. A distance d _tU be / ∞nai between the outer skin 11 of tube 22 and the adjacent wall of a channel is between 0.2 and 0.4 millimeters. FIG. 2 shows a second embodiment of a tube 10 'of exchanger, similar to the tube 10. In this example, the channels 12 of one of the rows 15 are predominantly arranged in staggered rows with respect to 15. In order to do this, at least one of the channels, or even two of the channels, of one and the same row has a length L _{ca (ia} , which is greater than that of the other channels 12. This allows the channels 12 of a row are arranged in staggered relation to those of the other, in this case they are channels arranged just next to the end channels 20 which have a longer length. the channels are not aligned in pairs with the channels of the second row, which makes it possible to optimize the mechanical strength and the thermal efficiency of the tube.

The invention is not limited to the embodiments presented and other embodiments will become apparent to those skilled in the art. The exchanger tubes described above are most often made by folding, however, they can also be manufactured by extrusion. Alternatively, such tubes may have fins on their inner walls to create multiple channels. In addition, the tubes as described in the example may comprise additional rows of channels so as to respond to particular thermal stresses. Furthermore, the length L _{ca (ia} , can vary from one channel to another of the same row, allowing different configurations in which the channels of one of the rows are not aligned with the channels of the other Moreover, it should be noted that combinations of the various embodiments described above are possible.

Claims

 1. Tube (10) for a motor vehicle heat exchanger extending in a longitudinal direction and having a cross section, the tube (10) having in its interior a plurality of longitudinal channels (12) for circulating a fluid and characterized in that at least a portion of the channels are distributed in the cross section of the tube (10) so as to define two distinct rows (15) of channels (10).

 2. Tube (10) according to claim 1, comprising a continuous strip (16) of material between the two rows (15).

3. Tube (10) according to any one of the preceding claims, wherein the channels (10) of one of the rows (15) are predominantly staggered with respect to channels (10) of the second row (15). ).

 4. Tube (10) according to any one of claims 1 to 2, wherein the channels (10) of one of the rows (15) are aligned in pairs with the channels (10) of the second row.

5. Tube according to any one of the preceding claims, having, according to the cross section of the tube, a length L _Tu be and a thickness e _Tu be, each of the rows being substantially parallel to the length of the tube L _You need

6. Tube according to any one of the preceding claims, wherein, according to the cross section of the tube, each channel of a row has a length L _{ca (ia} , taken in the direction of this row, the row of channels having a length L g _{lis ed,} the sum of the lengths L _{ca (ia /} channels of the array divided by the length of the Lrangée row being greater than or equal to 0.75, preferably greater than 0.8, more preferably greater than 0.85.

7. Tube according to any one of the preceding claims, wherein the tube has a thickness e _tU be, between 1 and 2 millimeters.

Tube according to any one of the preceding claims, wherein the channels arranged in a row have a width l _{cana /} , taken in the perpendicular direction of the row, between 0.3 and 0.7 millimeters.

9. A tube as claimed in any one of the preceding claims, wherein the channels arranged in a row have a length L _{ca (ia} , taken in the direction of the row of between 0.5 and 5 millimeters.

Tube according to any one of the preceding claims, wherein two consecutive channels of a row are separated by a distance d _cana i / _cana i of between 0.2 and 0.4 millimeters.

1 1. Tube according to any one of the preceding claims, wherein the tube comprises an outer skin and the channels of a row comprise a wall adjacent to the outer skin, the distance d _tU be / channel between the outer skin of the tube and the wall adjacent channel being between 0.2 and 0.4 millimeters.

 12. Heat exchanger for a motor vehicle comprising a plurality of tubes according to any one of the preceding claims, the tubes extending substantially parallel to each other, the distance between the axes of two consecutive tubes being between 6 and 10 millimeters, preferably between 6 and 8 millimeters.