"Cooling system using a two-phase refrigerant to cool a plurality of components"

Description

DESCRIPTION of the industrial invention entitled: “Cooling system using a two-phase refrigerant fluid, for cool a plurality of components”, by: CRF Consortium Company, Italian nationality, Strada Torino, 50 - 10043 Orbassano TO. Designated inventors: GARGANO Marcello; WILAND Michael; GEORGE Alexander. Filed on: August 19, 2024 **** DESCRIPTION TEXT Field of invention The present invention relates to refrigeration systems for the cooling of a plurality of components, in particular for cooling of a plurality of on-board systems of a vehicle, such as the battery electric, the electric traction motor and the passenger compartment of an electric vehicle. Background of the invention In recent times, there is a need to integrate the systems of cooling of the various on-board components of a vehicle. Studies and experiences conducted by the Applicant have however led to identify a series of problems that can undermine the efficiency and the reliability of a cooling system, used to fulfill a temperature regulation function of multiple vehicle components at the same time. The main problem is related to the fact that each circuit of refrigeration associated with a given component requires a power of different cooling and consequently a different flow rate of refrigerant different. This requires the need to control the flow rate of the fluid refrigerant in the various circuits of the system, always ensuring proper operation efficient and reliable. Purpose of the invention It is therefore an object of the present invention to to create a cooling system capable of cooling a plurality of different components at the same time, in particular a plurality of systems on board a vehicle, which ensures efficient and reliable operation of the system, despite the different cooling powers required by the different components. A further object of the invention is to achieve the above objective with a constructionally simple and low-cost system. Summary of the invention In order to achieve the above-mentioned aims, the invention has as its object a cooling system using a two-phase refrigerant, for cool a plurality of components, in particular a plurality of systems on board a vehicle, such as the electric battery, the electric motor of traction and the passenger compartment of an electric vehicle, wherein said system includes at least one refrigerant circuit comprising: - a compressor, - a condenser for the refrigerant fluid coming from the compressor, - an electrically controlled expansion valve, to expand the refrigerant fluid coming from the condenser, and - a separator tank to separate the liquid phase from the vapor of the refrigerant contained in it, called separator tank having: - a first inlet to receive expanded refrigerant fluid from the expansion valve, - a first outlet through which the refrigerant is fed to the aforementioned compressor, - a second outlet, to supply the refrigerant fluid in phase liquid from said separator tank to at least one of a plurality of heat exchangers associated with a plurality of components to be cooled, and - a second inlet, to bring the fluid into the separator tank refrigerant that has passed through said at least one heat exchanger, wherein, further, said cooling system includes at least one unit control electronics, configured to control the expansion valve in order to maintain the total mass of refrigerant in the separator tank between a predetermined minimum threshold and a predetermined maximum threshold, where the separator tank has a main chamber communicating with a still pipe that is arranged and configured so that the level of the refrigerant in the still pipe is essentially a direct function of the total mass of refrigerant in the separator tank, and where the electronic control unit is configured to control the valve expansion as a function of the output signal from a measuring device level associated with said still pipe, so as to maintain the level of liquid inside the still tube, and consequently the total mass of fluid refrigerant in the separator tank, between said predetermined minimum threshold and said predetermined maximum threshold. The electronic control unit can be configured to detect the level of liquid in the still tube with a certain periodicity and to control consequently the expansion valve with said periodicity. The electronic unit can also be configured to control the valve of expansion with reference to multiple threshold values ​​of the liquid level in the pipe calm, both upwards and downwards. For example, the expansion valve can be controlled to generate several discrete changes in flow rate of the fluid, as different threshold values ​​are exceeded, upwards or downwards. Or the expansion valve can be adjusted so continuous. Thanks to the above mentioned features, the electronic control unit of the system according to the invention is able to monitor the total mass of fluid present in the aforementioned separator tank, and to regulate the aforementioned valve expansion, varying the flow rate of the refrigerant entering the tank separator through the aforementioned first entrance, in order to maintain the mass total amount of refrigerant in the separator tank substantially constant, at vary the flow rates of two-phase fluid entering the tank from the multiple heat exchangers. Considering that inside the tank the two-phase fluid can be in continuously boiling and in a turbulent state due to the hydraulics of the system and therefore it is not possible to establish a stationary and stable liquid level calm, the system described above allows, in particular, to create in the pipe calms a liquid level equivalent to the steady state of the two-phase fluid and in order to brilliantly solve the problem of controlling the total mass contained in the aforementioned separator tank. It must be considered that the thermal power absorbed by each heat exchanger associated with the cooling system described above is variable over time. The refrigerant fluid that comes out of a heat exchanger and returns to the separator tank via said second inlet is partly steam and partly liquid. The percentage of steam depends on the power heat absorbed in the heat exchanger and by further control choices and is therefore variable. Consequently, the flow rate of steam from the tank separator goes to the compressor and is also variable from moment to moment. If it is not controls the balance of the masses entering and exiting the tank separator, there is a risk that the separator tank will become empty or completely full. If the separator tank empties completely, the liquid pump sucks steam and is unable to feed the heat exchanger which no longer receives refrigerant fluid and can therefore no longer perform its function as cooling of the associated component. If the separator tank is if it fills completely with liquid, there is a risk that the compressor receives liquid fluid and get damaged. On the other hand, check the amount of fluid contained in the reservoir separator, placing flow meters at the inlets and outlets of the separator, would not lead to accurate and reliable detection, due to the two-phase nature (liquid and vapor) of the refrigerant. In pursuing her studies and experiences in this field, the Applicant he had initially thought of using a level meter placed directly inside the separator tank. However, even this solution, in itself, does not allow for reliable detection, due to the turbulence which the fluid is subjected to inside in the separator tank, both due to the flows of fluid entering the tank, both due to vibrations and oscillations which a tank installed on board a vehicle is subject, and finally also to the phase of the refrigerant fluid that is boiling inside the separator tank. Such phenomena, always present, would induce an unreliable and unprecise measurement. However, all the above issues have been resolved in the above system. described, thanks to the provision of a level measuring device associated with the above mentioned still pipe, which is arranged and configured in such that the level of the refrigerant in the still pipe is essentially a direct function of the total mass of refrigerant in the separator tank, not affected by the disturbing phenomena described above. Of course a level sensor associated with a still pipe is of if it is a known technique and the Applicant certainly does not claim to protect it as invention of this device taken in isolation. On the contrary, the concept fundamental aspect of the present invention is to apply such a device per se known in a two-phase fluid cooling system, in which one or more separator tanks are connected to one or more heat exchangers to cool simultaneously multiple components that absorb different thermal power and variable over time, in order to simply solve the problem of ensuring reliable operation of separator tanks. Furthermore, the application of such device to a refrigeration system is the only way to know the mass present in the tank in continuous agitation due to fast dynamics characteristics of refrigerant systems, and is therefore the only way to control the mass balance in the separation tank where they flow and a plurality of flows flow out with different liquid / vapor ratios. In a preferred embodiment, the level measuring device comprises a float arranged within the still pipe and configured to occupy substantially the entire cross-section of the still tube, and a sensor of any type, capable of detecting the position of the float within the tube of calm. In one embodiment, the sensor is a contactless sensor, such as for example an optical sensor or a magneto-resistive sensor. In the case of a sensor optical, the sensor can be rigidly connected to an upper end of the still tube and be configured to detect the distance from the sensor of a upper surface of the float (which is configured to always remain only partially immersed in the fluid within the still tube). In a different embodiment, the sensor may be of the type including a guide and measuring rod, on which the float is guided and which allows you to detect the position of the float with respect to the said rod In a first example, the still pipe is arranged outside a casing defining the main chamber of the separator tank, while in a second example, the still pipe is arranged inside the said main chamber of the separator tank. In both cases, the still pipe has a communicating lower end with the main chamber adjacent to a lower end of the chamber main and an upper end communicating with the main chamber in adjacent to an upper end of the main chamber. In one embodiment, the upper end of the still tube communicates with the main chamber of the separator tank via a passage narrow passage of a certain size. This narrow passage allows for equalize the vapor phase pressure between the still pipe and the main chamber of the separator tank when the pressure variations are slow and / or moderate, while allowing to maintain a minimum overpressure in the pipe calm when rapid pressure drops occur in the main chamber of the separator tank. This is to prevent the refrigerant in the pipe from calm evaporates quickly, making the float jump and thus giving lead to inaccurate level measurements. As a replacement for the aforementioned narrow passage it is also possible provide an automatic valve (check valve) that allows a flow bidirectional when the pressure difference between tank 10 and discharge pipe T is lower than a predetermined value and which does not allow flow from the pipe calm T towards the main chamber 17 of the separator tank 10 when the delta of pressure exceeds the predetermined value. In this second case the pressure between tank 10 and still pipe T is equalized by the opening from side of the liquid but rapid boiling under the float is avoided. The cooling system according to the invention can be implemented according to different configurations. In a first example, the aforementioned second inlet and the second aforementioned second outlet of the separator tank are configured for the circulation of refrigerant fluid through a plurality of heat exchangers associated with different components to be cooled. In another for example, several separator tanks can be foreseen, each having its own second exit and its second entrance configured for the circulation of the refrigerant fluid through a respective heat exchanger of a plurality of heat exchangers associated with different components to be cooled. Detailed description of the invention Further features and advantages of the invention will result from the description that follows with reference to the attached drawings, provided for information purposes only non-limiting example, where: Figure 1 is a diagram of a cooling system according to the invention, according to a first simplified configuration, Figure 2 is a diagram of a reference system according to the invention. in a second configuration, Figure 3 is a diagram of a cooling system according to the invention in a third configuration, Figure 4 is a schematic figure showing a measuring device of level associated with the separator tank, in an example not part of the present invention, Figure 5 schematically illustrates a first form of implementation of the separator tank, or each separator tank, forming part of the system according to the invention, Figure 6 shows a variant of Figure 5, Figure 7 illustrates the variant of Figure 6 in an inclined condition, Figure 8 shows a variant of the sensor device associated with the tube calm down, and Figure 9 is a schematic sectional view along the line IX-IX of the figure 8. In figure 1, reference 1 indicates as a whole a system of cooling using a two-phase refrigerant. Figure 1 refers to a simplified example, where the refrigerant of system 1 is made circulate through a single heat exchanger 2, associated with a specific component to be cooled, such as the electric battery of a electric vehicle. The cooling fluid circulating in system 1 is used to cool an additional fluid in the heat exchanger 2 cooling (for example air or a dielectric oil, or water, or an oil lubricant, or other temperature-regulating fluid) that is used to cool the electric battery of the electric vehicle. Of course, the case described above is given here only as an example, it being evident that the system according to the invention is of general application. Still referring to figure 1, the number 3 indicates a compressor which receives refrigerant fluid from a line 4 and supplies refrigerant fluid to the outlet compressed, via a line 5, to a capacitor 6. The structure and operation of compressor 3 and condenser 6 is not described or illustrated here, as such construction details may be made in any known way. In the example, capacitor 6 is associated with a fan 6 which feeds a flow of air through the condenser 6 in order to cause the refrigerant to condense. The refrigerant exiting from the condenser 6 reaches a valve via a line 8 expansion 9, electrically controlled, of any known type. Reference 10 indicates a separator tank, to separate the liquid phase from the vapor phase of the refrigerant contained in it. The construction structure of the separator tank 10 can be made in any known way. The separator tank 10 has a first inlet 11, to receive fluid refrigerant expanded by the expansion valve 9, a first outlet 12 (which is associated with a pressure regulator 18 of any known type), through which the refrigerant fluid is fed to the aforementioned compressor 3, a second outlet 13, to feed the liquid-phase refrigerant from the separator tank 10 to the heat exchanger 2, via a line 14 in which a pump 15, for example electrically operated. The outgoing refrigerant from heat exchanger 2 returns to separator tank 10, via a line 16 and a second entrance 20. In heat exchanger 2, the refrigerant fluid coming from the separator tank 10 absorbs a variable thermal power Q, depending on of the needs of the component for which the heat exchanger 2 is cooling is dedicated. The separator tank 10 comprises a casing H of any known type, defining within it a main chamber 17 for the refrigerant fluid. The fluid refrigerant contained in the main chamber 17 is in a two-phase state, i.e. in partly in the liquid state and partly in the vapor state. As already mentioned above illustrated, for the correct functioning of the system, it is necessary to monitor constantly and continuously the flows entering and exiting the chamber main 17 of the separator tank 10, in order to prevent the tank 10 can empty completely or fill completely. To this end, in the system according to the invention, the expansion valve 9 ad electric drive is checked, with a certain periodicity, by at least one electronic control unit E, based on an indicative signal S of the total mass of refrigerant contained in the separator tank 10. The S signal is sent by a level sensor device associated with a still tube T, having a lower end 22 (see figure 5) communicating with the main chamber 17 of the separator tank 10, in adjacent to the lower end of the main chamber 17, and one end upper 23 communicating with the main chamber 17 of the separator tank 10, adjacent to the upper end of the main chamber 17. Thanks to the above arrangement, the liquid level in the still tube T it is not affected by the turbulence to which the refrigerant fluid is subject inside the main chamber 17 of the separator tank 10. This turbulence arises both from the fluid flows entering the main chamber 17, both from the vapor state in boiling of part of the fluid in chamber 17, both from possible vibrations and movements to which the separator tank 10 is subject if it is installed at on board a vehicle. The solution described above therefore allows us to obtain a measure reliable coolant level in the T-tube, not affected from turbulence in the main chamber 17. Figure 4 shows a theoretical solution where a sensor device level L (e.g. an optical sensor) is used to detect the distance from the sensor L of the free surface V of the fluid in the separator tank 10. In the case of such solution, the output signal from sensor device L could not be considered a direct function of the total amount of fluid mass coolant contained in tank 10. Figure 5 shows the separator tank detail on an enlarged scale. 10 of figure 1, with the associated still tube T. Inside the still tube T there is a float F, configured in such a way so as to occupy almost the entire cross-section of the still tube T, whereby the vertical movement of the float F inside the tube T is driven by the same T tube. In the example shown, the level sensor device comprises a non-contact optical sensor, capable of detecting the distance of the float F from the L-sensor device. The optical L-sensor device can be made of any known way and is typically suited to operating in reflection. The float F is configured in such a way that it is always immersed only partially in the liquid inside the still tube T, so the upper end of the float F is always outside the liquid in the still tube T and is therefore "visible" from the L sensor. Of course, nothing excludes the use of any other type of sensor contactless (e.g. a magneto-resistive sensor) to detect the level of the liquid in the still tube T. In the preferred embodiment illustrated in Figure 5, the end the upper end of the still tube T communicates with the upper end of the chamber main 17 of the separator tank 10 through a narrow passage 19 of determined width. As already indicated above, the narrow passage 19 allows to equalize the pressure of the vapor phase in the still tube T and in the main chamber 17, when pressure variations are slow and / or moderate, while allowing a slight overpressure to be maintained in the stilling tube T compared to the main chamber 17, when rapid pressure drops occur in the main chamber 17 of the separator tank 10. This prevents the fluid in the still tube T evaporates quickly causing the float F and thus giving rise to inaccurate measurements. The aforementioned passage ristretto 19 can also be replaced by an automatic valve (check valve) which allows a bidirectional flow when the pressure delta between tank 10 and the T pressure pipe is lower than a predetermined value and does not allow the flow from the still pipe T to the main chamber 17 of the separator tank 10 when the pressure delta exceeds the predetermined value. In this second case the pressure between tank 10 and still pipe T is equalized through the opening on the liquid side but a rapid boiling under the is avoided floating. Figure 6 shows a variant of Figure 5, where the still tube T is made inside the casing H of the separator tank 10. Figure 7 illustrates a condition in which the separator tank 10 is located in a position inclined with respect to the vertical direction. In this case, the system can be equipped with means to detect the inclination of the tank and the electronic control unit can be configured to process the signal in output from the sensor device L, taking into account this inclination, in order to transform the data relating to the position of the float F in the still pipe into a figure relating to the total mass quantity of the refrigerant contained in the separator tank 10. Figure 2 illustrates a first preferred configuration of the system. cooling 1 according to the invention, wherein the cooling fluid coming from from the second outlet 13 of the separator tank 10 is sent in a plurality of lines 14A, 14B, 14C arranged in parallel, in which respective pumps are provided power supply 15A, 15B, 15C. Through lines 14A, 14B, 14C, the fluid refrigerant is sent to three heat exchangers 2A, 2B, 2C, associated with three several components to be cooled, after which the refrigerant fluid coming out of the heat exchangers return via lines 16A, 16B, 16C, to the second input 20 of the separator tank 17. In the case of the embodiment of figure 2, therefore, a single Separator tank 10 is associated with all heat exchangers 2A, 2B, 2C. Figure 3 illustrates a second preferred embodiment, in which are three heat exchangers 2A, 2B, 2C are foreseen for the cooling of three different components, similarly to what is shown in Figure 2. However, in this In this case, the three heat exchangers 2A, 2B, 2C are associated with respective circuits including separator tanks 10A, 10B, 10C, expansion valves 9A, 9B, 9C, and fuel pumps 15A, 15B, 15C. In the example in figure 3, a single Electronic control unit E receives signals from sensor devices L1, L2, L3, configured to detect the level in the still pipes T1, T2, T3, associated with the tanks separators 10A, 10B, 10C. In the case of figure 3, the refrigerant fluid along the line 8 coming out of capacitor 6 splits into three lines 8A, 8B, 8C, which conduct the refrigerant fluid to the three expansion valves 9A, 9B, 9C. For the otherwise, each separator tank operates in the manner described above. with reference to figures 1 and 5. Figure 8 shows a variant of the level sensor associated with the pipe. calm T. In this case the still tube is arranged concentrically inside of the separator tank 10 and the sensor L is of the known type including a rod of guide and measure K on which the float F is guided. As visible in figure 9, in this case preferably the two inputs 11, 20 are directed tangentially to the separator tank 10, which is of shape cylindrical. In this way a centrifugal separation effect is obtained between liquid and steam. As is evident from the above description, the system according to The invention ensures precise and reliable operation of the tank separator, or separator tanks, with which the system is equipped, with means simple and low cost. Naturally, without prejudice to the principle of the invention, the details of construction and forms of implementation may vary widely from as described and illustrated purely by way of example, without thereby departing within the scope of the present invention, as defined in the appended claims.

Claims

CLAIMS 1. Cooling system, using a two-phase refrigerant, for cooling a plurality of components, in particular on-board systems of a vehicle, such as the electric battery, the electric traction motor and the passenger compartment of an electric vehicle, said system including at least one refrigerant circuit comprising: - a compressor (3), - a condenser (6) for the refrigerant coming from the compressor (3), - an electrically controlled expansion valve (9; 9A, 9B, 9C), for expanding the refrigerant coming from the condenser (6), and - at least one separator tank (10;10A, 10B, 10C), for separating the liquid phase from the vapour phase of the refrigerant contained therein, said at least one separator tank having: - a first inlet (11), for receiving refrigerant fluid expanded from the expansion valve (9), - a first outlet (12), through which the refrigerant fluid is fed to the aforementioned compressor (3), - a second outlet (13), for feeding the refrigerant fluid in liquid phase from said separator tank (10; 10A, 10B, 10C) to at least one of a plurality of heat exchangers (2; 2A, 2B, 2C) associated with different components to be cooled, and - a second inlet (20), for returning to the separator tank (10; 10A, 10B, 10C) the refrigerant fluid which has passed through said at least one heat exchanger (2;2A, 2B, 2C), wherein said system further includes an electronic control unit (E), configured to control said expansion valve (9) in order to maintain the total mass of refrigerant fluid in the separator tank between a predetermined minimum threshold and a predetermined maximum threshold, wherein the separator tank (10; 10A, 10B, 10C) has a main chamber (17) communicating with a still pipe (T; T1, T2, T3) which is arranged and configured such that the level of refrigerant fluid in the still pipe (T) is substantially a direct function of the total mass of refrigerant fluid in the separator tank (10, 10A, 10B, 10C), and wherein the electronic control unit (E) is configured to control the expansion valve (9) as a function of the output signal from a level measuring device (F, L) associated with said still pipe (T;T1, T2,T3), so as to maintain the liquid level within the still pipe, and consequently the total mass of refrigerant in the separator tank, between said predetermined minimum threshold and said predetermined maximum threshold.; 2. System according to claim 1, characterised in that said level measuring device (L, F) comprises a float (F), arranged within the still pipe (T; T1, T2, T3) and configured to occupy substantially the entire cross-section of the still pipe, and a sensor (L) for detecting the position of the float.

3. System according to claim 2, characterised in that the sensor (L) is a contactless sensor (L), for example an optical sensor or a magneto-resistive sensor.

4. System according to claim 3, characterised in that said float (F) is configured to always remain only partially immersed in the fluid within the still tube (T; T1, T2, T3) and that said contactless sensor (L) is an optical sensor rigidly connected to an upper end of said still tube (T) and configured to detect the distance from the sensor (L) of an upper surface of said float (F).

5. System according to claim 2, characterised in that the sensor (L) comprises a guide and measuring rod (K), on which the float (F) is guided.

6. System according to claim 5, characterised in that the - 14 still tube (T) is arranged concentrically inside the separator tank (10), that the separator tank (10) has a cylindrical shape and that the two inlets (11, 20) of the separator tank (10) are arranged tangentially to the separator tank (10) so as to obtain a centrifugal separation effect between liquid and vapour.

7. System according to claim 1, characterised in that the separator tank (10; 10A, 10B, 10C) has a casing (H) defining said main chamber (17) and that the still pipe (T; T1, T2, T3) is arranged outside or inside the casing (H) and has: a lower end (22), communicating with the main chamber (17) adjacent to a lower end of the main chamber (17), and an upper end (23), communicating with the main chamber (17) adjacent to the upper end of the main chamber (17).

8. System according to claim 7, characterised in that the upper end (23) of the still pipe (T; T1, T2, T3) communicates with the main chamber (17) of the separator tank (10; 10A, 10B, 10C) via a narrow passage (19) of a determined width.

9. System according to claim 1, characterised in that the second inlet (20) and the second outlet (13) of the separator tank (10) are configured for the circulation of the refrigerant fluid through a plurality of heat exchangers (2A, 2B, 10A) associated with different components to be cooled.

10. System according to claim 1, characterized in that it comprises a plurality of separator tanks (10A, 10B, 10C), each having the second outlet (13) and the second inlet (20) configured for the circulation of the refrigerant fluid through a respective heat exchanger of a plurality of heat exchangers (2A, 2B, 2C) associated with the different components to be cooled.