THERMALLY ACTIVE UNIT AND A METHOD THEREOF

TECHNICAL FIELD

[0001] At least one embodiment of the present invention pertains to a device and a method, and more particularly, to a device and a method for estimating an operational status of a thermally active unit.

BACKGROUND

[0002] Air-cooled electric energy storage systems are typically used in Electric Vehicle (EV), Plug-in Hybrid Electric Vehicle (PHEV), and/or Hybrid Electric Vehicle (HEV) applications. Generally, a device that generates air flow for the air coolingincludes a fan.

[0003] In some applications in the automobile industry.cooling air is extracted from a vehicle cabin. The air quality in terms of temperature, absolute pressure, humidity, and/or particle load of the extracted air cannot be controlled by a controller and must be accepted asdelivered.

[0004] Currently, in order to determine cooling requirements, typically the temperature of a thermally active unit such as battery cells or modules of the electric energy storage system are measured by one or more temperature sensors. The measured temperatures are used as reference variables or set points to adjust the fan speed in order to adjust the required air mass flow. For this purpose, the fan speed is typically controlled by the energy storage system management device, i.e., a Battery Management System (BMS), in case of a Li-battery. Although the fan speed can be increased or decreased, the amount of increment or decrement in air flow cannot be determined precisely, therefore the temperature of the thermally active unit might not be adjusted accurately.

[0005] Further, the above solely relies on the temperature of the thermally active unit, and the solution adjusts the temperature of the thermally active unit only after a temperature of thethermally active unit is overheated. The above solution employs feedback or closed loop control, which cannot optimally predict an operational status of the thermally active unit.

[0006] Accordingly, a new device and method may be needed to predict operational status of the thermally active unit, and/or accurately adjust temperature of the thermally active unit.

SUMMARY

[0007] Embodiments of the present invention provide a device, a method, a system and computer readable mediumofestimating operational status of a thermally active unit based on a heat loss of the thermally active unit, a first temperature of the thermally active unit and the difference between a temperature T^of a fluid inlet of a housing that holds the thermally active unit and the temperature T _oui of a fluid outlet of the housing.

[0008] In an embodiment, a device comprises a housing, the housing having a fluid inlet and a fluid outlet;a thermally active unit within the housing;a fluid conveying device positioned to convey fluid within the housing;a first temperature sensor configured to measure a first temperature T^of the thermally active unit;a second temperature sensor configured to measure a temperature T _in of the fluid at the fluid inlet of the housing;a third temperature sensor configured to measure a temperature T _out of the fluid at the fluid outlet of the housing; anda controller communicatively coupled to the first temperature sensor, the second temperature sensor and the third temperature sensor, and configured tocalculate a heat loss iT _joss depending on the electric current passing through the thermally active unit, and a stored thermal energy E _stored \n the thermally active unit, and estimating an operational status of the thermally active unit based on the heat loss E _loss , the first temperature, the stored thermal energy ¾i ₀ ed ^{in tne} thermally active unit and the difference between the temperature T _; and the temperature T _OMt .

[0009] In an embodiment, a method comprises measuring a first temperature of a thermally active unit, wherein the thermally active unit is configured to be within a housing;measuring a temperature T _; of a fluid at a fluid inlet of the housing, the fluid being conveyed within the housing by a fluid conveying device; measuring a temperature T _out of the fluid at a fluid outlet of the housing; calculating a heat loss iT _joss depending on the electric current passing through the thermally active unit and a stored thermal energy E _stored in the thermally active unit within a time interval At, estimating an operational status of the thermally active unit based on the heat loss E _loss , the first temperature the stored thermal energy E _stored , and the difference between the temperature T _in and the temperature T _out .

[0010] In an embodiment, a systemcomprisesa temperature monitoring module, configured to receive a first temperature T _j Of a thermally active unit within a housing from a first temperature sensor, a temperature T _; of the fluid at a fluid inlet of the housing from a second temperature sensor, and a temperature T _out of the fluid at an fluid outlet of the housing from a third temperature sensor;a calculating module, configured to calculate a heat loss E _loss of the thermally active unit and a stored thermal energy E _stored in the thermally active unit; and an estimating module, configured to estimate an operational status of the thermally active unit based on a heat lossi^of the thermally active unit, the first temperature τγ, the stored thermal energy £ _{Sio ed} and the difference between the temperature T _; and the temperature T _OMt ..

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] One or more embodiments of the present invention are illustrated byway of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements.

[0012] Fig. 1 is a diagram illustrating a vehicle systemaccording to an embodiment of the invention.

[0013] Fig. 2 is a high-level extent diagram illustrating an example of the architecture of thecontroller of Fig. 1.

[0014] Fig. 3 is a block diagram illustrating elements of a processor or memory or a combination thereof of Fig.2.

[0015] Fig.4 is a block diagram illustrating heat transfer in the thermally active unit. [0016] Fig.5 is a diagram illustrating a device according to an embodiment. [0017] Fig.6 is a diagram illustrating a device according to another embodiment. [0018] Fig.7 is a diagram illustrating a device according to another embodiment. [0019] Fig. 8A shows a flow chart of a method according to an embodiment of the invention.

[0020] Fig. 8B shows a flow chart of a method according to an embodiment of the invention.

[0021] Fig. 8C shows a flow chart of a method according to an embodiment of the invention.

DETAILED DESCRIPTION

[0022] References in this description to "an embodiment," "one embodiment," or the like, mean that the particular feature, function, structure or characteristic being described is included in at least one embodiment of the present invention. Occurrences of such phrases in this specification do not necessarily all refer to the same embodiment. On the other hand, such references are not necessarily mutually exclusive either.

[0023] In embodiments of the invention, the term fluid includes at least one of liquids, gases or their combination that can flow and deform. The gas mayinclude air or other gases that can easily carry away heat. The liquid mayincludea heat transfer liquid, such as water, or water with additives, such as corrosion inhibitors and antifreeze. The combination of the liquid and gas can include a substance that may undergo a phase transition to change from gas to liquid or vice versa.

[0024] In order for an easy understanding of the invention, symbols used in the following description are introduced first in Table 1 :

Table 1

Symbol Unit Description

Cpactive mass kJ/(kgK) Specific heat capacity atconstantpressure of the thermally active unit

V fluid kJ/(kgK) Specific heat capacity atconstantpressure of the fluid

I A Electric current passing through the thermally active unit

Tractive mass kg Mass of the thermally active unit

m fluid Kg/s Mass flow of the fluid throughthe thermally active unit

Q fluid W Fluid heat flow

QLOSS W Thermal output generated by the thermally active unit

Qstored W Heat flowof the thermally active unit within the housing

R Ω Internal electric resistance of the thermally active unit t s Time length of a time interval

Tj K Temperature of the thermally active unit at the beginning of the time interval

T ₂ K Temperature of the thermally active unit at the end of the time interval

T ¹ i-n K Temperature of the fluid at the fluidintake of the housing

T out K Temperature of the fluid at the fluidoutlet of the housing

[0025] Fig. 1 is a diagram illustratinga vehicle systemlO according to an embodiment of the invention.

[0026] As shown in Fig. 1, the system 10 comprises a housing 100, at least one thermally active unit 180, a first temperature sensor 110, a second temperature sensor 120, a third temperature sensor 130, a fluid conveying device 170, and a controller 140. The housing 100 has a fluid inlet 102 and a fluid outlet 104. Channels 150 and 160 are shown for the purpose of illustrating fluid flow into and out of the housing 100. Those having ordinary skill in the art can understand that the channels 150 and 160 are optional and can be omitted. As shown in Fig. 1, the fluid inlet 102 of the housing 100 receives fluid. The fluid outlet 104 of the housing 100 discharges fluid. In an embodiment, the fluid inlet is positioned to receive fluid from a different location within the vehicle system 10 and/or from outside the vehicle system 10. The first sensor 110 is positioned adjacentto or on at least one the thermally active unit 180. The second sensor 120 is positioned at thefluid inlet 102 of the housing 100 (e.g., in the fluid inlet 102, or adjacentto the fluid inlet 102, etc.), and the third sensor 130 is positioned at thefluid outlet 104 of the housing 100. Those having ordinary skill in the art can understand that although this embodiment uses vehicle system 10 as an example, it is only illustrative and embodiments of the invention are not restricted to vehicle system, it can further apply to other electric systems, etc..

[0027] In the above embodiment, only one first temperature sensor, one second temperature sensor and one third temperature sensor are shown in Fig. 1. However, those having ordinary skill in the art can appreciate that the number of the sensors are not limited by the above embodiment. For example, in an embodiment, the thermally active unit may include a plurality of sub units, for example, a plurality of cells. The system 10 may include a plurality of first temperature sensors. Each of the first temperature sensors is positioned adjacent a respective cell and obtain a respective temperature. The first temperature can be obtained, for example, by averaging the respective temperature obtained by the plurality of first temperature sensors. Alternatively, the first temperature can be obtained by selecting the maximum of the plurality of the temperatures. In an embodiment, the system 10 can further include a plurality of second temperature sensors.

[0028] Figure 1 illustrates that the housing 100 encapsulates a plurality of battery cells. However, those having ordinary skill in the art can understand that housing 100 may include walls surrounding a single battery cell, for fire prevention for example. For example, when battery cells are separated by dividers, two adjacent dividers can be viewed as two walls of the housing. In other words, the housing 100 may include only a single battery cell instead of a whole battery cell package.

[0029] The thermally active unit 180 may comprise any unit that may generate heat, for example, when current passesthrough the thermally active unit 180, or when the thermally active unit 180 does work through movement relative to other components. The thermally active unit 180 may include an energy storage device, such as a battery pack or battery cells, and it may alternatively include other electrical component with a fluid cooling system that uses current and can generate heat when the current passesthrough, for example, a luminaire in a projector.

[0030] When the thermally active unit 180 heats up, it is desirable that fluid, and cooling fluid in particular.beprovided to the thermally active unit 180, so that the thermally active unit 180 can be cooled down, and the performance of the thermally active unit 180 may not be severely degraded due to the heat. However, sometimes warming fluid is also desirable. For example, when in cold weather, the performance of the battery cells is degraded. Therefore warm fluid flow to the battery cells may be desirable to improve battery performance.

[0031] Fig.2 is a high-level extent diagram illustrating anexample architecture 200 of the control unit 140 of Figure 1. The architecture 200 includes one or more processors 210 and memory 220 coupled to an interconnect 240. The interconnect 240 shown in Fig. 2 is an abstraction that represents any one or more separate physical buses, point-to-point connections, or both, connected by appropriate bridges, adapters, or controllers. [0032] The processor(s) 210 is/are the central processing unit (CPU) of the architecture 200 and, thus, control the overall operation of the architecture 200. In certain embodiments, the processor(s) 210 accomplish this by executing software or firmware stored in memory 220. The processor(s) 21 0 may be, or may include, one or more programmable general-purpose or special-purpose microprocessors, digital signal processors (DSPs), programmable controllers, application specific integrated circuits (ASICs), programmable logic devices (PLDs), or the like, or a combination of such devices.

[0033] The memory 220 is or includes the main memory of the architecture 200. The memory 220 represents any form of random access memory (RAM), read-only memory (ROM), flash memory, or the like, or a combination of such devices. In use, the memory 220 may contain, among other things, software or firmware code for use in implementing at least some of the embodiments of the invention introduced herein.

[0034] Note that the output device(s) 230 and the input device(s) 250, like other devices, are optional. The interconnect 240 provides the connection between the input device 250, the output device 230 and the processor 210. The interconnect 240 provides the architecture 200 with the ability to communicate with other components in the device 1 0, or to provide the interface to other computers, devices, etc. (e.g., the temperature sensors) via WiFi or wired connections etc. The interconnect 240 may be, for example, an Ethernet adapter or Fibre Channel adapter. The input device 250 may include a touch screen, keyboard, and/or mouse, etc. The output device 230 may include a screen and/or speakers, etc.

[0035] The techniques introduced above can be implemented by programmable circuitry programmed/configured by software, firmware and/or hardware , or entirely by special-purpose circuitry, or by a combination of such forms. Such special-purpose circuitry (if any) can be in the form of, for example, one or more application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), etc.

[0036] Software or firmware to implement the techniques introduced here may be stored on a machine-readable storage medium and may be executed by one or more general-purpose or special-purpose programmable microprocessors. A "machine- readable medium", as the term is used herein, includes any mechanism that can store information in a form accessible by a machine (a machine may be, for example, a computer, network device, cellular phone, personal digital assistant (PDA), manufacturing tool, any device with one or more processors, etc.). For example, a machine-accessible medium includes recordable/non-recordable media (e.g., read-only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; etc.), etc.

[0037] The term "module", as used herein, means: a) special-purpose hardwired circuitry, such as one or more application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), or other similar device(s); b) programmable circuitry programmed with software and/or firmware, such as one or more programmed general-purpose microprocessors, digital signal processors (DSPs) and/or microcontrollers, or other similar device(s); or c)software or d) a combination of the forms mentioned in a), b)and/or c).

[0038] Fig. 3 is a block diagram illustrating elements of a memory 220, a processor 210 or a combination thereofof Fig. 2, which includes a temperaturemonitoring module 310, a calculating module 320, anestimating module 330, a warning module 340 and astateadjustingmodule 350.

[0039] As shown in Fig.3, the temperature monitoring module 310 receives a first temperature of a thermally active unit 180 from the first temperature sensor 110, a temperature T _in of the fluid at a fluid inlet 102 of the housing 100from the second temperature sensor 120, and a temperature T _oui pf the fluid at a fluid outlet 104 of the housing 100 from the third temperature sensor 130.

[0040] The calculating module 320 calculates a heat loss of the thermally active unit 180.

[0041] Theestimating module 330 estimates an operational status of the thermally active unit 180 based on a heat lossi^of the thermally active unit 180, the first temperature, a stored thermal energy E _stored in the thermally active unit, and the difference between the temperature T^and the temperature T _out .

[0042] The current monitoring module 360 receives an electric current / passing through the thermally active unit from a current meter. The calculating module 320 calculates the heat loss within the time interval At based on the measured electric current / and an estimated resistance R of the thermally active unit, according to the equations:

Em* = ^{z 2} x R) dt At = t ₂ - t _t (1 )

[0043] The operational status of the thermally active unit 180 may be estimated by calculating an actual mass flow of the fluid that passes through the thermally active unit 180 by dividing the difference between the heat loss and the stored thermal energy by the product of a specific heat capacity of the fluid and a difference between the temperature T _out and the temperature 7k The stored thermal energy in the thermally active unit 180 can be calculated by multiplying a mass of the thermally active unit 180, a specific heat capacity of the thermally active unit 180 and the difference of the first temperature and a second temperature, according to the equation according to the equations:

or,

[0044] ^Stored ^~ J _tl . ^m active mass ^ Vactive mass ^ - dt .(2)

[0045] The second temperature T ₂ is measured by the first temperature sensor 1 10 at a second time which is different from a first time when the first temperature 7i_is measured.

[0046] The estimating module 330 may further compare the actual mass flow with an ideal mass flow.

[0047] The warning module 340 outputs warnings that can be aural and/or visual or from any other signal qualitybased on the operational status of the thermally active unit 180. For example, if the above comparison result exceeds a predetermined value, the warning module 340 may output a beep or other audio signal to indicate that the operational status of the thermally active unit 180 needs to be adjusted. The warning module 340, like many other components, is optional.

[0048] Alternatively or additionally, the processor 210 includes a state adjusting module 350 to adjust state of the fluid conveying device 170. The fluid conveying device may include a fan, a valve, or a pump. The state of the fluid conveying device

170 includes, for example, speed, such as revolutions per minute (RPM) of the fan, power of the pump, degree of open of the valve, pressure, etc. [0049] Alternatively or additionally, the processor 210 may include a comparing module 370 and a target monitoring module 380. The target monitoring module 380 obtains an ideal mass flow of the fluid conveying device 170. The comparing module 370 compares the actual mass flow with the ideal mass flow. The state adjusting module 350 adjusts mass flow of the fluid or adjust power supplied to the thermally active unit if a comparison result exceeds a predetermined value.

[0050] Alternatively, the target monitoring module 380 obtains a target temperatureTg.The state adjusting module 350 adjusts the actual mass flow according to the target temperatureT ₃ . To be specific, the target temperature T ₃ of the thermally active unit 180 is at a third time t ₃ different from the first time t _t when the first temperature T _t is measured. The calculating module is further configured to calculate the stored thermal energy based on the mass m _activemass of the thermally active unit, the specific heat capacity cp _activemass of the thermally active unit and the first temperature T _j _and the target temperature T ₃ , according to the equations: E _stored =

The target actual mass flow of the fluid that passes through the thermally active unit is calculated based on the difference between the heat loss, the stored thermal energy, the specific heat capacity of the fluid and a difference between the temperature T _; and the temperature T _out , according to the equations:

~ ^stored

fluid — _M °):

^C V fluid .'in 'out)

[0051] The state adjusting module 350 adjusts the fluid conveying device according to the target mass flow.

[0052] Fig. 3 illustrates that the processor 210 includes the temperature sensing module 310, the calculating module 320, anestimating module 330, a warning module 340, a state adjusting module 350, a current monitoring module 360, a comparing module 370 and a target monitoring module 380. However, those having ordinary skill in the art can understand that any or all of the above modules can be reside in the memory 220, or in the combination of the processor 210 and memory 220 instead.

[0053] Fig. 4 is a block diagram 40 illustrating heat transfer in the thermally active unit 180. As shown in Fig.4, the thermally active unit 180 generates heat when electric current passes by the thermally active unit 180. As this heat is undesired, the heat generated is also called heat loss of the thermally active unit 180, which is called Q _loss . A part of the heat loss is stored in the thermally active unit 180 which is represented as¾ _{to ed} . Some part of the heat loss is carried away by the fluid that passes through the thermally active unit 180, which is called ζ> _ία .

[0054] The related physicalenergy equation is as follows: thermal losses Q _/oss produced inside the thermally active unit 180 are equal to the amount of energyQ _siore[J stored inside the mass of the thermally active unit 180 plus the amount of heatC y removed by the fluid passing through the thermally active unit 180 plus any thermal energy losses C passing through the housing 100 of the thermally active unit 180 byconvection, conduction or radiation. Under neglection of the latter losses Q _xxx , the fluid volume flowm _a ; can be defined according to the following simplified energy equation:

[0055] Qfluid ⁼ Qloss ^~ Qstored )

[0056] whereby

Qfluid ⁼ Qfluid ^{X c} Pfluid ^X (Tin ^~ ^owt ) (^)

[0057] and

Qioss = l ² x R (9)

[0058] and stored ^~

[0059] In the following equations, Q _flu i _d = ^{d Qf} ™ ^{l d} js a time derivative value. All the other symbols with dotted over the symbols mean a time derivative value. In order to determine the fluid mass flow _air by using above energy equation, the following variables need to be measured over a defined time intervalt:

[0060] - the temperature T^at thefluid inlet 102 of the housing 100, at the second temperature sensor 120;

[0061] - the temperature T _out at the fluid outlet 104 of the housing 100, at the thirdtemperature sensor 130; [0062] - change of temperature of the thermally active unit 180: ΔΤ = T ₂ -T at the first temperature sensor 1 10. Wherein the first temperature Ti is measured at a time j, and the secondtemperature T ₂ is measured at a second timet, which is different from a first time ti. To be more specific, the difference between ti and t ₂ is the time interval At; and

[0063] - electric current I that passes through the thermally active unit 180; and [0064] - time interval At.

[0065] A current meter (not shown in figures) is communicatively coupled to the thermally active unit 180 and measuresthe electric current I passing through the thermally active unit 180. The controller 140 calculates the heat loss based on the measured electric current and an estimated resistance of the thermally active unit 180.

[0066] The resistance of the thermally active unit 180 can be estimated based on the first temperature TjOf the thermally active unit 180, a state of charge of the thermally active unit 180, and a state of health of the thermally active unit 180.

[0067] State of charge (SOC) is the equivalent of a fuel gauge for the battery pack in a battery electric vehicle (BEV), hybrid vehicle (HEV), or plug-in hybrid electric vehicle (PHEV). The units of SOC are percentage points (0% = empty; 100% = full). SOC is normally used when discussing the current state of a battery in use. SOC usually cannot be determined directly. In general there are four methods to determine SOC indirectly:chemical, voltage, current integration and pressure method.

[0068] State of health (SOH) is a figure of merit of the condition of a battery (or a cell, or a battery pack), compared to its ideal conditions. The units of SOH are percent points (100% = the battery's conditions match the battery's specifications). Typically, a battery's SOH will be 100% at the time of manufacture and will decrease over time and use. The designer of a BMS (battery management system) may use any of the following parameters (singly or in combination) to derive a random value for the SOH: Internal resistance, impedance or conductance; Capacity; Voltage; Self-discharge; Ability to accept a charge; Number of charge-discharge cycles, etc.

[0069] The mass of the thermally active unit is typically, i.e., in case of a battery device, the mass of the battery cells or battery modules and the battery housing. The temperature value of the thermally active unit is typically measured in the thermally active unit 180, for example the electric energy storage system.

[0070] With regard to the time of the time intervalAt, controller 140iscapable of measuring time. Thus no additionalhardware is needed.

[0071] The above equations (1 ) to (4) show a time derivatives notation of variables. Additionally, the above equations can be used to further derive an integral respectively. For example, from the equation (3) Q _loss = P _loss = I ² x R, the accumulated thermal lossiT _;oss caused by the electric current passing through the electric resistance of the current carrying storage device internal components within a time interval At can be obtained according to the above equation (1):

Eioss = & ² x R) dt (†)

[0072] Further, according to the above equation(10) Q _{sio e d} = P _{sio ed} = mactivemass X cPactivemass x ^~ ?i ) ,the accumulated thermal energy E _stored of the thermally active can be obtained according to the above equation (3), which is reproduced below:

[0073] Further, according to the above equation (8) Q _fluid = P _fluid = m _fiuid x ^C P fluid x (Άη - T _out ) , ^tne accumulated thermal energy £„ _; of the fluid passing through the thermally active unit 180 within a time interval At, can be determined:

[0074] E _fluid = g(m _fluid X c _{P fluid} x T) dt ( )

[0075] The duration of the time interval At can be fixed or flexible. The time interval may be measured by any clock-like device within the vehicle system 10.

[0076] Referring back to Fig. 1 , in order to determine the status of the thermally active unit, the temperature of thermally active unit 180 is measured by the first temperature sensors 1 10 and the measurement resultcanbe used to determine the stateof the fluid conveying device 170 so as to adjust thefluid mass flow. For this purpose, the statethe fluid conveying device 170 is typically controlled by the controller140. Alternatively, as discussed above, if there area plurality of first sensors 1 10 in the system 10, the temperature of the thermally active unit 180 can be either a maximum or an average of all the temperatures measured by the plurality of first sensors or any other temperature value. Further, the state of the fluid conveying device 170 will be described in detail in the following contents.

[0077] At least some embodiments of the present invention further determinewhether, for a given state of the fluid conveying device 170, for example, a given speed of the fluid conveying device 170, a reduced heat transfer capacity for the thermally active unit 180 which is indicated by an increased temperature at the first temperature sensor 1 10, is a consequence of increased fluid intake temperature into the thermally active unit 180, or is a consequence of reduced fluid volume flow.

[0078] The reduced fluid volume flow inside the housing 100 can have different causes. For example, the fluid conveying device 1 70, for example, the fan can be damaged and can for various reasonsoperate at a reduced speed in relation to the set value and thus transferring less fluid. Another possibility is that the fluid intake is blocked, e.g., a passenger could have placed an object on top of the fluid inlet 102.

[0079] It is known that fans can feedback a speed signal to the controller 140. By this signal the controller 140 can determine the theoretical or ideal fluid volume flow corresponding to the fan speed in the particular application scenarios.

[0080] With the addition of at least two temperature sensors 120, 130 to the vehicle systeml O, which are located respectively atthe fluid intake 102, and at the fluid outlet 104, it is possible to measure the fluid-in and fluid-out temperatures, thus determine the fluid mass flow within the housing 100.

[0081] These two temperatures and other available data are used by the controller 140 to determine the thermal energy extracted from the housing100 by the conveying fluid. Specifically, by adding at least two temperature sensors 120, 130 at the fluidintake 102 and at the fluid outlet 104 of the vehiclesysteml O, it is possible to estimate the actual fluid mass flow according to the above energy equations, as follows:

Γ [Λ0Λ0Ο82Ί] m " _fiuid =—— Q—flui—d —=

^C V fluid ^X L' in ' out)

[0083] That is, an actual mass flow m _fiuid of the fluid that passes through the thermally active unit180is calculatedby dividing the difference between the heat loss Qioss = / ² x fiand the stored thermal energy Q _stored = _activemass x cp _activemass x (T ₂ - T _t ) by the product of a specific heat capacity cp _fluid of the fluid and a difference Άη - r _OMt between the temperature r _0[Ji and the temperature 7k

[0084] Further, with the second temperature sensor 120, the fluid intake temperature is explicitly known as well. The knowledge of the fluid intake temperature subsequently allows the controller 140 to determine whether a change in the temperature of the thermally active unit 180 is caused by a change in heat losses due to a change in electric current (electric load), or a change in fluid intake temperature or a combination of both.

[0085] The additional knowledge of the fluid outlet temperature subsequently allows the controller 140 to determine whether the above change in the temperature of the thermally active unit 180 is caused by a change in estimated actual fluid mass flow, or a combination of the change in estimated actual fluid mass flow with the change in heat losses due to a change in electric current, or a change in fluid intake temperature.

[0086] The knowledge of the actual fluid mass flow as a result of calculation based on the above equation (8) allows the controller 140 to correlate the actual fluid mass flow with the ideal fluid mass flow which is derived from the fan speed, and subsequently to determine whether the fluid volume flow through the housing 10Ois within set boundaries of the system or beyond.

[0087] For example, the controller 140 obtainsthe ideal mass flow based on the stateof the fluid conveying device 170.The controller 140 further compares the actual mass flow with the ideal mass flow.The comparison can takes in any form, for example, dividingthe ideal mass flow by the actual mass flow, or subtracting the actual mass flow from the ideal mass flow.The larger the comparison result, the larger the difference between the ideal mass flow and the actual mass flow is.

[0088] Then the controller 140 generates a warning indication if a comparison result exceeds a predetermined value.

[0089] Alternatively, or in addition, the controller 140 adjusts state of the fluid conveying device 170if a comparison result exceeds the predetermined value. The controller 140 requests the fluid conveying device 170 to adjust itsstateto compensate for the difference of the actual mass flow of the fluid passing through the thermally active unit 180and the ideal fluid mass flow until the comparison result equals or is less than a first adjustmentfactor.

[0090] The predetermined value is adjustable depending on the actual application scenario. Further the predetermined valueand the first adjustment factor are adjustable depending on the actual application. Further, those having ordinary skill in the art should understand that the predetermined value and the first adjustment factor can take on same or different values.

[0091] In another embodiment, the second temperature sensor 120 measures a temperaturer ' of the fluid at the fluid inlet 102 of the housing 100 at a fourthtimet ₄ different fromthetime when the temperature^ is measured. The third temperature sensor 130 measures a temperature T ^f of the fluid at the fluid outlet 104 of the out

housing 100 at the fourthtimet ₄ . The controller 140 estimatesthe operational status of the thermally active unit 180 by calculating another actual mass flow of the fluid that passes through the thermally active unit by dividing the difference between the heat loss and the stored thermal energy by the product of a specific heat capacity of the fluid and a difference between the temperature T ^f . and the temperaturer ' The

in out controller 140 further compares the change from the one actual mass flow to the other actual mass flow with the ideal mass flow. Accordingly, the change in actual fluid volume flow in relation to the idealfluid volume flow can be estimated. The change can have different causes.

[0092] The controller 140 can react by generating a warning indication if the comparison result exceeds a predetermined value.

[0093] Alternatively, the warning signal can be stored or communicated for different purpose. For example, the warning signal can be communicated to a communication bus or an interface within the vehicle system. The warning signal can be used to temporarily or permanently set an error flag in the diagnostics system for the vehicle systemi O. It can be used to inform the driver, for example, to check whether any obstacles are blocking the fluid intake 102.

[0094] In another embodiment, the controller 140 can react by adjusting the stateof the fluid conveying device 170 if a comparison result exceeds a predetermined value. Therefore, the thermally active unit can be protected by adjusting fluid mass flow. For example, when more cooling fluid needs to be provided to the thermally active unit 180, the controller 140 may instruct the fluid conveying device 170 to generate and convey more fluid to the thermally active unit 180. Alternatively, when less fluid is needed by the thermally active unit 180, for example, in a cold weather, when the thermally active unit needs to be warmed up in order to resume normal operation, the controller 140 may instruct the fluid conveying device 170 to convey less fluid to the thermally active unit 180, so that the thermally active unit 180 can warm up quickly. For example, if the temperature T _in at the fluid inlet 104 detected by the second temperature sensor120 is too cold (for example, when the vehicle system 10 just starts up in winterand the thermally active unit 180 is too cold which is not suitable to work), less actual mass flowis desirable. With less actual mass flow within the housing 100, a larger part of the heat loss is converted to the heat stored in the thermally active unit 180 instead of being carried away by the fluid flow. Therefore thethermally active unit 180 can quickly warmed up.

[0095] Alternatively, a temperature of the fluid generated by the fluid conveying device 170 may be adjusted. The controller 140 may further adjust the temperature of the fluid generated by the fluid conveying device 1 70. For example, when the thermally active unit needs to be warmed up in a cold weather, the controller 140 may instruct the fluid conveying device 170 to increase the temperature of its generated fluid.

[0096] In another embodiment, the controller 140 can react by instructing to adjust power supplied to the vehicle system 10 if a comparison result exceeds a predetermined value. The controller 140 reduces the available or accessible electric power throughput through the thermally active unit 180 by a secondadjustment factor in order to protect the electric energy storage device. The second adjustmentfactor can take on different values. Therefore, the thermally active unit 180 is proactively protected by reducing power availability, therefore reducing the electric current passing through the thermally active unit 170. The second adjustment factor is adjustable depending on the actual application.

[0097] In another embodiment, the controller 140 obtains a target temperature, and adjusts the actual mass flow according to the target temperature. For example, the controller 140 can obtain a target mass flow according to the target temperature and then increase or decrease the state of the fluid conveying device 1 70 so as to reach the target mass flow. In this manner, the actual mass flow for the thermally active unit can be adjusted accurately, thus the temperature of the thermally active unit 180 can be adjusted accurately.

[0098] As for gas-based fluid convey device 170, the fluid conveying device 170 may comprise a fan, and the air mass flow state can be controlled by providing more power to the fans so as to increase speed such as RPM of the fans. Therefore, the state for the gas-based fluid convey device may include power, speed of the gas-based fluid convey device.

[0099] As for liquid-based fluid convey device 170, the fluid conveying device 170 may comprise a pump or a valve, and the liquid mass flow speed can be controlled by adjusting power for the pump or the degree of open of the valve so that the liquid mass delivered by the pump or the liquid mass passing through the valve can be controlled. Therefore, the state of the liquid-based fluid convey device may include power, degree of openness, pressure or speed of the liquid-based fluid convey device.

[00100] Fig. 5 is a diagram illustrating a device 50 according to an embodiment. A first temperature sensor 510, a second temperature sensor 520, and a third temperature sensor 530 shown in Fig.5 are similar to the first temperature sensor 110, the second temperature sensor 120, and the third temperature sensor 130 shown in Fig. 1. A controller 540 is similar to the controller 120 shown in Fig. 1. A fluid inlet 502 and a fluid outlet 504 are similar to the fluid inlet 102 and the fluid outlet 104 shown in Fig. 1. A thermally active unit 580 is similar to the thermally active unit 180 shown in Fig. 1. Therefore these elements are not discussed in details. The fluid conveying device 170 shown in Fig. 1 includes a suction fan 590 as shown in Fig. 5. A fluid inlet of the suction fan 590 is connected to the fluid outlet 504 of the housing 500 by a suction duct 595. Alternatively, the fluid intake of the suction fan 590 can be directly connected to the thermally active unit 580 within the housing 500 without the suction duct 595. The fluid is sucked through and out of the housing 500.

[00101] Fig.6 is a diagram illustratinga device according to another embodiment. A first temperature sensor 610, a second temperature sensor 620, and a third temperature sensor 630 shown in Fig.6 are similar to the first temperature sensor 110, the second temperature sensor 120, andthe third temperature sensor 130 shown in Fig. 1. The controller 640 is similar to the controller 120 shown in Fig. 1. A fluid inlet 602 and a fluid outlet 604 are similarto the fluid inlet 102 and the fluid outlet 104 shown in Fig. 1. A thermally active unit 680 is similar to the thermally active unit 180 shown in Fig. 1. Therefore these elements are not discussed in details. In this embodiment, alternatively, the fluid conveying device 170 shown in Fig. 1 includes a blower fan 690 as shown in Fig.6. The fluid outlet of the blower fan 690 is connected to the housing 600 directly. Alternatively, the fluid outlet of the blower fan 690 can be connected to the housing 600 by a blower duct 695. The fluid is blown into and through the housing 600.

[00102] FIG. 7 is a diagram illustrating a device 70 according to another embodiment.A first temperature sensor 710, a second temperature sensor 720, and a third temperature sensor 730 shown in Fig.7 are similar to the first temperature sensor 110, the second temperature sensor 120, andthe third temperature sensor 130 shown in Fig. 1. The controller 740 is similarto the controller 120 shown in Fig. 1. A fluid inlet 702 and a fluid outlet 704 are similarto the fluid inlet 102 and the fluid outlet 104 shown in Fig. 1. A thermally active unit 780 is similar to the thermally active unit 180 shown in Fig. 1. Therefore these elements are not discussed in details. As shown in Fig. 7, a leak 706 could occur somewhere on the suction side between the suction fan 790 and fluid outlet 704 of the housing 700, or a leak can occur near the fluid inlet 702 of the housing 700 thus bypassing fluid. Note that elements with similar reference signs as Fig. 1 represent similar elements as Fig. 1, and the description of which are omitted for simplicity. As for a gas-based cooling system, the leak 706 in the suction duct 795 between the housing 700 and suction fan 790, or, a leak in the blower duct between blower fan and the housing 700, or any blockage or partial blockage of the hardware of the cooling system, or a combination of the above may contribute to the difference between the actual air volume flow with respect to the ideal air volume flow. As for a liquid-based cooling system, the leak in the tube that carrying the cooling liquid, or the deterioration of the cooling liquid itself, for example, sedimentation of the cooling liquid, increase of viscosity (so that the mobility of the liquid decreases) may cause the degrade of the performance of the cooling liquid.

[00103] Fig. 8Aillustrat.es a flow chart of a method 800Aaccording to an embodiment of the invention.

[00104] As shown in Fig.8A, the method 800A comprises measuring (in block 810) a first temperature of a thermally active unit. The thermally active unit is within a housing, and the thermally active unit generates a heat loss, cooled by fluid passing through the thermally active unit and stores a thermal energy. The method 800A further comprises (in block 820) measuring a temperature^ of the fluid at a fluid inlet of the housing; measuring (in block 830) a temperature T _out of the fluid at a fluid outlet of the housing; calculating (in block 840) a heat loss of the thermally active unit; andestimating (in block 850) an operational status of the thermally active unit based on the heat loss, the first temperature and the difference between the temperature T _in and the temperature^,..

[00105] Alternatively, the method 800A further comprises measuring an electric current passing through the thermally active unit; andcalculating the heat loss based on the measured electric current and an estimated resistance of the thermally active unit.

[00106] Alternatively, the method 800A further comprises estimating the resistance of the thermally active unit based on the first temperature, a state of charge of the thermally active unit, and a state of health of the thermally active unit.

[00107] Alternatively, the method 800A further comprises measuring a second temperature^ of the thermally active unit at a second time t ₂ diffe rent from a first time^ when the first temperature^ is measured; andcalculating a stored thermal energy in the thermally active unit by multiplying a mass of the thermally active unit, a specific heat capacity of the thermally active unit and the difference of the first temperature and the second temperature^ ,

[00108] Alternatively, the block 850 further comprises calculating an actual mass flow of the fluid that passes through the thermally active unit by dividing the difference between the heat loss and a stored thermal energy in the thermally active unit by the product of a specific heat capacity of the fluid and a difference between the temperature r _OMi andthe temperature^, according to the equations:

Qfiui _d = ^Ει °"-^°"* (5), and

TN _■ — Qfluid

mfluid - _fT . _ _T W-

^C V fluid .'in 'out)

[00109] Fig. 8B shows a flowchart of a method 800B according to another embodiment of the invention. Blocks 810, 820, 830, 840 are the same as those shown in Fig.8A, therefore the detailed description of these blocks are omitted. Alternatively, as shown in Fig. 8B, the method 800Bfurther comprises obtaining (in block 850B) an ideal mass flow based on the stateof the flu id conveying device; andcomparing (in block 860B) the actual mass flow with the ideal mass flow. Alternatively, the method 800B may further comprise generating (in block 870B) a warning ind ication , if a comparison result exceeds a predetermined value. For example, the warn ing indication may be generated on the dashboard of the vehicle. Upon the warn ing signal, user of the veh icle system 10 may check whether a flu id in let to the thermal ly active un it is blocked, a leak occurs or a malfunction is found in the fluid conveying device, etc. Those skilled in the art can u nderstand that the block 850B and the block 810 do not have to be performed in the order recited. In other words, the block 850B and block 810 can be implemented substantially simu ltaneously or in different orders.

[0011 0] Alternatively or in add ition , the method 800Bmay further comprise adjusting (in block 870C) mass flow of the flu id , if a comparison resu lt exceeds a predetermined value. The fluid conveying device may changes mass flow of the fluid with in the housinguntil an u pdated comparison result equals or less than a first adjustment factor.

[0011 1] Alternatively or in addition.the method 800Bmay fu rther compriseadj usting(in block 870D) power suppl ied to the thermally active u nit, if a comparison resu lt exceeds a predetermined val ue. For example, a power system that suppl ies power to the thermal ly active u nit may reduce power supply so that less current passes through the thermal ly active un it and as a result less heat is generated by the thermally active un it.

[0011 2] Those having ord inary skill in the art can understand that the term "AN D/OR" above the blocks 870B, 870C and 870D means any one of or any combination of the blocks 870B, 870C and 870D can be implemented in the method 800B.

[0011 3] Fig. 8Cshows a flowchart of a method 800Caccord ing to another embodiment of the invention. Blocks 810, 820, 830, 840 are the same as those shown in Fig. 8A, therefore the detailed description of these blocks are omitted . Alternatively or in addition.the method 800Cmay fu rther comprise obtaining (in block 850E) a target temperatu reT ₃ ; andadjusting (in block 860E) the actual mass flow accord ing to the target temperatu reT ₃ . For example, the method 800Ccomprises obtain ing the target temperatu re T ₃ of the thermal ly active un it at a th ird time t ₃ different from the first time t _t when the first temperatu re T _L is measu red; andcalculating the stored thermal energy based on the mass m _active ^^of the thermally active unit, the specific heat capacity the target temperature T ₃ , according to the equations:

it- nactive -0

[00114] Those skilled in the art can understand that the block 850E and the block 810 do not have to be performed in the order recited. In other words, the block 850E and block 810 can be implemented substantially simultaneously or in different orders.

[00115] Referring back to Fig. 800A, alternatively or in addition, the method 800A may further comprise measuring a temperature T ' ^of the fluid at the fluid inlet of the housing at a fourth time t ₄ different from a time when the temperature T _in is measured; measuring a temperature T ^f of the fluid at the fluid outlet of the housing at the fourth timet ₄ . Block 850further comprises calculating another actual mass flow of the fluid that passes through the thermally active unit by dividing the difference between the heat loss and the stored thermal energy by the product of a specific heat capacity of the fluid and a difference between the temperature T ' . and the temperature T ^f

in out

[00116] Alternatively or in addition, block 850 further comprises obtaining an ideal mass flow based on the state of the fluid conveying device; and comparing the variation of actual mass flow, or in other words, the changefrom the one actual mass flow to the otheractual mass flow, with the ideal mass flow. The method 800A further comprises generating a warning indication if a comparison result exceeds a predetermined value.

[00117] Alternatively or in addition, block 850 further comprises obtaining an ideal mass flow based on the state of the fluid conveying device; and comparing the change in actual mass flow with the ideal mass flow. The method 800A further comprises adjusting state of the fluid conveying deviceif a comparison result exceeds a predetermined value.

[00118] Alternatively or in addition, block 850 further comprises obtaining an ideal mass flow based on a state of the fluid conveying device; and comparing the change in actual mass flow with the ideal mass flow. The method 800A further comprises adjusting power supplied to the thermally active unit if a comparison result exceeds a predetermined value.

[0011 9] Note that any and all of the embodiments described above can be combined with each other, except to the extent that it may be stated otherwise above or to the extent that any such embodiments might be mutually exclusive in function and/or structure.

[00120] Although the present invention has been described with reference to specific exemplary embodiments, it will be recognized that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense.

[00121] From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the scope of the invention. Accordingly, the invention is not limited except as by the appended claims.