FR2764647A1 - ECONOMICAL CONSTRUCTION BOOST AIR COOLER - Google Patents

Abstract

The charge air cooler comprises a bundle formed by an alternating stack of flat tubes (1) intended to be traversed by the charge air and spacers (2) defining between the tubes free spaces for the circulation of a flow of cooling air. According to the invention, the tubes are formed by folded sheet metal strips without the insertion of elements capable of producing turbulence in the flow of charge air and have a height in the direction of stacking of between 1.75 and 3 mm, the ratio between this height and that of the spacers being between 1/3 and 2 / 3. Application to the cooling of the charge air of the thermal engine driving a motor vehicle.

Description

A Economically built charge air cooler

  The invention relates to a heat exchanger for cooling

  distribution of the charge air of a heat engine, in particular of the drive engine of a motor vehicle, comprising a beam formed by an alternating stack of

  flat tubes intended to be traversed by the air of supercharging-

  tation and spacers defining between the tubes free spaces for the circulation of a cooling air flow. The supercharging of an internal combustion engine consists in supplying it with compressed air and not directly with atmospheric air, so as to increase the mass of oxygen available in the combustion chambers. The compression of the air is accompanied by a strong rise in temperature, therefore

  a reduction in its density at a determined pressure

  born, which goes against the objective. It is therefore

necessary to cool this air.

  Bundles of flat tubes and spacers are commonly used for both charge air coolers and other types of heat exchangers, including heaters for cooling the same heat engines. In the case of a charge air cooler, to obtain both a low pressure drop and efficient cooling of the charge air, and a good resistance of the tubes to the pressure thereof, we use hitherto tubes having a height, that is to say a dimension in the direction of stacking, relatively high, and whose internal volume is furnished with disturbers intended to produce turbulence in the flow of air , these disturbers being brazed to the internal faces of the tubes so as to prevent them from swelling under the effect of

pressure.

  The manufacture and installation of increased disruptors

  the cost of heat exchangers.

  The object of the invention is to remedy this drawback.

  The invention relates in particular to a heat exchanger of the kind defined in the introduction, and provides that the tubes are formed by folded sheet metal strips without the insertion of elements capable of producing turbulence in the flow of charge air and have a height in the direction of the stack between 1.75 and 3 mm, the ratio between this height and that of the spacers being between

1/3 and 2/3.

  Surprisingly, the reduction in the height of the tubes

  does not cause excessive pressure drop, and removing it

  The disturbance does not harm the heat exchanges and the resistance of the tubes to pressure, the reduction in the height of the tubes being compensated by an increase in

  their number, with equal dimensions of the exchanger, and favori-

  itself heat exchange and resistance to pressure.

  Optional features of the invention, complementary

  or alternative, are set out below:

  - The height of the tubes is approximately 2 mm.

  - The sheet metal strip constituting each tube is folded so as to form at least one reinforcing spacer connecting together the two main walls of the tube, in an intermediate region of the length of its section

  transverse. Such spacers strengthen the screw tubes.

  both internal pressure and beam clamping force. Their presence and number are

depending on said length.

  - The sheet metal strip constituting each tube is brazed on itself so as to ensure the seal between the inside of the tube and if necessary the connection between the two walls

  main through the spacer.

  The characteristics and advantages of the invention will be

  described in more detail in the description below, in

  referring to the attached drawings, in which: - Figure 1 is a partial perspective view of the bundle of tubes and spacers of a charge air cooler according to the invention; and - Figures 2 and 3 are graphs comparing the performance of a cooler according to the invention and a

  state of the art cooler.

  FIG. 1 partially represents, in perspective, a few tubes 1 and a few spacers 2 interposed between the tubes in the bundle of a charge air cooler according to the invention. Each tube 1 is formed by a strip of sheet metal folded so as to form two generally opposed opposite main walls 3 and 4 connected together by two end walls 5 and 6. The two marginal regions 7 of the strip are folded towards the inside from the wall 4, and joined to one another, their free edges coming to bear on the inside face of the wall 3. The regions 7, brazed together and to the wall 3, form a spacer of enhancement. They also divide the interior volume of the tube into two conduits

  parallels free of any obstacle.

  Each interlayer 2 is a possible metal sheet-

  fitted with louvers, wavy according to a sensitive profile-

  sinusoidal, the corrugation ridges alternately coming into contact with the wall 3 of a tube and with the wall 4

from a neighboring tube.

  The dividers define intervals between the tubes

  of a height Hi in which a flow of cooling air

  can run parallel to the generators of

  spacers, i.e. perpendicular to the direction

  Longitudinal tion of the tubes, according to which the charge air to be cooled circulates in them. The spacers are brazed to the walls 3, 4 of the tubes to ensure good thermal contact and good rigidity of the bundle. At each end of the stack, in a known manner, a terminal insert is interposed between a terminal tube and an outer cheek, not shown. Also in known manner, the tubes 1 open at their two ends into manifolds, not shown.

  between which the air to be cooled circulates through

diary of the tubes.

  The structure described above, already used for other types of heat exchanger, in particular cooling radiators for heat engines, gives excellent results for charge air coolers, on the double condition that the height Ht of the tubes, measured in the stacking direction of the beam, is between 1.75 and 3 mm, and the Hi / Ht ratio is between

1.5 and 3.

  FIGS. 2 and 3 represent curves showing the variation of the thermal power P exchanged between the charge air and the cooling air, and of the density efficiency of the charge air, respectively, as a function of the speed Ve cooling air flow

  passing through the heat exchanger, measured for cooling

  seur according to the invention and for a conventional cooler

with disruptors.

  Curve C1 in FIG. 2 and curve C3 in FIG. 3 correspond to the control cooler, and curves C2 and

  C4 corresponding to the cooler of the invention.

  The table below gives the main constructive characteristics of the bundles of the two coolers, as well as the experimental values shown in Figures 2 and 3.

BOARD

  l_ Invention indicator Number of sets of 2 tubes 13 26 Number of spacers 14 27 Dimensions (mm) ABAB Tube 39.75 7.6 38.5 2 Wall thickness 0.6 0.27 Spacer 85 6.5 85 5, 1 Wall thickness 0.1 0.1 Hi / Ht 0.86 2.55 Beam 85 189.8 85 189.7 Outdoor air speed (m / s) P (kW) R (%) P (kW) R ( %)

2.5 5.6 18.9 6.17 22.7

4 6.87 25.8 7.36 30

5.5 7.5 30 8.05 34.1

7 8.51 36.7 8.62 38.1

  In each bundle, two identical tubes are mutually juxtaposed in the direction A (see FIG. 1) of circulation of the outside air, in each interval between two spacers. B represents the stacking direction of the tubes and the spacers. For the two coolers, the useful length of the tubes between the two manifolds

  is 183.4 mm. The two beams therefore have the same size.

  sharply. The two coolers were tested under the following conditions:

  for compressed air to be cooled: flow rate = 0.15 kg / s, press-

  sion = 1.8 bar, temperature = 130 C;

  for outdoor air: temperature = 30 C.

  The power P is the heat power exchanged between the compressed air and the outside air. The density yield R Pi - Pi

  is the ratio, P Pi in which P ', p2 and Pmax represent

  Pmax - Pi tent respectively the density of the compressed air at

  inlet and outlet of the cooler and the density

  that theoretical compressed air at the outlet of the cooler if its temperature was reduced to 30 C. It can be seen that the charge air cooler according to the invention exhibits, despite the absence of disturbers, better performance than the cooler classic including disruptors.

Claims (4)

Claims   1. Heat exchanger for cooling the charge air of a heat engine, in particular of the drive engine of a motor vehicle, comprising a bundle formed by an alternating stack of flat tubes (1) intended to be traversed by charge air and spacers (2) defining spaces between the tubes   free for the circulation of a cooling air flow   ment, characterized in that the tubes are formed by folded sheet metal strips without the insertion of elements specific to   produce turbulence in the charge air flow   tion and have a height in the direction of stacking between 1.75 and 3 mm, the ratio between this height   and that of the dividers being between 1/3 and 2/3.   2. Heat exchanger according to claim 1, character-   risé in that the height of the tubes is approximately 2 mm.   3. Heat exchanger according to one of claims 1 and   2, characterized in that the sheet metal strip constituting each tube is folded so as to form at least one spacer of   reinforcement (7) connecting together the two main walls   blades (3, 4) of the tube, in an intermediate region of the   length of its cross section.   4. Heat exchanger according to one of claims   above, characterized in that the strip of sheet metal   killing each tube is brazed on itself so as to seal between the inside of the tube and if necessary the connection between the two main walls by through the spacer.