THERMAL MANAGEMENT AND FILTER SYSTEM FOR ELECTRIC VEHICLES

Abstract

Thermal management system (1) for an electric vehicle (20), comprising: a first thermal circuit (110) for controlling a battery temperature; a filter (150) arranged upstream of the battery (50) in the first thermal circuit (110) for filtering liquid coolant; a second thermal circuit (120) in fluid communication with the first thermal circuit (110) for providing temperature control for a vehicle system other than the battery (50).

Description

The present invention relates to a thermal management and filtering system for a battery in an electric vehicle.Vehicles such as battery-electric vehicles (BEVs), plug-in electric vehicles (PEVs), or hybrid-electric vehicles (HEVs) include a battery such as a high voltage battery that functions as a power source for the vehicle. The capacity and the life of the battery may vary depending on the operating temperature of the battery. Generally, it is desirable to maintain the battery within a predetermined temperature range while the vehicle is operating or while the vehicle is charging.WO 2013 / 003 843 A2 discloses a cooling system for a vehicle with an electric motor, comprising a refrigerant-to-refrigerant heat exchanger.US 2012 / 0 247 713 A1 describes a battery temperature control system for a vehicle having a battery as a power source comprising a battery module having at least one battery cell and at least one liquid distribution pipe element. In order to change the temperature of the liquid, a heat exchanger is arranged in the liquid distribution pipe element.Vehicles with batteries may include a cooling system for providing temperature control of the battery to thereby maintain charge capacity, extend battery life, and improve other performance characteristics of the battery.It is an object of the invention to provide a thermal management system for an electric vehicle and a method for operating the same, which, in addition to temperature control of the battery, also enables temperature control of other vehicle systems.This object is achieved by thermal management systems for an electric vehicle according to Claims 1 and 10 and by a method according to Claim 17.In one embodiment, a thermal management system for an electric vehicle is provided. The thermal management system includes a first thermal circuit for regulating a battery temperature. A filter for filtering liquid coolant is disposed upstream of the battery in the first thermal circuit. The thermal management system also includes a second thermal circuit in fluid communication with the first thermal circuit. The second thermal circuit provides temperature control for a vehicle system other than the battery.In another embodiment, the first thermal circuit includes a heat exchanger adjacent the battery for regulating battery temperature. The heat exchanger has a constricted flow path.In another embodiment, the battery includes a plurality of battery cells, and the heat exchanger includes a plurality of heat exchange fins separating each of the battery cells. The heat exchanger fins provide a liquid coolant to regulate the temperatures of each of the battery cells.In yet another embodiment, the filter is disposed upstream of the heat exchanger.In another embodiment, the filter has a filtration transfer function based on a filter characteristic of the heat exchanger.In yet another embodiment, the filter transfer function comprises a filtration efficiency of 90 percent for a particle size, and the heat exchanger has a filtration efficiency of 100 percent for the particle size.In another embodiment, the first thermal circuit includes a pump. The filter is arranged downstream of the pump.In another embodiment, the thermal management system includes a third thermal circuit in thermal communication with the first and second thermal circuits for providing temperature control to a second vehicle system other than the battery.In another embodiment, the third thermal circuit includes an air conditioning system configured to control passenger compartment temperature.In another embodiment, a thermal management system for a battery in an electric vehicle is provided. The battery thermal management system includes a plurality of battery cells. A plurality of heat exchange fins are disposed between each of the battery cells to provide a liquid coolant for regulating battery temperature. A filter is disposed upstream of the ribs. The filter has a filtration transfer function based on a filter characteristic of the fins.In another embodiment, the battery thermal management system includes a pump for circulating the liquid coolant. The filter is arranged downstream of a pump.In another embodiment, the filter is a high pressure bypass filter.In another embodiment, the filter transfer function comprises a filtration efficiency of 90 percent for a particle size and the heat exchanger has a filtration efficiency of 100 percent for the particle size.In yet another embodiment, each of the heat exchange fins has a restricted flow path. The filtration transfer function of the narrowed flow paths is based on an evaluation of the heat exchanger fins according to the filter test method ISO 16889.In another embodiment, the battery cells, the heat exchanger fins, and the filter are arranged in a first thermo-loop. The first thermo-loop is selectively in fluid communication with a second thermo-loop that provides temperature control for a vehicle system other than the battery.In yet another embodiment, the liquid coolant is one of water or glycol.In another embodiment, a method for controlling the temperature of a battery in an electric vehicle is provided. A heat exchanger is provided for supplying a liquid coolant for regulating the battery temperature. A filter is provided. A filtration transfer function of the filter is based on a filtration characteristic of the heat exchanger.In another embodiment, the filtration characteristic is a filtration efficiency (FE).In another embodiment, the filtration characteristic comprises a third holding capacity (DHC).In yet another embodiment, the method includes evaluating a battery heat exchanger fin according to a filter test method to determine the filtration characteristic.The aforementioned embodiments and other aspects of the disclosure will be more fully understood in view of the appended drawings and the following detailed description of the exemplary embodiments. FIG. 1 is a schematic illustration of a battery-powered electric vehicle according to an embodiment; FIG. 2 is a schematic illustration of a battery thermal management system according to an embodiment; FIG. 3 is a perspective view of a filter according to an embodiment; FIG. 4 is a cross-sectional view of a filter according to an embodiment; FIG. 5 is a perspective view of a portion of a heat exchanger according to an embodiment; FIG. 6 is a cross-sectional view of a heat exchanger according to an embodiment; FIG. 7 is a simplified plan view of a portion of a heat exchanger according to an embodiment; FIG. 8 shows a filter selection method; FIG. 9 shows a characteristic curve based on the cumulative volume at different particle sizes; and FIG. 10 shows a characteristic curve based on the degree of filtration at various particle sizes.As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.Referring to FIG. 1, an electric vehicle 20, such as a battery powered vehicle (BEV), is illustrated in accordance with one or more embodiments. FIG. 1 illustrates only one type of BEV architecture and is not intended to be limiting. The present disclosure may be applied to any suitable BEV.The vehicle 20 or BEV is a fully electric vehicle that is propelled by electric power, such as by an electric motor 24, and without assistance from an internal combustion engine. The motor 24 receives electric power and provides rotational mechanical output power. The engine 24 is connected to a transmission 38 for adjusting the output torque and the speed of the engine 24 through a predetermined gear ratio. The transmission 38 is connected to a set of drive wheels 40 through an output shaft 42. Other embodiments of the vehicle 20 include multiple motors (not shown) for propelling the vehicle 20. A high voltage bus 44 electrically connects the motor 24 to an energy storage system 46 through an inverter 48.The energy storage system 46 includes a main battery 50 and a battery energy control module (BECM) 52, according to one or more embodiments. the BECM is configured to connect the vehicle 20 to a power source 78, such as a 110V source or a 220V source, and to transmit the received power to the battery 50 or the transmission control system 30. The main battery 50 is a high voltage battery or traction battery that can output electrical power to operate the motor 24. The main battery 50 is a battery pack made up of one or more battery modules. Each battery module may include one battery cell or a plurality of battery cells. The battery cells are heated and cooled using a fluid cooling system, air cooling system, or other cooling method known in the art. The BECM 52 functions as a controller for the main battery 50. the BECM 52 also includes an electronic monitoring system that controls the temperature and state of charge of each of the battery cells. The battery 50 includes at least one temperature sensor 51 such as a thermistor or the like. The sensor 51 is in communication with the BECM 52 to provide temperature data regarding the battery 50.The engine 24, transmission control module (TCM) 30, transmission 38, and inverter 48 are collectively referred to as driveline 54. The vehicle controller 26 communicates with the driveline 54 to coordinate the function of the driveline 54 with other vehicle systems. The controller 26, the BECM 52, and the TCM 30 are shown as separate control modules. The control system for the vehicle 20 may include any number of controllers and may be integrated into a single controller or may have different modules. Some or all of the controllers may be controlled by a local area network for vehicle monitoring computers (CAN. The controller area network) or other system may be connected. The control system may be configured to control operation of the various components of the driveline 54 and the battery 50 under any of a number of different conditions, including in a manner that thermally controls temperature in the battery 50 and the vehicle cabin or the passenger compartment, and for charging and discharging operations of the battery 50.The TCM 30 is configured to control specific components within the driveline 54, such as the motor 24 and / or the inverter 48. The vehicle controller 26 monitors the temperature of the engine 24 and receives a throttle request (or a desired engine torque request) from the driver. Using this information, the vehicle controller 26 provides a motor torque request to the TCM 30. The TCM 30 and the inverter 48 convert the direct current (DC) voltage supply through the main battery 50 into signals used to control the motor 24 according to the motor torque request.The vehicle controller 26 provides information to the driver through a user interface 60. The user interface 60 may include features that enable a user to input requests or desired vehicle operating or charging parameters or other vehicle operating parameters to the controller 26. The user interface 60 may include a touch screen surface, a wireless connection to a remote station such as a mobile device or computer, and other input interfaces known in the art. The vehicle controller 26 may also receive input signals indicative of current operating conditions of the vehicle systems. For example, the vehicle controller 26 may receive input signals from the BECM 52 representing states of the battery 50 and input signals from the driveline 54 representing states of the motor 24 and the inverter 48. The vehicle controller 26 provides an output, such as an engine status or state of charge status, to the user interface 60 which is visually communicated to the driver. The controller 26 mediates between the various user requests to thermally control the vehicle 20 during both charging and operation.The vehicle 20 includes a climate control system 62 for heating and cooling various vehicle components. The climate control system 62 includes a high voltage electric heater 64 and a high voltage HVAC electric compressor 66, according to one or more embodiments. the heater 64 is used to heat coolant circulating through the heater core, and the compressor 66 is used to cool the refrigerant that cools the passenger compartment and in some situations the battery. Both the heater 64 and the compressor 66 may draw electrical energy directly from the main battery 50. The climate control system 62 may include a controller (not shown) for communicating with the vehicle controller 26 via the CAN bus 56 or may be incorporated into the controller 26. The on / off status of the climate control system 62 is communicated to the vehicle controller 26 and may be based on, for example, the status of an operator-operated switch or the automatic control of the climate control system 62 based on associated functions such as window defrosting. The climate control system 62 may be connected to the user interface 60 to allow a user to set a temperature for the passenger compartment or reprogram a temperature for a future operating cycle of the vehicle.The vehicle 20 includes a secondary battery 68, such as a 12 volt battery, according to one embodiment. The secondary battery 68 may be used to power various accessories of the vehicle, such as headlights and the like, which are collectively referred to herein as accessories 70. A DC-DC converter 72 may be electrically interposed between the main battery 50 and the secondary battery 68. The DC-DC converter 72 adjusts or "transforms" the voltage level "down" to allow the main battery 50 to charge the secondary battery 68. A low voltage bus 74 electrically connects the DC-DC converter 72 to the secondary battery 68 and the auxiliary loads 70.The vehicle 20 includes a AC charger 76 for charging the main battery 50. an electrical connector 78 connects the AC charger 76 to an external power supply (not shown) for receiving AC power. The AC charger 76 includes power electronics used to convert or "rectify" the AC power received from the external power supply to AC power to charge the main battery 50. The AC charger 76 is configured to receive one or more conventional voltage sources from the external power supply (e.g., 110 volts, 220 volts, etc.). In one or more embodiments, the power supply includes a device that utilizes renewable energy, such as a photovoltaic (PV) solar cell or a wind turbine (not shown).Also illustrated in FIG. 1 are simplified schematic representations of a driver operator system 80, a power steering system 82, and a navigation system 84. The driver operator system 80 includes brake, acceleration, and gear selection (shift) systems. The brake system includes a brake pedal, position sensors, pressure sensors, or a combination thereof, as well as a mechanical connection to vehicle wheels, such as prime mover wheels 40, to perform friction braking. The brake system may also be configured for regenerative braking, where braking energy may be sensed and stored as electrical energy in the main battery 50. The accelerator system includes an accelerator pedal having one or more sensors that, like the sensors in the brake system, provide information, such as the throttle request, to the vehicle controller 26. The gear selection system includes a shift lever for manually selecting a gear setting of the transmission 38.The navigation system 84 may include a navigation display, a global positioning system (GPS) unit, a navigation controller, and inputs (not shown) for receiving destination information or other data from a driver. The navigation system may be incorporated into the user interface 60 in some embodiments. The navigation system 84 may also communicate range and / or location information associated with the vehicle 20, its travel destinations, or other relevant GPS waypoints.FIG. 2 illustrates a plurality of integrated thermal circuits or loops forming a thermal management system 100 for use with the vehicle 20 illustrated in FIG. 1. The thermal management system 100 includes a battery thermal loop 110, an engine loop 120, and a passenger compartment loop 130.The battery thermal loop 110 may heat and cool the battery 50. The battery 50 is comprised of one or more battery packs, and a battery 50 having one pack is shown in FIG. 2. Each battery pack may include multiple cells. The battery 50 in FIG. 2 is illustrated as having three cells 104, although any number of cells may be used with a battery 50, as is known in the art. The battery cells 104 are separated by heat exchange fins, shown in more detail in FIG. 5, that are used to regulate the temperature of each of the battery cells 104.The controller 106, which may be a vehicle controller in communication with or incorporated into the battery control module, monitors the battery 50 to determine the state of charge and capacity of the battery 50. Each cell 104 may have an associated temperature sensor configured to measure the cell temperature. The temperature sensor is in communication with the controller 106 such that the controller 106 also monitors the battery temperature by monitoring the temperature of each battery cell 104. The controller 106 determines the temperature of the battery 50 by measuring or estimating the temperatures of the various battery cells 104.The controller 106 is also in communication with an ambient temperature sensor 102 on the vehicle. The ambient temperature sensor 102 is configured to measure the temperature of the external environment. A cabin temperature sensor 112 is also in communication with the controller 106 and measures the temperature of the cabin to provide feedback to the HVAC system for climate control in the cabin.The temperature of the battery 50 may be actively controlled using the battery thermal loop 110 controlled by the controller 106. The temperature of the battery 50 and each cell 104 determines the amount of charge that the battery 50 can take and the amount of charge that can be used when stored in the battery 50.The battery thermal loop 110 thermally controls the battery 50 to regulate the temperatures of the cells 104 to maintain the useful life of the battery 50, allow adequate charge, and meet the vehicle performance attributes. The battery thermal loop 110 provides active heating or active cooling of the battery cells 104 by liquid heat transfer in the heat exchange fins 300 (FIG. 5 ) of the battery cells 104. The battery thermal loop 110 may be integrated into a vehicle thermal system that includes both climate control heating and cooling elements and powertrain cooling elements.The battery thermo-loop 110 contains a fluid that circulates through cooling channels in the heat exchange fins 300 adjacent to the cells 104 in the battery to heat or cool the battery 50 primarily using convective heat transfer. The fluid is a liquid coolant, such as glycol or water, that helps control the temperature of the battery cells 104. A pump 114 controls the flow of fluid in the battery thermal loop 110. A heating element 116 acts as a heat source for the fluid to heat the fluid, which in turn actively heats the battery 50. The heating element 116 may be a heat exchanger with another thermal system in the vehicle for recovering waste heat, or it may be an independent heater, such as an electrically powered heater, including a positive thermal coefficient (PTC) heater.The battery thermal loop 110 also includes a chiller element 118 or heat sink that cools the fluid that in turn actively cools the battery 50. The chiller element 118 may be part of a vapor compression or vapor acquisition cycle, a heat exchanger with another element in the vehicle thermal systems, or another heat sink known in the art. The heat exchangers in the chiller element 118 may be co-current, counter-current, or other heat exchangers known in the art that adequately heat or cool the fluid in the battery thermal loop 110.The battery thermal loop 110 also includes the BECM 52. The BECM 52 may also generate heat and also require cooling during use to maintain the BECM 52 within an appropriate temperature range. The battery thermal loop 110 may also pass through the battery charger to actively heat or cool the BECM 52 and charging components. A battery valve 140 is provided for selectively coupling the battery thermal loop 110 and the motor loop 120.The engine loop 120 cools the traction motor 24, the transmission control system 30, and the DC-DC converter 72. The engine loop 120 also includes a radiator 122 and an engine pump 124 positioned to pump heat exchange fluid through the engine loop 120. The motor pump 124 may be disposed at an allowable position along the motor loop 120.When the radiator bypass valve 126 is in the first position, all of the heat exchange fluid flow is directed in direction A and through the radiator 122. Conversely, when the cooler bypass valve 126 is in the second position, the entire heat exchange fluid flow is directed in direction B. In direction B, the fluid bypasses the radiator 122 if possible, such as when the heat exchange fluid is below a threshold temperature. In direction B, bypassing the radiator 122 reduces the pressure drop across the radiator 122. The higher pressure fluid reduces the amount of work required of the pump 124, which reduces power consumption. By reducing the energy consumption of the vehicle, fuel efficiency is increased and / or the current range of the vehicle through the battery 50 is extended.A temperature sensor 128 may be provided for determining the temperature of the heat exchange fluid at a selected location in the engine loop 120. As shown, temperature sensor 128 may be positioned downstream of all thermal loads, such as motor 24, TCM 30, and DC-DC converter 72, to detect the highest temperature of the heat exchange fluid. Based on the temperature determined by the temperature sensor 128, a controller, such as the controller 106, may determine whether or not to place the radiator bypass valve 126 in the first position in which fluid flow in direction A is directed through the radiator 122, or in the second position when fluid flow bypasses the radiator 122 in direction B.The passenger compartment loop 130 includes the HVAC system for the vehicle or the climate system for the passenger compartment of the vehicle as shown. The passenger compartment loop 130 includes a fluid loop having a pump 132 and a chiller 134 for supplying cooled fluid to the HVAC system to supply cold air to the passenger compartment air nozzles.The passenger compartment loop 130 may also include a heater 136, such as a PTC heater, that supplies warm air to the passenger compartment. The passenger compartment loop 130 may include a recirculation loop for re-heating the passenger compartment air, and may also include a fresh air intake to additionally provide outside air to the passenger compartment.A cabin loop valve 144 is provided for selectively providing heat exchange fluid to the cabin loop. In a first position, the cabin loop valve 144 directs fluid flow in direction E to the cabin loop 130 and the heater core element 134. In the second position, the cabin loop valve 144 is arranged to direct fluid flow in direction F to the engine loop 120 to disconnect the cabin loop 130. The cabin loop valve 144 allows the cabin loop 130 to be disabled to conserve energy when the temperature is such that heating and / or cooling of the cabin is not required.The battery thermal loop 110, the engine loop 120, and the cabin loop 130 are three separate but integrated thermal loops. Loops 110, 120, and 130 may close three separate valves and function independently of each other using three separate pumps. Or, the loops 110, 120, and 130 may be selectively mixed such that, for example, waste heat from the engine 24 may be used to heat the passenger compartment or heat the battery 50. The multi-integrated thermal loop architecture minimizes the components that would be required in each of the loops 110, 120, and 130 if each loop were separate, thereby enabling cost and weight savings, for example.Also, the filter 150 may be incorporated into a thermal management system having a plurality of integrated thermal loops having a different configuration. For example, the filter may be disposed in a thermal management system in which a battery loop and a motor loop are disposed in parallel, such as U.S. Patent Application No. 13 / 757,291 (US 2014 / 0 216 709 A1), filed on Feb. 1, 2013, the disclosure of which is hereby incorporated by reference.However, a disadvantage of the multi-integrated thermal loop architecture is that contaminants from one loop may potentially contaminate another loop. In particular, contaminants and contaminants introduced into the battery thermal loop 110 could pose a major problem in the very narrow cooling channels of the heat exchange fins 300. Contaminants and contaminants may be present in the engine loop 120 or the cabin loop 130 from manufacturing and assembly processes or even from component wear.To protect the battery cells 104 from contamination in the thermal system, the battery thermal loop 110 also includes a filter 150. 150 is disposed upstream of the battery 50 to filter contaminants from the battery loop 110 as well as contaminants from the engine loop 120 or the climate loop 130 before the contaminants enter the narrow cooling channels 310 in the heat exchanger fins 300.As illustrated in FIG. 3, the filter 150 is a bypass filter. The filter includes a filter housing 152. The filter housing may be injection molded from plastic or may be a metal container or any other suitable material. The filter 150 also includes an inlet cover 154 and an outlet cover 156. The inlet cover 154 has an inlet connection 158. The inlet port 158 may include a barbed opening 160 for connection to the battery thermal loop 110. It is also contemplated that the inlet port 158 may include a threaded opening, a quick connect, or any other suitable opening for connecting to the battery thermal loop 110. Similarly, the outlet cover 156 has an outlet connection 162. In one embodiment, the inlet cover 154 and the outlet cover 156 are secured to the housing 152 by sonic welding. The inlet cover 154 and the outlet cover 156 may be secured to the housing 152 by any suitable means, such as hemming or welding. The inlet cover 154 and the outlet cover 156 may also include attachment features 164 configured to receive attachment elements or to be assembled to a component.FIG. 4 is a cross-sectional view through line 4- 4 of FIG. 3 ; the cross-sectional view illustrates the center tube 168 and the filter media 170 within the filter housing 152. The center tube 168 is a cylindrical net-like support structure on which the filter medium 170 is mounted. The center tube 168 and the filter media 170 include a seal 172 at a first end and a seal 174 at the second longitudinal end. Liquid coolant enters the inlet port 158 and may flow around the lateral sides 176 of the filter media 170, with fluid passing through the filter media 170 and then exiting the outlet port 162. The filter media 170 traps any contaminants along the lateral sides 176 to thereby prevent the contaminants from exiting the outlet spout 162.The filter 150 also includes a pressure relief valve 180. The pressure relief valve includes a ball 182 and a spring 184. When the filter media shell 170 becomes clogged with contaminants, fluid flow through the filter 150 may be restricted and system pressure may increase. In this situation, system pressure on ball 182 compresses spring 184 and allows fluid flow to bypass media sheath 170. The bypass valve 180 can be activated only in emergency situations with high contamination.FIG. 5 illustrates a heat exchanger fin 300 having cooling channels 310. Cooling paths 312 are formed in aluminum sheets. At least two heat exchanger fins 300 are joined together by brazing to form cooling channels 310 when the adjacent paths 312 are aligned, as shown in the cross-sectional view in FIG. 6. The cooling paths 312 may be formed as a depression in a serpentine pattern along the otherwise generally planar surface of the heat exchange fins 300. Shoulders 314 are formed between the paths 312. An outer flange 316 extends around the circumference of the heat exchanger fins 300. The shoulders 314 and the outer flanges 316 are generally in the same plane such that when two adjacent fins are joined together by brazing, the shoulders 314 and the outer flanges align with corresponding features on the adjacent heat exchanger fin 300 and form a brazed or soldered joint 318.The resulting cooling channels 310 formed between two heat exchanger fins 300 are convoluted passageways having a width B that can be about 10 to 15 millimeters wide. The distance C of the cooling channels 310 is a distance between the heat exchanger fins and may be less than 0.8 millimeters.The heat exchange fins 300 may be vertically positioned such that fluid passing through the passages flows from a lower inlet 320 to an upper outlet 322 of each heat exchange fin 300. Although this type of fluid passage geometry is optimized for heat exchange purposes by maximizing the surface area of the heat exchanger surface, it is very susceptible to contamination by contaminants. A low flow rate of the coolant within the passages results in low coolant velocity and laminar flow conditions (e.g., Reynolds number < 70) that prevent the flushing of contaminants and contaminants from the cooling channels 310 under normal operating conditions. As a result, the heat exchange fins 300 and the cooling channels 310 formed therein function similarly to individual filter elements.As shown in a simplified view of the cooling channels in FIG. 7, laminar fluid flow in the cooling channels 310 results in mechanical retention of larger contaminants 330. The larger contaminants 330 may be greater than the distance C and in this illustration greater than 0.8 millimeters. The fluid flow in the cooling channels 310 also promotes gravity deposition, wherein fine particulate matter 332 suspended in the coolant is deposited as contaminants on a bottom portion 336 of the vertical channels 338 by gravity separation under gravitational force.The filter 150 is used to ensure the purity of the cooling fluid and the cooling channels 310 of the heat exchange fins 300. The filter 150 is characterized by filtration efficiency (FE) or beta ratio according to international standards (ISO). The FE or beta ratio is a relationship between the number of particles greater than a predetermined size, upstream of the filter and downstream of the filter, using systems for counting standard contaminants and particles. The filter 150 may also be characterized by dirt holding capacity (DHCP). The DHC is defined as the weight of contaminants that can be captured by the filter media 170 until the filter reaches a predetermined final differential pressure.International Standard ISO 16889 is a multipass method for evaluating filtration performance of a filter element, which is most commonly used for measuring filtration performance, including filtration efficiency and dirt holding capacity, of filters.The FE and DHC of filter media are factors that aid in determining the surface area of filter media. The surface area of filter media affects the outside dimension of the filter assembly as well as the weight and cost of the filter. Generally, high FE and high DGC filters must be sized larger with high efficiency due to the lower fluid permeability (i.e., higher flow resistance) of filter media.The heat exchanger fins 300 used in BEVs present new challenges due to the extremely narrow cooling channels 310 that are very susceptible to contaminants and contaminants and themselves function as filters. The cooling channels 310 are configured to operate at very low flow rates to provide maximum convective cooling for the battery cells 104. In addition, the liquid coolant may be water or glycol coolant or a mixture thereof, which may cause oxidation leading to the generation of additional contaminants. Therefore, a unique filter and method for specifying a filter upstream of the heat exchange fins are required.Typically, an empirical approach is used to select a filter with an FE and a DHCP that provide sufficient protection for the heat exchanger fins 300. The empirical approach could result in excessive or insufficient filtration. In the case of excessive filtration, a very dense filter medium or filter medium with high filtration efficiency is used, resulting in a filter that provides excessive protection against contaminants, but at the same time provides additional resistance to hydraulic coolant flow that results in additional power consumption of an electrically operated coolant pump. If the filter media is too coarse or inefficient, it may allow large contaminants to pass downstream of the filter, which could lead to plugging of cooling channels.To determine the requirements of the filter 150 in selecting a filter that provides sufficient FE and DHC to protect the heat exchanger fins 300 from contaminants, a new filter selection method 400 illustrated in FIG. 8 has been developed. The heat exchanger fins 300 are evaluated as a lower efficiency functional filter located downstream of the primary filter 150, as represented by block 410. The heat exchanger fins 300 were evaluated using the experimental setup described in the ISO 16889 multipass efficiency method, as represented by block 412. The pressure is kept constant, while the flow rate could vary depending on the contamination state of the heat exchanger. The experiment is carried out for at least two hours until the flow rate is reduced by 20%.Based on the experiment, a filtration characteristic of the heat exchanger fins is determined, as represented by block 414. For example, a "percent retention" of impurity in the cooling channels 310 is calculated according to the guidelines of ISO 16889. According to an example shown in FIG. 10, within the cooling channels 310, 30% standard impurity dust was retained per weight, meaning that 70% of the impurity remained in suspension.The maximum particle size corresponding to 30% of the distribution is determined on the assumption that larger size particles are retained in the cooling channels 310 and using properties of cumulative distribution of standard dust weight versus particle size. Then, the filtration characteristics of the filter 150 are selected to be greater than the filtration characteristics of the heat exchange fins 300, as represented by block 416. The FE of the filter 150 may be selected according to ISO 16889 such that at least 90% of a particle size greater than a corresponding particle size found at a volume percentage point in a cumulative size and weight distribution according to ISO 16889 is equal to or less than the calculated "percent retention" of 90%.FIG. 9 illustrates a method for selecting the filtration characteristics of the medium of the filter 150 based on the filtration characteristics of the heat exchange fin at different particle sizes. The filtration characteristic is generated using a standard test method such as ISO 16889. The cumulative volume as a percentage of contaminants is shown on the y-axis. The particle size, measured in microns, is shown along the x-axis.FIG. 9 illustrates the filtration characteristics when impurity dust of a known volume and particle sizes is introduced into the heat exchange fins. The contaminant dust passing through the heat exchange fins is collected and analyzed for each of the particle sizes based on the percentage of contaminants passing through the heat exchange fins. For example, as shown in Figure 9, a known amount of 20-micron particles is introduced into the heat exchanger and only 70% pass through the heat exchanger fins. Therefore, 30% of the contaminants having the size of 20 micrometers are trapped in the cooling channels of the heat exchanger fin. The filtration characteristic 420 is empirically obtained. The filtration characteristic 420 may be used for obtaining the transfer function of the filter 150.FIG. 10 illustrates a method for selecting filter media based on the filtration characteristic of the heat exchange fin at various particle sizes. Filtration efficiency (FE) for a given particle size is shown on the y-axis. The particle size, measured in microns, is shown along the x-axis. Figure 10 illustrates these filtration test results (according to ISO 16889) which show a filtration efficiency of 90% for particle sizes above 20 microns. Filtration efficiency (FE) represents the number of particles greater than the predetermined particle size upstream of the filter minus the number of particles greater than the predetermined size downstream of the filter divided by the number of particles greater than the predetermined particle size upstream of the filter represented by the following equation:The filtration characteristic 430 may be used for obtaining the transfer function of the filter 150. Based on the filtration characteristics 420, 430 depicted in the graphs of FIGS. 9 and 10, there may be many options for selecting filter media suitable for the filter requirement as long as a minimum FE requirement is met, such as 90% efficiency at a particle size of 20 microns. Typically, the media selection process is terminated by identifying a media type having a minimum flow resistance per unit area that meets the aforementioned criteria.While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the terms used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. In addition, the features of various implementations of embodiments may be combined to form further embodiments of the invention.

Claims

A thermal management system (1) for an electric vehicle (20), comprising: a first thermal circuit (110) for regulating a battery temperature; a filter (150) disposed upstream of the battery (50) in the first thermal circuit (110) for filtering liquid coolant; a second thermal circuit (120) in fluid communication with the first thermal circuit (110) for providing temperature regulation to a vehicle system other than the battery (50).The thermal management system (1) of claim 1, wherein the first thermal circuit (110) comprises a heat exchanger having a constricted flow path adjacent the battery (50) for regulating battery temperature.The thermal management system (1) of claim 2, wherein the battery (50) comprises a plurality of battery cells (104), and the heat exchanger comprises a plurality of heat exchange fins (300) separating each of the battery cells (104) to provide a liquid coolant for controlling the temperatures of each of the battery cells (104).The thermal management system (1) of claim 2, wherein the filter (150) is disposed upstream of the heat exchanger.The thermal management system (1) of claim 2, wherein the filter (150) has a filtration transfer function based on a filter characteristic of the heat exchanger.The thermal management system (1) of claim 5, wherein the filtration transfer function has a filtration efficiency of 90 percent for a particle size, and the heat exchanger has a filtration efficiency of 100 percent for the particle size.The thermal management system (1) according to claim 1, wherein the first thermal circuit (110) comprises a pump (114), the filter (150) being arranged downstream of the pump (114).The thermal management system (1) of claim 1, further comprising a third thermal circuit (130) in thermal communication with the first (110) and second thermal circuits (120) for providing temperature control to a second vehicle system other than the battery (50).The thermal management system (1) of claim 8, wherein the vehicle system in the third thermal circuit (130) comprises an air conditioning system configured to regulate a passenger compartment temperature.A thermal management system (1) for a battery (50) of an electric vehicle (20), comprising: a plurality of battery cells (104); a plurality of heat exchange fins (300) disposed between each of the battery cells (104) to provide liquid coolant for controlling battery temperature; and a filter (150) disposed upstream of the heat exchange fins (300) and having a filtration transfer function based on a filter characteristic of the heat exchange fins (300).The thermal management system (1) for a battery (50) according to claim 10, further comprising a pump (114) for circulating the liquid coolant, wherein the filter (150) is disposed downstream of the pump (114).The thermal management system (1) for a battery (50) according to claim 10, wherein the filter (150) is a high-pressure bypass filter.The thermal management system (1) for a battery (50) of claim 10, wherein the filtration transfer function has a filtration efficiency of 90 percent for a particle size, and the heat exchanger has a filtration efficiency of 100 percent for the particle size.The thermal management system (1) for a battery (50) according to claim 10, wherein each of the heat exchange fins (300) has a constricted flow path, and the filtration transfer function of the constricted flow paths is based on evaluating the heat exchange fins (300) according to a filter test method according to ISO 16889.The thermal management system (1) for a battery (50) of claim 10, wherein the battery cells (104), the heat exchange fins (300), and the filter (150) are disposed in a first thermal loop selectively in thermal communication with a second thermal loop providing temperature control for a vehicle system other than the battery (50).The thermal management system (1) for a battery (50) according to claim 10, wherein the liquid coolant is one of water or glycol.A method for controlling a battery temperature in an electric vehicle (20), the method comprising: establishing a filtration transfer function of a filter (150) based on a filtration characteristic of a heat exchanger for providing a liquid coolant for controlling the battery (50).The method of claim 17, wherein the filtration characteristic comprises filtration efficiency.The method of claim 17, wherein the filtration characteristic comprises a dirt holding capacity.The method of claim 17, further comprising evaluating a battery heat exchanger fin (300) according to a filter test method to determine the filtration characteristic.

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