Abstract:
A multiplane fan cooling system and method is disclosed for a cooling system with first, second and intake planes; a first fan and heat exchanger on the first plane, a second fan and heat exchanger on the second plane, and a shared air cavity bounded at least partially by these three planes. Each fan pulls air into the shared air cavity through the intake plane and across its associated heat exchanger. The first fan cools the first heat exchanger, and counteracts the second fan from drawing air into the shared air cavity through the first heat exchanger. The second fan cools the second heat exchanger. The second fan can be activated to counteract the first fan from drawing air into the shared air cavity through the second heat exchanger. All the air in the shared air cavity can be available to each of the fans.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure relates to cooling fan control on a machine, and in particular to a cooling fan control system for a cooling package with cooling fans on multiple planes. 
       BACKGROUND 
       [0002]    Physically separating distinct cooling zones in a machine cooling system may resolve hot air recirculation to the active fan heat exchangers. This can lead to higher system efficiencies but it may also reduce the cleaning of the cooling package and the efficacy of reversing fans. Any flow divider to separate zones will take up space and will need to seal tightly enough to prevent recirculation airflow. This sealing and complex geometry of dividers and zones may trap dirt and debris. By using passive fans at lower speeds to avoid recirculation, the overall cooling package can become easier to clean with a small tradeoff in cooling system efficiency. 
         [0003]    It would be desirable to have a cooling system with an open cooling compartment where the cooling fans on different planes can pull ambient air from the same cooling compartment for cooling various machine systems without causing preheated air to be pulled back through other fans of the cooling system. 
       SUMMARY 
       [0004]    A multiplane fan cooling system is disclosed for a vehicle having a plurality of heat exchangers to cool vehicle systems. The multiplane fan cooling system includes a first plane with a first fan and a first heat exchanger, a second plane with a second fan and a second heat exchanger, an intake plane, a controller and a shared air cavity. The shared air cavity is bounded at least in part by the first, second and intake planes. The first fan is configured to pull ambient air through the intake plane into the shared air cavity and move it across the first plane and first heat exchanger when the first heat exchanger needs cooling. The second fan is configured to pull ambient air through the intake plane into the shared air cavity and move it across the second plane and second heat exchanger when the second heat exchanger needs cooling. The controller is configured to activate the first fan when the first heat exchanger needs cooling; activate the second fan when the second heat exchanger needs cooling; and activate the first fan to counteract air from being drawn into the shared air cavity through the first heat exchanger by the second fan. The controller can also be configured to control a speed of the first fan to counteract air from being drawn into the shared air cavity through the first heat exchanger by the second fan. The controller can also be configured to activate the second fan to counteract air from being drawn into the shared air cavity through the second heat exchanger by the first fan. The controller can also be configured to control a speed of the second fan to counteract air from being drawn into the shared air cavity through the second heat exchanger by the first fan. All of the air in the shared air cavity can be available to each of the first and second fans. 
         [0005]    The multiplane fan cooling system can also include a first sensor that provides first temperature readings of a first vehicle system cooled by the first heat exchanger, and a second sensor that provides second temperature readings of a second vehicle system cooled by the second heat exchanger. The controller can determine a first fan speed for the first fan based on the first sensor readings, determine a second fan speed for the second fan based on the second sensor readings, determine a first fan command for the first fan based on the first and second fan speeds, determine a second fan command for the second fan based on the first and second fan speeds; transmit the first fan command to the first fan, and transmit the second fan command to the second fan. 
         [0006]    The multiplane fan cooling system can also include a third heat exchanger on the first plane, where the first fan is configured to pull ambient air through the intake plane into the shared air cavity and move it across the first plane and the first and third heat exchangers when the first or third heat exchanger need cooling. The controller can be further configured to activate the first fan when the third heat exchanger needs cooling, and control the speed of the first fan to counteract air from being drawn into the shared air cavity through the first and third heat exchangers by the second fan. The multiplane fan cooling system can also include a first sensor that provides first temperature readings of a first vehicle system cooled by the first heat exchanger, a second sensor that provides second temperature readings of a second vehicle system cooled by the second heat exchanger, and a third sensor that provides third temperature readings of a third vehicle system cooled by the third heat exchanger. The controller can be configured to determine a first fan speed for the first fan based on the first and third sensor readings, determine a second fan speed for the second fan based on the second sensor readings, determine a first fan command for the first fan based on the first and second fan speeds, determine a second fan command for the second fan based on the first and second fan speeds, transmit the first fan command to the first fan, and transmit the second fan command to the second fan. 
         [0007]    The multiplane fan cooling system can also include a third fan and a third heat exchanger on the first plane, where the third fan is configured to pull ambient air through the intake plane into the shared air cavity and move it across the first plane and the third heat exchanger when the third heat exchanger needs cooling. The controller can be further configured to activate the third fan when the third heat exchanger needs cooling, control a speed of the first fan to counteract air from being drawn into the shared air cavity through the first heat exchanger by the second fan or the third fan, control a speed of the second fan to counteract air from being drawn into the shared air cavity through the second heat exchanger by the first fan or the third fan, and control a speed of the third fan to counteract air from being drawn into the shared air cavity through the third heat exchanger by the first fan or the second fan. The multiplane fan cooling system can also include a first sensor that provides first temperature readings of a first vehicle system cooled by the first heat exchanger, a second sensor that provides second temperature readings of a second vehicle system cooled by the second heat exchanger, and a third sensor that provides third temperature readings of a third vehicle system cooled by the third heat exchanger. The controller can also be configured to determine a first fan speed for the first fan based on the first sensor readings, determine a second fan speed for the second fan based on the second sensor readings, determine a third fan speed for the third fan based on the third sensor readings, determine a first fan command for the first fan based on the first, second and third fan speeds, determine a second fan command for the second fan based on the first, second and third fan speeds, determine a third fan command for the third fan based on the first, second and third fan speeds, transmit the first fan command to the first fan, transmit the second fan command to the second fan, and transmit the third fan command to the third fan. All of the air in the shared air cavity can be available to each of the first, second and third fans. 
         [0008]    A method is disclosed for controlling a multiplane fan cooling system for a vehicle that includes an intake plane, a first heat exchanger plane, a second heat exchanger plane, and a shared air cavity bounded at least in part by the intake plane and the first and second heat exchanger planes. The first heat exchanger plane includes a first fan and a first heat exchanger configured to cool a first vehicle system, and the second heat exchanger plane includes a second fan and a second heat exchanger configured to cool a second vehicle system. The method includes monitoring the first and second vehicle systems to determine if any of the first and second vehicle systems need cooling; when the first vehicle system needs cooling, activating the first fan to draw ambient air into the shared air cavity through the intake plane and out across the first plane and the first heat exchanger; when the second vehicle system needs cooling, activating the second fan to draw ambient air into the shared air cavity through the intake plane and out across the second plane and second first heat exchanger; and activating the first fan to counteract air from being drawn into the shared air cavity through the first heat exchanger by the second fan. The method can also include activating the second fan to counteract air from being drawn into the shared air cavity through the second heat exchanger by the first fan. All of the air in the shared air cavity can be available to each of the first and second fans. The method can also include controlling a speed for the first fan to counteract air from being drawn into the shared air cavity through the first heat exchanger by the second fan, and controlling a speed for the second fan to counteract air from being drawn into the shared air cavity through the second heat exchanger by the first fan. 
         [0009]    The method can also include monitoring first sensor readings from a first sensor providing a temperature of the first vehicle system, monitoring second sensor readings from a second sensor providing a temperature of the second vehicle system, calculating a first independent fan speed for the first fan based on the first sensor readings, calculating a second independent fan speed for the second fan based on the second sensor readings, determining a first fan command for the first fan based on the first and second independent fan speeds, determining a second fan command for the second fan based on the first and second independent fan speeds, transmitting the first fan command to the first fan; and transmitting the second fan command to the second fan. 
         [0010]    The first heat exchanger plane can also include a third heat exchanger configured to cool a third vehicle system, and the method can also include monitoring the first, second and third vehicle systems to determine if any of the first, second and third vehicle systems need cooling; when the third vehicle system needs cooling, activating the first fan to draw ambient air into the shared air cavity through the intake plane an out across the first plane and the third heat exchanger; and controlling the speed of the first fan to counteract air from being drawn into the shared air cavity through the first and third heat exchangers by the second fan. The method can also include monitoring first sensor readings from a first sensor providing a temperature of the first vehicle system, monitoring second sensor readings from a second sensor providing a temperature of the second vehicle system, monitoring third sensor readings from a third sensor providing a temperature of the third vehicle system, calculating a first independent fan speed for the first fan based on the first and third sensor readings, calculating a second independent fan speed for the second fan based on the second sensor readings, determining a first fan command for the first fan based on the first and second independent fan speeds, determining a second fan command for the second fan based on the first and second independent fan speeds, transmitting the first fan command to the first fan; and transmitting the second fan command to the second fan. 
         [0011]    The first heat exchanger plane can also include a third fan and a third heat exchanger configured to cool a third vehicle system, and the method can also include monitoring the first, second and third vehicle systems to determine if any of the first, second and third vehicle systems need cooling; when the third vehicle system needs cooling, activating the third fan to draw ambient air into the shared air cavity through the intake plane an out across the first plane and the third heat exchanger; activating the third fan when the third heat exchanger needs cooling; controlling the speed of the first fan to counteract air from being drawn into the shared air cavity through the first heat exchanger by the second fan or the third fan; controlling the speed of the second fan to counteract air from being drawn into the shared air cavity through the second heat exchanger by the first fan or the third fan; and controlling the speed of the third fan to counteract air from being drawn into the shared air cavity through the third heat exchanger by the first fan or the second fan. The method can also include monitoring first sensor readings from a first sensor providing a temperature of the first vehicle system; monitoring second sensor readings from a second sensor providing a temperature of the second vehicle system; monitoring third sensor readings from a third sensor providing a temperature of the third vehicle system; calculating a first independent fan speed for the first fan based on the first sensor readings; calculating a second independent fan speed for the second fan based on the second sensor readings; calculating a third independent fan speed for the third fan based on the third sensor readings; determining a first fan command for the first fan based on the first, second and third independent fan speeds; determining a second fan command for the second fan based on the first, second and third independent fan speeds; determining a third fan command for the third fan based on the first, second and third independent fan speeds; transmitting the first fan command to the first fan; transmitting the second fan command to the second fan; and transmitting the third fan command to the third fan. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above-mentioned aspects of the present disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of the embodiments of the disclosure, taken in conjunction with the accompanying drawings, wherein: 
           [0013]      FIG. 1  illustrates an exemplary machine that can include a cooling package with multiple plane recirculation fan control; 
           [0014]      FIG. 2  illustrates an exemplary cooling compartment that includes a cooling package with multiple fans and a baffle; 
           [0015]      FIG. 3  illustrates a right-rear perspective of an exemplary cooling compartment that includes a cooling package with multiple fans with no separators or baffles; 
           [0016]      FIG. 4  illustrates a right-side perspective of the cooling compartment of  FIG. 3  with the heat exchangers and side walls removed; and 
           [0017]      FIG. 5  illustrates an exemplary flow diagram for cooling package fan control. 
       
    
    
       [0018]    Corresponding reference numerals are used to indicate corresponding parts throughout the several views. 
       DETAILED DESCRIPTION 
       [0019]    The embodiments of the present disclosure described below are not intended to be exhaustive or to limit the disclosure to the precise forms in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present disclosure. 
         [0020]      FIG. 1  shows an exemplary vehicle, a loader  100 , which can include a cooling package with multiple plane recirculation fan control. The loader  100  includes an operator cab  102 , traction devices  104 , which can be wheels, tracks or other devices, a work implement  106 , an engine compartment  108  and a cooling compartment  110 . The engine compartment  108  includes an engine that powers the various systems of the loader  100  and these systems can generate heat. The cooling compartment  110  can include a cooling package with multiple fans to cool the various systems of the loader  100 . The cooling compartment  110  includes a rear plane  112 , a top plane  114 , a left side plane  116 , a right side plane  118  (opposite the left side plane  116 ), and a front plane  120 . The front plane  120  can include a plate, or baffle, separating the cooling compartment  110  from the engine compartment  108 . Some of the planes  112 - 120  of the cooling compartment  110  can include heat exchangers coupled to various systems of the vehicle  100 , and fans to cool these heat exchangers. 
         [0021]    The use of multiple planes in a machine cooling package provides opportunities for separate zone cooling. Air flow for the separate zones can be generated with multiple fans that may have independent speed control. Different systems require different cooling, so each zone can have a distinct minimum and maximum temperature fan response. Separate sensors can be used to track the temperatures of the various systems, and to determine when the cooling fans should be activated and the required speeds for the activated cooling fans. One challenge with this arrangement is recirculation when the fans are running at different speeds. Heated air from one heat exchanger with a higher minimum temperature may be pushed into a heat exchanger that requires cooling and this can reduce the cooling capacity of the overall system. Some solutions use a baffle to seal-off and separate the zones from one another, but baffles can reduce the performance of the fans, trap debris and moisture, add weight, and add cost. Instead of a baffle, the cooling system can allow air flow between the zones and control fan speed to counter recirculation of preheated air where it is not desired. 
         [0022]      FIG. 2  illustrates an exemplary cooling compartment  210  that includes a cooling package with an air cavity  240 , multiple fans and a baffle  202 . The top plane  214  includes one or more fans  224  to cool one or more heat exchangers  234 , the left side plane  216  includes one or more fans  226  to cool one or more heat exchangers  236 , and the right side plane  218  includes one or more fans  228  to cool one or more heat exchangers  238 . The rear plane  212 , closest to the viewer, is open to allow the fans to draw fresh, ambient air into the air cavity  240 . The front plane  220 , furthest from the viewer, is closed to separate the cooling compartment  210  from the engine compartment. The baffle  202  separates the air cavity  240  into three sections: a top section  244  where the top fans  224  on the top plane  214  can pull ambient air through the rear plane  212  to cool the top heat exchangers  234 , a left section  246  where the left fans  226  on the left plane  216  can pull ambient air through the rear plane  212  to cool the left heat exchangers  236 , and a right section  248  where the right fans  228  on the right plane  218  can pull ambient air through the rear plane  212  to cool the right heat exchangers  238 . 
         [0023]    The baffle  202  prevents air flow and recirculation between the top section  244 , the left section  246 , and the right section  248  of the air cavity  240  of the cooling compartment  210 . Thus, if the right fans  228  are actively pushing air through the right heat exchangers  238  to cool them, then all of that air being pulled into the right section  248  is ambient air being pulled through the rear plane  212  and not air being pulled from the top section  244  through the top heat exchangers  234  or air being pulled from the left section  246  through the left heat exchangers  236 . Similarly, if the right fans  228  are actively pushing air at a relatively high speed through the right heat exchangers  238  to cool them and the left fans  226  are not active because the left heat exchangers  236  do not presently need cooling and the top fans  224  are actively pushing air at a relatively low speed through the top heat exchangers  234  to cool them, then the air being pulled into the right section  248  and the top section  244  is ambient air being pulled through the rear plane  212 , and there is no recirculation of preheated air being pulled from the other sections of the air cavity  240  through their associated heat exchangers. These are just a couple of examples of the baffle  202  preventing air flow and recirculation between the multiple sections  244 ,  246 ,  248  of the air cavity  240  of the cooling compartment  210 , and it applies equally to any pulling and recirculation of preheated air between the various sections of the air cavity  240 . 
         [0024]      FIGS. 3 and 4  illustrate an exemplary cooling compartment  310  that includes a cooling package with a shared air cavity  340 , multiple fans and no separators or baffles.  FIG. 3  shows the cooling compartment  310  from a right-rear perspective and  FIG. 4  shows the cooling compartment  310  with the heat exchangers and side walls removed from a right-side perspective. The top plane  314  includes one or more fans  324  to cool one or more heat exchangers  334 , the left side plane  316  includes one or more fans  326  to cool one or more heat exchangers  336 , and the right side plane  318  includes one or more fans  328  to cool one or more heat exchangers  338 . The rear plane  312  is open to allow the fans  324 ,  326 ,  328  to draw fresh, ambient air into the shared air cavity  340 . The rear plane  312  may have a screen or grill  362  to help keep debris and dirt from entering the shared air cavity  340 . The front plane  320  is closed to separate the cooling compartment  310  from the engine compartment. A cooling system controller  304  receives signals from the heat exchangers  334 ,  336 ,  338  indicating whether or not they need cooling, and the cooling system controller  304  can separately activate the fans  324 ,  326 ,  328  to pull ambient air through the rear plane  312  into the shared air cavity  340  to cool the associated heat exchangers  334 ,  336 ,  338 , respectively. 
         [0025]    Each of the heat exchangers  334 ,  336 ,  338  can include one or more separate heat exchangers for the various systems of the vehicle, for example radiators, hydraulic oil coolers, transmission coolers, refrigerant condensers, fuel coolers, power electronics coolers, etc. These heat exchangers can be separated on the same plane of the cooling compartment  310  and the fans can be grouped based on the separation of the heat exchangers. For example, the right heat exchangers  338  can include a hydraulic oil cooler at the top and a power electronics cooler at the bottom, configured so a top fan group  352  of two fans of the right fans  328  can blow air over the hydraulic oil cooler at the top of the right heat exchangers  338 , and a bottom fan group  354  of two fans of the right fans  328  can blow air over the power electronics cooler at the bottom of the right heat exchangers  338 . The cooling system controller  304  can be configured to separately activate and deactivate the top fan group  352  as one fan group to cool the hydraulic oil cooler at the top of the right heat exchangers  338 , and the bottom fan group  354  as another fan group to cool the power electronics cooler at the bottom of the right heat exchangers  338 . The heat exchangers can also be stacked so that air blown by one or more of the fans  324 ,  326 ,  328  blows over an inner heat exchanger and then over an outer heat exchanger and then out of the vehicle. 
         [0026]    The cooling system controller  304  can activate one or more groups of the fans  324 ,  326 ,  328  at low forward speeds to reduce or prevent pulling of preheated air into the shared air cavity  340  through a heat exchanger on another plane of the cooling compartment  310  and recirculation of the heated air generated by an active high speed fan command. For example, if a heat exchanger requests airflow, for example the top heat exchangers  334 , the cooling system controller  304  will activate the associated fan group, the top fans  324  at fan speeds sufficient to move the required mass flow rate of air from inside the shared air cavity  340  to cool the top heat exchangers  334 . This will create a low pressure inside the shared air cavity  340  which can draw ambient air in through the rear plane  312  and also can reverse air flow through the right and/or left side heat exchangers  336 ,  338  and fans  326 ,  328  bringing preheated air back into the shared air cavity  340 . This recirculation of preheated air degrades cooling because it is almost always hotter than the ambient air which degrades the cooling of the heat exchangers needing cooling and can overcool a heat exchanger that does not need cooling. To reduce or prevent the pulling of preheated air through the right and/or left side heat exchangers  336 ,  338 , the cooling system controller  304  can activate the right and/or left side fans  326 ,  328  at a sufficient fan speed to reduce or prevent drawing of air through an inactive fan or reverse flow of air through a fan activated at a lower fan speed into the shared air cavity  340 . The cooling system controller  304  can activate any group of fans on any of the cooling planes  314 ,  316 ,  318  of the cooling compartment  310  to counteract the pulling of air through a heat exchanger and into the shared air cavity  340  whether the associated fans are not currently needed for cooling or are pushing a smaller mass flow of air than other fans. 
         [0027]    When any fan group is activated, the cooling system controller  304  can determine whether one or more other fan groups should be activated to reduce or prevent recirculation of preheated air. A recirculation data matrix can be pre-calculated and used to determine whether other fan groups should be activated. For example, the fans of the embodiment of the cooling compartment  310  shown in  FIGS. 3 and 4  can be separated into four groups: a first fan group including four fans  326  on the left side plane  316 , a second fan group including a top right fan group  352  of two fans  328  on the right side plane  318 , a third fan group including a bottom right fan group  354  of two fans  328  on the right side plane  318 , and a fourth fan group of two fans on the top plane  314 . The fan groups can be configured based on the various system heat exchanger zones that are included in the top, left and right side heat exchangers  334 ,  336 ,  338 , respectively. In this example, there is a first heat exchanger zone including one or more heat exchangers on the left side plane  316  cooled by the first fan group, a second heat exchanger zone including one or more heat exchangers at the top of the right side plane  318  cooled by the second fan group, a third heat exchanger zone including one or more heat exchangers at the bottom of the right side plane  318  cooled by the third fan group, and a fourth heat exchanger zone including one or more heat exchangers on the top plane  314  cooled by the fourth fan group. 
         [0028]    The cooling system controller  304  can receive temperature readings for the various heat exchangers and determine when to activate each fan group and the appropriate fan speeds, or can receive fan activation commands for each fan group and the appropriate fan speeds. From this information, the cooling system controller  304  can generate a temperature control vector with a commanded fan speed for each fan group. The temperature control vector can be multiplied by the recirculation data matrix to determine the fan speed commands for each fan zone as shown below: 
         [0000]      (temperature command 1,temperature command 2,temperature command 3,temperature command 4){matrix}=(zone 1 command,zone 2 command,zone 3 command,zone 4 command) 
         [0000]    Additional control zones and additional temperature commands will increase the size of the temperature control vector, the fan zone command vector and the recirculation data matrix. 
         [0029]    The recirculation data matrix can be calculated based on the configuration and geometry of the vehicle, the heat exchanger zones, the fan groups and other factors. The recirculation data matrix can be set up to turn the passive fan groups (fan groups where associated heat exchangers do not require air flow) just fast enough to not have air flow through the heat exchangers that do not require cooling; and to increase the speeds of active fan groups (fan groups where associated heat exchangers desire air flow) just fast enough to push the desired air flow through the associated heat exchangers despite the air flow pulled by other fan groups. An example recirculation data matrix is: 
         [0000]    
       
         
           
               
             
               
                 
                   1 
                 
                 
                   0.5 
                 
                 
                   0.5 
                 
                 
                   0.5 
                 
               
               
                 
                   0 
                 
                 
                   1 
                 
                 
                   0 
                 
                 
                   0 
                 
               
               
                 
                   0 
                 
                 
                   0 
                 
                 
                   1 
                 
                 
                   0 
                 
               
               
                 
                   0 
                 
                 
                   0 
                 
                 
                   0 
                 
                 
                   1 
                 
               
             
           
         
       
     
         [0000]    This recirculation data matrix indicates that when the first fan group is activated, each of the other fan groups is activated at half of the speed of the first fan group to prevent the first fan group from pulling air through heat exchanger zones two, three and four. This recirculation data matrix also indicates that the second, third or fourth fan groups will only pull air through their associated heat exchanger zone, so the other fan groups do not need to be activated to prevent recirculation of preheated air. The recirculation data matrix can have off-axis non-zero terms anywhere necessary to reduce or prevent pulling of air through other heat exchanger zones. 
         [0030]    When a fan group is activated, the pre-calculated recirculation data matrix can be used to determine the necessary fan speeds for the other fan groups to reduce or prevent pulling of air through other heat exchanger zones into the shared air cavity  340 . As an example, when only the first and fourth heat exchanger zones need cooling and the first fan group should be operated at 50% of maximum speed to provide sufficient cooling for the first heat exchanger zone, and the fourth fan group should be operated at 40% of maximum speed to provide sufficient cooling for the fourth heat exchanger zone, then the temperature control vector could be:
       [0.5, 0, 0, 0.4].       
 
         [0032]    Multiplying the example temperature control vector by the example recirculation data matrix results in fan speed commands of:
       [0.5, 0.25, 0.25, 0.65]
 
which indicates that fan group 1 should be run at 50% speed, fan group 2 should be run at 25% speed, fan group 3 should be run at 25% speed, and fan group 4 should be run at 65% speed.
       
 
         [0034]      FIG. 5  illustrates an exemplary flow diagram for cooling package fan control. At block  502 , the controller cycles through the vehicle system temperature readings, for example temperature readings for engine coolant, front axle coolant, rear axle coolant, brakes, transmission oil, hydraulic oil, charged air cooler, fuel temperature, etc. For each of the vehicle system temperature readings, at block  504  the controller determines the fan zone that cools that particular vehicle system. At block  506 , the controller checks whether other vehicle systems cooled by that fan zone need cooling. If no other vehicle systems cooled by that fan zone need cooling then control passes to block  508 , otherwise control passes to block  510 . 
         [0035]    If no other vehicle systems cooled by that fan zone need cooling then, at block  508 , the controller determines the fan speed for that fan zone to provide the necessary cooling of that particular system. Control then passes to block  512 . 
         [0036]    If other vehicle systems cooled by that fan zone need cooling then, at block  510 , the controller determines the maximum fan speed required for that fan zone to provide the necessary cooling of the vehicle systems that need cooling. Control then passes to block  512 . 
         [0037]    At block  512 , the controller updates the temperature control vector (TCV) with the zone fan speed determined at block  508  or block  510 . The zone fan speed can be a value between 0 and 1, where 0 means the fan does not need to be run and 1 indicates the fan should be run at full speed. At block  514 , the controller multiples the temperature control vector by the recirculation data matrix (RDM) to determine the zone fan command vector (ZFCV) with the fan speed commands for each fan zone. As explained above, the RDM can be calculated to take into account any necessary fan speed to counteract the recirculation of preheated air through the shared air cavity. At block  516 , the controller sends the fan speed commands to each fan zone. The controller then cycles back to block  502  to process the temperature reading for the next vehicle system. 
         [0038]    Over time, debris can build up on the various faces of the cooling compartment and interfere with the system recirculation control. The fan groups can be activated in reverse to clear or reduce the debris on the various faces of the cooling compartment. 
         [0039]    As an alternative to using the pre-calculated recirculation data matrix, air flow sensors can be used to provide readings for the direction and mass flow of air through each of the heat exchanger zones and the cooling system controller can activate the associated fan groups for each heat exchanger zone to the necessary speed to counteract recirculation and provide the desired air flow through each heat exchanger zone. 
         [0040]    As another alternative, temperature sensors can be used to provide temperature readings inside the shared air cavity near each fan group and the cooling system controller can take into account the heat exchanger zone temperature and the temperature inside the shared air cavity near the associated fan group to determine the necessary speed to counteract recirculation and provide the desired air flow through each heat exchanger zone. 
         [0041]    As yet another alternative, fan temperature sensors can be used as feedback. A fan temperature sensor can be embedded in each fan and the cooling system controller can take into account the fan temperatures to determine the necessary speed to reduce or prevent recirculation and provide the desired air flow. This could reduce the overall cost of the system and protect the sensor. It could also allow the system to cool off the internals of the fans to provide longer fan life. 
         [0042]    Recirculation is also a risk in the event of a fan failure in a cooling zone. If the other fans in the zone increase speed to maintain vehicle operation, then this can increase recirculation at the location of the failed fan. Temperature sensors could be used to sense a fan failure if the fan did not provide feedback to the cooling system controller  304 . 
         [0043]    While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that illustrative embodiment(s) have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. It will be noted that alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present invention as defined by the appended claims.