Heat exchange process using low gwp fluids

Abstract

The invention relates to a method for heat exchange with an object, said method comprising the use of a heat transfer fluid wherein said heat transfer fluid comprises one or more fluorinated nitro compounds according to general formula (I) wherein:-at least two of R1, R2, R3 and R4 are independently selected from H, Cl and F, with the proviso that at least one is H or Cl. -those of R1, R2, R3 and R4 that are not H, F or Cl are selected from the group consisting of partially halogenated alkyl groups, fully halogenated alkyl groups wherein the alkyl chain is C1-C4 and the halogen is selected from Cl and F. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a method for exchanging heat with an object using a composition comprising a selected fluorinated nitro compound having a low GWP as a heat transfer fluid. Background Art

[0002] The use of heat transfer fluids in heating and cooling systems is known in the art; typically, heat transfer fluids include water, aqueous brines, alcohols, glycols, ammonia, hydrocarbons, ethers, and various halogen derivatives of these materials, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HFCs), (per)fluorinated polyethers (PFPEs), and the like.

[0003] Heat transfer fluids are used to transfer heat from one object to another, typically from a heat source to a heat sink, in order to cool the heat source, heat the heat sink, or remove unwanted heat generated by the heat source. The heat transfer fluid provides a thermal path between the heat source and the heat sink; it can be circulated through a loop system or other flow system to improve heat flow or it can be in direct contact with the heat source and heat sink. Simpler systems use only a gas stream as the heat transfer fluid, more complex systems use specially designed gases or liquids that are heated or cooled in one part of the system and then delivered in thermal contact with the target location.

[0004] The preferred method of using heat transfer fluid of the present invention is such a method, in which fluid is used to transfer heat with electric or electronic device, and particularly for removing the unnecessary heat produced by the operation of electric or electronic device. This application has very high industrial importance, because electric and electronic device typically has a relatively narrow temperature range, and their performance is optimal in this temperature range. These applications include constant temperature bath and cooling circuit, which will be specifically described in detail later. It should be noted that fluid of the present invention is a dielectric fluid, so they are electrical insulators, and can be in direct contact with electronic devices such as wires and integrated circuits, to transfer heat and from electric and electronic device transfer heat. In addition, when these fluids are used in cooling circuit, wherein they circulate in closed pipelines (as described in more detail below), so that they should not directly contact the conductive part of the device, it is particularly advantageous to use dielectric fluid, because it reduces the risk of damage to electric or electronic device in the case of leakage.

[0005] Computing devices such as computers, servers, etc. generate a lot of heat. Large-scale developments that concentrate a large number of computers in a shared location (such as a server farm) are becoming more and more common. The industry of server farms, Bitcoin mines and other supercomputing applications is developing rapidly. The key factor that determines the construction strategy of such facilities is a control system that allows heat to be exchanged with such computing devices. This system (often referred to as a "thermal management system") is typically used to cool the computing device during its operation, but it can also be used for heating, such as when starting the system in a cold environment. Air is still the most commonly used fluid, however, its disadvantage is that a large air gap is required between electronic boards, which causes the facility to have a very large footprint. Air cooling also requires a large number of air conditioning engines, and their energy consumption is extremely high and accounts for a large part of the operating cost of such facilities.

[0006] Server thermal management solutions based on the use of heat transfer fluids (especially liquid heat transfer fluids) have been gaining a lot of attention recently because they are both energy-efficient (using less energy than traditional air conditioning systems) and allow more servers, processors, and circuit boards to be packed into a smaller space.

[0007] Other important specialized applications of heat transfer fluids can be found, for example, in the semiconductor industry (TCU, constant temperature baths, vapor phase soldering) and in the battery industry, especially the vehicle battery industry, for their thermal management systems.

[0008] There are a variety of heat transfer fluids that are used in industry for a variety of applications, however, in some cases choosing the right fluid can be critical. Several heat transfer fluids that were commonly used in the past are no longer viable due to their toxicity (ammonia, ethylene glycol), others are being phased out due to their environmental profile, as they are not biodegradable and / or because they are considered to be harmful to the Earth's ozone layer and / or act as greenhouse gases if dispersed in the environment.

[0009] Fluorinated liquids are very effective heat transfer fluids. Commercial products exist, such as Solvay's and 3M's Fluorinert TM : These are liquid polymers or oligomers that are dielectric, have high heat capacity, low viscosity, are non-toxic and chemically inert, so they can be in direct contact with electronic boards and also do not chemically interact with most materials. The disadvantage associated with these fluorinated fluids used so far is their high GWP value.

[0010] GWP (Global Warming Potential) is a property that can be determined for a given compound, which indicates how much heat a given greenhouse gas can trap in the atmosphere (think of "1" as a reference value for CO2) and how much heat it can release over a specific time interval, typically 100 years (GWP 100) is calculated.

[0011] GWP 100 The determination is made by combining experimental data on the atmospheric lifetime of the compound and its radiative efficiency with specific calculation tools, which are standard in the art and are described in an extensive review published, for example, in Hodnebrog et al. Review of Geophysics, 51 / 2013, pp. 300-378. Highly stable halogenated molecules such as CF4 and chlorinated / fluorinated alkanes have very high GWP. 100 (7350 for CF4 and 4500 for CFC-11).

[0012] Over the years, heat transfer fluids with high GWP values ​​have been phased out by the industry and replaced by heat transfer fluids with lower GWP values. 100 replacement of compounds with the lowest possible GWP 100 The value of heat transfer fluids remains an ongoing concern.

[0013] Hydrofluoroethers, especially isolated hydrofluoroethers, tend to have relatively low GWP 100 values, while their other properties are comparable to those of the CFCs used in the past, for which reason some hydrofluoroethers have been used industrially and are popular as heat transfer fluids and are marketed, for example, by 3M Company under the trade name Sale.

[0014] Due to the wide temperature range over which the hydrofluoroethers are liquids and due to their low viscosity over a wide temperature range, these hydrofluoroethers are widely described as heat transfer media, which makes them useful as low temperature secondary refrigerants for applications in secondary circuit refrigeration systems where the viscosity should not be too high at the operating temperature.

[0015] Fluorinated ethers are described, for example, in US5713211 to 3M, US2007 / 0187639 to Dupont, and WO 2007 / 099055 and WO2010034698 to Solvay Solexis SpA.

[0016] However, although much lower than CFCs, the GWP of isolated HFEs is 100 Still within the range from 70 to 500 as shown in US 5713211 (Table 5):

[0017]

[0018] Other HFOs have been commercialized as heat transfer fluids, such as by Chemours (OpteonTM ). These compounds have a very low GWP of about 1, but unlike the previously cited compounds, they are more flammable, which therefore limits their areas of use.

[0019] International PCT Patent Application EP 2020 / 057121 to Solvay Specialty Polymers Italy SpA generally describes the use of halogenated vinyl ethers as heat transfer fluids having low GWP, low flammability, and good dielectric properties and heat capacity. There remains a continuing need to provide even more efficient methods for efficient heat transfer using heat transfer fluids that have an even better balance of good thermal and dielectric properties, are liquid over a wide temperature range, are non-flammable, and have very low GWP 100 (30 and below). Summary of the invention

[0020] The present invention relates to a method for exchanging heat with an object, the method comprising using a heat transfer fluid, wherein the heat transfer fluid comprises one or more fluorinated nitro compounds according to the general formula (I):

[0021]

[0022] in:

[0023] - At least two of R1, R2, R3 and R4 are independently selected from H, Cl and F, provided that at least one is H or Cl.

[0024] - those of R1, R2, R3 and R4 which are not H, F or Cl are selected from partially halogenated alkyl, fully halogenated alkyl, wherein the alkyl chain is C1-C4 and the halogen is selected from Cl and F. DETAILED DESCRIPTION

[0025] "Electronic computing device" is intended to mean any single computer board or array of single computer boards that includes a microprocessor CPU, GPU, SSD and DDR memory and performs computing work, thus including not only large server farms, Internet servers, Bitcoin mining farms, but also smaller single computers, Internet servers, computer gaming devices. Both large and small facilities can benefit from the heat transfer method of the present invention.

[0026] The term "semiconductor device" in the present invention includes any electronic device that utilizes the properties of semiconductor materials. Semiconductor devices are manufactured both as single devices and integrated circuits, which are composed of multiple (which can range from two to billions) devices manufactured and interconnected on a single semiconductor substrate or "wafer". The term "semiconductor device" includes both basic components, such as diodes and transistors, and complex structures built from these basic components, which extend to analog, digital and mixed signal circuits, such as processors, memory chips, integrated circuits, circuit boards, optical and solar cells, sensors, etc. The term "semiconductor device" also includes any intermediate or unfinished product of the semiconductor industry derived from a semiconductor material wafer.

[0027] The present invention relates to a method for exchanging heat with an object, the method comprising using a heat transfer fluid, wherein the heat transfer fluid comprises one or more compounds having the following general formula:

[0028]

[0029] in:

[0030] - At least two of R1, R2, R3 and R4 are independently selected from H, Cl and F, provided that at least one is H or Cl.

[0031] - those of R1, R2, R3 and R4 which are not H, F or Cl are selected from partially halogenated alkyl, fully halogenated alkyl, wherein the alkyl chain is C1-C4 and the halogen is selected from Cl and F.

[0032] In the above general formula (I), when present, the partially halogenated alkyl, fully halogenated alkyl is preferably fluorinated and more preferably has a carbon chain of C1 to C3, even more preferably C1. A particularly preferred perfluorinated alkyl is -CF3.

[0033] In particularly preferred embodiments, the heat transfer fluid of the present invention comprises one or more compounds according to formula (I), wherein at least two of R1, R2, R3 and R4 are F.

[0034] Furthermore, in particularly preferred embodiments, the heat transfer fluid of the present invention comprises one or more compounds according to general formula (I), wherein at least one of R1, R2, R3 and R4 is Cl, and even more preferably wherein two of R1, R2, R3 and R4 are Cl.

[0035] Compounds in this class can be synthesized starting from common fluoroolefins and hydrofluoroolefins (HFOs) via nitrofluorination, which will be described in more detail below. When an olefin containing a C=C double bond is subjected to nitrofluorination, the double bond is saturated, a -NO2 group is added to one of the carbon atoms forming the double bond, and a -F group is added to the other carbon atom.

[0036] The nitro group can be bound to one or the other of the two carbon atoms forming the double bond. As a result, the nitrofluorination of an asymmetric olefin may result in a mixture of two different isomers. In the mixture, one of the two compounds may be present in a higher amount than the other. Without being bound by theory, it is believed that both the polarity of the double bond and the steric hindrance effect play a role in the selectivity of the reaction.

[0037] Nitrofluorination of olefins is a known process and is described, for example, in Knunyants, IL, German, LS, and Rozhkov, IN (1963). "Aliphatic fluoro nitro compounds Communication 1. Conjugated nitrofluorination of olefins". Bulletin of the Academy of Sciences, USSR Division of Chemical Science, 12 (11), 1794–1797. https: / / doi.org / 10.1007 / BF00843794 middle.

[0038] However, nitrofluorination reactions leading to the preparation of the nitro compounds of the present invention have not yet been described.

[0039] The nitrofluorination of the fluorinated compound can be carried out as is generally known for other olefins. Preferably, the nitrofluorination reaction for preparing the fluorinated olefins of the present invention is carried out in two steps:

[0040] Preparation and characterization of 1-nitro / fluorine mixtures

[0041] Reaction of 2-halogenated olefins with nitro / fluorine mixtures

[0042] Step 1. Preparation of nitro / fluorine mixture

[0043] The nitro / fluorine mixtures useful in the present invention can be prepared using several different methods, including but not limited to:

[0044] a- Mix pure nitric acid and anhydrous hydrogen fluoride in a molar ratio equal to or higher than 1:1 (HF / HNO3). (The preferred range of the molar ratio is 5:1-10:1)

[0045] b- As in method "a", carbonyl difluoride and nitric acid are reacted to form a nitro / fluorine mixture.

[0046] Step 2 - Reaction of halogenated olefins with nitro / fluorine mixtures

[0047] Halogenated olefins are slowly added to a nitro / fluorine mixture placed in a metal reactor in a stoichiometric ratio or slightly above the stoichiometric ratio. The internal temperature is carefully monitored. While the reaction is proceeding, the reactor is maintained at a temperature within the range of 20°C-120°C for a period of between 3 hours and 24 hours. The choice of temperature depends on the selected olefin and its reactivity and stability. Generally speaking, below 20°C, the reaction kinetics are too slow, and above 120°C, some olefins may be unstable. At the end of the reaction, the reactor is unloaded, and the crude product is separated and purified.

[0048] The nitrofluorination reaction can be carried out in a pressurized reactor or in a stirred tank reactor at atmospheric pressure.

[0049] The nitrofluorination methods described should not be considered limiting. The skilled person will be able to make variations and modifications to these methods and, in particular, scale up the methods for industrial application following conventional chemical engineering procedures.

[0050] The method of the present invention can be used to exchange heat with any object. When the object is an electronic computing device (such as a computer server, for example), the method of the present invention is particularly useful. In fact, the method of the present invention uses a stable, dielectric, non-flammable and non-corrosive heat transfer fluid, so it can also be used in systems using so-called "immersion cooling" or "direct contact cooling". In these systems, these fluids are placed in direct contact with electronic circuit boards. Such fluids can be gaseous, liquid (single-phase immersion cooling) or in gas / liquid equilibrium (i.e., near the boiling point of the liquid in the so-called "two-phase immersion cooling") at their operating temperature.

[0051] In immersion cooling, electronic computer devices including complete servers (such as CPUs, GPUs, memory and other electronic products) are completely immersed in a thermally conductive dielectric liquid or coolant, the temperature of which is controlled by using a circulation system that pumps the liquid through pipes to a heat exchanger or radiator-type cooler to remove heat from the coolant.

[0052] Server immersion cooling has become a popular solution for server cooling solutions because it allows for a significant reduction in energy use by eliminating expensive air conditioning infrastructure. These systems are replaced by efficient low-speed liquid circulation pumps and simpler heat exchanger and / or radiator systems.

[0053] The temperature used in liquid immersion cooling is determined by the maximum temperature at which the immersed device can operate reliably. For servers, this temperature range is typically between 15°C and 65°C, although in some cases this range extends up to 75°C.

[0054] Current commercial applications for immersion cooling range from commercial server cooling solutions for data centers, server clusters, HPCC applications and cryptocurrency mining to mainstream cloud-based and web-hosted architectures. Liquid immersion cooling is also used for thermal management of computing devices associated with LEDs, lasers, X-ray machines and magnetic resonance imaging devices.

[0055] The method of the invention is suitable for both single-phase immersion cooling and two-phase immersion cooling. In a single-phase immersion cooling system, the server is immersed in a dielectric fluid bath. Heat is transferred to the fluid via direct contact with the electronic components. The fluid is usually kept at a constant temperature by a recirculation system typical of a thermostatic bath. There may be a more or less complex control system that controls the instantaneous temperature of the fluid and the temperature of the server that optimizes the temperature of the fluid at each moment.

[0056] Two-phase immersion cooling is a technology promoted by Allied Control and some other companies that involves immersing the electronics in a closed tank with a bath of dielectric fluid in which the dielectric fluid has a boiling point corresponding to the desired temperature at which the bath can be set. When the electronics are heated to the boiling point of the dielectric fluid, the fluid becomes a vapor minus the heat. The vapor then condenses on a lid or coil condenser placed above the bath and settles again in the bath. This type of design is particularly popular because it does not require the recirculation of the dielectric fluid and allows more electronics to be packed in a small space.

[0057] The heat transfer fluids according to the invention, i.e. heat transfer fluids comprising one or more compounds according to general formula (I) as defined above, can be formulated with compounds having a boiling point between 40°C and 90°C (see examples in the experimental part below) and are therefore particularly suitable for two-phase immersion cooling.

[0058] Still in the field of computer device cooling, the method of the invention may also be used in non-immersion cooling systems, in which a heat transfer fluid circulates in a closed system and is in thermal contact with the processor through a plate of thermally conductive material, such as the server cooling solution produced by Ebullient under the name "Modular Loop". The use of a dielectric fluid, such as the heat transfer fluid of the invention, is in any case beneficial, since the risk of leakage is always present, and conductive liquids may have a destructive effect on electronics.

[0059] The method of the present invention can also be applied, for example, in the semiconductor industry, where temperature control during the manufacture of semiconductor devices is very important. In this case, the object with which the heat transfer fluid of the present invention exchanges heat is a semiconductor device. Temperature control units (TCUs) are used throughout the production line for manufacturing semiconductor devices, and the heat transfer fluid according to the present invention can be used to remove unwanted heat during steps such as wafer etching and deposition processes, ion implantation, and photolithography processes. The heat transfer fluid is typically circulated through a wafer mount, and each processing tool that requires temperature control has its own separate TCU.

[0060] Some particularly important tools that include the TCU are silicon wafer etcher, stepper, and asher. Etching is performed using reactive plasma at a temperature in the range of 70°C to 150°C, and during the plasma treatment, the temperature of the wafer must be precisely controlled over the entire temperature range. After the plasma treatment, the etched parts are typically immersed in a solvent to remove the etched parts. This second step typically does not require temperature control because it is performed at mild or ambient temperature. When an "etcher" is mentioned in the present invention, it is intended to be a device in which plasma treatment at high temperatures is performed and therefore a TCU is required.

[0061] Steppers are used for photolithography of wafers to form reticles that are then used to expose photosensitive masks. The process is carried out at temperatures between 40°C and 80°C, however temperature control is extremely important as the wafer needs to be maintained at a precise fixed temperature (+ / -0.2°C) throughout the process to ensure good results.

[0062] Ashing is the process of removing the photosensitive mask from the wafer and is carried out at temperatures from 40° C. to 150° C. The system uses plasma and here too precise temperature control is particularly important.

[0063] Another related process is plasma enhanced chemical vapor deposition (PECVD), in which films of silicon oxide, silicon carbide and / or silicon nitride are grown on a wafer in a chamber. Also in this case, although the temperature at which this step is carried out can be selected in the range between 50° C. and 150° C., the wafer must be uniformly maintained at the selected temperature during the deposition process.

[0064] In a semiconductor device production facility, each etcher, asher, stepper and plasma enhanced chemical vapor deposition (PECVD) chamber typically has its own TCU in which the heat transfer fluid according to the present invention may be recirculated, applying the method of the present invention.

[0065] Another process step using the heat transfer fluid of the present invention in the semiconductor industry is vapor phase reflow (VPR) soldering. This is the most common method for connecting surface mount devices, multi-chip modules and hybrid components to circuit boards. In this method, the solder material is applied in the form of a paste, and then the semiconductor device (e.g., an unfinished circuit board) is placed in a closed chamber, where a heat transfer fluid at its boiling point is in equilibrium with its gas phase. The fluid in the gas phase transfers heat to the solder paste, which is then melted and the contacts are stabilized. In this case, the fluid is in direct contact with the circuit board so that it must be dielectric and non-corrosive. It is important for this application that the heat transfer fluid contains a compound with a boiling point sufficient to melt the solder paste. Also in this method, a heat transfer fluid according to the present invention can be used.

[0066] Another system is the thermal shock test, which is a key part in the production process of many semiconductor devices. In the thermal shock test, the semiconductor device is tested at two very different temperatures. Although there are different standards, in general, the test includes subjecting the semiconductor device to high and low temperatures and then testing the physical and electronic properties of the device. Typically, the semiconductor device to be tested is directly alternately immersed in a hot bath (which can be at a temperature from 60°C to 250°C) and a cold bath (which can typically be at a temperature from -10°C to -100°C). The transfer time between the two baths must be minimized, usually less than 10 seconds. Also in this test, the fluid that makes up the bath is in direct contact with the device and therefore must be dielectric and non-corrosive. In addition, in order to avoid contamination of the bath, it is highly preferred to use the same fluid in both the cold bath and the hot bath. Therefore, a heat transfer fluid that exists in liquid form over a wide temperature range is preferred. In this case as well, the heat transfer fluid according to the present invention can be used in this method.

[0067] Heat transfer fluids used in the manufacture of semiconductor devices are typically liquids that are dielectric, non-corrosive, and exist in a liquid state over a wide temperature range with a relatively low viscosity that makes them easily pumpable.

[0068] The method of the present invention can be used in all steps of the manufacture of semiconductor devices that require the semiconductor devices to exchange heat with a heat transfer fluid. In particular, when using semiconductor processing equipment such as etchers, ashers, steppers and plasma enhanced chemical vapor deposition (PECVD) chambers: each of these devices requires precise temperature control and / or heat dissipation, and therefore they include a temperature control unit (TCU) that can include the selected heat transfer fluid of the method of the present invention.

[0069] Furthermore, in thermal shock testing (which is an integral part of semiconductor device manufacturing, since only those devices that pass the test are further processed), the semiconductor devices are cooled and heated using at least two baths made of heat transfer fluid, one cold bath typically at a temperature from -10°C to -100°C, and one hot bath typically at a temperature from 60°C to 250°C. The method of the invention can be advantageously performed selecting a suitable compound or blend of compounds according to formula (I) to make the heat transfer fluid of the baths. Due to the large temperature range over which the fluid is in the liquid state, the heat transfer fluid should preferably be selected so that the same heat transfer fluid can be used in both baths, so that there is no risk of cross contamination of the baths.

[0070] The method of the invention can also be applied to vapor phase soldering, in fact, the selected heat transfer fluid of the method of the invention can be formulated so as to have a boiling point consistent with that of the solder paste, so that a semiconductor device containing a solder paste that still has to be "cured" can be introduced into a closed chamber containing the selected heat transfer fluid of the method of the invention, which is in equilibrium with the vapor it heats. The heated vapor transfers heat to the semiconductor device, thereby melting the solder paste and thus fixing the contacts (as required). For this application, it will be necessary to use a high boiling point compound according to the general formula in the heat transfer fluid.

[0071] An additional advantage is that a single heat transfer fluid can be used in multiple applications, potentially allowing a single heat transfer fluid to be used throughout a semiconductor device manufacturing facility.

[0072] Another field in which the method of the invention can be applied is the thermal management of batteries, in particular rechargeable batteries, such as vehicle batteries for cars, trams, trains and the like.

[0073] At present, in all industrial sectors, most of the development in the field of rechargeable batteries is concentrated on lithium-ion based batteries based on different types of lithium salts. Batteries based on lithium manganese oxide, lithium iron phosphate and lithium nickel manganese cobalt oxide are used in, for example, vehicles, power tools, electric bicycles, etc. Batteries based on lithium cobalt oxide are typically used in smaller size and less dense applications, such as mobile phones, portable computers and cameras. Batteries based on lithium nickel cobalt aluminum oxide and lithium titanate are being considered in applications requiring high power and / or capacity such as electric power systems and grid storage. Of course, new technologies outside the field of lithium-ion based batteries are also being explored and continuously developed. The method of the present invention is independent of the specific battery technology and is applicable to both current and future generations of battery systems.

[0074] Unlike conventional power systems, batteries, and especially rechargeable batteries, have strict requirements on their operating environment. Batteries tend to operate under optimal conditions within a relatively narrow temperature range.

[0075] Generally speaking, low temperatures have an impact on battery chemistry, reducing the reaction rate and thus the current when charging or discharging. High temperatures, on the contrary, increase the reaction rate and, at the same time, also increase the energy dissipation, thereby generating even more excessive heat, which may lead to an uncontrolled increase in temperature, which may cause irreversible damage to the battery cells. For a typical Li-ion battery, temperatures exceeding 80°C may start exothermic chemical reactions, even in only part of its structure, which leads to a further increase in the battery temperature and ultimately to a complete breakdown of the battery, with the risk of fire and explosion.

[0076] On the other hand, practical applications of batteries require that they be effective over a wider temperature range. For example, vehicle batteries need to function properly in any environment in which one expects to use them, so they need to be operable over a temperature range from -20°C to +40°C and above. In addition to this, the charge and discharge cycles of the battery may generate heat within the battery itself, making it even more difficult to maintain the battery within an acceptable temperature range.

[0077] Indicative figures for a typical Li-ion battery show that the usable range is usually from -20°C to 60°C, but good power output is only obtained from 0°C to 40°C, with optimum performance only available from 20°C to 40°C. Temperature also affects battery duration, in fact the number of charge / discharge cycles a battery can undergo before being considered exhausted drops rapidly below 10°C due to anodic plating and above 60°C due to degradation of the electrode materials. The temperature range for optimum performance may be different for different battery chemistries and configurations, however, all current commercial batteries have a relatively narrow temperature window in which their performance is optimum. It is also generally important to ensure that the entire battery is uniformly maintained at the same temperature, without hot or cold zones, as this may reduce its lifetime and safety.

[0078] For this reason, the integration of a battery thermal management system (BTMS) in commercial battery assemblies has become standard today, especially when the safety, reliability and lifetime of the battery are important considerations. These BTMS can be more or less complex, depending on the type of battery, however a common element is the presence of a heat transfer fluid such as a gas or liquid that exchanges heat with the battery to heat or cool it.

[0079] Battery thermal management systems (BTMS) are therefore extremely important, especially in applications that require high power and high reliability, such as vehicle batteries. A BTMS can be more or less complex, depending on the application, but each BTMS has at least the function of cooling the battery when the battery temperature is too high and the function of heating the battery when the battery temperature is too low, typically using a heat transfer fluid that exchanges heat with the battery. Other common features of a BTMS are an insulation system that reduces the effect of the external environment on the battery temperature, and a ventilation system that helps dissipate harmful gases that may be generated within the battery pack. However, the method of the present invention specifically relates to the heat exchange function of the BTMS and can be easily applied to any BTMS and integrated with its other functions and features.

[0080] BTMS using liquids as heat transfer fluids are common, since liquids can transfer more heat faster than gases. Typically, the fluid is circulated by a pump within a closed system that is in thermal contact with the battery and a second system that has the function of heating and / or cooling the fluid to the desired temperature. This second system may include any combination of a refrigeration system and a heating system, or the heating and cooling functions may be combined in a heat pump. The circulating fluid absorbs heat from the battery or releases heat to the battery, and then circulates in the second system to bring the fluid back to the desired temperature. There may be a more or less complex control system that controls the instantaneous temperature of the fluid and the temperature of the battery that optimizes the temperature of the fluid at each moment.

[0081] In some systems, the heat transfer fluid can be in direct contact with the battery cell, which is then immersed in the heat transfer fluid. Obviously, in these cases, the fluid must be dielectric in order to protect the battery cell and its electronic components. In other cases, the heat transfer fluid circulates in a separate closed system that only exchanges heat through indirect contact slots (e.g., heat exchange plates made of metal or other thermally conductive materials). In this type of system, dielectric fluids may also be beneficial because closed systems have a high risk of leakage anyway.

[0082] In particular for high power batteries, fluid (particularly liquid) based thermal management systems are being used and the method of the present invention provides a method for reducing GWP. 100 Improved thermal management.

[0083] The heat transfer fluid according to the present invention can be applied as a heat transfer fluid in a BTMS.

[0084] In addition to the applications listed, the method of the invention can also be applied to any heat exchange method, for example for heating or cooling compartments (e.g. food compartments), including those on board of aircraft, vehicles or ships; for heating or cooling industrial production equipment; for heating or cooling batteries during their operation; for forming a constant temperature bath.

[0085] As mentioned in the introduction, the heat transfer fluids used in these fields contain fluorine compounds. In particular, hydrofluoroethers have been applied in these fields due to their chemical inertness, dielectric properties, their being liquid and pumpable (typically with a viscosity between 1 and 50 cps at the use temperature), a wide T range, low flammability and relatively low GWP.

[0086] Commercially available hydrofluoroethers used in these fields are, for example, Novec TM series that combine all of these properties with a relatively low GWP ranging from about 70 to 300 100 combination.

[0087] Nevertheless, due to the regulatory environment, GWP is currently a critical property and there is always a need to develop new heat exchange fluids with even lower GWP than currently commercialized hydrofluoroethers.

[0088] Applicants have unexpectedly discovered that the heat transfer fluids employed in the methods of the present invention are non-flammable, provide efficient heat transfer, can be used over a wide temperature range, and have dielectric and thermal properties that are equal to or improved upon other materials commercialized as heat transfer fluids. Unexpectedly, the heat transfer fluids used in the present invention have extremely low GWP. 100, typically below 30 and for some materials even below 3, as will be shown below in the experimental section. This is a particularly unexpected result and in fact previous reviews (such as Hodnebrog et al. cited above) did not investigate or suggest fluorinated compounds with nitro groups as low GWP compounds.

[0089] Thus, using these selected compounds according to general formula (I), it is possible to formulate compositions having a GWP of less than 30, preferably less than 10, even more preferably less than 5. 100 The heat transfer fluids according to the invention also have low toxicity, show good heat transfer characteristics over the entire range and relatively low viscosity. In addition, the fluids of the invention have good electrical compatibility, i.e. they are non-corrosive, have high dielectric strength, high volume resistivity and low solvency for polar materials. The electrical properties of the fluids of the invention are such that they can be used in immersion cooling systems for electronic products in direct contact with circuits, as well as in indirect contact applications using loops and / or conductive plates.

[0090] The heat transfer fluid for use in the method of the present invention preferably comprises more than 5% by weight, more preferably more than 50% by weight, even more preferably more than 90% by weight of one or more compounds according to formula (I) as defined above. In one embodiment, the heat transfer fluid is made entirely of one or more compounds according to general formula (I).

[0091] In some embodiments, the heat transfer fluids of the present invention comprise a blend of chemical compounds according to the general formula.

[0092] In another aspect, the present invention also encompasses an apparatus comprising an electronic computing device and a heat transfer fluid, wherein the heat transfer fluid comprises one or more fluorinated nitro compounds according to formula (I) as defined above.

[0093] In a further aspect, the invention relates to a device comprising a battery, preferably a rechargeable battery, a thermal management system for said battery, said thermal management system for said battery comprising a heat transfer fluid for heat exchange with said battery, wherein said heat transfer fluid comprises one or more fluorinated nitro compounds according to general formula (I) as defined above.

[0094] Should the disclosure of any patents, patent applications, and publications incorporated herein by reference conflict with the description of the present application to the extent that it renders a term unclear, the present description shall take precedence.

[0095] The present invention will now be described in more detail with reference to the following examples, the purpose of which is merely illustrative and not limiting the scope of the present invention.

[0096] standard:

[0097] Electrical characteristics are measured according to the following standards:

[0098] Dielectric Constant - ASTM D924-15

[0099] Specific Heat—ASTM E1269

[0100] Examples

[0101] The following fluoroolefins according to general formula (I) are subjected to nitrofluorination:

[0102] A1112 (1,2-dichloro-1,2-difluoroethylene)

[0103] TrFE(Trifluoroethylene)

[0104] The nitrofluorination reaction was carried out in a stainless steel reactor (0.6 L internal volume) charged with 6.7 mol of AHF (anhydrous hydrogen fluoride) and charged with 0.73 mol of WFNA (white fuming nitric acid >95%) transferred under vacuum. The contents were stirred and the temperature was raised to the temperature shown in the table below.

[0105] Then, a steel bottle containing 0.6 mol of olefin was connected to the reactor using a metal joint and a valve. The connecting valve was then opened to allow the olefin to enter the reactor.

[0106] The system was kept at a constant temperature for the time shown in the table below, and then the reactor was cooled to room temperature.The contents of the reactor were then transferred to a mixture of water and ice (1180 g) in a plastic wash bottle.

[0107] The organic phase was then separated from the water / ice mixture using a plastic separatory funnel and washed twice with 10% potassium hydroxide solution and subsequently dried over anhydrous magnesium sulfate.

[0108] Finally, after filtration to remove magnesium sulfate residues, the organic phase was distilled in a 30 cm, Φ14 mm Hempel column with Raschig rings equipped with a reflux condenser.

[0109] The obtained material was analyzed by 19F-NMR spectroscopy.

[0110] Table 1 summarizes the reaction conditions and the products obtained:

[0111] Table 1

[0112]

[0113] Chemical names of nitrofluorination products:

[0114] A1112:

[0115] NCFC-113=1,2-dichloro-1,1,2-trifluoro-2-nitroethane

[0116] TrFE:

[0117] NHFC-124=1,1,1,2-tetrafluoro-2-nitroethane

[0118] The nitro compounds obtained were tested for flammability (all were found to be non-flammable and non-combustible).

[0119] The compounds of the present invention have unexpectedly good specific heat capacities, which ensure more efficient heat transfer. This is combined with other desirable properties (non-flammability, low GWP and very low dielectric constant) consistent with other materials. These property combinations make the materials of the present invention particularly suitable as heat transfer fluids. The heat transfer fluids comprising these compounds can be used for all mentioned applications involving heat exchange with electronic computing devices, batteries or semiconductor devices.

Claims

1. A method for exchanging heat with an object, the method comprising using a heat transfer fluid, wherein the heat transfer fluid comprises one or more fluorinated nitro compounds according to formula (I): in: - at least two of R1, R2, R3 and R4 are independently selected from H, Cl and F, provided that at least one is H or Cl, - those of R1, R2, R3 and R4 which are not H, F or Cl are selected from partially halogenated alkyl, fully halogenated alkyl, wherein the alkyl chain is C1-C4 and the halogen is selected from Cl and F.

2. The method according to claim 1, wherein: The one or more fluorinated nitro compounds comprise at least 5% by weight, preferably greater than 50% by weight, more preferably greater than 90% by weight of the heat transfer fluid.

3. A method according to any preceding claim, wherein: The heat transfer fluid has a GWP of less than 30, preferably less than 10, more preferably less than 5, determined according to the method reported by Hodnebrog et al. in Review of Geophysics, 51 / 2013, pp. 300-378. 100 .

4. A method according to any preceding claim, wherein: The object is an electronic computing device.

5. The method according to claim 4, wherein: The electronic computing device is one or more servers.

6. The method according to claim 4 or 5, wherein: The electronic computing device includes one or more electronic circuit boards, and the method includes the step of bringing the electronic circuit boards into direct contact with the heat transfer fluid.

7. The method according to claims 4 to 6, which is a single-phase immersion cooling method.

8. The method according to claims 4 to 6, which is a two-phase immersion cooling method.

9. The method according to claims 1 to 3, wherein: The object is a battery, preferably a rechargeable battery, more preferably a rechargeable vehicle battery.

10. The method according to claims 1 to 3, wherein: The object is a semiconductor device.

11. The method according to claim 10, wherein: One or more semiconductor processing devices selected from an etcher, an asher, a stepper, and a plasma enhanced chemical vapor deposition (PECVD) chamber are used, the semiconductor processing device comprising at least one temperature control unit (TCU) in thermal exchange with the semiconductor device, wherein the TCU contains the heat transfer fluid.

12. The method according to claim 10, wherein: The method is a method for thermal shock testing of a semiconductor device, the method comprising, in any order: i. cooling the semiconductor device to a temperature comprised between -10°C and -100°C using a first bath made of a first fluid, and ii. heating the semiconductor to a temperature comprised between 60° C. and 250° C. using a second bath made of a second fluid, Wherein one or preferably both of the first and second fluids are heat transfer fluids according to claims 1-3.

13. The method according to claim 10, wherein: The method is a method for vapor phase soldering of semiconductor devices, and the method comprises: i. providing a semiconductor device comprising a solder paste, ii. providing a closed chamber containing said heat transfer fluid at its boiling point so that heated vapor of said heat transfer fluid is generated within said closed chamber iii. introducing said semiconductor device into said closed chamber into contact with said vapor of said heat transfer fluid, thereby melting said solder paste by contact with said heated vapor.

14. An apparatus comprising an electronic computing device and a heat transfer fluid, wherein the heat transfer fluid comprises one or more fluorinated nitro compounds according to formula (I): in: - at least two of R1, R2, R3 and R4 are independently selected from H, Cl and F, provided that at least one is H or Cl, - those of R1, R2, R3 and R4 which are not H, F or Cl are selected from partially halogenated alkyl, fully halogenated alkyl, wherein the alkyl chain is C1-C4 and the halogen is selected from Cl and F.

15. A device comprising a battery, preferably a rechargeable battery, a thermal management system for the battery, the thermal management system for the battery comprising a heat transfer fluid in heat exchange with the battery, wherein the heat transfer fluid comprises one or more fluorinated nitro compounds according to formula (I): in: - at least two of R1, R2, R3 and R4 are independently selected from H, Cl and F, provided that at least one is H or Cl, - those of R1, R2, R3 and R4 which are not H, F or Cl are selected from partially halogenated alkyl, fully halogenated alkyl, wherein the alkyl chain is C1-C4 and the halogen is selected from Cl and F.

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