Heat exchanger for a system for cooling electronic components

Abstract

A heat exchanger (1) comprising: - a cooling plate (9) configured to be in contact with a first part (P1) of the electronic components (5) and comprising a circulation channel for a first heat-transfer fluid, - a two-fluid exchanger (7) comprising a first fluid circuit (C1) in fluidic communication with the circulation channel of the cooling plate (9) to form a circulation loop (B) for the first heat-transfer fluid, and a second fluid circuit (C2) configured to receive a second heat-transfer fluid, wherein the heat exchanger (1) also comprises an additional cooling plate (11) arranged in contact with the two-fluid exchanger (7), and at least one heat-transfer element (13a, 13b, 13c) arranged between the additional cooling plate (11) and a second part (P2) of the electronic components (5).

Description

Description Title of the invention: Heat exchanger for an electronic component cooling system

[0001] The present invention relates to a heat exchanger for an electronic component cooling system.

[0002] Servers used for data processing (commonly referred to as information technology or "IT") typically include printed circuit boards (PCBs) on which electronic components such as integrated circuits are arranged, which may include central processing units (CPUs), random access memory (RAM), etc. All of these electronic components generate heat when in use. In order to keep the contents of servers at an optimal temperature to maximize server performance, it is essential to dissipate the heat generated and / or cool the components concerned.

[0003] Typically, the electronic components used in servers are air-cooled. A heat sink with fins or similar elements is typically used to dissipate heat into the surrounding air. Such a heat sink is then placed in contact with the surface of the electronic chip. This contact can be direct or via a thermal interface material between the two components. In addition to the heat sink, one or more fans can be used to circulate air to remove heat from the heat sink. Such a heat sink can be used in combination with cooling on the server installation side, such as air conditioning. However, this cooling method is not particularly efficient.It also has a high operating cost and requires very large spaces to manage the air used for cooling.

[0004] Immersion liquid cooling is an alternative to air cooling. In some cases, liquid cooling allows for more efficient heat transfer from electronic components, and therefore greater cooling power. Examples of such liquids are dielectric fluids or mineral oil.

[0005] Liquids with a high specific heat capacity are particularly advantageous.

[0006] However, immersion liquid cooling imposes strong technical constraints linked to the sealing of the boxes in which the printed circuits are immersed as well as the weight of these boxes which must be able to be supported by the buildings in which they are installed.

[0007] It is therefore necessary to find a solution that can effectively dissipate the heat from the electronic components of servers while limiting the technical constraints imposed by this cooling of the electronic components.

[0008] To this end, the invention relates to a heat exchanger for an electronic component cooling system comprising: - a cooling plate configured to be in contact with a first part of the electronic components and comprising a channel for circulating a first heat transfer fluid, - a dual-fluid exchanger comprising a first fluid circuit in fluid communication with the circulation channel of the cooling plate to form a circulation loop of the first heat transfer fluid and a second fluid circuit configured to receive a second heat transfer fluid, in which the heat exchanger also comprises an additional cooling plate arranged in contact with the dual-fluid exchanger and at least one heat transfer element arranged between the additional cooling plate and a second part of the electronic components.

[0009] Such an exchanger allows several separate elements or several separate circuits to be cooled from a single source, thus simplifying the circuit. In addition, the cooling power can be adapted according to each of the components to be cooled.

[0010] According to another aspect of the present invention, the additional cooling plate is a passive cooling plate. By passive is meant that no fluid circulates in the cooling plate.

[0011] According to another aspect of the present invention, the heat transfer element is one of the following list: - a metal spring such as a coil spring, - a flexible evaporator-condenser conduit or heat pipe comprising a two-phase fluid configured to evaporate at a first end in contact with an electronic component and to condense at a second end in contact with the additional cooling plate.

[0012] According to another aspect of the present invention, the heat transfer element is screwed onto the additional cooling plate.

[0013] According to another aspect of the present invention, the additional cooling plate is screwed onto the dual-fluid exchanger.

[0014] According to another aspect of the present invention, the additional cooling plate comprises a thermal foam arranged at the interface with the bi-fluid exchanger to maximize the heat exchanges with the bi-fluid exchanger. The thermal foam comprises for example a graphite sheet having a thickness of between 10 microns and a few millimeters.

[0015] According to another aspect of the present invention, the bi-fluid exchanger comprises an aluminum support, preferably fixed by brazing, and on which the additional cooling plate is fixed.

[0016] According to another aspect of the present invention, the bi-fluid exchanger is a plate exchanger.

[0017] According to another aspect of the present invention, the first heat transfer fluid circulating in the circulation loop is a two-phase fluid and the heat exchanger is configured to allow said two-phase fluid to evaporate during its passage in the circulation channel of the cooling plate and to condense during its passage in the first fluid circuit of the two-fluid exchanger.

[0018] According to another aspect of the present invention, the cooling plate is configured to control the flow rate of the two-phase fluid by capillary pumping.

[0019] According to another aspect of the present invention, the cooling plate comprises a porous structure forming a wick configured to control the flow rate of the two-phase fluid by capillary pumping.

[0020] According to another aspect of the present invention, the cooling plate comprises a floating valve configured to regulate the flow rate of liquid phase two-phase fluid entering the circulation channel of the cooling plate in dependence on the amount of liquid phase two-phase fluid present in the circulation channel of the cooling plate such that the greater the evaporation of the two-phase fluid in the cooling plate, the greater the flow rate of liquid phase two-phase fluid entering the cooling plate.

[0021] The present invention also relates to a system comprising a heat exchanger as described above and electronic components in which the first part of the electronic devices is associated with a first thermal power and the second part of the electronic devices is associated with a second thermal power, lower than the first thermal power.

[0022] According to another aspect of the present invention, the electronic devices are arranged on a printed circuit board, the first portion of the electronic devices comprising one or more processors and the second portion of the electronic devices comprising other components of the printed circuit board.

[0023] According to another aspect of the present invention, the system is a data server.

[0024] The present invention also relates to a method of using a heat exchanger as described above comprising a two-phase fluid circulation loop connecting a hot source and a cold source and in which the two-phase fluid is configured to evaporate as it passes through the hot source and to condense as it passes through the cold source.

[0025] According to another aspect of the present invention, the hot source comprises one or more electronic components and the cold source comprises a bi-fluid exchanger.

[0026] Other advantages and characteristics will appear on reading the description of several illustrative but non-limiting examples of the present invention, as well as the appended drawings in which:

[0027] [Fig 1] Figure 1 is a schematic representation of a heat exchanger according to a first embodiment of the present invention;

[0028] [Fig.2] Figure 1 is a schematic representation of a heat exchanger according to a second embodiment of the present invention;

[0029] [Fig.3] Figure 3 is a schematic representation of a two-phase fluid circulation loop between two thermal devices;

[0030] [Fig.4] Figure 4 is a schematic representation of a cooling plate including a floating valve for regulating the flow of two-phase fluid.

[0031] In these figures, identical elements have the same reference numbers.

[0032] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments.

[0033] In this description, certain elements or parameters may be indexed, such as first element or second element, as well as first parameter and second parameter, or 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 such names can easily be interchanged without departing from the scope of this description. This indexing also does not imply an order in time, for example, to assess this or that criterion.

[0034] The present invention relates to a heat exchanger for a cooling system for electronic components, in particular for electronic components of a data server.

[0035] Figure 1 represents a schematic view of such a heat exchanger 1 according to a first embodiment.

[0036] The electronic components 5 and the heat exchanger 1 can be arranged in a housing 3.

[0037] The different electronic components 5 can be associated with different thermal powers, that is to say that they can generate more or less heat and therefore require more or less significant heat dissipation to limit their temperature.

[0038] The electronic components 5 are for example subdivided into a first part PI associated with a first thermal power, a second part P2 associated with a second thermal power lower than the first thermal power and a third part P3 associated with a third thermal power lower than the second thermal power.

[0039] The first part PI of the electronic components 5 comprises for example a processor 5a (“Central Processing Unit (CPU)” in English) or several processors 5a, the second part P2 of the electronic components 5 comprises for example random access memory (RAM) and / or a power supply and the third part comprises for example transistors and other simple electronic components.

[0040] All of the electronic components 5 can be arranged on a single printed circuit board 6 (“Printed Circuit Board (PCB)” in English).

[0041] The heat exchanger 1 comprises a cooling plate 9 configured to be in contact with the first part PI of the electronic components 5, here the processor 5a. The cooling plate 9 comprises a circulation channel configured to receive a first heat transfer fluid.

[0042] The heat exchanger 1 also includes a two-fluid exchanger 7.

[0043] The bi-fluid exchanger 7 comprises a first fluid circuit Cl in fluid communication with the circulation channel of the cooling plate 9 to form a circulation loop B of the first heat transfer fluid.

[0044] The first heat transfer fluid is for example a two-phase fluid configured to evaporate during its passage through the cooling circulation channel 9 and to condense during its passage through the first fluid circuit Cl of the two-fluid exchanger.

[0045] The dual-fluid exchanger 7 also comprises a second fluid circuit C2 configured to receive a second heat transfer fluid.

[0046] The inlet of the second fluid circuit C2 is for example connected to a conduit 12 for supplying the second heat transfer fluid. The supply conduit 12 may be a conduit supplying different cabinets (“racks” in English) of the data server and which may be connected to a central heat exchanger (not shown) of the data server.

[0047] The outlet of the second fluid circuit C2 is for example connected to a return conduit 18 of the second heat transfer fluid. The return conduit 18 of the heat transfer fluid is for example connected to the central heat exchanger of the server of data. The second heat transfer fluid is, for example, water or glycol water.

[0048] The two-phase fluid of the circulation loop B is chosen so that during its circulation in the circulation loop B, the two-phase fluid evaporates during its passage through the cooling plate 9 which constitutes with the first part PI of the electronic components 5 a hot source and to condense during its passage through the two-fluid exchanger 17 which constitutes a cold source. This evaporation and this condensation make it possible to achieve a circulation of the two-phase fluid in the circulation loop B, the flow rate of two-phase fluid being all the greater as the temperature of the cooling plate 9 is high.

[0049] According to an alternative embodiment shown in Figure 3, the circulation loop B comprises a porous structure 19 forming a wick at the cooling plate 9. The porous structure 19 is arranged in the circulation channel of the two-phase fluid of the cooling plate 9. The porous structure 19 is configured to control the flow rate of the two-phase fluid by capillary pumping. Indeed, the gas phase of the two-phase fluid evaporated in the cooling plate 9 returns to the two-fluid exchanger 17 via a first section SE1 of the circulation loop B. This evaporation causes the two-phase fluid to be sucked into the liquid phase from the two-fluid exchanger 17 in the second section SE2 of the circulation loop B, the two-phase fluid condensing as it passes through the two-fluid exchanger 17.

[0050] According to an alternative embodiment shown in Figure 4, the circulation loop B comprises a floating valve 21 at the cooling plate 9. The floating valve 21 is arranged in the circulation channel of the two-phase fluid of the cooling plate 9. The floating valve 21 is configured to regulate the flow rate of the two-phase fluid in the liquid phase entering the cooling plate 9 as a function of the quantity of two-phase fluid in the liquid phase present in the cooling plate 9 so that the greater the evaporation of the two-phase fluid in the cooling plate 9, the more the level of the floating valve 21 drops and the greater the flow rate of two-phase fluid in the liquid phase coming from the two-fluid exchanger 17 and entering the cooling plate 9.The two-phase fluid in the gas phase evaporated in the cooling plate 9 returns to the two-fluid exchanger 17 via the circulation loop B. The two-phase fluid is then condensed in the two-fluid exchanger 17 to return to the cooling plate 9 in the liquid state.

[0051] Thus, the circulation of the two-phase fluid in the circulation loop B can be done without requiring a pump and without any energy input other than the heat produced by the processor 5a in contact with the cooling plate 9.

[0052] Heat exchanger 1 also includes a cooling plate additional 11 arranged in contact with the bi-fluid exchanger 7 and in particular near the second fluid circuit C2 in which the second heat transfer fluid circulates.

[0053] The additional cooling plate 11 may be passive, i.e. devoid of a fluid circulation channel. The additional cooling plate 11 in particular allows heat exchange by conduction. The additional cooling plate 11 may be a metal plate, in particular made of steel or aluminum.

[0054] The additional cooling plate 11 may comprise a thermal foam (“thermal pad” in English) arranged at the interface with the dual-fluid exchanger 7 to maximize the heat exchanges with the dual-fluid exchanger 7. The thermal foam comprises, for example, a graphite sheet with a thickness of between 100 microns and a few millimeters. The thermal foam may also comprise other elements such as silicone.

[0055] The heat exchanger 1 also comprises at least one heat transfer element arranged between the additional cooling plate 11 and the second part P2 of the electronic components 5. The heat transfer element is in contact on the one hand with the additional cooling plate 11 at a first end and on the other hand with at least one of the electronic components 5 of the second part P2 of the electronic components 5.

[0056] The heat transfer element is for example a metal spring 13a such as a helical spring.

[0057] The heat transfer element may also be a flexible evaporator-condenser conduit 13b, also called a heat pipe, containing a two-phase fluid configured to evaporate at a first end of the heat transfer element in contact with the electronic component(s) 5 of the second part P2 and to condense at the second end of the heat transfer element in contact with the additional cooling plate 11.

[0058] The heat transfer element can also be made of a thermally conductive material such as a plastic material loaded with metal particles or any other material having a high thermal conductivity (for example >1W.ml.Kl). The heat transfer element is for example screwed onto the additional cooling plate 11 like the heat transfer element 13c of Figure 2. The thermal element can also be glued.

[0059] A fan 14 may also be arranged in the housing 3 to promote cooling of the electronic components by convection, in particular for the electronic components 5 of the third part P3 which are not in contact with a heat transfer element. The heat produced by the electronic components of the third part P3 is then transferred to the bi-fluid exchanger 7 by convection via the air present in the housing 3. In the absence of the housing 3, the heat of the components of the third part is dissipated into the surrounding air.

[0060] The present invention also relates to a system comprising a heat exchanger 1 as described previously as well as electronic components 5. The system is for example a data server comprising a plurality of heat exchangers 1 as described previously connected to a central heat exchanger and a general circuit allowing the circulation of the heat transfer fluid to the different heat exchangers via supply 12 and return 18 conduits.

[0061] The present invention also relates to a method of using a heat exchanger 1 as described previously comprising a circulation loop of a two-phase fluid, for example the circulation loop B, connecting a hot source, for example the cooling plate 9 in contact with the processor 5a, and a cold source, for example the two-fluid exchanger 7, and in which the two-phase fluid is configured to evaporate during its passage in the hot source, here the cooling plate 9, and to condense during its passage in the cold source, here the two-fluid exchanger 7. The flow rate of the two-phase fluid is for example controlled by a floating valve 21 or a porous structure 19 forming a wick configured to carry out capillary pumping.

[0062] Thus, the present invention makes it possible, through the use of a heat exchanger 1 comprising at least two separate cooling devices for different electronic components 5 having different thermal powers from a single heat transfer fluid, to cool the different electronic components 5 simply and effectively while limiting the weight of the device for cooling the electronic components 5.

Claims

Claims

1. Heat exchanger (1) for an electronic component cooling system (5) comprising: - a cooling plate (9) configured to be in contact with a first part (PI) of the electronic components (5) and comprising a channel for circulating a first heat transfer fluid, - a dual-fluid exchanger (7) comprising a first fluid circuit (Cl) in fluid communication with the circulation channel of the cooling plate (9) to form a circulation loop (B) of the first heat transfer fluid and a second fluid circuit (C2) configured to receive a second heat transfer fluid, characterized in that the heat exchanger (1) also comprises an additional cooling plate (11) arranged in contact with the dual-fluid exchanger (7) and at least one heat transfer element (13a, 13b, 13c) arranged between the additional cooling plate (11) and a second part (P2) of the electronic components (5), and in that the additional cooling plate (11) is a passive cooling plate.

2. A heat exchanger (1) according to claim 1 wherein the heat transfer element (13a, 13b, 13c) is one of the following: - a metal spring (13a) such as a helical spring, - a flexible evaporator-condenser conduit (13b) comprising a two-phase fluid configured to evaporate at a first end in contact with an electronic component (5) and to condense at a second end in contact with the additional cooling plate (11).

3. Heat exchanger (1) according to the preceding claim in which the heat transfer element (13c) is screwed onto the additional cooling plate (11).

4. Heat exchanger (1) according to one of the preceding claims in which the two-fluid exchanger (7) comprises an aluminum support (7a), preferably fixed by brazing, and on which the additional cooling plate (11) is fixed.

5. Heat exchanger (1) according to one of the preceding claims in which the bi-fluid exchanger (7) is a plate exchanger.

6. Heat exchanger (1) according to one of the preceding claims in which the first heat transfer fluid circulating in the circulation loop (B) is a two-phase fluid, the heat exchanger (1) being configured to allow said two-phase fluid to evaporate during its passage through the circulation channel of the cooling plate (9) and to condense during its passage through the first fluid circuit (Cl) of the two-fluid exchanger (7).

7. Heat exchanger (1) according to the preceding claim in which the cooling plate (9) is configured to control the flow rate of the two-phase fluid by capillary pumping.

8. Heat exchanger (1) according to the preceding claim wherein the cooling plate (9) comprises a floating valve (21) configured to regulate the flow rate of the two-phase fluid in liquid phase entering the circulation channel of the cooling plate (9) as a function of the quantity of two-phase fluid in liquid phase present in the circulation channel of the cooling plate (9) such that the greater the evaporation of the two-phase fluid in the cooling plate (9), the greater the flow rate of two-phase fluid in liquid phase entering the cooling plate (9).

9. Method of using a heat exchanger (1) according to one of the preceding claims comprising a circulation loop of a two-phase fluid connecting a hot source and a cold source and in which the two-phase fluid is configured to evaporate during its passage through the hot source and to condense during its passage through the cold source.

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