Patent Publication Number: US-2022214071-A1

Title: Air supply system

Description:
TECHNICAL FIELD 
     The present disclosure relates to an air supply system that uses a duct to distribute air supplied to a target space such as a room inside a building. 
     BACKGROUND ART 
     Patent Literature 1 (JP 2001-304614 A) discloses an air conditioning system provided with a main air conditioner unit including a heat exchange coil, and a fan unit including a fan that sends heat-exchanged air. Each fan unit in Patent Literature 1 is connected to a plurality of outlets through ducts, such that the heat-exchanged air is distributed to a plurality of outlets and ventilated to air conditioning zones by the single main air conditioner unit. 
     A controller in Patent Literature 1 controls a pump motor of a pump unit with an adjustable flow rate that sends a heat medium from a heat source to the heat exchange coil, and the rotational speed of a fan motor in the plurality of fan units. A sensor is provided in the plurality of outlets, and the controller controls the air flow volume of each fan and the heat medium flow rate of the heat exchange coil according to variations in the total numerical value of blow-out air flow volume signals from the sensors. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     The rotational speed of each fan motor in the plurality of fan units described in Patent Literature 1 is controlled by a single controller provided externally to the plurality of fan units. The controller in Patent Literature 1 controls the rotational speed of the fan motor of each fan unit while checking the blow-out air flow volume signals from the plurality of sensors provided in the plurality of outlets in each fan unit. Consequently, the control load on the controller according to Patent Literature 1 is increased. 
     Reducing the control load is an issue to be addressed in an air supply system provided with a fan unit having a controllable air flow volume. 
     Solution to Problem 
     An air supply system according to a first aspect is provided with a first unit, a second unit, a duct, a first detector, and a first controller. The first unit includes a first fan. The second unit includes a second fan that supplies first air to a target space. The duct sends the first air delivered from the first unit by the first fan to the second unit. The first detector detects information about second air in the target space. The first controller communicates with the second unit and the first detector. The second unit includes a second detector that detects the air flow volume sent by the second fan, and a second controller that controls the rotation speed of the second fan. The first controller determines a target air flow volume of the second unit on the basis of the information about the second air acquired from the first detector, and transmits an instruction indicating the target air flow volume to the second controller. The second controller controls the rotation speed of the second fan such that the air flow volume detected by the second detector approaches the target air flow volume. 
     In the air supply system according to the first aspect, the second unit receives the indicated value of the air flow volume from the first controller, and the second controller can automatically control the air flow volume in the second unit itself without depending on the first controller. It is sufficient to supply the indicated value of an appropriate air flow volume from the first controller to the second unit, and the control load on the first controller can be reduced. 
     The air supply system according to the second aspect is the system according to the first aspect, in which the first unit includes a heat exchanger through which a heat medium flows. The heat exchanger causes heat to be exchanged between the first air sent by the first fan and the heat medium. 
     In the air supply system according to the second aspect, the first unit can exchange heat with the heat medium in the heat exchanger and send the air-conditioned first air to the second unit. The second unit can use the air-conditioned first air to air-condition the target space. 
     The air supply system according to the third aspect is the system according to the second aspect, in which the first detector is a temperature sensor, a CO 2  concentration sensor, or a humidity sensor, and the first controller determines the target air flow volume of the second unit on a basis of a set temperature, a set CO 2  concentration, or a set humidity of the target space set in advance and a value detected by the first detector. 
     In the air supply system according to the third aspect, the first controller can control the air flow volume of the second unit according to the target air flow volume to keep at least one of the temperature, the humidity, and the CO 2  concentration of the target space in a suitable range. 
     The air supply system according to the fourth aspect is the system according to any of the first aspect to the third aspect further including a third detector, disposed on a downstream side of the first unit, that detects a pressure of the first air sent by the first fan. The first controller controls a rotation speed of the first fan to keep a value of the pressure acquired from the third detector in a predetermined range. 
     By keeping the value of the pressure on the downstream side of the first unit in a predetermined range, the air supply system according to the fourth aspect can eliminate excess power consumption occurring in the first fan and the second fan compared to the case where the value of the pressure on the downstream side of the first unit is outside the predetermined range. 
     The air supply system according to the fifth aspect is the system according to any of the first aspect to the fourth aspect, including a plurality of second units. The duct sends the first air sent from the first unit by the first fan to the plurality of second units. A plurality of first detectors are respectively provided in correspondence with the plurality of second units. The first controller determines a plurality of target air flow volumes of the plurality of second units on a basis of the information about the second air in the target space acquired from the plurality of first detectors, and transmits instructions indicating each target air flow volume to each second controller. 
     In the air supply system according to the fifth aspect, the first controller can control the output of the first fan to match the air quantity of the first air supplied by the plurality of second fans. With this arrangement, the air supply system can lower power consumption. 
     The air supply system according to the sixth aspect is the system according to the fifth aspect, in which in a case of changing an operating state of at least one of the plurality of second fans or changing the air flow volume of at least one of the plurality of second fans, the first controller prioritizes increasing an output of a fan with high fan efficiency or decreasing the output of a fan with low fan efficiency from among the first fan and the plurality of second fans. 
     In the air supply system according to the sixth aspect, the first controller controls to prioritize increasing the output of a fan with high fan efficiency, or decreasing the output of a fan with low fan efficiency, from among the first fan and the plurality of second fans. This configuration reduces the energy consumption of the air supply system. 
     The air supply system according to the seventh aspect is the system according to the sixth aspect, in which the first controller determines the output of the first fan to maintain a constant processing static pressure in the second fan with the highest fan efficiency from among the plurality of second fans or to maximize the rotation speed of the second fan with the highest fan efficiency from among the plurality of second fans. 
     In the air supply system according to the seventh aspect, the first controller determines the output of the first fan to maintain a constant processing static pressure in the second fan with the highest fan efficiency from among the plurality of second fans or to maximize the rotation speed of the second fan with the highest fan efficiency from among the plurality of second fans. With this configuration, the output of a second fan with low fan efficiency can be reduced preferentially. 
     The air supply system according to the eighth aspect is the system according to the sixth aspect, in which the first controller determines the output of the first fan to maintain a constant processing static pressure in the second fan with the lowest fan efficiency from among the plurality of second fans or to minimize the rotation speed of the second fan with the lowest fan efficiency from among the plurality of second fans. 
     In the air supply system according to the eighth aspect, the first controller determines the output of the first fan to maintain a constant processing static pressure in the second fan with the lowest fan efficiency from among the plurality of second fans or to minimize the rotation speed of the second fan with the lowest fan efficiency from among the plurality of second fans. With this configuration, the output of a fan with high fan efficiency can be increased preferentially. 
     The air supply system according to the ninth aspect is the system according to the seventh or eighth aspect, including a plurality of differential pressure sensors that detect the processing static pressure in the plurality of second fans, and the controller determines the output of the first fan on a basis of detected values from the plurality of differential pressure sensors. 
     The air supply system according to tenth aspect is the system according to the seventh or eighth aspect, in which in a case where the air flow volume of the second fan with a maximum fan efficiency among the plurality of second fans does not reach the target air flow volume, the first controller increases the output of the first fan. 
     In the air supply system according to the tenth aspect, the first controller can increase the output of the first fan to cause the air flow volume of the fan with the maximum fan efficiency among the plurality of second fans to reach the target air flow volume. 
     The air supply system according to the eleventh aspect is the system according to any of the sixth to tenth aspect, and further includes a fourth detector that detects an air flow volume of the first air sent by the first fan. The first controller uses at least one of the plurality of second detectors or the fourth detector to compare the fan efficiencies of the first fan and the plurality of second fans. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual diagram illustrating the configuration of an air supply system according to an embodiment. 
         FIG. 2  is a conceptual diagram illustrating an example of the configuration of an air supply system according to a modification. 
         FIG. 3  is a block diagram for explaining the configuration of a controller. 
         FIG. 4  is a conceptual diagram illustrating another example of the configuration of an air supply system according to a modification. 
         FIG. 5  is a conceptual diagram illustrating another example of the configuration of an air supply system according to a modification. 
         FIG. 6  is a conceptual diagram illustrating another example of the configuration of an air supply system according to a modification. 
         FIG. 7  is a block diagram for explaining the configuration of the controller illustrated in  FIG. 6 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     (1) Overall Configuration 
     An air supply system  10  illustrated in  FIG. 1  is provided with a first unit  20 , second units  30 , a duct  40 , and a controller  50 . The first unit  20  includes a first fan  21 . Each of the plurality of second units  30  includes a second fan  31 . Each second fan  31  supplies air from the second unit  30  to a target space  100 . The target space  100  is a room inside a building, for example. The room is a space where the movement of air is restricted by a floor, a ceiling, and walls, for example. The plurality of second units  30  are installed with respect to one or a plurality of target spaces  100 . In  FIG. 1 , as a representative example of the air supply system  10  provided with a plurality of second units  30 , an example is illustrated in which the air supply system  10  provided with two second units  30  is installed with respect to a single target space  100 . The number of second units  30  may also be three or more, and is set appropriately. As described above, two or more target spaces  100  in which the second units  30  are installed may also exist. 
     The duct  40  distributes first air SA delivered from the first unit  20  by the first fan  21  to the plurality of second units  30 . The duct  40  includes a main pipe  41  and a branch pipe  42  branching from the main pipe  41 . In  FIG. 1 , a case where the main pipe  41  is disposed outside the first unit  20  is illustrated, but the main pipe  41  may also be disposed inside the first unit  20 , and may also be disposed to extend from the inside of the first unit  20  to the outside of the first unit  20 . The case where the main pipe  41  is disposed inside the first unit  20  also includes the case where a portion of a casing of the first unit  20  functions as the main pipe  41 . In  FIG. 1 , an example is illustrated, in which an entrance  41   a  of the main pipe  41  is connected to the first unit  20 . The first fan  21  is disposed inside the first unit  20 . Here, all of the air blown out from the first fan  21  is configured to flow into the duct  40 . 
     An exit  41   b  of the main pipe  41  of the duct  40  is connected to an entrance  42   a  of the branch pipe  42 . A plurality of exits  42   b  of the branch pipe  42  are connected to the plurality of second units  30 . 
     Each second unit  30  and the target space  100  are joined by a ventilation passage  81 . An entrance  81   a  of the ventilation passage  81  is connected to the second units  30 . Each second fan  31  produces air flow inside each second unit  30 , the air flow proceeding from the exits  42   b  of the duct  40  to the entrance  81   a  of the ventilation passage  81 . From a different perspective, each second fan  31  is suctioning the first air SA from the exits  42   b  of the branch pipe  42 . Each second fan  31  can change the static pressure inside each second unit  30  (in front of the entrance  81   a  of the ventilation passage  81 ) by changing the rotation speed of each second fan  31  itself. Assuming that the static pressure in the duct  40  is constant, each second fan  31  can increase the rotation speed to thereby raise the static pressure inside each second unit  30  (in front of the entrance  81   a  of the ventilation passage  81 ). If the static pressure inside each second unit  30  rises, the air quantity of the first air SA flowing through the ventilation passage  81  increases. By changing the air quantity in this way, the supplied air flow volume that is blown out from an exit  81   b  of each ventilation passage  81  into the target space  100  changes. 
     The controller  50  includes a main controller  51  and a plurality of sub-controllers  52 . The main controller  51  and the plurality of sub-controllers  52  are interconnected to form the controller  50 . The main controller  51  controls the rotation speed of the first fan  21 . In other words, the main controller  51  controls the output of the first fan  21 . If the output of the first fan  21  increases, the state of the first fan  21  changes in the direction of increasing air flow volume sent from the first fan  21 . 
     One sub-controller  52  is provided with respect to each second unit  30 . Each sub-controller  52  outputs an instruction related to changing the air flow volume to the corresponding second fan  31 . Each sub-controller  52  stores a target air flow volume. If the supplied air flow volume is insufficient with respect to the target air flow volume, each sub-controller  52  outputs an instruction (an instruction related to changing the air flow volume) for increasing the rotation speed of the second fan  31 . Conversely, if the supplied air flow volume is excessive with respect to the target air flow volume, each sub-controller  52  outputs an instruction (an instruction related to changing the air flow volume) for decreasing the rotation speed of the second fan  31 . 
     The controller  50  obtains information about the air quantity of the air supplied to the target space  100  by the plurality of second fans  31 . The information about the air quantity indicates the quantity of air to be supplied to the target space  100  per second, for example, and the quantity of air to be supplied may also be referred to as the necessary supplied air flow volume. The controller  50  determines the demand output from the first fan  21  on the basis of the obtained information about the air quantity. The controller  50  controls the output of the first fan  21  to meet the determined demand output. Specifically, each sub-controller  52  obtains information about the air quantity of each corresponding second unit  30  from the second unit  30 . Each sub-controller  52  outputs the information about the air quantity to the main controller  51 . 
     (2) Detailed Configuration 
     (2-1) First Unit  20   
     Besides the first fan  21  already described, the first unit  20  includes a heat exchanger  22 , a fourth detector  23 , a temperature sensor  24 , and a water quantity adjustment valve  25 . The heat exchanger  22  is supplied with cold water or hot water for example as a heat medium from the heat source unit  60 . The heat medium supplied to the heat exchanger  22  may also be a liquid other than cold water or hot water, such as brine, for example. For the fourth detector  23 , an air flow sensor, a wind speed sensor, or a differential pressure sensor may be used, for example. 
     The fourth detector  23  detects the air flow volume sent by the first fan  21 . The fourth detector  23  is connected to the main controller  51 . The fourth detector  23  transmits the value of the air flow volume detected by the fourth detector  23  to the main controller  51 . The air flow volume detected by the fourth detector  23  is the volume of air flowing through the main pipe  41  of the duct  40 . In other words, the air flow volume detected by the fourth detector  23  is the total volume of supplied air flow supplied to the target space  100  from the plurality of second units  30 . 
     The temperature sensor  24  detects the temperature of the first air SA sent from the first fan  21  to the duct  40 . The temperature sensor  24  is connected to the main controller  51 . The temperature sensor  24  transmits the value of the temperature detected by the temperature sensor  24  to the main controller  51 . 
     The first unit  20  is joined to the target space  100  through a ventilation passage  82 . Second air RA passing through the ventilation passage  82  and returning from the target space  100  is sent through the heat exchanger  22  to the duct  40  by the first fan  21 . The second air RA returning from the target space  100  is air that existed inside the target space  100 . When passing through the heat exchanger  22 , the returning second air RA exchanges heat with the cold water or hot water flowing through the heat exchanger  22  to become conditioned air. The water quantity adjustment valve  25  adjusts the amount of heat imparted to the first air SA that exchanges heat in the heat exchanger  22  and is sent to the duct  40 . The opening degree of the water quantity adjustment valve  25  is controlled by the main controller  51 . If the opening degree of the water quantity adjustment valve  25  is increased, the amount of water flowing through the heat exchanger  22  increases, and more heat is exchanged per unit time between the heat exchanger  22  and the first air SA. Conversely, if the opening degree of the water quantity adjustment valve  25  is decreased, the amount of water flowing through the heat exchanger  22  decreases, and less heat is exchanged per unit time between the heat exchanger  22  and the first air SA. 
     (2-2) Second Unit  30   
     Besides the second fan  31  already described, each second unit  30  includes a second detector  32 . The second detector  32  detects the air flow volume sent by the second fan  31 . Each second detector  32  is connected to a corresponding sub-controller  52 . The value of the air flow volume detected by the second detector  32  is transmitted to the sub-controller  52 . The air flow volume detected by the second detector  32  is the volume of air flowing through the ventilation passage  81 . In other words, the air flow volume detected by each second detector  32  is the supplied air flow volume supplied to the target space  100  from each second unit  30 . For the second detector  32 , an air flow sensor, a wind speed sensor, or a differential pressure sensor may be used, for example. 
     (2-3) Remote Sensor  70   
     A plurality of remote sensors  70  function as temperature sensors. Each remote sensor  70  is configured to transmit data indicating the temperature of the second air RA in the target space  100  to a corresponding sub-controller  52 . 
     (3) Operation of Air Supply System  10   
     Each of the plurality of sub-controllers  52  receives a detected value of the temperature of the target space from the connected remote sensor  70  respectively. Each sub-controller  52  stores data indicating a set temperature. For example, the data indicating the set temperature is transmitted to each sub-controller  52  in advance from a remote controller (not illustrated) or the like. Each sub-controller  52  stores the data indicating the set temperature received from the remote controller or the like in a storage device  52   b  (see  FIG. 3 ) such as built-in memory. Each sub-controller  52  transmits the value of the set temperature to the main controller  51 . On the basis of the set temperature, the main controller  51  determines a target air flow volume for each second unit  30  according to the temperature of the second air RA detected by the corresponding remote sensor  70 . The main controller  51  transmits the value of the target air flow volume to each sub-controller  52 . 
     The main controller  51  determines the output of the first fan  21  according to the total combined target air flow volume to be supplied to the target space  100 . 
     For example, if the case where the static pressure at the exit  41   b  of the main pipe  41  (entrance  42   a  of the branch pipe  42 ) takes an intermediate value between the static pressure at the entrance  41   a  of the main pipe  41  and the static pressure at the exits  42   b  of the branch pipe  42  is compared to the case of taking a larger value than the intermediate value, the ratio of the output of the first fan  21  is larger than the ratio of the output of the plurality of second fans  31  in the case of taking a larger value than the intermediate value. Conversely, if the case where the static pressure at the exit  41   b  of the main pipe  41  (entrance  42   a  of the branch pipe  42 ) takes the intermediate value is compared to the case of taking a value smaller than the intermediate value, the ratio of the output of the first fan  21  is smaller than the ratio of the output of the plurality of second fans  31  in the case of taking a smaller value. An efficient range exists for the ratio of the output of the first fan  21  and the output of the plurality of second fans  31 . Accordingly, the main controller  51  determines the output of the first fan  21  such that an efficient ratio is achieved. In other words, the main controller  51  determines the outputs of the first fan  21  to be a predetermined suitable output with respect to the total combined target air flow volume. 
     For example, if a method of determining the output of the first fan  21  like the following is considered, a range of the output of the first fan  21  suitable for reducing the power consumption of the output of the first fan  21  is demonstrated to exist. If the output of the first fan  21  is raised such that the total power consumption by the first fan  21  and the plurality of second fans  31  rises, the output of the first fan  21  is gradually decreased, and if the output of the first fan  21  is determined before the total power consumption by the first fan  21  and the plurality of second fans  31  rebounds, the range of the determined output is a range in which the power consumption is smaller compared to other ranges. Conversely, if the output of the first fan  21  is decreased such that the total power consumption by the first fan  21  and the plurality of second fans  31  rises, the output of the first fan  21  is gradually raised, and if the output of the first fan  21  is determined before the total power consumption by the first fan  21  and the plurality of second fans  31  rebounds, the range of the determined output is a range in which the power consumption is smaller compared to other ranges. If the output of the first fan  21  is decreased such that the total power consumption by the first fan  21  and the plurality of second fans  31  rises, the output of the first fan  21  is gradually raised, and if the output of the first fan  21  is determined before the total power consumption by the first fan  21  and the plurality of second fans  31  rebounds, the range of the determined output is a range in which the power consumption is smaller compared to other ranges. Conversely, if the output of the first fan  21  is decreased such that the total power consumption by the first fan  21  and the plurality of second fans  31  decreases, the output of the first fan  21  is gradually decreased, and if the output of the first fan  21  is determined before the total power consumption by the first fan  21  and the plurality of second fans  31  rebounds, the range of the determined output is a range in which the power consumption is smaller compared to other ranges. However, the method of determining the appropriate output of the first fan  21  is not limited to such a method. 
     After the main controller  51  determines the target air flow volume and transmits the value of the target air flow volume to each of the sub-controllers  52 , each sub-controller  52  adjusts the rotation speed of the second fan  31  in each corresponding second unit  30 , except for the second unit  30  with the highest fan efficiency. The numbers of revolutions of the plurality of second fans  31  are adjusted independently from each other. 
     At this time, for the determined output of the first fan  21 , the rotation speed of the second fan  31  in the second unit  30  with the highest fan efficiency is at a maximum. Here, in the case where the static pressure at the entrance  42   a  of the branch pipe  42  is the same and the supplied air flow volume to be supplied to the target space  100  is the same, the second unit  30  with the highest fan efficiency is the second unit  30  with the lowest energy consumption. Also, in the case where the static pressure at the entrance  42   a  of the branch pipe  42  is the same and the supplied air flow volume to be supplied to the target space  100  is the same, the second unit  30  with the lowest fan efficiency is the second unit  30  with the highest energy consumption. 
     Each sub-controller  52  controls the rotation speed of each second fan  31  such that the supplied air flow volume matches the target air flow volume. The plurality of sub-controllers  52  control the numbers of revolutions of the plurality of second fans  31  independently from each other. If the air flow volume detected by the second detector  32  is small compared to the target air flow volume, each sub-controller  52  increases the rotation speed of each second fan  31 . If the air flow volume detected by the second detector  32  is large compared to the target air flow volume, each sub-controller  52  decreases the rotation speed of each second fan  31 . If the rotation speed of the second unit  30  with the highest fan efficiency falls, the main controller  51  makes an adjustment by changing the output of the first fan  21  such that the rotation speed of the second unit  30  with the highest fan efficiency is maximized. 
     When changing the air flow volume, in the case of changing the operating state of at least one of the plurality of second fans  31  or changing the air flow volume of at least one of the plurality of second fans  31 , the main controller  51  prioritizes increasing the output of a fan with high fan efficiency or decreasing the output of a fan with low fan efficiency from among the first fan  21  and the plurality of second fans  31 . In other words, in the case of increasing the volume of air flow to be supplied to the target space  100 , the main controller  51  determines the output of the first fan  21  and the target air flow volume of the plurality of second units  30  to increase the output of a fan with high fan efficiency from among the first fan  21  and the plurality of second fans  31 . Conversely, in the case of decreasing the volume of air flow to be supplied to the target space  100 , the main controller  51  determines the output of the first fan  21  and the target air flow volume of the plurality of second units  30  to decrease the output of a fan with high fan efficiency from among the first fan  21  and the plurality of second fans  31 . 
     However, in the case where the air flow volume of the second unit  30  with the maximum fan efficiency among the plurality of second units  30  does not reach the target air flow volume, the main controller  51  increases the output of the first fan  21 . At this time, the main controller  51  increases the output of the first fan  21  and also keeps the rotation speed of the second fan  31  in the second unit  30  with the maximum fan efficiency at maximum. 
     (4) Modifications 
     (4-1) Modification 1A 
     The above embodiment describes a case where, when the main controller  51  determines the output of the first fan  21 , the main controller  51  maximizes the rotation speed of the second fan  31  with the highest fan efficiency from among the plurality of second fans  31 . 
     However, when the main controller  51  determines the output of the first fan  21 , the main controller  51  may also be configured to determine the output of the first fan  21  to minimize the rotation speed of the second fan  31  with the lowest fan efficiency from among the plurality of second fans  31 . In this case, the corresponding sub-controller  52  adjusts the rotation speed of the second fan  31  in each second unit  30  other than the second unit  30  with the lowest fan efficiency. The numbers of revolutions of the plurality of second fans  31  are adjusted independently from each other. 
     Also, in the case where the main controller  51  reduces the target air flow volume, the main controller  51  may also be configured to determine the output of the first fan  21  to maintain a constant processing static pressure in the second fan  31  with the highest fan efficiency from among the plurality of second fans  31 . In the case of such a configuration, the second unit  30  with a constant processing static pressure among the second units  30  can keep the rotation speed of the highly efficient second fan  31  high compared to the others, and consequently keep the air supply system  10  as a whole at high efficiency. Thus, in the case of adopting a configuration that keeps the processing static pressure constant, each second unit  30  is provided with a differential pressure sensor  33  (see  FIG. 2 ) for detecting the processing static pressure in each second fan  31 , for example. Alternatively, the controller  50  may be configured to calculate the processing static pressure from the detection result of the second detector  32  and the rotation speed of the second fan  31 . The controller  50  determines the output of the first fan  21  on the basis of the detected value from the differential pressure sensor  33  in the second unit  30  with the highest fan efficiency. In this case, the corresponding sub-controller  52  adjusts the rotation speed of the second fan  31  in each second unit  30  other than the second unit  30  maintained at a constant processing differential pressure. The numbers of revolutions of the plurality of second fans  31  are adjusted independently from each other. 
     Also, in the case where the main controller  51  increases the target air flow volume, the main controller  51  may also be configured to determine the output of the first fan  21  to maintain a constant processing static pressure in the second fan  31  with the lowest fan efficiency from among the plurality of second fans  31 . In the case of such a configuration, the second unit  30  with a constant processing static pressure among the second units  30  can keep the rotation speed of the low efficient second fan  31  low compared to the others, and consequently keep the air supply system  10  as a whole at high efficiency. Thus, in the case of adopting a configuration that keeps the processing static pressure constant, each second unit  30  is provided with a differential pressure sensor  33  (see  FIG. 2 ) for detecting the processing static pressure in each second fan  31 , for example. Alternatively, the controller  50  may be configured to calculate the processing static pressure from the detection result of the second detector  32  and the rotation speed of the second fan  31 . The controller  50  determines the output of the first fan  21  on the basis of the detected value from the differential pressure sensor  33  in the second unit  30  with the lowest fan efficiency. In this case, the corresponding sub-controller  52  adjusts the rotation speed of the second fan  31  in each second unit  30  other than the second unit  30  maintained at a constant processing differential pressure. The numbers of revolutions of the plurality of second fans  31  are adjusted independently from each other. 
     (4-2) Modification 1B 
     The foregoing embodiment describes a case where the remote sensor  70  includes a temperature sensor, but the remote sensor  70  may also include at least one function from among a temperature sensor, a CO 2  concentration sensor, and a humidity sensor, for example. In the case of such a configuration, each of the plurality of sub-controllers  52  receives a detected value of at least one of the temperature, the CO 2  concentration, and the humidity of the target space  100  from the connected remote sensor  70 . Each sub-controller  52  stores data regarding a setting value of the detection target of the remote sensor  70 . Each sub-controller  52  transmits at least one setting value from among the temperature, the CO 2  concentration, and the humidity to the main controller  51 . On the basis of the setting values, the main controller  51  determines the target air flow volume of each second unit  30  according to the detected value from the corresponding remote sensor  70 . The main controller  51  transmits the value of the target air flow volume to each sub-controller  52 . 
     (4-3) Modification 1C 
     The foregoing embodiment describes a case where the first unit  20  includes the heat exchanger  22 . However, the first unit  20  may also take a configuration that does not include the heat exchanger  22 . For example, the air supply system  10  may be configured as a system that ventilates the target space  100  when the CO 2  concentration of the target space  100  is high. 
     (4-4) Modification 1D 
     The controller  50  is achieved by a computer. The controller  50  is provided with control computing devices  51   a  and  52   a , and storage devices  51   b  and  52   b . For the control computing devices  51   a  and  52   a , a processor such as a CPU or GPU may be used. The control computing devices  51   a  and  52   a  read out programs stored in the storage devices  51   b  and  52   b , and perform predetermined image processing and arithmetic processing according to the programs. Furthermore, the control computing devices  51   a  and  52   a  may follow the programs to write arithmetic results to the storage devices  51   b  and  52   b  or read out information stored in the storage devices  51   b  and  52   b . In  FIG. 3 , various function blocks achieved by the control computing devices  51   a  and  52   a  are illustrated. The storage devices  51   b  and  52   b  may be used as databases. 
     (4-5) Modification 1E 
     As illustrated in  FIG. 4 , an outdoor air introduction unit  110  may also be attached to the first unit  20 . The outdoor air introduction unit  110  includes a third fan  111  and a fifth detector  112 . The outdoor air introduction unit  110  uses the third fan  111  to take in and send outdoor air OA from outside the target space  100  to the first unit  20 . The fifth detector  112  detects the air flow volume of the outdoor air OA sent to the first unit  20 . The fifth detector  112  transmits the detected value of the sent air flow volume of the outdoor air OA to the main controller  51 . In the case where the outdoor air OA is sent from the outdoor air introduction unit  110  to the first unit  20 , the main controller  51  may be configured to correct the control of the output of the first fan  21  according to the sent air flow volume of the outdoor air OA. For the fifth detector  112 , an air flow sensor, a wind speed sensor, or a differential pressure sensor may be used, for example. 
     (4-6) Modification 1F 
     As illustrated in  FIG. 5 , in the air supply system  10  according to Modification 1F, a pressure sensor  90  acting as a third detector is disposed on the downstream side of the first unit  20  of the air supply system  10  according to the embodiment illustrated in  FIG. 1 . The pressure sensor  90  detects the pressure of the first air SA sent by the first fan  21 . For example, the pressure sensor  90  is disposed near the first unit  20  in the duct  40 , or in other words, near the entrance  41   a  of the duct  40 . The configuration other than the pressure sensor  90  is similar to the air supply system  10  according to the foregoing embodiment, and therefore a description is omitted. The main controller  51  acquires the value of the pressure of the first air SA detected by the pressure sensor  90 . The main controller  51  controls the rotation speed of the first fan  21  to keep the value of the pressure of the first air SA in a predetermined range. If the value of the pressure of the first air SA is below a lower limit of the predetermined range, the main controller  51  increases the rotation speed of the first fan  21 . If the value of the pressure of the first air SA is above an upper limit of the predetermined range, the main controller  51  decreases the rotation speed of the first fan  21 . 
     Moreover, as illustrated in  FIG. 6 , the pressure sensor  90  acting as the third detector may also be disposed on the downstream side of the first unit  20  of the air supply system  10  according to Modification 1E illustrated in  FIG. 4 . In  FIG. 7 , the configuration of the controller  50  in  FIG. 6  is illustrated. 
     (5) Characteristics 
     (5-1) 
     The air supply system  10  described above is provided with the first unit  20 , the second units  30 , the duct  40 , the remote sensors  70  acting as the first detector, and the main controller  51  acting as the first controller. Each second unit  30  includes the second fan  31  that supplies the first air SA to the target space  100 . The duct  40  sends the first air SA sent from the first unit  20  by the first fan  21  to the second units  30 . The remote sensors  70  detect information about the second air RA in the target space  100 . The information about the second air RA is the temperature of the second air RA, the CO 2  concentration of the second air RA, or the humidity of the second air RA, for example. The main controller  51  communicates with the second units  30  and the remote sensors  70 . Each second unit  30  includes the second detector  32  acting as a second detector that detects the air flow volume sent by the second fan  31 , and the sub-controller  52  acting as a second controller that controls the rotation speed of the second fan. the main controller  51  determines the target air flow volume of each second unit  30  on the basis of the information about the second air RA acquired from the remote sensors  70 , namely the detected value of the temperature, the detected value of the CO 2  concentration, or the detected value of the humidity. The main controller  51  transmits an instruction indicating the determined target air flow volume to the sub-controllers  52 . Each sub-controller  52  controls the rotation speed of the second fan  31  such that the air flow volume detected by the second detector  32  approaches the target air flow volume. 
     In the air supply system  10  thus configured, the second unit  30  receives the indicated value of the air flow volume from the main controller  51 , and the sub-controller  52  can automatically control the air flow volume in the second unit  30  itself without depending on the main controller  51 . Thus, it is sufficient to supply the indicated value of an appropriate air flow volume from the main controller  51  to the second unit  30 , and the control load on the main controller  51  can be reduced. 
     (5-2) 
     In the air supply system  10  according to the embodiment described above, the first unit  20  can exchange heat with the heat medium in the heat exchanger  22  and send the air-conditioned air to a plurality of second units  30 . The plurality of second units  30  can use the air-conditioned air to air-condition the target space  100 . 
     (5-3) 
     The controller  50  of the air supply system  10  described above determines the air flow volume of the air supplied by the plurality of second units  30  according to at least one of the temperature, the humidity, and the CO 2  concentration of the target space  100 , and controls the air flow volume of each of the plurality of second units  30 . In such an air supply system  10 , the controller  50  can control the air flow volume of each of the plurality of second units  30  to keep at least one of the temperature, the humidity, and the CO 2  concentration of the target space  100  in an suitable range. 
     (5-4) 
     The air supply system  10  according to Modification 1F is provided with the pressure sensor  90 , which is disposed on the downstream side of the first unit  20  and acts as a third detector that detects the pressure of the first air SA sent by the first fan  21 . The main controller  51  controls the rotation speed of the first fan  21  to keep the value of the pressure acquired from the pressure sensor  90  in a predetermined range. As the result, by keeping the value of the pressure on the downstream side of the first unit  20  in a predetermined range, the air supply system can eliminate excess power consumption occurring in the first fan  21  and the second fan  31  compared to the case where the value of the pressure on the downstream side of the first unit  20  is outside the predetermined range. 
     (5-5) 
     In the air supply system  10  described above, the main controller  51  can control the output of the first fan  21  to a suitable value to match the total combined air flow volume supplied to the target space  100 . The total supplied air flow volume is an example of the air quantity of the first air SA in the plurality of second fans  31 . Through such control by the main controller  51 , the air supply system  10  is capable of moderating the energy consumption of the system as a whole. 
     (5-6) 
     The air supply system  10  described above can be configured such that in a case of changing an operating state of at least one of the plurality of second fans  31  or changing the air flow volume of at least one of the plurality of second fans  31 , the main controller  51  prioritizes increasing an output of a fan with high fan efficiency or decreasing the output of a fan with low fan efficiency from among the first fan  21  and the plurality of second fans  31 . In the air supply system  10  configured in this way, the main controller  51  prioritizes increasing the output of a fan with high fan efficiency or decreasing the output of a fan with low fan efficiency to moderate the energy consumption of the air supply system  10 . 
     (5-7) 
     In the air supply system  10  described above, the main controller  51  is configured to determine the output of the first fan  21  to maintain a constant processing static pressure in the second fan  31  with the highest fan efficiency from among the plurality of second fans  31  or to maximize the rotation speed of the second fan  31  with the highest fan efficiency from among the plurality of second fans  31 , and thereby prioritizes decreasing the output of a second fan  31  with a low fan efficiency. As a result of prioritizing decreasing the output of a second fan  31  with a low fan efficiency, such a configuration can reduce the energy consumption compared to the case of decreasing the output of a second fan  31  with a higher fan efficiency. 
     (5-8) 
     In the air supply system  10  described above, the main controller  51  is configured to determine the output of the first fan  21  to maintain a constant processing static pressure in the second fan  31  with the lowest fan efficiency from among the plurality of second fans  31  or to minimize the rotation speed of the second fan  31  with the lowest fan efficiency from among the plurality of second fans  31 , and thereby prioritizes increasing the output of a fan with a high fan efficiency. As a result of prioritizing increasing the output of a second fan  31  with a high fan efficiency, such a configuration can reduce the energy consumption compared to the case of increasing the output of a second fan  31  with a lower fan efficiency. 
     (5-9) 
     In the air supply system  10  described above, in the case where the air flow volume of the second fan  31  with the maximum fan efficiency among the plurality of second fans  31  does not reach the target air flow volume, the main controller  51  increases the output of the first fan  21 . In the air supply system  10  configured in this way, the main controller  51  can increase the output of the first fan  21  to cause the air flow volume of the second fan  31  with the maximum fan efficiency among the plurality of second fans  31  to reach the target air flow volume. 
     The embodiments of the present disclosure have been described above, but it will be understood that various modifications can be made to the embodiments and details without departing from the object and the scope of the present disclosure recited in the claims. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10 : Air supply system 
               20 : First unit 
               21 : First fan 
               22 : Heat exchanger 
               23 : Fourth detector 
               30 : Second unit 
               31 : Second fan 
               32 : Second detector 
               33 : Differential pressure sensor 
               40 : Duct 
               50 : Controller 
               51 : Main controller (example of first controller) 
               52 : Sub-controller (example of second controller) 
               70 : Remote sensor (example of first detector) 
               90 : Pressure sensor (example of third detector) 
           
         
       
    
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2001-304614 A