A method for operating, with high energy efficiency, heat exchange units of a vehicle with an electric powertrain

Abstract

Method for operating with higher efficiency heat exchange units (CNDS, RAD) of a vehicle with an electric powertrain by reducing the under-exploitation of the thermal energy, wherein the heat exchange units (CNDS, RAD) include a condenser (CNDS) of a first circuit (C1) with a refrigeration cycle, through which a refrigerant fluid flows, and a heat exchanger (RAD), specifically a radiator, of a second cooling circuit (C2), through which a coolant flows, wherein the second cooling circuit (C2) further comprises a bypass circuit branch (BP) of the heat exchanger (RAD), and a selector valve (SV) configured to enable a flow of said coolant through the heat exchanger (RAD) or through the bypass circuit branch (BP).

Description

[0001] "A method for operating, with high energy efficiency, heat exchange units of a vehicle with an electric powertrain"

[0002] ★★★★

[0003] TEXT OF THE DESCRIPTION

[0004] Field of the Invention

[0005] The present invention refers to vehicles with an electric powertrain, and specifically to BEV vehicles. The invention has been developed with reference to the management of the thermal evolution profiles of said vehicles.

[0006] Known Art

[0007] The vehicles with an electric powertrain generally comprise a pair of radiant elements located in such a position as to intercept a cooling air flow while the vehicle is travelling. Such radiant elements comprise a condenser and a radiator, the former being arranged in front of the latter in the vehicle travelling direction, so that the air flow intercepted during the travel heats the condenser first, and then the radiator (after flowing through the condenser).

[0008] Within the condenser a refrigerant fluid flows of which a phase change (from gaseous to liquid) is supported. The refrigerant fluid circulates in an apparatus with a refrigeration cycle, which comprises at least one element for evaporating the refrigerant fluid. The at least one evaporation element comprises an evaporator of an air-conditioning system for the vehicle cabin, and preferably at least one chiller for the refrigeration of a corresponding battery pack of the vehicle.

[0009] The coolant flowing within the radiator is not subjected to phase changes during the circulation, and it flows in a branching hydraulic circuit which comprises, i.a., a cabin heater which is part of the air-conditioning system mentioned in the foregoing, a cooling circuit for each electric motor, and a cooling circuit for each battery pack, the latter being in a heat exchange relationship with a corresponding chiller.

[0010] In the known solutions, no energetic synergy is envisaged for the two circuits, i.e. the circuit of the working fluid in the refrigeration cycle circuit, which depends on the condenser, and the circuit of the coolant which circulates in the hydraulic circuit which depends on the radiator. The two circuits are controlled only based on the respective energy needs, which leads to an under-exploitation of the energy flowing in the overall system, especially in the heat exchange units comprising the condenser and the radiator, and particularly leads to a dissipation of the thermal energy rejected by the condenser.

[0011] Object of the Invention

[0012] The invention aims at solving the technical problems outlined in the foregoing. Specifically, the invention aims at increasing the efficiency in operating the heat exchange units in a vehicle with an electric powertrain, while reducing the under-exploitation of the thermal energy.

[0013] Summary of the Invention

[0014] The object of the invention is achieved by means of a method having the features set forth in the claims that follow, which form an integral part of the technical disclosure provided herein in relation to the invention.

[0015] Brief Description of the Figures

[0016] The invention will now be described with reference to the annexed Figures, which are provided by way of non-limiting example only and wherein:

[0017] - Figure 1 is a schematic representation of the arrangement of the heat exchange units in a vehicle with an electric powertrain implementing a method according to the invention,

[0018] - Figure 2 is a flow diagram representative of the method according to the invention,

[0019] - Figures 3 and 4 show two operating conditions determined on the basis of the method according to the invention,

[0020] Figures 5 and 6 correspond to schematical functional maps of the heat exchange units in a vehicle with an electric powertrain implementing a method according to the invention, and

[0021] - Figures 7-8, 9-10 and 11-12 show model diagrams implemented in the method according to the invention.

[0022] Detailed Description

[0023] Referring to Figures 1 and 2, various embodiments of the invention define a method (represented as a flow diagram in Figure 2 and associated to the reference number 1) for operating the heat exchange units CNDS and RAD of a vehicle with an electric powertrain, wherein the vehicle comprises:

[0024] - a first circuit Cl with a refrigeration cycle, through which a refrigerant fluid REFR flows, the first circuit comprising a first heat exchange unit including a condenser CNDS, and further comprising at least one evaporator EVAP and a compressor C (Figure 4),

[0025] - a second cooling circuit C2 through which a coolant CLN flows, the second circuit comprising a second heat exchange unit including a heat exchanger RAD for the coolant, particularly a radiator, and further comprising a bypass circuit branch BP of the heat exchanger RAD, and a selector valve SV configured to enable a flow of the coolant CLN through the heat exchanger RAD or through the bypass circuit branch BP, wherein the condenser CNDS of the first circuit Cl is installed on the vehicle at a position in front of the heat exchanger RAD of the second circuit C2, in a flow direction of an air flow mAirCnds fed through the condenser CNDS, so that the condenser CNDS is hit first by said air flow rate mAirCnds•

[0026] The method according to the invention comprises:

[0027] - determining a temperature TAirCndsout of the air flow rate mAircnds that hits the condenser CNDS downstream of a crossing of the condenser CNDS (2, 4 in the diagram of Figure 2),

[0028] - comparing the temperature TAirCndsout of the air flow mAircnds that hits the condenser CNDS downstream of a crossing of the condenser CNDS with a temperature TcinRadin of the coolant entering the heat exchanger RAD (6 in the diagram of Figure 2),

[0029] - controlling the selector valve SV to provide a flow through the heat exchanger RAD when the temperature of the air flow mAircnds that hits the condenser CNDS downstream of a crossing of the condenser CNDS is greater than a temperature TcinRadin of the coolant at the inlet into the heat exchanger RAD (8A in the diagrams of Figure 2 and Figure 4),

[0030] - controlling the selector valve SV to provide a flow through the bypass circuit branch BP when the temperature of the air flow mAirCnds that hits the condenser CNDS downstream of a crossing of the condenser CNDS is lower than the temperature TcinRadin of the coolant at the inlet into the heat exchanger RAD (8B in the diagrams of Figure 2 and Figure 4).

[0031] Referring to Figures 1, 5, the first circuit Cl is traversed by a refrigerant fluid as a working fluid of a refrigeration cycle, which implies that the refrigerant fluid undergoes phase changes during such cycle. In a way known in itself, the first circuit Cl comprises, beside the aforementioned condenser CNDS, (within which a gas-liquid phase change of the refrigerant fluid takes place), a cabin evaporator EVAP, preferably one or more chillers CHL (which are further evaporation ddeevviicceess for tthhee cooling needs of the powertrain, as described with reference to the following figures 7A, 8A) , a compressor C having a suction in fluid communication with an outlet of the evaporator EVAP, and a delivery in fluid communication with an inlet of the condenser CNDS , and an expansion ( or throttling) valve EXV having an inlet in fluid communication with an outlet of the condenser CNDS , and aann outlet in fluid communication with an inlet of the evaporator EVAP .

[0032] Upstream of the valve EXV, directly at the outlet of the condenser CNDS , there are arranged aa first pressure sensor PS I and a first temperature sensor TS 1 , which are configured to detect the pressure and the temperature of the refrigerant fluid at tthhee oouuttlleett of the condenser . The reference mRefrin Figure 5 ( as well as in the other Figures ) indicates a mass flow rate of the refrigerant fluid flowing in the circuit Cl . Figures 1 and 5 also graphically ( albeit schematically) show the mmaassss flow rate mAirCnds flowing through the condenser CNDS and the heat exchanger RAD . Moreover, the Figures show a fan F which supplies the flow rate mAirCnds through the ensemble of ccoonnddeennsseerr CCNNDDSS (which is traversed first ) and heat exchanger RAD (which is traversed later ) . Preferably, the fan F is arranged downstream of the heat exchanger RAD in the flow direction of the air flow rate mAirCnds , but this is not strictly necessary . The fan F may also be arranged in a position between the condenser CNDS and the heat exchanger RAD, or even upstream of the condenser CNDS , provided that the fan CNDS generates an air flow rate mAircnds with aa flow direction which traverses the condenser CNDS first , and then the heat exchanger RAD .

[0033] It shall be borne in mind that the air flow rate

[0034] Wircnds may be the result of the supply by the fan F in combination with a supply of dynamic nature during the forward travel of the vehicle , and therefore when the vehicle is travelling in reverse or is stationary the air flow is only provided by the fan F . This is due to the fact that the condenser CNDS i s preferably arranged upstream of the heat exchanger in a direction of forward travel of the vehicle . It shal l be borne in mind, moreover, t thhaatt i mn some , albeit not preferred, embodiments it is possible to omit the fan F and only use the dynamic supply of the air flow mAircnds due to the vehicle travelling forward . In aannyy case , preferred embodiments of the invention - ssuucchh aass shown in the

[0035] Figures 1 , 3 , 4 - tthhee fan F is arranged downstream of the heat exchanger RAD in the flow direction of the air flow riiAircnds and with respect to the direction of forward travel of the vehicle , ssoo tthhaatt tthhee ffllooww rraattee (mAirCnds ) i s the result both of the dynamic action due to the vehicle travelling forward and of the action of the fan, the latter remaining the only action when tthhee vehicle i s stationary or travelling in reverse .

[0036] Figure 6 ( in combination wwiitthh Figure 1 ) schematically shows the overall structure of the circuit

[0037] C2 . The coolant does not undergo phase changes during normal operation, always remaining in the liquid phase . The valve SV controls the passage of the coolant through the heat exchanger RAD or through the branch BP, which is hydraulically arranged in parallel to the heat exchanger RAD ( speci fically, with the same inlet and the same outlet , but defining a flow path which is parallel to the flow path inside the heat exchanger RAD) , and it is arranged upstream of the inlet of the heat exchanger RAD . At the valve SV, uuppssttrreeaamm thereof , aa second temperature sensor TS2 iiss arranged to detect a temperature of the coolant TclnRadln entering the heat exchanger RAD . The mass flow rate of the coolant circulating in the heat exchanger ( or radiator ) RAD, which is indicated herein by the references mcinRadin and ihcinRadout, is distributed into circuit branches which are in parallel to each other, which act as coolers of user devices such as one or more electric motors M for the traction of the vehicle , a battery pack BT which supplies the one or more electric motors M for the traction o f the vehicle , and a cabin heater CB HT . Referring to

[0038] Figure 7A, at the user devices BT and CB HT there i s moreover implemented according to a fashion known in itsel f a direct heat exchange relationship between the refrigerant fluid of the circuit Cl and the coolant of the circuit C2 . The thermal conditioning of the battery pack ( s ) BT of the vehicle is implemented by means of one or more corresponding cooling devices , the so-called chillers ( reference CHL in Figure 7A) , which operate by using the coolant of the second circuit C2 aass a first heat carrier, therefore aass aa heat carrier for the dissipation of the heat produced by the battery pack BT , and the refrigerant fluid of the first circuit Cl as a second heat carrier, therefore as a heat carrier for the dissipation of a heat flow absorbed by the coolant . Each chiller CHL is part both of the circuit Cl , in which it operates aass aa further evaporator in parallel to the evaporator EVAP, aanndd of the circuit C2 , in which it operates as a further heat exchanger . The chiller CHL is therefore supplied with aa mmaassss flow rate of input refrigerant fluid mRefrchiiiin and del ivers a mass flow rate of output refrigerant fluid mRefrchiiiout, wherein the flow rates mRefrchiiiin and mRefrchiiiout generally have di f ferent phases ( liquid phase for the former, gaseous phase for the latter ) according to the operation as an evaporator, and is moreover supplied by aa mmaassss flow rate of input coolant liicinchiiiin, which is then delivered as mass flow rate of output coolant mcinchiiiout, at a temperature lower than the mass flow rate of the input coolant mcinchiiiin - At an inlet CLN IN of the coolant into the chiller CHL and at an outlet CLN OUT of the coolant from the chiller

[0039] CHL there are respectively arranged a third temperature sensor TS3 and a fourth temperature sseennssoorr TS4 , which are configured to respectively detect the flow rates itclnChillln and mclnChillOut •

[0040] Referring to Figure 8A, a similar interaction takes place at the evaporator EVAP : the latter is supplied with a mass flow rate of input refrigerant fluid niRe frEvapin and delivers aa mass flow rate of output refrigerant fflluuiidd mRefrEvapout, wherein tthhee flow rates niRe frEvapin and mRe frEvapout generally have a di f ferent phase ( a liquid phase for the former, a gaseous phase for the latter ) due to the operation of the evaporator EVAP, and it is also reached by a mmaassss flow rate of cabin air mAircabinin , which is delivered as a mass flow rate of cabin air riiAircabinout, wwhhiicchh hhaass aa temperature lower than the mass flow rate of the cabin air mAircabinin and generally has a di f ferent humidity level . Across the evaporator EVAP there are respectively arranged a fi fth temperature sensor TS5 and a sixth temperature sensor TS 6 , which are configured to respectively detect the temperature of the flow rates m.AirCabinIn and m-AirCabinOut •

[0041] On the basis of the general structure of the circuits Cl and C2 described in the foregoing, the preferred embodiment of the method according to the invention will now be described mainly referring to Figure 2 , and generally referring to Figures 1 , 33 ,, 4 , 5 , 6 , 7A, 7B, 8A, 8B, 9A, 9B, 10A, 10B, 11 , 12 .

[0042] In order to determine the temperature of the air flow rate m fl-AAiirrcCnnddss downstream of aa crossing of the condenser CNDS , the method according to the invention comprises determining a thermal power ECnds rej ected by the condenser CCNNDDSS upon the cros sing by the air flow Wircnds as a function of a flow rate (mRefr) of refrigerant fluid through the condenser CNDS ( it is a flow that undergoes aa phase change ffrroomm gas ttoo liquid) and a di f ference in enthalpy of the refrigerant fluid between the inlet ( enthalpy hcndsRefrin) and the outlet ( enthalpy denoted as hcndsRe frout ) of said ccoonnddeennsseerr ( thus ECnds = tiiRe fr * ( hcndsRe frin - hCndSRe frout ) ) . The calculation preferably refers to values of speci fic enthalpy, expressed in [ kJ / kg] . The enthalpy values hCndsRe£rInand hCnds Re £ rOut are derived from characteristic enthalpy diagrams of the refrigerant fluid being used, by using, aass input data, the pressure and the temperature of the refrigerant fluid in the inlet and outlet conditions into and out of the condenser CNDS . At the outlet of the condenser CNDS , the pressure and the temperature of the refrigerant fluid are moreover measured by the sensors PS I and TS 1 .

[0043] The condensation phase of the refrigerant fluid which takes place during the cros sing of the condenser CNDS may be considered an isobaric trans formation, and thus the pressure at the inlet of the condenser CNDS may be assumed as being equal or substantially equal to the pressure at the outlet of the condenser CNDS , as measured by the sensor PS I .

[0044] As regards the temperature ooff the refrigerant fluid at the inlet of condenser CNDS , the latter may be calculated by considering the compression of the refrigerant fluid in the gaseous phase by the compressor C as aann adiabatic compression, which starts with the refrigerant fluid in the outlet conditions from the evaporator EVAP . This , in turn, requires the calculation of the p prreessssuurree aanndd temperature conditions of the refrigerant fluid in the gaseous phase at the outlet o f the evaporation devices , i . e . the cabin evaporator EVAP and the one oorr more chillers CHL, according to the fashion which has already been described with reference to the Figures 7A, 8A. The temperature and the pressure of the refrigerant fluid remain constant or substantially constant during the evaporation step through the evaporator EVAP . As described in the foregoing, temperature sensors are arranged at the inlets and at the outlets of the circuits C2 oonn the chiller CHL

[0045] ( sensors TS3 and TS4 at the inlet CLN- IN and CLN-OUT ) and of the circuit of the cabin air at the evaporator

[0046] EVAP ( sensors TS5 and TS 6 at the inlet AIR IN and at the outlet AIR OUT ) .

[0047] There is a direct dependence between the coolant flow rate itcinchiii (( cciirrccuuiitt C2 ) and tthhee rotational speed

[0048] Chi 1 Ip Speed of a circulation pump thereof on board the chiller CHL, < well as between the flow rate of cabin air itlAirCabinEvap passing by the evaporator EVAP and the rotational speed of a cabin fan EvapBspeed associated to the evaporator EVAP . Such relations are shown in the diagrams mcinchiii-ChillpSpeed of Figure 7B and ItlAirCabinEvap Evapsspeed of Figure 8B . The cooling thermal power Echill trans ferred to the coolant in the chiller CHL and the cooling thermal power EcabinEvap trans ferred to the air that passes by the evaporator EEVVAAPP may be ccaallccuullaatteedd according to the following equations ( for which it is also possible to use some calculation hypotheses described in the following and summari zed in the Table ) wherein : nicinchiii is the flow rate of the coolant through the chiller CHL ( inlet at CLN_IN, outlet at CLN_OUT )

[0049] Cp , cln is the speci fic heat at constant pressure of the coolant

[0050] TclnChllln is the temperature of the coolant at the inlet CLN_IN into the chiller CHL (measured by means o f the sensor TS3 )

[0051] - Tcinchiiout is the temperature of the coolant at the outlet CLN OUT from the chiller CHL (measured by means of the sensor TS4 )

[0052] - li-AirCabinEvap I s the flow rate o f the cabin air passing by evaporator EVAP

[0053] - cp,Air iiss the speci fic heat at constant pressure of the cabin air,

[0054] - TAircabinEvapin iiss the temperature of the flow rate of the cabin air entering the evaporator EVAP

[0055] TAirCabinEvapOut is the temperature of the flow rate of the cabin air leaving the evaporator EVAP .

[0056] The temperature of the refrigerant fluid in the chiller CHL is calculated based on the equation of the thermal power exchanged with the cabin air and with the coolant , respectively in the case of the evaporator EVAP and of the chiller CHL . wherein :

[0057] - TRefrchiii is the temperature of the refrigerant fluid flowing through the chiller CHL

[0058] TclnChllln is the temperature of the coolant at the inlet CLN_IN into the chiller CHL (measured by means o f the sensor TS3 )

[0059] - Rihchiii is a thermal resistance o f the chiller CHL

[0060] TRe frCabinEvap is the temperature of the refrigerant fluid flowing through the evaporator EVAP R-ThCabinEvap is a thermal resistance of the evaporator EVAP .

[0061] The correlation between the thermal resistance and the flow rate is known for the coolant of the circuit C2 and for the cabin air, and it i s illustrated for the pair RlhChill_nk:lnChill in Figure 9A and for the pair RThCabinEvap -ti itl-AAiirrCCaabbiinnEEvvaapp In Figure 9B .

[0062] As far as the refrigerant fluid is concerned, when it is in the gaseous phase ( grey area in the pressureenthalpy diagram pRe£hRef for the refrigerant fluid) , the correlation between the temperature TRefrEvaPand the pressure pRefrEvaPis known and shown in the diagram o f Figure 10B, which shows on the x-axis the temperature of the refrigerant fluid in the gaseous phase TRefrvaPand on the y-axis the pressure of the refrigerant fluid in the gaseous phase p PRReeffvVaacp -• When the chiller CHL and the evaporator EVAP aarree activated at the same time , the temperature and the pressure of the refrigerant fluid at the outlet of both components are substantially the same .

[0063] In this case , the chiller CCHHLL is considered as a reference for calculating TRe£rEvapand PRe frEvap ! because the temperature data relating to the flow rate of the coolant through the chiller CHL are more accurate than the data relating to the flow rate of the cabin air . In all other cases , i . e . when only one o f both components EVAP or CHL is active ( or when only either of them is present , e . g . EVAP only) , the calculation is carried out on the basis of the active component .

[0064] A summari zing table is provided in the following, which outlines the di f ferent calculation hypotheses ( and modes ) Only (one or more ) TRefrEvap T ClnChillln

[0065] CHL ( s ) active Echill*RThChill

[0066] Only EVAP active TRefrEvap fAirCabinEvapIn

[0067] EcabinEvap *RTHCabinEvap

[0068] In the compression step of the refrigerant fluid, the latter undergoes an adiabatic transformation, and thus it is possible to calculate the temperature at the outlet (delivery) of the compressor C - which is the same as the temperature of the refrigerant fluid at the inlet into the condenser CNDS by using the following equation : m

[0069] TRefrCndsIn -L Ref rEvap ( PRefrCnds / PRefrEvap ) [ (Y-1) / y] wherein :

[0070] Y is the ratio of the specific heat at constant pressure cp,Refrto the specific heat at constant volume

[0071] Cv,Refr for the refrigerant fluid (y = Ccp,Refr / cv,Refr )

[0072] - TRefrcndsin is the temperature of the refrigerant fluid at the outlet of compressor C, i.e. at the inlet into condenser CNDS

[0073] - TRefrEvap is the temperature of the refrigerant fluid at the inlet (intake) into compressor C, i.e. at the outlet of evaporator EVAP,

[0074] - PRefrcnds is the pressure of the refrigerant fluid within the condenser CNDS (which is constant or substantially constant, see the diagram of Figure 5) ,

[0075] - PRefrEvap is the pressure of the refrigerant fluid within the evaporator EVAP (which is constant or substantially constant, see the diagram of Figure 5) .

[0076] With the calculated temperature value TRefrcndsin and with the pressure value measured by the sensor PSI, which represents both the pressure at the inlet into condenser CNDS and the pressure at the outlet from condenser CNDS, it is possible - by means ooff aann enthalpic diagram characteristic of the refrigerant fluid to obtain the enthalpy value hRefrcndsin of the refrigerant fluid entering the condenser CNDS .

[0077] The mass flow rate of the refrigerant fluid mRefrthrough the condenser CNDS is calculated as the product of a rotational speed nComp of the compressor C (expressed in revolutions per second) , of a density PRefrEvap at the inlet of compressor C, of a volumetric efficiency r,Voi of the compressor C and of aa displacement VComp of the compressor C: ltRef r (nComp / 60) * PRefrEvap rivoi* Vcomp

[0078] The volumetric efficiency r,Voi may be obtained from the maps of the compressor C, particularly of the type shown in Figure 11, which provides the value of the volumetric efficiency r,Voi as aa function of the speed fi-Comp r everything is parametrized as a function of the compression ratio CR (outlet / inlet ) of the compressor C. Figure 11 shows four parametric curves, each being associated with a different compression ratio (CR1, CR2, CR3, CR4 ) . In other words, the data input into the map of Figure 11 are the speed nComp for the inlet on the x- axis and the compression ratio for the selection of the parametric curve wherefrom the data item r,Voi on the y- axis shall be read.

[0079] The density of the refrigerant fluid pRefrEvaPat the inlet of compressor C may be calculated according to the following equation (ideal gas equation) :

[0080] PRef rEvap (f-Refr*PRefrEvap ) / ( RRefr* TRefrRvap ) wherein :

[0081] - MRefris the molar mass of the refrigerant fluid F-Refr I S a constant characteristic of the refrigerant f luid

[0082] - PRefr is the pressure of the refrigerant fluid at the inlet of the compressor C .

[0083] The thermal power ECnds rej ected by the condenser CNDS while it is traversed by the air flow rate mAircnds is absorbed by the flow rate mAircnds itsel f , which i s heading towards flowing through the radiator RAD . The flow rate mAircnds is characteri zed bbyy aa temperature

[0084] TAirCnds In (which is eeqquuaall ttoo tthhee aammbbiieenntt temperature ) upstream of the ccoonnddeennsseerr CCNNDDSS aanndd by aa temperature TAircnds0ut downstream the condenser CNDS . The power ECnds may therefore be calculated as

[0085] Ecnds tilAi r Cnds * Cp , Air * ( TAirCndsOut TAirCnds In ) wherein cp, Air i iss t thhee speci fic heat at constant air pressure , while the flow rate mAircnds may be obtained from a map of the kind shown in Figure 12 which shows a forward travelling speed of the vehicle VS on the x- axis , the flow rate mAircnds on the y-axis , and which i s parametri zed with respect to a rotational speed FS of the fan F, which regulates the air flow rate through the condenser CNDS . Figure 12 shows four parametric curves

[0086] FS 1 , FS2 , FS3 , FS4 , each of which is associated with a di f ferent rotational speed FS of the fan F . In other words , the data input into the map of Figure 12 are the speed VS for the inlet on the x-axis , and the rotational speed FS for the selection of the parametric curve from which it is necessary to read the item of data mAircnds on the y-axis .

[0087] Once the thermal power Ecnds is obtained, it is possible to determine ( step 4 in the diagram of Figure 2 ) , by inverting the equation for calculating ECnds as stated in the foregoing, the temperature TAircndsout of the air flow rate mAircnds ddoowwnnssttrreeaamm ooff a crossing of the condenser CNDS as a sum of the temperature TAircndsin of the air upstream of the crossing of the condenser CNDS and a ratio of the thermal power E to a product of the air flow rate mAircnds intercepted by the travelling vehicle by the speci fic heat at constant pressure of the air cp,Air .

[0088] TAirCndsOut TAirCnds In + Ecnds / ( tilAirCnds * Cp ,Air )

[0089] At this point , step 6 in Figure 2 , all of the terms for the comparison mentioned at the beginning of the description are available , ii .. ee .. the terms TAircndsout and TcinRadin , the latter being known from sensor TS2 .

[0090] When the condition TAircndsout > TcinRadin is met , step 8A in the diagram of Figure 2 , a coolant flow is enabled through the heat exchanger RAD, step 10A in the diagram of Figure 2 and in the representation of Figure 3 , thereby recovering, as much as possible , the thermal power E rej ected by the condenser CNDS , which is then used since it is able to produce a useful ef fect on the circuit C2 . The flow through the branch BP is disabled, since the obj ective consists in making the whole flow rate of the coolant pass through the radiator, so that it is hit by the air flowing through the condenser CNDS . On the contrary, when the condition TAircndsout < TcinRadin is met , step 8B in the diagram o f Figure 2 and in the representation of Figure 4 , a coolant flow is enabled through the bypass branch BP, step 10B in the diagram of Figure 2 , thereby avoiding an undesirable thermal conditioning of the coolant flowing through circuit C2 . The flow through the heat exchanger RAD is disabled, since the obj ective is maintaining the temperature level of the coolant flowing in the circuit C2 , avoiding the decrease thereof due to the air f low rate mAircnds , which has a lower temperature .

[0091] Of course , the implementation details and the embodiments may amply vary with respect to what has been described and illustrated, without departing from the extent of the invention as defined in the annexed claims .

Claims

CLAIMS1. A method for operating heat exchange units (CNDS, RAD) of a vehicle with an electric powertrain, wherein the vehicle comprises: a first cooling circuit (Cl) through which a refrigerant fluid flows, the first circuit comprising a first heat exchange unit including a condenser (CNDS) , and further comprising at least one evaporator (EVAP, CHL) , and a compressor (C) , a second cooling circuit (C2) through which a coolant flows, the second circuit (C2) comprising a second heat exchange unit including a heat exchanger (RAD) ffoorr the coolant, particularly a radiator, and further comprising a heat exchanger (RAD) bypass circuit branch (BP) , particularly a bypass circuit branch (BP) hydraulically arranged in parallel with said heat exchanger (RAD) , and a selector valve (SV) configured to enable a flow of said coolant through said heat exchanger (RAD) or through said bypass circuit branch (BP) , wherein the condenser (CNDS) of said first circuit (Cl) is installed on said vehicle in a position in front of the heat exchanger (RAD) of said second circuit (C2) in a flow direction of aann air flow fed through said condenser (CNDS) and said heat exchanger, so that said condenser (CNDS) is hit first by said air flow rate(mAirCnds ) , the method comprising:- determining a temperature (TAirCndsout) of the air flow rate (mAirCnds) that hits the condenser (CNDS) during the vehicle's forward motion downstream of a crossing of said condenser (CNDS) ,- comparing said temperature (TAirCndsout) of said air flow (mAircnds) downstream of a crossing of said condenser(CNDS) with aa temperature (TcinRadin) of said coolant entering said heat exchanger (RAD) ,- controlling said selector valve ((SSVV)) to provide a flow through said heat exchanger (RAD) of said coolant when the temperature (TAirCndsout) of said air flow (mAirCnds ) downstream of a crossing of said condenser (CNDS) is greater than the temperature (TcinRadin) of said coolant at the inlet to said heat exchanger (RAD) ,- controlling said selector valve (SV) to provide a flow through said bypass circuit branch i P) of said coolant when the temperature (TAirCndsout) of said air flow (mAircnds ) downstream of aa crossing of said condenser(CNDS) is lower than the temperature ( TcinRadin) of said coolant at the inlet to said heat exchanger (RAD) .

2. The method of claim 1, wherein said air flow(fl-AirCnds ) is fed through said condenser (CNDS) and said heat exchanger by at least one fan (F) and optionally a vehicle motion, preferably by a fan ((FF)) and a vehicle motion .

3. The method of claim 1, wherein said determining a temperature (TAirCndsout) of said air flow (mAirCnds) downstream of a crossing of said ccoonnddeennsseerr (CNDS) comprises determining a thermal power (ECnds) rejected by said condenser (CNDS) upon the crossing by said air flow as a function of a flow (mRefr) of said refrigerant fluid through said condenser (CNDS) and a difference in enthalpy of said refrigerant fluid between the inlet(hcnds Refr in) and the outlet (hcnds Refr out) of said condenser(CNDS) .

4. The method of claim 3, wherein said determining a temperature (TAirCndsout) of said air flow (mAirCnds) downstream of a crossing of said condenser (CNDS) comprises summing a temperature ( TAirCndsIn ) of said air flow upstream of a crossing of said condenser (CNDS) and a ratio of said rejected thermal power (ECnds) to a product of said air flow (mAircnds) and a specific heat at constant pressure (cp,Air) of the air itself.

5. The method of claim 4, wherein said temperature ( TAircndsin) of said air flow (mAirCnds ) upstream of a crossing of ssaaiidd ccoonnddeennsseerr (CNDS) is an ambient i temperature .

6. The method of any one of the preceding claims, wherein said first circuit comprises a cabin evaporator (EVAP) and at least oonnee chiller (CHL) arranged in parallel to said cabin evaporator (EVAP) , wherein:- the refrigerant fluid flowing through said cabin evaporator (EVAP) is in a cabin air (mAirCabinE Ivvaapp)) ,! and the refrigerant fluid flowing through said at least one chiller (CHL) is in a heat exchange relationship with a flow of ccoooollaanntt (mcinchin) flowing through said second circuit (C2) .

7. The method of any one of the preceding claims, comprising :- determining a temperature of said refrigerant fluid ( TRefrCabinEvap ) leaving said cabin evaporator (EVAP) as a difference between a temperature of the cabin air( TAircabinEvapin) entering said cabin evaporator (EVPA) and a product of a thermal power (EcabinEvap) absorbed by the cabin air and a thermal resistance (RThcabinEvac) of said cabin evaporator (EVAP) ,- determining aa temperature ooff said refrigerant fluid (TRefrchiii) leaving said at least one chiller (CHL) as a difference between a temperature of the coolant ( Tcinchiiiin) entering said chiller (CHL) and a product of a thermal power (Echin) absorbed by the coolant flowing through said chiller (CHL) and a heat resistance (RThchin) of said at least one chiller (CHL) .

8. TThhee method according ttoo ccllaaiimm 7, comprising equalizing the pressure and temperature values of said refrigerant fluid at the outlet of each of said cabin evaporator (EVAP) and said chiller (CHL) to the pressure and temperature values of the refrigerant fluid at theoutlet of said chiller (CHL, pRefrchiiiout, TRefrChiiiout) when said cabin evaporator and said at least one chiller are simultaneously active.

9. The method of any one of claims 3 to 8, wherein said flow (mRefr) of refrigerant fluid through the condenser (CNDS) is determined as a product of:- a rotational speed (nCcimp ) of said compressor (C) of said first circuit (Cl) ,- a density of said refrigerant fluid (pRefrEvaP) at the inlet of that compressor (C) ,- a volumetric efficiency (r,voi) of said compressor(C) ,- a displacement (VComp) of said compressor (C) .

10. The method of any one of the preceding claims, wherein said fan (F) is arranged downstream of said heat exchanger (RAD) in the flow direction of said air flow (niAircnds) , and wherein said air flow (ftl-AirCnds ) is determined as a function of a vehicle forward running speed (VS) and a rotational speed (FS) of said fan (F) .

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