Technical Field

The present patent application relates to a method, a heat sink and a cooling system .

Prior Art

In particular, the present invention relates to a method, a heat sink and a cooling system configured to cool electronic components , such as for example Central Processing Units , generally known as CPUs .

In order to cool electronic components , such as the CPUs , closed loop cooling systems by means of trans fer liquid are known, said trans fer liquid removing heat via temperature drop or via phase change of the trans fer liquid . A closed loop cooling system via phase change comprises in a known manner a compression unit , an evaporator, a condensation unit , a lamination device .

The closed loop phase change cooling systems of known type have various drawbacks . For example , the trans fer liquid in the current systems must have a low evaporation temperature so that it is compatible with the operation temperature of the electronic apparatus and is a polluting chemical product which must not enter into contact with the outdoor environment and which thus forces the circuit to be closed, namely the evaporated liquid to then be condensed and recirculated . Also for this reason, a closed loop cooling system comprises a high number of components , which make the entire cooling system bulky and expensive both as to manufacturing and to management .

The closed loop cooling systems of known type have the drawback of shi fting the heat from the obj ect being cooled to the condenser , but the heat radiated by the condenser must then, in turn, be dissipated by means of further means , which typically entail further investments and electric energy consumption and, consequently, high management costs .

Description of the Invention

The obj ect of the present invention is to provide a method and a heat sink for phase change electronic components which exploits as trans fer liquid a non-polluting liquid, for example water, although ensuring operation temperatures compatible with electronic apparatuses .

The obj ect of the present invention is to provide a heat sink which allows manufacturing a cooling system suitable to cool electronic components .

The obj ect of the present invention is to provide a method, a heat s ink and a cooling system which are simple and cost-ef fective as to manufacturing and maintenance .

The obj ect of the present invention is to provide both a heat sink and a cooling system having reduced energy consumption and, consequently, reduced management costs .

According to the present invention, a method for dissipating heat is provided according to what claimed in the appended claims .

According to the present invention, a heat sink is provided according to what claimed in the appended claims .

According to the present invention, a cooling system is provided according to what claimed in the appended claims .

Brief Description of the Figures

The invention wi ll now be described with reference to the accompanying drawings , which illustrate non-limiting example embodiments thereof , wherein :

- Figure 1 schematically illustrates a cooling system according to the present invention;

Figure 2 schematically illustrates a heat sink according to the present invention;

- Figure 3 is a perspective and schematic view of a variation of a detail of the heat sink according to the present invention; and,

- Figure 4 is a schematic view of a variant of a cooling system according to the present invention .

Preferred Embodiment for Manufacturing the Invention

In Figure 1 , reference numeral 1 indicates a cooling system according to the present invention and configured, in particular, to be able to cool the electronic components C, for example electronic cards such as CPUs . According to a variation not illustrated, the cooling system 1 can be installed on any other heat source .

Advantageously, the cooling system 1 is an open loop system . Open loop means a circuit in which the trans fer liquid W is not recirculated .

In particular, the cooling system 1 comprises a dissipation unit E which comprises , in turn, a heat sink 2 and a cover 3 .

The heat sink 2 is installed, in use , in contact with a heat source H, in particular of the electronic components C . According to the illustrated example , the electronic components C are an electronic card .

The cover 3 has a box-shaped body 31 with an inner cavity 311 . The cover 3 can have any shape and dimension . The heat sink 2 is at least partially inserted inside the cover 3 , as it will be better illustrated in the following .

In particular, the cover 3 has : an inlet I I , which is connected to a delivery section Pl of trans fer liquid W; an inlet 12 which is connected to the environment outside of the cover 3 , in particular for allowing the entry of gas G; an outlet U for the exit of steam S . Advantageously, the gas G is air coming from the environment outside of the cover 3 . In case the line 4 and the line 5 are at least partially made by means of a single duct (not illustrated) it is possible that the inlet I I and the inlet 12 coincide .

The cooling system 1 further comprises a line 4 for the trans fer liquid W and a line 5 for the circulation of gas G . Advantageously, but not necessarily, the line 4 and the line 5 can be at least partially j oined, namely they can at least partially be made by means of a single duct in which both the trans fer liquid W and the gas G flow .

The cooling system 1 further comprises a delivery section Pl of trans fer liquid W and a gas circulation device G . Preferably, the gas circulation device G is a suction device A which is connected to the outlet U and is configured to create a vacuum inside the cavity 311 of the cover 3 .

According to the illustrated example , the cooling system 1 is housed inside an environment R having a controlled atmosphere , delimited by one or more walls D . According to the illustrated example , the environment R is the inside of a data center D . Advantageously, the delivery section Pl and the suction device A are arranged outside of the environment R . Just as the gas G is drawn not only outside of the data center D . Therefore , the cooling system 1 comprises :

- a duct 6 which fluidically connects the delivery section Pl to the inlet I I ;

- a duct 7 which fluidically connects the environment outside of the cover 3 , in particular outside of the data center D, to the inlet 12 ;

- a duct 8 which connects the outlet U to the suction device A.

The ducts 6 , 7 , 8 put the inside of the cover 3 into fluidic communication with the outside of the data center D .

Advantageously, the heat sink 2 is configured, as it will be better illustrated in the following, to obtain the evaporation of the trans fer liquid W inside the cover 3 .

The cooling system 1 is configured to supply trans fer liquid W to the heat sink 2 and to ventilate the inner cavity 311 of the cover 3 so as to prevent stagnations of steam S inside the cover 3 .

According to what illustrated in Figure 2 , the heat sink 2 comprises , in turn, a base 9 thermally coupled to the heat source H . According to the illustrated example , the base 9 is fixed in contact with the electronic card C . According to the variations not illustrated, the heat source can be of any shape and dimension . By way of example and in a known manner, the base 9 can be screwed and/or welded and/or glued to a respective electronic card C . In other words , advantageously, the base 9 is directly exposed to the heat source H without the interposition of intermediate elements (namely without the interposition of liquids or gases ) .

According to what illustrated in Figures 2 and 3 , the base 9 has a box-shaped body delimited by a bottom wall 10 and a side wall 11 . The bottom wall 10 is configured ( in a known manner and not illustrated, for example by means of slots 13 or fitting elements ) to fix to the heat source H, whereas the side wall 11 protrudes from the bottom wall 10 and forms a closed perimeter b . The bottom wall 10 and the side wall 11 laterally delimit a housing 12 of the base 9 . The shape and the dimensions of the base 9 illustrated in the figures are by mere example , according to the variations not illustrated, the bottom wall 10 and the side wall 11 can have di f ferent shapes and dimensions or can be absent . The heat sink 2 further comprises a body 14 at least partially inserted inside the housing 12 , as it will be better illustrated in the following . The body 14 protrudes outside of the housing 12 along a transverse axis XI .

The body 14 is made of a material M, which comprises at least one part made of hydrophilic material . At least one part of the inner surfaces of the pores is made of hydrophilic material . Advantageously, the material M is hydrophilic . Alternatively, the material M is made of non- hydrophilic material but the surfaces of the inner walls of the pores are at least partially coated with hydrophilic material . Preferably, the inner walls of the pores are made of hydrophilic material .

In the classic definition, the term hydrophilic means a substance that absorbs or adsorbs water . Generally, the characteristic of hydrophilicity of a material can refer to : the hygroscopicity, the solubility or the wettability . In the following, hydrophilicity means the wettability and is determined depending on the contact angle 0.

The material M at least partially has a porosity greater than 40% .

Porosity means the ratio between the volume percentage occupied by the pores and the total volume . The material M has a percentage of interconnected pores greater than 70% .

It is noted that the term "pores" means hollow structures having various dimensions which can include structures also commonly known as "capillary" .

Advantageously, the material M has a contact angle 0 less than 20 ° . It is noted that the expression "contact angle 0" means the angle formed by the tangent to the liquid- fluid interface , and by the tangent to the solid surface , at the contact line between the solid, liquid and gaseous phases . Various methods are known for detecting the contact angle 0, for example the Drop shape analysis (DSA) method, the Wilhelmy plate method, the Powder contact angle measurement using the Washburn method, the Top-view distance method.

Numerous hydrophilic materials both in nature and artificially produced are known. The clays extracted in nature are hydrophilic materials. Examples of artificial hydrophilic materials comprise: Nafion®; Biogel® by Polymeric Sciences, used in contact lenses; HydroThame® and HydroMed® by AdvanSource biomaterials, which can be extruded or injection-molded; and also some metal-organic materials such as, for example, those known as HMOFs .

Many of the aforementioned hydrophilic materials maintain their characteristic of hydrophilicity when both dry and wet. Some hydrophilic materials, such as clays, have a plastically deformable nature but they can be solidified, for example by baking.

Advantageously, the material M has a permeability coefficient k of more than 10-7 m/sec. The permeability coefficient k is calculated according to the reference regulation UNI CEN ISO/TS 17892-11.

Advantageously, the ratio between the weight of a sample of the material M saturated by immersion in a liquid and the weight of the same sample saturated by capillary ascent of said liquid is at least 75%.

Advantageously, in a given volume of the material M, the overall volume of pores having a diameter with dimensions ranging from 0.5 nm to approximately 0.1 pm is at least 10%.

Optionally, in a given volume of the material M, the overall volume of pores having a diameter ranging between 0.3 nm and 140 pm is greater than 2.5% of the total volume of the pores. Advantageously, but not necessarily, the material M is solid . In other words , the dimensions and the relative distribution of the pores with regard to wet material M (with deminerali zed water ) are equal to the dimensions and to the relative distribution of the pores with regard to dry material .

Advantageously, but not necessarily, the material M is rigid and can be used for manufacturing solid bodies stackable on top of each other .

Advantageously, the material M is of the type described in patent EP3347325 Bl , whose principles are to be understood integrally comprised herein . In particular, advantageously, the material M at least partially has an overall porosity ranging between 50% and 80% . Advantageously, the material M has a porosity comprised between 60 and 70% . The material M has a percentage of interconnected pores greater than 80% . Advantageously, the material M has a percentage of interconnected pores greater than 90% , and preferably than 95% .

Advantageously, the material M has a contact angle 0 less than 10 ° . Preferably, the material M has a contact angle 0 less than 5 ° . Advantageously, the contact angle 0 of the partially wet material M is substantially equal to the contact angle 0 of the dry material M .

Advantageously, the material M has a permeability coef ficient k of more than 10~ ⁶ m/ sec . Preferably, the permeability of the material M is more than 10~ ⁶ m/ sec and less than 10~ ⁴ m/ sec . Advantageously, the permeability of the material M is approximately 10~ ⁵ m/ sec .

Advantageously, the ratio between the weight of a sample of the material M saturated by immersion in a liquid and the weight of the same sample saturated by capillary ascent of said liquid is at least 90% , in particular 93% .

Advantageously, in a given volume of the material M, the overall volume of pores having a diameter with dimensions ranging from 0 . 3 nm to approximately 0 . 1 pm is at least 15% . Advantageously, in a given volume of the material M, the overall volume o f pores having a diameter with dimensions ranging from approximately 0 . 1 pm to approximately 0 . 3 nm ranges between 15% and 40% of the total volume of the pores .

Optionally, in a given volume of the material M the overall volume o f pores having a diameter ranging between 0 . 3 nm and 140 pm is greater than 5% of the total volume of the pores .

Advantageously, the material M is solid . In other words , the dimensions and the relative distribution of the pores with regard to wet material M (with deminerali zed water ) are equal to the dimensions and to the relative distribution of the pores with regard to dry material .

Advantageously, the material M is rigid and can be used for manufacturing solid bodies stackable on top of each other .

Advantageously, the heat sink 2 comprises a thermal conduction unit 15 which is in contact both with the base 9 and with the body 14 . The conduction unit 15 is made of material having a high thermal conductivity, such as for example a metal material . Preferably, the conduction unit 15 is made of a material chosen within the group of metals comprising : copper, aluminum, copper alloys , aluminum alloys .

Advantageously, the conduction unit 15 is in thermal contact both with the base 9 and with the body 14 . The conduction unit 15 and the base 9 can be a single block .

In particular, the body 14 has seats 16 configured to at least partially house the conduction unit 15 . According to the example illustrated in Figures 2 and 3 the seats 16 are through seats and pass through the body 14 along the axis XI . According to the illustrated example , each seat 16 is cylindrical . Without losing generality, the number, the shape and the distribution of the seats 16 can be di f ferent from what illustrated .

According to the example illustrated in Figure 2 , the conduction unit 15 comprises one or more branches 18 , each of which is at least partially embedded inside the body 14 . Preferably, each branch 18 is manufactured by means of melted metal casting ins ide respective seats 16 of the body 14 . In this manner, advantageously, the outer profile of each branch 18 is at least partially infiltrated and solidi fied in fissures and/or pores of the body 14 . In thi s manner, advantageously, the conductivity of the heat H from each branch 18 to the body 14 is optimi zed .

Alternatively, according to what illustrated in Figure 2 , the branches 18 are metal cylinders that protrude from the bottom wall 9 of the base 10 and are inserted in respective seats 16 of the body 14 .

The cooling system 1 has a supply area 19 of the trans fer fluid W to the body 14 . According to the i llustrated example , the supply area 19 is a tank, namely, a stagnation area of the trans fer fluid W, corresponding to the housing 12 delimited by the bottom wall 10 and by the side wall 11 of the base 10 . According to a variation not illustrated, the supply system directly inputs the trans fer fluid W in the body 14 . For example , the trans fer fluid W could be sprinkled on the body 14 , or ducts or intermediate bodies , such as sponges or the like , can inj ect the trans fer fluid W in predefined positions of the body 14 . Two or more or the following elements can be a single block : base 9 , bottom wall 10 , conduction unit 15 and/or branches 18 thereof and the housing 12 for the trans fer liquid W .

Advantageously, the cover 3 is configured to apply to the base 9 for forming a closed body that communicates with the outside through the inlets I I and 12 and the outlet U .

Advantageously, the environment inside the cover 3 is vacuumed, namely is subj ected to a suction generated by the suction fan A. In this manner , advantageously, the air of the environment R in which the cooling system 1 is arranged is suctioned inside the cover 3 , preventing the outflow of steam .

Alternatively and/or additionally to the suction fan A, the gas G can be input inside the cover 3 also by means of fans on the inlet duct of the gas G and the pressure inside the cover 3 could be greater instead of less than the external pressure .

In a variation (not illustrated) , the line 4 for the trans fer liquid W and the line 5 for the circulation of the gas G are j oined in a single line , which supplies both the trans fer liquid W and the gas G .

In another variation, the cooling system 1 further comprises an additional outlet line (not illustrated) with respect to the duct 8 . The additional outlet line is advantageously necessary for manufacturing an "overflow" mechanism for allowing the discharge of the trans fer liquid W when it is above a predetermined level .

Without losing generality and according to further variations (not illustrated) , each one of said lines 4 , 5 ( or additional outlet line ) and duct 8 can be manufactured by means of multiple lines , applied in di f ferent points of the cover 3 .

Advantageously, the cooling system 1 comprises a unidirectional valve element 20 arranged along the duct 7 . The valve element 20 is configured to allow the entry of gas G from the outside , for example air of the outdoor environment , and simultaneously prevent the outflow of gas and/or liquids . Advantageously, but not necessarily, the valve element 20 is configured to adj ust the flow rate of the gas G and the pressure of the gas G inside the cover 3 .

In Figure 4 , reference numeral 101 indicates a variation of the cooling system according to the present invention . In particular, the cooling system 101 comprises a plurality of heat sinks 2 , each of which is fixed to one or more electronic circuits inside a closed area R, such as for example a data center . The heat sinks 2 are connected to each other to a source of trans fer fluid W and to a suction fan A, which can also be arranged outside of the closed area R .

In use , the heat H generated by the heat source C is transmitted in a mainly conductive manner to the body 14 through the conduction unit 15 .

Advantageously, the conduction unit 15 comprises branches 18 embedded inside the body 14 , this allows the heat H to be distributed also in depth and in a distributed manner inside the body 14 . Therefore , advantageously, according to the present invention the heat H is not transmitted to the body 14 only through a flat wall , as it occurs for most of the known solutions .

Advantageously, the branches 18 are made by casting, so as to make a structure embedded inside the material M of the body 14 . This allows obtaining extended branches with an increase in surface seamlessly in contact favoring the di f fusion of the heat H by conduction and, therefore , increasing the ef ficiency of the body 14 .

For the cooling of the heat H, the trans fer liquid W is supplied inside the supply area 19 so that the body 14 is at least partially wet . The heat H, by passing through the body 14 , activates the phase change of the trans fer liquid W which generates steam S , thus absorbing the heat .

Advantageously, inside the heat sink 2 the trans fer liquid W is stagnant . In other words , there is no outlet for the trans fer liquid W since the cooling system 1 or 101 works open looped, therefore the trans fer liquid W once supplied to the body 14 is trans formed into steam S .

Advantageously, the trans fer liquid W can be filtered before being sent to the supply area 19 , so as to prevent the obstruction of the smaller pores of the material M of the body 14 .

The steam S is suctioned outside of the cover 3 by the suction fan A.

Advantageously, the body 14 is wet by the trans fer liquid W .

Advantageously, the trans fer liquid W is water . In this manner, the steam S exiting the suction fan A can be directly dispersed in the environment outside of the area R to be cooled .

In particular, the material M of the body 14 cools in contact with the trans fer liquid W tendentially up to the "humid bulb" temperature of the surrounding air .

Advantageously, the body 14 is inserted inside the leakproof cover 3 which, suitably connected to an inlet of gas G and an outlet U of steam S , allows obtaining a controlled ventilation environment .

Advantageously, the cover 3 is aerated in a controlled manner and such to optimi ze the cooling ability of the body 14 . In particular, when the body 14 is wet by the trans fer liquid W and is free to expel steam S it tends to autonomously reach the Wet Bulb Temperature , which is equal to or less than the Dry Bulb Temperature . The Wet Bulb Temperature depends on : the Dry Bulb Temperature ; the percentage of Relative Humidity; the air pressure . Therefore , by means of the suction fan A it is possible to adj ust the level of aeration inside the cover 3 so that the body 14 is always in the condition of expelling steam S ( in other words , it is necessary to prevent the presence inside the cover 3 of a % of Relative Humidity greater than given threshold values ) .

Advantageously, the suction fan A allows obtaining a continuous circulation of gas G and steam S so as to prevent the creation of possible condensates inside the cover 3 or the cooling system 1 or 101 .

Advantageously, the vacuum created inside the cover 3 allows improving the cooling system 1 or 101 favoring inside the material M both the absorption by capillarity and the evaporation . Furthermore , advantageously, the Wet Bulb Temperature is less ( thus increasing the cooling ability) i f the pressure inside the cover 3 is less .

Advantageously, the air G supplied inside the cover 3 is filtered and/or heated before being input inside the cover 3 so as to prevent the presence of solid particles that could obstruct the pores of the body 14 and to prevent inputting inside the cover 3 air with a high percentage of Relative Humidity .

Advantageously, at least the outer surface of the cover 3 has a low thermal conductivity, in this manner the heat H transmitted to the body 14 is not re-transmitted to the area R through the body of the cover 3 .

A further advantage is that the material M absorbs a quantity of water substantially equal to that which evaporates , unlike the traditional air cooling systems by means of liquid evaporation, namely "adiabatic" , or water cooling in cooling systems by means of trans fer liquid W without phase change , where the trans fer liquid W is in turn cooled by means of water evaporation, in which only a part of the water input in the evaporation system actually evaporates and the remaining is recovered or expelled . Therefore , the quantity of trans fer liquid W supplied to the supply area 19 is reduced, consequently reducing the necessary power of the delivery section Pl and the necessary overall quantity of trans fer liquid W . Advantageously, this entails a reduction in the installation, management and maintenance costs of the cooling system 1 or 101 according to the present invention . This also allows eliminating the problems of legionella typical of the current aforementioned adiabatic systems .

Advantageously, the cooling system 1 or 101 according to the present invention is an open loop phase change cooling system with the direct evaporation of the trans fer liquid W, in particular water, whose steam i s directly input into the outdoor environment . Therefore , the cooling system 1 or 101 according to the present invention is devoid of a numerous and complex series of components generally used for the closed loop phase change cooling systems .

Advantageously, the heat sink 2 according to the present invention is simple and cost-ef fective to manufacture . Advantageously, the heat sink 2 can be manufactured with natural non-pollutant and recyclable products .

The cooling system 1 or 101 according to the present invention is open looped, this allows reducing the mechanical components which are limited to a line 4 for the trans fer liquid E and a line 5 for the circulation of the gas G and of the steam with a suction fan A.

The heat sink 2 could be directly exposed to the heat H source C or by means of the interposition of intermediate trans fer fluids and/or thermal conductive pastes or other equivalent elements for optimi zing the thermal coupling .

With respect to the cooling systems by means of temperature drop of the trans fer liquid and thus not phase change , advantageously according to the above-described solution, the flow rate of transfer liquid W is reduced, for example in the order of 150 ml/hour for dissipating the heat H of a processor with the power of approximately 120 Watt . Such flow rate of liquid is less ( approximately 50 times less ) than the flow rate necessary for cooling said processor with a closed loop cooling system having water as trans fer liquid . This allows us ing a pump for the delivery section Pl with dimensions , powers which are definitely less than the pumps of the known water closed loop cooling systems .

Advantageously, the cooling system 1 or 101 according to the present invention is devoid of condensers .

Advantageously, temperature sensors can be placed in various points inside the base 9 , bottom wall 10 , conduction unit 15 and/or branches 18 thereof , housing 12 for the trans fer liquid, for example for calculating the quantity of heat H dissipated so as to be able to obtain energy ef f iciency/Co2 emission reduction certi ficates .

Further temperature and/or pressure and/or humidity sensors can be applied inside and outside the cover 3 and the inlet and/or outlet lines for optimi zing the operation of the heat sink 2 for example acting on the flow rate of the suction fan A, delivery section Pl and inlet valve 20 of the gas G .