FR3103032A1 - Evaporator for two-phase capillary pumped heat transfer system and associated manufacturing process - Google Patents

Abstract

The present invention relates to an evaporator (1) for a two-phase heat transfer system with capillary pumping (X) for a motor vehicle, said evaporator (1) comprising: a heat exchange plate (10) comprising a first face intended to come into contact of an element to be cooled and a second face, opposite the first face, intended to be in contact with a low-pressure refrigerant fluid, an impermeable hollow body (13) covering at least partially the second face of the heat exchange (10) so as to form a cavity, a porous mass (15) arranged in the cavity and delimiting with the heat exchange plate (10) a first chamber (13a) in which the refrigerant fluid is intended to circulate at low pressure and delimiting with the hollow body (13) a second chamber (13b) in which the high pressure refrigerant fluid is intended to circulate, at least two of the elements among the heat exchange plate (10), the hollow body (13) and the porous mass (15) being made of aluminum or aluminum alloy and brazed together. Abstract Figure: Fig 3

Description

Evaporator for two-phase heat transfer system with capillary pumping and associated manufacturing method

The present invention relates to the field of heat exchangers and more particularly to evaporators in the context of a two-phase heat transfer system with capillary pumping for a motor vehicle.

Two-phase heat transfer systems with capillary pumping are known in the prior art, in particular in the field of cooling electronic components such as electronic chips or processors and in the space field. A two-phase heat transfer system with capillary pumping generally comprises an evaporator placed at the level of the element to be cooled and a condenser in order to dissipate the calorific energy. Between this evaporator and this condenser circulates a two-phase heat transfer fluid whose movement is generally ensured by a porous element providing capillary pumping.

The evaporator comprises a heat exchange plate intended to come into contact with an element to be cooled, an impermeable hollow body at least partially covering the second face of the heat exchange plate so as to form a cavity and a porous mass arranged in the cavity in order to perform the capillary pumping. Generally, at least the heat exchange plate is made of copper. This material is expensive but because for use in the field of cooling electronic components the surface of said heat exchange plate is reduced, the costs remain limited. However, in the automotive field, the use of such a material is not suitable because the size of said evaporator is larger and therefore the use of copper would considerably increase the cost of the evaporator.

In addition, in order to ensure the tightness between the different elements of the evaporator, seals are generally placed between these elements, which increases the complexity and the manufacturing time.

One of the aims of the present invention is therefore to remedy at least partially the drawbacks of the prior art and to propose an improved evaporator for two-phase heat transfer systems with capillary pumping.

• une plaque d’échange thermique comportant une première face destinée à venir au contact d’un élément à refroidir et une deuxième face, opposée à la première face, destinée à être au contact d’un fluide réfrigérant à basse pression,
• un corps creux imperméable recouvrant au moins partiellement la deuxième face de la plaque d’échange thermique de sorte à former une cavité,
• une masse poreuse disposée dans la cavité et délimitant avec la plaque d’échange thermique une première chambre dans laquelle est destiné à circuler le fluide réfrigérant à basse pression et délimitant avec le corps creux une deuxième chambre dans laquelle est destiné à circuler le fluide réfrigérant à haute pression,

au moins deux des éléments parmi la plaque d’échange thermique , le corps creux et la masse poreuse étant réalisés en aluminium ou alliage d’aluminium et brasés l’un à l’autre.The present invention therefore relates to an evaporator for a two-phase heat transfer system with capillary pumping for a motor vehicle, said evaporator comprising:

• a heat exchange plate comprising a first face intended to come into contact with an element to be cooled and a second face, opposite the first face, intended to be in contact with a low-pressure refrigerant fluid,
• an impermeable hollow body at least partially covering the second face of the heat exchange plate so as to form a cavity,
• a porous mass disposed in the cavity and delimiting with the heat exchange plate a first chamber in which the low-pressure refrigerant fluid is intended to circulate and delimiting with the hollow body a second chamber in which the refrigerant fluid is intended to circulate at high pressure,

at least two of the elements among the heat exchange plate, the hollow body and the porous mass being made of aluminum or aluminum alloy and brazed together.

The use of aluminum or aluminum alloy makes it possible to have an inexpensive evaporator and whose tightness is improved due to brazing.

According to one aspect of the invention, the heat exchange plate is made of a polymer material filled with heat-conducting elements, the hollow body and the porous mass being made of aluminum or aluminum alloy.

According to another aspect of the invention, the heat exchange plate, the hollow body and the porous mass are all three made of aluminum or aluminum alloy.

According to one aspect of the invention, the porous mass is made of aluminum or aluminum alloy by sintering.

According to one aspect of the invention, the heat exchange plate comprises fins projecting into the first chamber.

The present invention also relates to a two-phase heat transfer system with capillary pumping for a motor vehicle comprising an evaporator as described above.

• assemblage :
  • d’une plaque d’échange thermique et comportant une première face destinée à venir au contact d’un élément à refroidir et une deuxième face, opposée à la première face, destinée à être au contact d’un fluide réfrigérant à basse pression, avec
  • un corps creux destiné à recouvrir au moins partiellement la deuxième face de la plaque d’échange thermique de sorte à former une cavité, et avec
  • une masse poreuse disposée dans la cavité et délimitant avec la plaque d’échange thermique une première chambre dans laquelle est destiné à circuler le fluide réfrigérant à basse pression et délimitant avec le corps creux une deuxième chambre dans laquelle est destiné à circuler le fluide réfrigérant à haute pression,
  • au moins deux des éléments parmi la plaque d’échange thermique, le corps creux et la masse poreuse étant réalisés en aluminium ou alliage d’aluminium,
• brasage des éléments réalisés en aluminium ou alliage d’aluminium et en contact les uns des autres.

The present invention further relates to a method for manufacturing an evaporator for a two-phase heat transfer system with capillary pumping for a motor vehicle, said method comprising the following steps:

• assembly :
  • of a heat exchange plate and comprising a first face intended to come into contact with an element to be cooled and a second face, opposite the first face, intended to be in contact with a low pressure refrigerant fluid, with
  • a hollow body intended to at least partially cover the second face of the heat exchange plate so as to form a cavity, and with
  • a porous mass disposed in the cavity and delimiting with the heat exchange plate a first chamber in which the low-pressure refrigerant fluid is intended to circulate and delimiting with the hollow body a second chamber in which the refrigerant fluid is intended to circulate at high pressure,
  • at least two of the elements among the heat exchange plate, the hollow body and the porous mass being made of aluminum or aluminum alloy,
• brazing of elements made of aluminum or aluminum alloy and in contact with each other.

Other characteristics and advantages of the present invention will appear more clearly on reading the following description, provided by way of illustration and not limitation, and the appended drawings in which:

FIG. 1 is a schematic representation of a two-phase heat transfer system with capillary pumping according to a first embodiment,

FIG. 2 is a schematic cross-sectional perspective representation of an evaporator according to a first embodiment and parallel to the direction of circulation of the refrigerant fluid,

Figure 3 is a schematic representation in perspective section of the evaporator of Figure 2 perpendicular to the direction of circulation of the refrigerant,

FIG. 4 is a schematic cross-sectional perspective representation of an evaporator according to a second embodiment and parallel to the direction of circulation of the refrigerant fluid,

Figure 5 is a schematic representation in perspective section of the evaporator of Figure 4 perpendicular to the direction of circulation of the refrigerant fluid,

Figure 6 is a flowchart of the steps of a method of manufacturing an evaporator.

In the various figures, identical elements bear the same reference numbers.

The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference is to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined and/or interchanged to provide other embodiments.

In the present description, it is possible to index certain elements or parameters, such as for example first element or second element as well as first parameter and second parameter or else first criterion and second criterion, etc. In this case, it is a simple indexing to differentiate and name elements or parameters or criteria that are close, but not identical. This indexing does not imply a priority of one element, parameter or criterion over another and it is easy to interchange such denominations without departing from the scope of the present description. Nor does this indexing imply an order in time, for example, to assess such and such a criterion.

Figure 1 shows a schematic representation of a two-phase heat transfer system with capillary pumping X comprising an evaporator 1 and a condenser 2 between which circulates a two-phase refrigerant commonly used in air conditioning circuits, such as 1234yf for example. The use of such a refrigerant allows use of the two-phase heat transfer system with capillary pumping X in the automotive field with less carcinogenic, mutagenic and toxic risks compared to the methanol commonly used in these two-phase heat transfer systems with pumping capillary. Obviously, the type of refrigerant is not limited to the example of the aforementioned 1234yf, but can be chosen in particular from ethanol, methane, propane or water.

The condenser 2 can be a heat exchanger arranged within an external air flow 200 in order to dissipate the heat energy absorbed at the level of the evaporator 1. The condenser 2 can thus be arranged on the front face of the motor vehicle .

As shown in Figures 2 and 3, the evaporator 1 comprises a heat exchange plate 10, a hollow body 13 and a porous mass 15. The heat exchange plate 10 comprises a first face 10a intended to come into contact with an element to be cooled and a second face 10b, opposite the first face 10a, intended to be in contact with a low-pressure refrigerant fluid. The hollow body 13 is itself impermeable and at least partially covers the second face 10b of the heat exchange plate 10 so as to form a cavity.

The porous mass 15 is placed in this cavity and delimits a first 13a and a second 13b chamber. This porous mass 15 allows the heat transfer fluid to pass by capillarity between the second 13b and the first 13a chamber. For this, the porous mass 15 comprises communicating pores, for example of an average diameter between 2 μm and 200 μm. The porous mass 15 delimits with the heat exchange plate 10, and more precisely with its second face 10b, a first chamber 13a in which the low-pressure refrigerant fluid is intended to circulate. The porous mass 15 delimits with the hollow body 13 a second chamber 13b in which the high-pressure refrigerant fluid is intended to circulate.

The porous mass 15 can thus be fixed on the internal face of the hollow body 13 as illustrated in FIGS. 2 and 3. Another possibility, illustrated in FIGS. 4 and 5, is that the heat exchange plate 10, more precisely its second face 10b, comprises a flange 11 on which is fixed the porous mass 15 so as to define the first chamber 13a.

The second chamber 13b also includes an inlet 14a for heat transfer fluid. This coolant fluid inlet 14a can more particularly be made at the level of the hollow body 13. The first chamber 13a comprises for its part a coolant fluid outlet 14b. This heat transfer fluid outlet 14b can be made at the level of the hollow body 13 as illustrated in the example of Figures 2 and 3 or at the level of the heat exchange plate 10 as illustrated in the example of Figures 4 and 5.

Within the two-phase heat transfer system with capillary pumping X, the coolant fluid inlet 14a is connected to a coolant fluid outlet of the condenser 2. The coolant fluid outlet 14b is for its part connected to a coolant fluid inlet of the condenser 2. The heat transfer fluid arriving in the second chamber 13b is at "high" pressure and in the liquid phase. This "high" pressure refrigerant fluid comes from the condenser 2 and passes from the second 13b to the first 13a chamber crossing the porous mass 15 by capillarity. This passage from one chamber to another allows the movement of the heat transfer fluid within the two-phase heat transfer system with capillary pumping X and allows a drop in pressure of said heat transfer fluid. The heat transfer fluid arriving in the first chamber 13a via the porous mass 15 then passes to "low" pressure. By high and low pressure, it is meant here that the heat transfer fluid in the second chamber 13b is at a higher pressure than the heat transfer fluid within the first chamber 13a.

The "low" pressure refrigerant fluid within the first chamber 13a in contact with the second face 10b of the heat exchange plate 10 changes to the gaseous state by taking heat energy from said heat exchange plate 10 which thus allows the element to be cooled to be cooled in contact with its first face 10a. The heat transfer fluid in the gaseous state then joins the condenser 2 at the level of which it returns to the liquid state by yielding heat energy to the external air flow 200.

In order to facilitate the exchanges between the heat transfer fluid and the heat exchange plate 10, the second face 10b of said heat exchange plate 10 may comprise fins 10c projecting into the first chamber 13a. These fins 10c can in particular be parallel to each other and oriented in the direction of circulation of the heat transfer fluid in order to limit pressure drops. The porous mass 15 can also be in contact with the tops of said fins 10c so that they serve as an attachment point for said porous mass 15. The fins 10c can thus form channels within the first chamber 13a in which the heat transfer fluid circulates. .

At least two of the elements among the heat exchange plate 10, the hollow body 13 and the porous mass 15 are made of aluminum or aluminum alloy and brazed to each other. The use of a material such as aluminum or aluminum alloy allows good thermal conduction while limiting the production costs of the evaporator 1 in particular compared to a material such as copper. This is all the more important because the evaporator 1 can have a large size depending on its destination within the motor vehicle. In addition, the use of aluminum for at least two of these elements makes it possible to braze them to each other in order to fix them and also to obtain a seal at the level of this fixing. This is particularly important at the level of the contact zones between the heat exchange plate 10 and the hollow body 13 in order to have a sealed cavity, but also between the porous mass 15 and the hollow body 13 and/or the plate of heat exchange 10 to form the first chamber 13a.

According to a first embodiment, the heat exchange plate 10 can be made of a polymer material loaded with thermal conductive elements. The hollow body 13 and the porous mass 15 are then made of aluminum or aluminum alloy and brazed to each other. This embodiment is possible only when the porous mass 15 is attached to the hollow body 13 as illustrated in Figures 2 and 3.

According to a second embodiment, the heat exchange plate 10, the hollow body 13 and the porous mass 15 are all three made of aluminum or aluminum alloy. This embodiment is possible regardless of the conformation of the evaporator 1 illustrated in Figures 2 to 5.

It is of course entirely possible to imagine other embodiments in which at least two of these elements are made of aluminum or aluminum alloy and made of contacts in order to be brazed together.

When the porous mass 15 is made of aluminum or aluminum alloy, the latter can in particular be obtained by sintering. The hollow body 13 and the heat exchange plate 10 can be obtained by stamping or machining when they are made of aluminum or aluminum alloy.

• d’une plaque d’échange thermique 10 comportant une première face 10a destinée à venir au contact d’un élément à refroidir et une deuxième face 10b, opposée à la première face 10a, destinée à être au contact d’un fluide réfrigérant à basse pression, avec
• un corps creux 13 destiné à recouvrir au moins partiellement la deuxième face de la plaque d’échange thermique 10 de sorte à former une cavité, et avec
• une masse poreuse 15 disposée dans la cavité et délimitant avec la plaque d’échange thermique 10 une première chambre 13a dans laquelle est destiné à circuler le fluide réfrigérant à basse pression et délimitant avec le corps creux 13 une deuxième chambre 13b dans laquelle est destiné à circuler le fluide réfrigérant à haute pression.

The present invention also relates to a method of manufacturing an evaporator 1 for a two-phase heat transfer system with capillary pumping X for a motor vehicle. FIG. 6 shows a flowchart of the different steps of said method. This method includes in particular a first assembly step 101:

• of a heat exchange plate 10 comprising a first face 10a intended to come into contact with an element to be cooled and a second face 10b, opposite to the first face 10a, intended to be in contact with a coolant at low pressure, with
• a hollow body 13 intended to at least partially cover the second face of the heat exchange plate 10 so as to form a cavity, and with
• a porous mass 15 disposed in the cavity and delimiting with the heat exchange plate 10 a first chamber 13a in which the low-pressure refrigerant fluid is intended to circulate and delimiting with the hollow body 13 a second chamber 13b in which is intended to circulate the refrigerant at high pressure.

Among the heat exchange plate 10, the hollow body 13 and the porous mass 15 at least two of these elements are made of aluminum or aluminum alloy.

A second step 102 of brazing elements made of aluminum or aluminum alloy and in contact with each other.

Thus, it is clear that the evaporator 1, due to the fact that at least two of these elements are made of aluminum or aluminum alloy, makes it possible to have an economical evaporator 1 for use within a motor vehicle but allows also a good seal.

Claims (7)

Evaporator (1) for a capillary pumped two-phase heat transfer system (X) for a motor vehicle, said evaporator (1) comprising:

• a heat exchange plate (10) comprising a first face intended to come into contact with an element to be cooled and a second face, opposite the first face, intended to be in contact with a low-pressure refrigerant fluid,
• an impermeable hollow body (13) at least partially covering the second face of the heat exchange plate (10) so as to form a cavity,
• a porous mass (15) disposed in the cavity and delimiting with the heat exchange plate (10) a first chamber (13a) in which the low-pressure refrigerant fluid is intended to circulate and delimiting with the hollow body (13) a second chamber (13b) in which the high-pressure refrigerant fluid is intended to circulate,

characterized in that at least two of the elements among the heat exchange plate (10), the hollow body (13) and the porous mass (15) are made of aluminum or aluminum alloy and brazed together 'other. Evaporator (1) according to claim 1, characterized in that the heat exchange plate (10) is made of a polymer material charged with heat-conducting elements, the hollow body (13) and the porous mass (15) being made of aluminum or aluminum alloy. Evaporator (1) according to claim 1, characterized in that the heat exchange plate (10), the hollow body (13) and the porous mass (15) are all three made of aluminum or aluminum alloy. Evaporator (1) according to any one of the preceding claims, characterized in that the porous mass (15) is made of aluminum or aluminum alloy by sintering. Evaporator (1) according to any one of the preceding claims, characterized in that the heat exchange plate (10) comprises fins (10c) projecting into the first chamber (13a). Two-phase heat transfer system with capillary pumping (X) for a motor vehicle comprising an evaporator (1) according to any one of the preceding claims. Method for manufacturing an evaporator (1) for a capillary pumped two-phase heat transfer system (X) for a motor vehicle, said method comprising the following steps:

• assembly :
  • of a heat exchange plate (10) and comprising a first face intended to come into contact with an element to be cooled and a second face, opposite the first face, intended to be in contact with a coolant at low pressure, with
  • a hollow body (13) intended to at least partially cover the second face of the heat exchange plate (10) so as to form a cavity, and with
  • a porous mass (15) disposed in the cavity and delimiting with the heat exchange plate (10) a first chamber (13a) in which the low-pressure refrigerant fluid is intended to circulate and delimiting with the hollow body (13) a second chamber (13b) in which the high-pressure refrigerant fluid is intended to circulate,
  • at least two of the elements among the heat exchange plate (10), the hollow body (13) and the porous mass (15) being made of aluminum or aluminum alloy,
• brazing of elements made of aluminum or aluminum alloy and in contact with each other.