Ventilation air conditioning system

Abstract

A ventilation air conditioning system (100) comprises: a heat source machine (1) that heats a heat medium; a radiator (2) that radiates the heat of the heat medium in a space to be heated; a ventilation device (3) that has a heat exchanger (31) for performing heat exchange between the air to be supplied to the inside of the room from the outside of the room and the air to be discharged from the inside of the room to the outside of the room, and that supplies the air to the inside of the room and discharges the air from the inside of the room; an outside air heater (36) that, by using the heat medium, heats the air that has been taken from the outside of the room, before being brought into the heat exchanger (31); and a heat medium circulation circuit part (22) that constitutes a flow path of the heat medium which is carried from the heat source machine (1) to the heat radiator (2) and the outside air heater (36) and is returned to the heat source machine (1).

Description

ventilation and air conditioning system

[0001] The present disclosure relates to a ventilation air-conditioning system including a ventilation device having a heat exchanger, a heat source unit that heats a heat medium, and a radiator that heats a space by utilizing the heat of the heat medium.

[0002] A known ventilation system includes an intake fan that sends air taken in through an outdoor air inlet to an indoor air outlet, an exhaust fan that sends air taken in through an indoor air inlet to an outdoor air outlet, and a heat exchanger. The heat exchanger exchanges heat between air flowing from the outdoor air inlet to the indoor air outlet and air flowing from the indoor air inlet to the outdoor air outlet. In such ventilation systems, when the outdoor temperature drops significantly, the indoor air taken in through the indoor air inlet is cooled by the outdoor air taken in through the outdoor air inlet, which can cause water vapor contained in the indoor air to freeze in the heat exchanger. Therefore, conventional ventilation systems with heat exchangers have a problem in that the ventilation airflow rate can be reduced due to freezing in the heat exchanger.

[0003] Patent Document 1 discloses a ventilation device in which a first set temperature and a second set temperature lower than the first set temperature are set, and when the outside air temperature is equal to or lower than the first set temperature and higher than the second set temperature, the intake air blower operates intermittently, and when the outside air temperature is equal to or lower than the second set temperature, the intake air blower is stopped to perform type 3 ventilation. In the ventilation device disclosed in Patent Document 1, when the outside air temperature is equal to or lower than the second set temperature, the heat exchanger is warmed by air taken in from the indoor air inlet, thereby preventing a decrease in ventilation air volume due to freezing on the heat exchanger.

[0004] Patent No. 4656777

[0005] In the conventional technology disclosed in Patent Document 1, depending on the outdoor temperature conditions, the operation of the supply air blower is stopped for a certain period of time, which results in an insufficient volume of supply air being secured indoors. The insufficient volume of supply air is compensated for through openings in the building. In this case, outside air at the outdoor temperature flows into the room, resulting in a significant increase in the heating load compared to when supply air is supplied with heat exchange.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a ventilation and air-conditioning system that can prevent a decrease in ventilation air volume due to freezing in the heat exchanger and can reduce the heating load.

[0007] In order to solve the above-mentioned problems and achieve the object, the ventilation and air conditioning system of the present disclosure comprises a heat source unit that heats a heat medium, a radiator that radiates heat from the heat medium in the space to be heated, a ventilation device that has a heat exchanger that performs heat exchange between air supplied from outside to inside the room and air exhausted from inside the room to outside, and that supplies air to the room and exhausts air from the room, an outdoor air heater that uses a heat medium to heat air that is taken in from outside and before it is introduced into the heat exchanger, and a heat medium circulation circuit unit that forms a flow path for the heat medium that is transported from the heat source unit to each of the radiator and the outdoor air heater and returned to the heat source unit.

[0008] The ventilation air-conditioning system according to the present disclosure has the advantage of being able to prevent a decrease in ventilation air volume due to freezing in the heat exchanger, and being able to reduce the heating load.

[0009] FIG. 1 shows an example of the configuration of a ventilation air-conditioning system according to embodiment 1. FIG. 2 shows an example of the configuration of a ventilation air-conditioning system according to embodiment 1. FIG. 3 shows an example of the configuration of a ventilation air-conditioning system according to embodiment 1. FIG. 4 shows a flowchart illustrating the procedure for operation by the ventilation air-conditioning system according to embodiment 1. FIG. 1 shows an example of the configuration of a ventilation air-conditioning system according to embodiment 2. FIG. 2 shows an example of the configuration of a ventilation air-conditioning system according to embodiment 2. FIG. 3 shows an example of the configuration of a ventilation air-conditioning system according to embodiment 2. FIG. 4 shows a flowchart illustrating the procedure for operation by the ventilation air-conditioning system according to embodiment 2. FIG. 5 shows an example of the configuration of a control circuit according to embodiment 1 or 2. FIG. 6 shows an example of the configuration of a dedicated hardware circuit according to embodiment 1 or 2.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ventilation air-conditioning system according to an embodiment will be described in detail below with reference to the drawings.

[0011] Embodiment 1. Fig. 1 is a first diagram showing an example configuration of a ventilating air-conditioning system 100 according to Embodiment 1. The ventilating air-conditioning system 100 is a system that ventilates and air-conditions a room. The ventilating air-conditioning system 100 includes a heat source unit 1, a radiator 2, and a ventilation device 3.

[0012] The heat source unit 1 and the radiator 2 constitute an air conditioning system that circulates a heat medium through the radiator 2 to condition the air inside a room. The heat source unit 1 heats the heat medium. In the first embodiment, the heat source unit 1 is a heat pump type heat source unit. The heat source unit 1 is not limited to a heat pump type heat source unit, and may be a heat source unit that heats the heat medium by burning a fossil fuel such as kerosene or gas. In the first embodiment, the heat medium is, for example, tap water. The heat medium is not limited to tap water, and may be a dedicated liquid whose components have been adjusted to prevent freezing or rust.

[0013] The radiator 2 radiates heat from the heat medium in a space to be heated. In the first embodiment, the space to be heated is an interior of a building 4. The radiator 2 is a radiant radiator such as a floor heating panel or a panel heater, or a fan coil unit such as a fan convector. The radiator 2 includes a heat medium circuit section 21, which is a flow path for the heat medium within the radiator 2. The heat medium circuit section 21 has two connection ports 21a and 21b. The heat medium flows into the radiator 2 from the connection port 21a or the connection port 21b. When the heat medium flows into the radiator 2 from the connection port 21a, the heat medium passes through the heat medium circuit section 21 and flows out of the radiator 2 from the connection port 21b. When the heat medium flows into the radiator 2 from the connection port 21b, the heat medium passes through the heat medium circuit section 21 and flows out of the radiator 2 from the connection port 21a.

[0014] The ventilation device 3 ventilates the room of the building 4 by discharging the air inside the room to the outside, which is outside the building 4, and sending the outdoor air into the room. The ventilation device 3 has a heat exchanger 31 that exchanges heat between the air supplied from the outside to the room and the air discharged from the room to the outside, and supplies air to the room and exhausts air from the room.

[0015] The heat source machine 1 includes a hot water generator 11 and a heat pump unit 12. The hot water generator 11 generates hot water, which is a heated heat medium. The hot water generator 11 includes a heat exchanger 111 in which heat exchange occurs between a heat medium and a refrigerant, a transfer pump 112 that transports the heat medium, a heat medium tank 113 in which the heat medium is stored, and a heat medium circuit section 114, which is a flow path for the heat medium within the heat source machine 1. The heat medium circuit section 114 has two connection ports 114a and 114b. The connection port 114a is the inlet of the heat medium circuit section 114. The connection port 114b is the outlet of the heat medium circuit section 114. The heat medium flows into the heat source machine 1 from the connection port 114a. The heat medium that flows into the heat source machine 1 circulates through the heat medium circuit section 114 and then reaches the connection port 114b.

[0016] The heat pump unit 12 circulates the refrigerant in the refrigerant circulation circuit 121. In the heat exchanger 111, the heat medium is heated by heat transfer from the refrigerant flowing in the refrigerant circulation circuit 121 to the heat medium flowing in the heat medium circuit 114. The hot water generator 11 heats the heat medium by utilizing the heat taken in by the refrigerant in the heat pump unit 12.

[0017] The heat medium that flows into the heat source unit 1 from the connection port 114a is recovered in the heat medium tank 113. The heat medium that leaves the heat medium tank 113 passes through the transfer pump 112 and is then heated in the heat exchanger 111. The heat medium heated in the heat exchanger 111 flows out of the heat source unit 1 from the connection port 114b.

[0018] The ventilation and air-conditioning system 100 includes a heat medium circulation circuit section 22. The heat medium circulation circuit section 22 constitutes a flow path for the heat medium that is transported from the heat source unit 1 to each of the radiator 2 and the outdoor air heater 36 and returned to the heat source unit 1. Details of the outdoor air heater 36 will be described later. The heat medium circulation circuit section 22 is made up of a plurality of pipes. Each of the plurality of pipes that make up the heat medium circulation circuit section 22 is a copper pipe, a steel pipe, or a plastic pipe. By wrapping each pipe with a thermal insulating material, the heat radiation loss of the heat medium in the heat medium circulation circuit section 22 is reduced.

[0019] In the first embodiment, the ventilation device 3 is installed in the attic of a building 4. The roof of the building 4 is provided with an outdoor air inlet 41 for taking in air outside the building 4 and an outdoor air outlet 42 for discharging air outside the building 4. The ceiling of the room is provided with an indoor air outlet 43 for supplying air into the room and an indoor air inlet 44 for taking in air from inside the room. An outdoor air duct 45, an exhaust duct 46, an air supply duct 47, and a return air duct 48 are installed in the attic.

[0020] The ventilation device 3 is not limited to being installed in the attic. The ventilation device 3 may be installed in any space within the building 4, such as under the floor, in the attic, in a machine room, or in a living space.

[0021] One end of the outdoor air duct 45 is connected to the outdoor air inlet 41. The other end of the outdoor air duct 45 is connected to the outdoor air duct 32 in the ventilation device 3. One end of the exhaust duct 46 is connected to the outdoor outlet 42. The other end of the exhaust duct 46 is connected to the exhaust air duct 33 in the ventilation device 3. One end of the supply air duct 47 is connected to the indoor outlet 43. The other end of the supply air duct 47 is connected to the supply air duct 34 in the ventilation device 3. One end of the return air duct 48 is connected to the indoor inlet 44. The other end of the return air duct 48 is connected to the return air duct 35 in the ventilation device 3.

[0022] In Fig. 1, the white arrow marked "OA" represents the state in which air outside the building 4 is drawn into the outdoor air inlet 41. In Fig. 1, the white arrow marked "EA" represents the state in which air is blown out of the building 4 from the outdoor air outlet 42. In Fig. 1, the white arrow marked "SA" represents the state in which air is blown into the room from the indoor air outlet 43. In Fig. 1, the white arrow marked "RA" represents the state in which indoor air is drawn into the indoor air inlet 44.

[0023] The outside air duct 32, the exhaust air duct 33, the supply air duct 34, and the return air duct 35 are provided inside the housing 30 of the ventilation device 3. The heat exchanger 31 is housed inside the housing 30. Inside the housing 30, there are arranged an intake fan that sends air taken in from outside into the room, and an exhaust fan that sends air taken in from inside the room to the outside. The intake fan and the exhaust fan are not shown in Figure 1.

[0024] The intake air blower generates an intake airflow that enters the housing 30 through the outdoor air inlet 41 and the outdoor air duct 45. The intake airflow passes through the outdoor air duct 32, the heat exchanger 31, and the intake air duct 34 in that order within the housing 30. The intake airflow that has passed through the housing 30 passes through the intake air duct 47 and the indoor air outlet 43 and is blown out into the room. The exhaust air blower generates an exhaust airflow that enters the housing 30 through the indoor air inlet 44 and the return air duct 48. The exhaust airflow passes through the return air duct 35, the heat exchanger 31, and the exhaust air duct 33 in that order within the housing 30. The exhaust airflow that has passed through the housing 30 passes through the exhaust duct 46 and the outdoor air outlet 42 and is blown out to the outside.

[0025] The intake air blower and the exhaust air blower may each be disposed outside the housing 30. The ventilation device 3 may be provided with two or more intake air blowers and two or more exhaust air blowers.

[0026] The heat exchanger 31 has a primary air passage through which the exhaust air flows and a secondary air passage through which the intake air flows. Within the heat exchanger 31, the primary air passage and the secondary air passage are perpendicular to each other. The primary air passage and the secondary air passage are formed as a laminate composed of alternately bonded sheet materials and spacing members. The sheet material is, for example, flattened flat paperboard. The spacing member is, for example, corrugated paperboard. Corrugated paperboard is paper with a corrugated texture. Within the heat exchanger 31, total heat exchange between the exhaust air flow and the intake air flow occurs via the flat paperboard. Note that the primary air passage and the secondary air passage are not shown in FIG. 1 .

[0027] In the laminate, corrugated paperboards are alternately stacked with flat paperboards sandwiched between them, with the corrugated paperboards oriented so that the directions of the folds are perpendicular to each other. As a result, primary air passages and secondary air passages are alternately provided in the heat exchanger 31 in the stacking direction. The flat paperboards exchange sensible heat and latent heat between the intake airflow and the exhaust airflow without mixing the intake airflow and the exhaust airflow. Note that the heat exchanger 31 may perform only one of sensible heat exchange and latent heat exchange.

[0028] Here, the heat exchanger 31 is an orthogonal heat exchanger in which the intake airflow direction and the exhaust airflow direction are perpendicular to each other, but this is not limited to this. The heat exchanger 31 may also be a counterflow heat exchanger in which the intake airflow direction and the exhaust airflow direction are 180 degrees apart. The shape of the spacing member may be sawtooth, sinusoidal, rectangular, or any of these shapes modified. The spacing member may also be a combination of multiple plate pieces.

[0029] The outdoor air heater 36 uses a heat medium to heat air taken in from outside the room before it is introduced into the heat exchanger 31. A heat medium circuit section through which the heat medium passes is provided within the outdoor air heater 36. The heat medium circuit section within the outdoor air heater 36 has two connection ports 36a and 36b. The heat medium flows into the outdoor air heater 36 from the connection port 36a or the connection port 36b. When the heat medium flows into the outdoor air heater 36 from the connection port 36a, the heat medium passes through the heat medium circuit section and flows out of the outdoor air heater 36 from the connection port 36b. When the heat medium flows into the outdoor air heater 36 from the connection port 36b, the heat medium passes through the heat medium circuit section and flows out of the outdoor air heater 36 from the connection port 36a. Note that FIG. 1 omits the illustration of the heat medium circuit section within the outdoor air heater 36, except for the connection ports 36a and 36b.

[0030] The outdoor air heater 36 shown in Fig. 1 is disposed in the outdoor air duct 32. The outdoor air duct 32 is an air duct through which air that flows into the ventilation device 3 from outside the room reaches the heat exchanger 31. When the heat medium is transported from the heat source unit 1 to the outdoor air heater 36 in the heat medium circulation circuit unit 22, heat of the heat medium passing through the heat medium circuit unit in the outdoor air heater 36 is transferred to air passing through the outdoor air duct 32. As a result, the air before being introduced into the heat exchanger 31 is heated in the outdoor air duct 32.

[0031] The outside air heater 36 is, for example, a plate-fin type heater in which a number of metal plates are connected to metal pipes that constitute a heat medium circuit section. The heat of the heat medium passing through the metal pipes is transmitted from the metal pipes and metal plates to the air surrounding the metal pipes and metal plates, thereby heating the air in the outside air duct 32. Note that the outside air heater 36 is not limited to a plate-fin type heater, and may be a heater made of a single metal pipe. The outside air heater 36 may heat the air in the outside air duct 32 by passing a heat medium through a metal pipe that is in contact with the inner wall of the outside air duct 32.

[0032] By installing the outdoor air heater 36, which heats the air before it is introduced into the heat exchanger 31, inside the outdoor air duct 32, the number of steps in the construction work to install the equipment inside the building 4 can be reduced compared to when the outdoor air heater 36 is installed outside the ventilation device 3.

[0033] The ventilation and air-conditioning system 100 switches the heat medium circulation circuit unit 22 between a first state in which the transport of the heat medium to the outdoor air heater 36 is stopped, and a second state in which the heat medium is transported to the outdoor air heater 36. The heat medium circulation circuit unit 22 has a first flow path 25 and a second flow path 26. The first flow path 25 is a flow path through which the heat medium that has passed through the radiator 2 returns to the heat source unit 1 in the first state. The second flow path 26 is a flow path through which the heat medium is transported to the outdoor air heater 36 in the second state.

[0034] The ventilation and air-conditioning system 100 includes a flow path switching valve 23, which is a first valve, and a directional control valve 24, which is a second valve. The flow path switching valve 23 switches the flow path of the heat medium between a first flow path 25 and a second flow path 26. The flow path switching valve 23 functions as a switching unit that switches the heat medium circulation circuit unit 22 between a first state in which the delivery of the heat medium to the outdoor air heater 36 is stopped, and a second state in which the heat medium is delivered to the outdoor air heater 36. The flow path switching valve 23 has three connection ports 23a, 23b, and 23c.

[0035] The directional control valve 24 switches the flow direction of the heat medium in the heat medium circulation circuit section 22. In the second state, the directional control valve 24 switches the flow direction of the heat medium between a direction in which the heat medium that has flowed from the heat source unit 1 to the radiator 2 passes through the outdoor air heater 36 and returns to the heat source unit 1, and a direction in which the heat medium that has flowed from the heat source unit 1 to the outdoor air heater 36 passes through the radiator 2 and returns to the heat source unit 1. The directional control valve 24 has four connection ports 24a, 24b, 24c, and 24d.

[0036] The connection port 23a of the flow path switching valve 23 is connected to the connection port 21b of the radiator 2 via a pipe. The connection port 23b of the flow path switching valve 23 is connected to the connection port 24c of the directional control valve 24 via a pipe. The connection port 23c of the flow path switching valve 23 is connected to the connection port 36a of the outdoor air heater 36 via a pipe. The connection port 24a of the direction switching valve 24 is connected to the connection port 114b of the heat source unit 1 via a pipe. The connection port 24b of the direction switching valve 24 is connected to the connection port 21a of the radiator 2 via a pipe. The connection port 24d of the direction switching valve 24 is connected to the connection port 114a of the heat source unit 1 via a pipe. The connection port 36b of the outdoor air heater 36 is connected to a connection point 27 via a pipe. The connection point 27 is provided in the pipe between the connection port 23b of the flow path switching valve 23 and the connection port 24c of the directional control valve 24. The first flow path 25 is a flow path between the connection port 23b of the flow path switching valve 23 and the connection point 27. The second flow path 26 is a flow path between the connection port 23c of the flow path switching valve 23 and the connection port 36a of the outdoor air heater 36, and a flow path between the connection port 36b of the outdoor air heater 36 and the connection point 27.

[0037] The ventilation and air-conditioning system 100 includes a control device 5 that controls the ventilation and air-conditioning system 100. The control device 5 is connected to each of the heat source unit 1, the ventilation device 3, the flow path switching valve 23, and the direction switching valve 24 by communication lines. The control device 5 controls each of the heat source unit 1, the ventilation device 3, the flow path switching valve 23, and the direction switching valve 24 by sending control signals via the communication lines. In Fig. 1, the dashed lines between the control device 5 and each of the heat source unit 1, the ventilation device 3, the flow path switching valve 23, and the direction switching valve 24 represent communication lines.

[0038] The control device 5 instructs the flow path switching valve 23 to switch the flow path by sending a control signal to the flow path switching valve 23. The flow path switching valve 23 performs an operation to switch the flow path in accordance with the control signal sent from the control device 5. The control device 5 instructs the direction switching valve 24 to switch the flow path by sending a control signal to the direction switching valve 24. The direction switching valve 24 performs an operation to switch the flow path in accordance with the control signal sent from the control device 5. The direction switching valve 24 switches the flow path, thereby switching the direction in which the heat medium flows in the heat medium circulation circuit unit 22.

[0039] The ventilation and air-conditioning system 100 is equipped with an outdoor air temperature detector that detects the temperature of outdoor air. The ventilating and air-conditioning system 100 shown in Figure 1 is equipped with two outdoor air temperature detectors 51, 52. The outdoor air temperature detector 51 is arranged in the outdoor air duct 32 inside the ventilation device 3. The outdoor air temperature detector 51 detects the temperature of the air passing through the outdoor air duct 32, thereby detecting the temperature of the outdoor air. The outdoor air temperature detector 52 is arranged in the heat pump unit 12. The outdoor air temperature detector 52 detects the temperature of the outdoor air in the heat pump unit 12.

[0040] The outdoor air heater 36 heats the air in the outdoor air duct 32 at a position downwind from the position where the outdoor air temperature detector 51 detects the air temperature. The outdoor air temperature detector 51 detects the air temperature at a position upwind from the position where the air is heated by the outdoor air heater 36, and is therefore able to detect the temperature of the air before it is heated. This allows the ventilation and air-conditioning system 100 to accurately detect the temperature of the outdoor air using the outdoor air temperature detector 51.

[0041] The control device 5 is connected to each of the two outside air temperature detectors 51, 52 via communication lines. In FIG. 1 , the dashed lines between each of the outside air temperature detectors 51, 52 and the control device 5 represent the communication lines. Each of the two outside air temperature detectors 51, 52 outputs a signal indicating the detected temperature to the control device 5 via the communication line. In this way, the control device 5 acquires information on the temperature detected by each of the two outside air temperature detectors 51, 52. The control device 5 controls each of the flow path switching valve 23 and the directional control valve 24 based on the temperatures detected by the outside air temperature detectors 51, 52.

[0042] The ventilation and air-conditioning system 100 may have only one of the two outdoor temperature detectors 51, 52. The ventilation and air-conditioning system 100 may use one of the two outdoor temperature detectors 51, 52 as a primary outdoor temperature detector and the other as an auxiliary outdoor temperature detector. For example, the control device 5 may acquire temperature information based on a signal from the primary outdoor temperature detector, and when a signal cannot be acquired from the primary outdoor temperature detector, acquire temperature information based on a signal from the auxiliary outdoor temperature detector. The ventilation and air-conditioning system 100 may acquire information indicating the outdoor temperature from a temperature detection means other than the outdoor temperature detectors 51, 52. In the following description, the control device 5 acquires temperature information based on a signal from the primary outdoor temperature detector, the outdoor temperature detector 51.

[0043] Next, the operation of the ventilation and air-conditioning system 100 will be described. The control device 5 compares the temperature detected by the outside air temperature detector 51 with a first temperature, which is a preset temperature. If the temperature detected by the outside air temperature detector 51 is higher than the first temperature, the control device 5 instructs the flow path switching valve 23 to open the first flow path 25 and close the second flow path 26. If the temperature detected by the outside air temperature detector 51 is higher than the first temperature, the flow path switching valve 23 opens the first flow path 25 and closes the second flow path 26. In other words, if the temperature detected by the outside air temperature detector 51 is higher than the first temperature, the flow path switching valve 23 sets the heat medium circulation circuit unit 22 to a first state in which the transport of the heat medium to the outside air heater 36 is stopped.

[0044] In the example shown in FIG. 1, the flow path switching valve 23 opens the first flow path 25 by opening the connection port 23a and the connection port 23b, and closes the second flow path 26 by closing the connection port 23c.

[0045] Furthermore, when the temperature detected by the outside air temperature detector 51 is higher than the first temperature, the control device 5 instructs the directional control valve 24 to pass the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. When the temperature detected by the outside air temperature detector 51 is higher than the first temperature, the directional control valve 24 passes the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. As a result, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the radiator 2 returns to the heat source unit 1 through the connection point 27.

[0046] 1 shows the ventilating air-conditioning system 100 when the heat medium circulation circuit unit 22 is in the first state. The straight arrows and broken line arrows shown in Fig. 1 indicate the direction in which the heat medium flows in the heat medium circulation circuit unit 22.

[0047] When the heat medium circulation circuit unit 22 is in the first state, the heat medium flowing out from the connection port 114b of the heat source unit 1 passes through the connection ports 24a and 24b of the directional control valve 24 and flows into the radiator 2 from the connection port 21a of the radiator 2. The heat medium that has flowed through the heat medium circuit unit 21 in the radiator 2 flows out from the connection port 21b of the radiator 2, then passes through the connection ports 23a and 23b of the flow path switching valve 23, passes through the connection point 27, and reaches the connection port 24c of the directional control valve 24. That is, the heat medium passes through the first flow path 25 and reaches the connection port 24c of the directional control valve 24. The heat medium passes through the connection ports 24c and 24d of the directional control valve 24 and reaches the connection port 114a of the heat source unit 1. The heat medium that flows into the heat source unit 1 from the connection port 114a of the heat source unit 1 is heated in the heat source unit 1 and flows out of the heat source unit 1 again from the connection port 114b of the heat source unit 1.

[0048] 1, the dashed line in flow path switching valve 23 indicates that the heat medium passes between connection port 23a and connection port 23b in flow path switching valve 23. In Fig. 1, one of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24a and connection port 24b in direction switching valve 24, and the other of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24c and connection port 24d in direction switching valve 24.

[0049] When the temperature detected by the outside air temperature detector 51 is equal to or lower than a first temperature, the control device 5 instructs the flow path switching valve 23 to close the first flow path 25 and open the second flow path 26. When the temperature detected by the outside air temperature detector 51 is equal to or lower than the first temperature, the flow path switching valve 23 closes the first flow path 25 and opens the second flow path 26. In other words, when the temperature detected by the outside air temperature detector 51 is equal to or lower than the first temperature, the flow path switching valve 23 puts the heat medium circulation circuit unit 22 into a second state in which the heat medium is transported to the outside air heater 36.

[0050] Furthermore, when the temperature detected by the outside air temperature detector 51 is equal to or lower than the first temperature, the control device 5 compares the temperature detected by the outside air temperature detector 51 with a second temperature. The second temperature is a preset temperature that is lower than the first temperature. When the temperature detected by the outside air temperature detector 51 is higher than the second temperature, the control device 5 instructs the directional control valve 24 to pass the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. When the temperature detected by the outside air temperature detector 51 is higher than the second temperature, the directional control valve 24 passes the heat medium between the connection ports 24a and 24b and passes the heat medium between the connection ports 24c and 24d. As a result, the directional control valve 24 changes the direction in which the heat medium flows in the heat medium circulation circuit section 22 so that the heat medium that flows from the heat source unit 1 to the radiator 2 passes through the outdoor air heater 36 and returns to the heat source unit 1.

[0051] When the temperature detected by the outside air temperature detector 51 is equal to or lower than a second temperature, the control device 5 instructs the directional control valve 24 to pass the heat medium between the connection ports 24a and 24c and between the connection ports 24b and 24d. When the temperature detected by the outside air temperature detector 51 is equal to or lower than the second temperature, the directional control valve 24 passes the heat medium between the connection ports 24a and 24c and passes the heat medium between the connection ports 24b and 24d. As a result, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the outside air heater 36 passes through the radiator 2 and returns to the heat source unit 1.

[0052] Figure 2 is a second diagram showing an example configuration of the ventilating air-conditioning system 100 according to Embodiment 1. Figure 2 shows the ventilating air-conditioning system 100 when the heat medium circulation circuit unit 22 is in a second state and the temperature detected by the outside air temperature detector 51 is higher than a second temperature. That is, Figure 2 shows the ventilating air-conditioning system 100 when the temperature detected by the outside air temperature detector 51 is equal to or lower than the first temperature and higher than the second temperature. The straight arrows and broken line arrows shown in Figure 2 indicate the direction in which the heat medium flows in the heat medium circulation circuit unit 22.

[0053] When the heat medium circulation circuit unit 22 is in the second state and the temperature detected by the outdoor air temperature detector 51 is higher than the second temperature, the flow path of the heat medium from the connection port 114b of the heat source unit 1 to the connection port 23a of the flow path switching valve 23 is the same as that shown in FIG. 1 . The heat medium that reaches the connection port 23a of the flow path switching valve 23 passes through the connection port 23c and heads from the connection port 23c to the outdoor air heater 36. The heat medium flows into the outdoor air heater 36 from the connection port 36a of the outdoor air heater 36. The heat medium that flows through the heat medium circuit unit in the outdoor air heater 36 flows out from the connection port 36b of the outdoor air heater 36, then passes through the connection point 27 and reaches the connection port 24c of the directional control valve 24. That is, the heat medium passes through the second flow path 26 and reaches the connection port 24c of the directional control valve 24. The heat medium passes through connection ports 24c and 24d in the directional control valve 24 and reaches connection port 114a of the heat source unit 1. The heat medium that flows into the heat source unit 1 from connection port 114a of the heat source unit 1 is heated within the heat source unit 1 and flows out of the heat source unit 1 again from connection port 114b of the heat source unit 1.

[0054] 2, the dashed line in flow path switching valve 23 indicates that the heat medium passes between connection port 23a and connection port 23c in flow path switching valve 23. In Fig. 2, one of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24a and connection port 24b in direction switching valve 24, and the other of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24c and connection port 24d in direction switching valve 24.

[0055] 2 , the flow path switching valve 23 opens the connection ports 23a and 23c to open the second flow path 26, and closes the connection port 23b to close the first flow path 25. The directional control valve 24 passes the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d, thereby changing the flow direction of the heat medium from the heat source unit 1 to the radiator 2 to return to the heat source unit 1 through the outdoor air heater 36.

[0056] Figure 3 is a third diagram showing an example configuration of the ventilating air-conditioning system 100 according to Embodiment 1. Figure 3 shows the ventilating air-conditioning system 100 when the heat medium circulation circuit unit 22 is in the second state and the temperature detected by the outside air temperature detector 51 is equal to or lower than the second temperature. That is, Figure 3 shows the ventilating air-conditioning system 100 when the temperature detected by the outside air temperature detector 51 is equal to or lower than the first temperature and also equal to or lower than the second temperature. The straight arrows and broken line arrows shown in Figure 3 indicate the direction in which the heat medium flows in the heat medium circulation circuit unit 22.

[0057] When the heat medium circulation circuit section 22 is in the second state and the temperature detected by the outdoor air temperature detector 51 is equal to or lower than the second temperature, the heat medium flowing out from the connection port 114b of the heat source unit 1 passes through the connection ports 24a and 24c of the directional control valve 24 and heads toward the outdoor air heater 36 via the connection point 27. The heat medium flows into the outdoor air heater 36 from the connection port 36b of the outdoor air heater 36. The heat medium that has flowed through the heat medium circuit section in the outdoor air heater 36 flows out from the connection port 36a of the outdoor air heater 36, and then reaches the connection port 23c of the flow path switching valve 23. The heat medium that has reached the connection port 23c of the flow path switching valve 23 passes through the connection port 23a and flows into the radiator 2 from the connection port 21b of the radiator 2. The heat medium that flows through the heat medium circuit section 21 in the radiator 2 flows out from the connection port 21a of the radiator 2, then passes through the connection ports 24b and 24d in the directional control valve 24, and reaches the connection port 114a of the heat source unit 1. The heat medium that flows into the heat source unit 1 from the connection port 114a of the heat source unit 1 is heated within the heat source unit 1, and flows out of the heat source unit 1 again from the connection port 114b of the heat source unit 1.

[0058] 3, the dashed line in flow path switching valve 23 indicates that the heat medium passes between connection port 23a and connection port 23c in flow path switching valve 23. In Fig. 3, one of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24a and connection port 24c in direction switching valve 24, and the other of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24b and connection port 24d in direction switching valve 24.

[0059] In the example shown in Fig. 3, the flow path switching valve 23 opens the second flow path 26 by opening the connection ports 23a and 23c, and closes the first flow path 25 by closing the connection port 23b. The direction switching valve 24 passes the heat medium between the connection ports 24a and 24c and between the connection ports 24b and 24d, thereby changing the flow direction of the heat medium from the heat source unit 1 to the outdoor air heater 36 to return to the heat source unit 1 through the radiator 2. The flow direction of the heat medium in the heat medium circulation circuit unit 22 in Fig. 3 is opposite to that shown in Fig. 2.

[0060] As described above, the flow path switching valve 23 switches the heat medium circulation circuit unit 22 to the first state when the temperature detected by the outside air temperature detector 51 is higher than the first temperature, and switches the heat medium circulation circuit unit 22 to the second state when the temperature detected by the outside air temperature detector 51 is equal to or lower than the first temperature. In this way, the flow path switching valve 23 switches the heat medium circulation circuit unit 22 between the first state and the second state based on the detection result by the outside air temperature detector 51. This allows the ventilation and air conditioning system 100 to switch between heating the air taken into the heat exchanger 31 from outside and stopping the heating of the air taken into the heat exchanger 31 from outside, depending on the level of the outside air temperature.

[0061] 4 is a flowchart showing the procedure of the operation of the ventilation air-conditioning system 100 according to Embodiment 1. A program for realizing the procedure shown in FIG.

[0062] In step S1, the ventilation and air-conditioning system 100 starts operation of the ventilation device 3. The control device 5 starts operation of the ventilation device 3 by sending a control signal to the ventilation device 3. The heat source unit 1 does not need to be in a powered state at the time of step S1.

[0063] In step S2, the control device 5 acquires the value of the outside air temperature. The outside air temperature detector 51 detects the outside air temperature, which is the temperature of the air outside the room, when the ventilation device 3 is in an energized state. The outside air temperature detector 51 sends a signal indicating the detected outside air temperature to the control device 5. The control device 5 acquires the value of the outside air temperature from the outside air temperature detector 51 by receiving the signal sent from the outside air temperature detector 51. When the control device 5 acquires the value of the outside air temperature from the outside air temperature detector 51, the heat source unit 1 does not need to be in an energized state at the time of step S2. When the control device 5 acquires the value of the outside air temperature from the outside air temperature detector 52, the heat source unit 1 is in an energized state at the time of step S2. The outside air temperature detector 52 detects the outside air temperature when the heat source unit 1 is in an energized state.

[0064] In step S3, the control device 5 determines whether the outside air temperature is higher than the first temperature. If the control device 5 determines that the outside air temperature is higher than the first temperature (step S3, Yes), it instructs the flow path switching valve 23 to open the first flow path 25 and close the second flow path 26. In step S4, the flow path switching valve 23 opens the first flow path 25 and closes the second flow path 26 in accordance with the instruction from the control device 5. In this way, when the temperature detected by the outside air temperature detector 51 is higher than the first temperature, the heat medium circulation circuit unit 22 enters a first state in which the transport of the heat medium to the outside air heater 36 is stopped.

[0065] Following step S4, the control device 5 instructs the directional control valve 24 to pass the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. In accordance with the instruction from the control device 5, the directional control valve 24 passes the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. As a result, in step S5, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the radiator 2 returns to the heat source unit 1 through the connection point 27. When the heat source unit 1 is operating, the heat medium flows through the heat medium circulation circuit unit 22 and is transported to the radiator 2, as shown in FIG. 1 .

[0066] If the control device 5 determines that the outside air temperature is not higher than the first temperature (No in step S3), that is, if the control device 5 determines that the outside air temperature is equal to or lower than the first temperature, the control device 5 instructs the flow path switching valve 23 to close the first flow path 25 and open the second flow path 26. In step S6, the flow path switching valve 23 closes the first flow path 25 and opens the second flow path 26 in accordance with the instruction from the control device 5.

[0067] Following step S6, the control device 5 determines in step S7 whether the outside air temperature is higher than the second temperature. If it is determined that the outside air temperature is higher than the second temperature (step S7, Yes), the control device 5 instructs the directional control valve 24 to pass the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. In accordance with the instruction from the control device 5, the directional control valve 24 passes the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. As a result, in step S8, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the radiator 2 passes through the outside air heater 36 and returns to the heat source unit 1. When the heat source unit 1 is operated, the heat medium flows through the heat medium circulation circuit unit 22 as shown in FIG. 2 and is transported to the radiator 2 and the outdoor air heater 36 .

[0068] If the control device 5 determines that the outside air temperature is not higher than the second temperature (No in step S7), that is, if the control device 5 determines that the outside air temperature is equal to or lower than the second temperature, the control device 5 instructs the directional control valve 24 to pass the heat medium between the connection ports 24a and 24c and between the connection ports 24b and 24d. In accordance with the instruction from the control device 5, the directional control valve 24 passes the heat medium between the connection ports 24a and 24c and between the connection ports 24b and 24d. As a result, in step S9, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the outdoor air heater 36 passes through the radiator 2 and returns to the heat source unit 1. When the heat source unit 1 is operating, the heat medium flows through the heat medium circulation circuit unit 22 and is transported to the outdoor air heater 36 and the radiator 2, as shown in FIG. 3 .

[0069] Thus, the ventilation and air-conditioning system 100 completes the operation according to the procedure shown in Fig. 4. While the operation of the ventilation device 3 continues, the ventilation and air-conditioning system 100 periodically acquires the value of the outside air temperature using the control device 5, and repeats the operation from step S2 to step S5, step S8, or step S9.

[0070] In the above description, the flow path switching valve 23 switches the heat medium circulation circuit unit 22 to the second state when the outside air temperature matches the first temperature, but this is not limited to this. The flow path switching valve 23 may switch the heat medium circulation circuit unit 22 to the first state when the outside air temperature matches the first temperature. The flow path switching valve 23 may at least switch the heat medium circulation circuit unit 22 to the first state when the outside air temperature is higher than the first temperature, and switch the heat medium circulation circuit unit 22 to the second state when the outside air temperature is lower than the first temperature.

[0071] In the above description, the directional control valve 24 changes the flow direction of the heat medium from the heat source unit 1 to the outdoor air heater 36 to return to the heat source unit 1 through the radiator 2 when the outdoor air temperature matches the second temperature, but this is not limited to this. When the outdoor air temperature matches the second temperature, the directional control valve 24 may change the flow direction of the heat medium from the heat source unit 1 to the radiator 2 to return to the heat source unit 1 through the outdoor air heater 36. The directional control valve 24 may at least change the flow direction of the heat medium from the heat source unit 1 to the radiator 2 to return to the heat source unit 1 through the outdoor air heater 36 when the outdoor air temperature is higher than the second temperature, and change the flow direction of the heat medium from the heat source unit 1 to the outdoor air heater 36 to return to the heat source unit 1 through the radiator 2 when the outdoor air temperature is lower than the second temperature.

[0072] When the outdoor air temperature is higher than the first temperature, the possibility of freezing in the heat exchanger 31 is low even if heating is not performed by the outdoor air heater 36. When the temperature detected by the outdoor air temperature detector 51 is higher than the first temperature, the flow path switching valve 23 sets the heat medium circulation circuit unit 22 to a first state in which the delivery of heat medium to the outdoor air heater 36 is stopped. When the outdoor air temperature is higher than the first temperature, the ventilation air-conditioning system 100 can prevent a decrease in ventilation air volume due to freezing in the heat exchanger 31 even if the delivery of heat medium to the outdoor air heater 36 is stopped. Furthermore, by stopping the delivery of heat medium to the outdoor air heater 36, the ventilation air-conditioning system 100 can reduce the energy consumption of the heat source unit 1.

[0073] When the outside air temperature is lower than the first temperature, the possibility of freezing in the heat exchanger 31 increases unless heating is performed by the outside air heater 36. When the temperature detected by the outside air temperature detector 51 is lower than the first temperature, the flow path switching valve 23 sets the heat medium circulation circuit unit 22 to a second state in which the heat medium is transported to the outside air heater 36. When the temperature detected by the outside air temperature detector 51 is lower than the first temperature, the ventilation air-conditioning system 100 reduces freezing in the heat exchanger 31 by transporting the heat medium to the outside air heater 36. By reducing freezing in the heat exchanger 31, the ventilation air-conditioning system 100 can prevent a decrease in ventilation air volume due to freezing in the heat exchanger 31.

[0074] When the outside air temperature is higher than the second temperature, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit section 22 so that the heat medium that has flowed from the heat source unit 1 to the radiator 2 passes through the outside air heater 36 and returns to the heat source unit 1. In this case, the heat medium that leaves the heat source unit 1 is transported to the radiator 2 before the outside air heater 36. By transporting the heat medium that has undergone heat dissipation in the radiator 2 to the outside air heater 36, the ventilation and air-conditioning system 100 can efficiently use the thermal energy generated in the heat source unit 1 to heat the air passing through the outside air duct 32.

[0075] When the outdoor air temperature is lower than the second temperature, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that flows from the heat source unit 1 to the outdoor air heater 36 passes through the radiator 2 and returns to the heat source unit 1. In this case, the heat medium leaving the heat source unit 1 is transported to the outdoor air heater 36 before being transported to the radiator 2. The ventilation and air-conditioning system 100 can secure a large amount of thermal energy to be released in the outdoor air duct 32 regardless of the indoor heating load. This allows the ventilation and air-conditioning system 100 to reduce icing in the heat exchanger 31 when the outdoor air temperature drops significantly. By reducing icing in the heat exchanger 31, the ventilation and air-conditioning system 100 can prevent a decrease in ventilation air volume due to icing in the heat exchanger 31.

[0076] According to the first embodiment, the ventilation air-conditioning system 100 includes an outdoor air heater 36 that uses a heat medium to heat air taken in from outside before it is introduced into the heat exchanger 31, and a heat medium circulation circuit unit 22 that forms a flow path for the heat medium that is transported from the heat source unit 1 to the radiator 2 and the outdoor air heater 36 and then returned to the heat source unit 1. By heating the air using the outdoor air heater 36, the ventilation air-conditioning system 100 can prevent a decrease in ventilation air volume due to freezing in the heat exchanger 31. The ventilation air-conditioning system 100 can ensure a sufficient indoor supply air volume because it continues to supply air by the ventilation device 3 regardless of the outdoor temperature conditions. The ventilation air-conditioning system 100 can reduce the heating load compared to when type 3 ventilation is performed because it continues to supply air that exchanges heat with the ventilation device 3. As described above, the ventilation air-conditioning system 100 has the effect of preventing a decrease in ventilation air volume due to freezing in the heat exchanger 31 and reducing the heating load.

[0077] Embodiment 2 Fig. 5 is a first diagram showing an example configuration of a ventilating air-conditioning system 101 according to embodiment 2. The ventilating air-conditioning system 101 is a system that ventilates and air-conditions a room. The ventilating air-conditioning system 101 includes a heat source unit 1, a radiator 2, and a ventilation device 3.

[0078] 1 is not provided in the ventilation device 3 of the ventilation air-conditioning system 101. The ventilation air-conditioning system 101 includes an outdoor air heater 49 provided in an outdoor air duct 45. In the second embodiment, the same components as those in the first embodiment above are denoted by the same reference numerals, and the following description will mainly focus on configurations that differ from those in the first embodiment.

[0079] The outdoor air heater 49 heats air in the outdoor air duct 45 through which air passes when it is taken into the ventilation device 3 from the outdoors. That is, the outdoor air heater 49 heats the air taken in from the outdoors before it is introduced into the heat exchanger 31. The outdoor air heater 49 uses a heat medium to heat the air taken in from the outdoors before it is introduced into the heat exchanger 31.

[0080] A heat medium circuit section through which a heat medium passes is provided within the outdoor air heater 49. The heat medium circuit section within the outdoor air heater 49 has two connection ports 49a, 49b. The heat medium flows into the outdoor air heater 49 from the connection port 49a or the connection port 49b. When the heat medium flows into the outdoor air heater 49 from the connection port 49a, the heat medium passes through the heat medium circuit section and flows out of the outdoor air heater 49 from the connection port 49b. When the heat medium flows into the outdoor air heater 49 from the connection port 49b, the heat medium passes through the heat medium circuit section and flows out of the outdoor air heater 49 from the connection port 49a. Note that in FIG. 5, parts of the heat medium circuit section within the outdoor air heater 49 other than the connection ports 49a, 49b are not shown.

[0081] When the heat medium is being transported from the heat source unit 1 to the outdoor air heater 49 in the heat medium circulation circuit section 22, the heat of the heat medium passing through the heat medium circuit section in the outdoor air heater 49 is transferred to the air passing through the outdoor air duct 45. As a result, the air before being introduced into the heat exchanger 31 is heated in the outdoor air duct 45.

[0082] The outside air heater 49 is, for example, a plate-fin type heater in which a number of metal plates are connected to metal pipes that constitute the heat medium circuit section. The heat of the heat medium passing through the metal pipes is transmitted from the metal pipes and metal plates to the air surrounding the metal pipes and metal plates, thereby heating the air in the outside air duct 45. Note that the outside air heater 49 is not limited to a plate-fin type heater, and may be a heater made of a single metal pipe. The outside air heater 49 may heat the air in the outside air duct 45 by passing a heat medium through a metal pipe that is in contact with the inner wall of the outside air duct 45.

[0083] By providing the outdoor air heater 49 that heats the air in the outdoor air duct 45 before it is introduced into the heat exchanger 31, the ventilation device 3 can be made smaller than when the outdoor air heater 49 is installed inside the ventilation device 3. Furthermore, when the shape of the outdoor air heater 49 is designed to match the processing air volume, the degree of freedom in the shape of the outdoor air heater 49 can be increased.

[0084] The ventilation and air-conditioning system 101 switches the heat medium circulation circuit unit 22 between a first state in which the delivery of the heat medium to the outdoor air heater 49 is stopped, and a second state in which the heat medium is delivered to the outdoor air heater 49. The first flow path 25 is a flow path through which the heat medium that has passed through the radiator 2 returns to the heat source unit 1 in the first state. The second flow path 26 is a flow path that delivers the heat medium to the outdoor air heater 49 in the second state. The flow path switching valve 23 switches the heat medium circulation circuit unit 22 between the first state in which the delivery of the heat medium to the outdoor air heater 49 is stopped, and the second state in which the heat medium is delivered to the outdoor air heater 49. In the second state, the directional control valve 24 switches the direction in which the heat medium flows between the direction in which the heat medium flowing from the heat source unit 1 to the radiator 2 passes through the outdoor air heater 49 and returns to the heat source unit 1, and the direction in which the heat medium flowing from the heat source unit 1 to the outdoor air heater 49 passes through the radiator 2 and returns to the heat source unit 1.

[0085] The connection port 23c of the flow path switching valve 23 is connected to the connection port 49a of the outdoor air heater 49 via a pipe. The connection port 49b of the outdoor air heater 49 is connected to the connection point 27 via a pipe. The first flow path 25 is a flow path between the connection port 23b of the flow path switching valve 23 and the connection point 27. The second flow path 26 is a flow path between the connection port 23c of the flow path switching valve 23 and the connection port 49a of the outdoor air heater 49, and a flow path between the connection port 49b of the outdoor air heater 49 and the connection point 27.

[0086] The outdoor air temperature detector 51 detects the temperature of the air at a position downwind from the position where the outdoor air heater 49 heats the air. Therefore, when the heat medium circulation circuit unit 22 is in the second state, the outdoor air temperature detector 51 detects the temperature of the air heated by the outdoor air heater 49. The control device 5 obtains information about the temperature of the air heated by the outdoor air heater 49 from the outdoor air temperature detector 51. The ventilation and air conditioning system 101 detects the temperature of the outdoor air using an outdoor air temperature detector 52 arranged in the heat pump unit 12. The control device 5 obtains information about the outdoor air temperature from the outdoor air temperature detector 52.

[0087] Next, the operation of the ventilation and air-conditioning system 101 will be described. The control device 5 compares the outside air temperature detected by the outside air temperature detector 52 with a first temperature, which is a preset temperature. When the outside air temperature is higher than the first temperature, the control device 5 sends a control signal to the flow path switching valve 23, instructing the flow path switching valve 23 to open the first flow path 25 and close the second flow path 26. When the outside air temperature is higher than the first temperature, the flow path switching valve 23 opens the first flow path 25 and closes the second flow path 26. In other words, when the temperature detected by the outside air temperature detector 52 is higher than the first temperature, the flow path switching valve 23 puts the heat medium circulation circuit unit 22 into a first state in which the transport of the heat medium to the outside air heater 49 is stopped.

[0088] In the example shown in FIG. 5, the flow path switching valve 23 opens the first flow path 25 by opening the connection port 23a and the connection port 23b, and closes the second flow path 26 by closing the connection port 23c.

[0089] Furthermore, when the outside air temperature is higher than a first temperature, the control device 5 instructs the directional switching valve 24 to pass the heat medium between connection port 24a and connection port 24b and between connection port 24c and connection port 24d. When the outside air temperature is higher than the first temperature, the directional switching valve 24 passes the heat medium between connection port 24a and connection port 24b and between connection port 24c and connection port 24d. As a result, the directional switching valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the radiator 2 returns to the heat source unit 1 through connection point 27.

[0090] Figure 5 shows the ventilating air-conditioning system 101 when the heat medium circulation circuit unit 22 is in the first state. The straight arrows and broken line arrows in Figure 5 indicate the direction in which the heat medium flows in the heat medium circulation circuit unit 22. When the heat medium circulation circuit unit 22 is in the first state, the manner in which the heat medium flows is the same as when the heat medium circulation circuit unit 22 is in the first state in embodiment 1.

[0091] 5, the dashed line in flow path switching valve 23 indicates that the heat medium passes between connection port 23a and connection port 23b in flow path switching valve 23. In Fig. 5, one of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24a and connection port 24b in direction switching valve 24, and the other of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24c and connection port 24d in direction switching valve 24.

[0092] When the outside air temperature is equal to or lower than a first temperature, the control device 5 instructs the flow path switching valve 23 to close the first flow path 25 and open the second flow path 26. When the outside air temperature is equal to or lower than the first temperature, the flow path switching valve 23 closes the first flow path 25 and opens the second flow path 26. In other words, when the temperature detected by the outside air temperature detector 52 is equal to or lower than the first temperature, the flow path switching valve 23 puts the heat medium circulation circuit unit 22 into a second state in which the heat medium is transported to the outside air heater 49.

[0093] When the temperature detected by the outside air temperature detector 52 is equal to or lower than the first temperature, the control device 5 compares the temperature detected by the outside air temperature detector 51 with the first temperature. That is, when the temperature detected by the outside air temperature detector 52 is equal to or lower than the first temperature, the control device 5 compares the temperature of the air heated by the outside air heater 49 with the first temperature. When the temperature of the air heated by the outside air heater 49 is higher than the first temperature, the control device 5 instructs the directional control valve 24 to pass the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. The directional control valve 24 is in a state where the heat medium is passed between the connection ports 24a and 24b and between the connection ports 24c and 24d. As a result, when the temperature of the air heated by the outdoor air heater 49 is higher than the first temperature, the directional control valve 24 changes the direction in which the heat medium flows in the heat medium circulation circuit section 22 so that the heat medium that flows from the heat source unit 1 to the radiator 2 passes through the outdoor air heater 49 and returns to the heat source unit 1.

[0094] When the temperature of the air heated by the outdoor air heater 49 is equal to or lower than a first temperature, the control device 5 instructs the directional switching valve 24 to pass the heat medium between the connection ports 24a and 24c and to pass the heat medium between the connection ports 24b and 24d. The directional switching valve 24 is in a state where the heat medium is passed between the connection ports 24a and 24c and between the connection ports 24b and 24d. As a result, when the temperature of the air heated by the outdoor air heater 49 is equal to or lower than the first temperature, the directional switching valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 to a direction where the heat medium that has flowed from the heat source unit 1 to the outdoor air heater 49 passes through the radiator 2 and returns to the heat source unit 1.

[0095] Figure 6 is a second diagram showing an example configuration of a ventilating air-conditioning system 101 according to Embodiment 2. Figure 6 shows the ventilating air-conditioning system 101 when the heat medium circulation circuit unit 22 is in the second state and the temperature of the air heated by the outdoor air heater 49 is higher than the first temperature. That is, Figure 6 shows the ventilating air-conditioning system 101 when the outdoor air temperature is equal to or lower than the first temperature and the temperature of the air heated by the outdoor air heater 49 is higher than the first temperature. The straight arrows and broken line arrows shown in Figure 6 indicate the direction in which the heat medium flows in the heat medium circulation circuit unit 22.

[0096] When the heat medium circulation circuit section 22 is in the second state and the temperature of the air heated by the outdoor air heater 49 is higher than the first temperature, the heat medium flow path from the connection port 114b of the heat source unit 1 to the connection port 23a of the flow path switching valve 23 is the same as that shown in FIG. 2 . The heat medium that reaches the connection port 23a of the flow path switching valve 23 passes through the connection port 23c and heads from the connection port 23c to the outdoor air heater 49. The heat medium flows into the outdoor air heater 49 from the connection port 49a of the outdoor air heater 49. The heat medium that flows through the heat medium circuit section in the outdoor air heater 49 flows out from the connection port 49b of the outdoor air heater 49, then passes through the connection point 27 and reaches the connection port 24c of the directional control valve 24. That is, the heat medium passes through the second flow path 26 and reaches the connection port 24c of the directional control valve 24. The flow path of the heat medium from the connection port 24c of the directional control valve 24 to the connection port 114a of the heat source unit 1 is the same as that shown in FIG.

[0097] 6, the dashed line in flow path switching valve 23 indicates that the heat medium passes between connection port 23a and connection port 23c in flow path switching valve 23. In Fig. 6, one of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24a and connection port 24b in direction switching valve 24, and the other of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24c and connection port 24d in direction switching valve 24.

[0098] 6 , the flow path switching valve 23 opens the connection ports 23a and 23c to open the second flow path 26, and closes the connection port 23b to close the first flow path 25. The directional control valve 24 passes the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d, thereby changing the flow direction of the heat medium from the heat source unit 1 to the radiator 2 to return to the heat source unit 1 through the outdoor air heater 49.

[0099] Figure 7 is a third diagram showing an example configuration of a ventilating air-conditioning system 101 pertaining to Embodiment 2. Figure 7 shows the ventilating air-conditioning system 101 when the heat medium circulation circuit unit 22 is in the second state and the temperature of the air heated by the outdoor air heater 49 is equal to or lower than a first temperature. That is, Figure 7 shows the ventilating air-conditioning system 101 when the temperature detected by the outdoor air temperature detector 52 is equal to or lower than the first temperature and the temperature of the air heated by the outdoor air heater 49 is equal to or lower than the first temperature. The straight arrows and broken line arrows shown in Figure 7 indicate the direction in which the heat medium flows in the heat medium circulation circuit unit 22.

[0100] When the heat medium circulation circuit section 22 is in the second state and the temperature of the air heated by the outdoor air heater 49 is equal to or lower than the first temperature, the heat medium flowing out from the connection port 114b of the heat source unit 1 passes through the connection ports 24a and 24c of the directional control valve 24 and heads toward the outdoor air heater 49 via the connection point 27. The heat medium flows into the outdoor air heater 49 from the connection port 49b of the outdoor air heater 49. After flowing through the heat medium circuit section inside the outdoor air heater 49, the heat medium flows out from the connection port 49a of the outdoor air heater 49 and then reaches the connection port 23c of the flow path switching valve 23. The flow path of the heat medium from the connection port 23c of the flow path switching valve 23 to the connection port 114a of the heat source unit 1 is the same as that shown in FIG. 3 .

[0101] 7, the dashed line in flow path switching valve 23 indicates that the heat medium passes between connection port 23a and connection port 23c in flow path switching valve 23. In Fig. 7, one of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24a and connection port 24c in direction switching valve 24, and the other of the two dashed lines in direction switching valve 24 indicates that the heat medium passes between connection port 24b and connection port 24d in direction switching valve 24.

[0102] In the example shown in Fig. 7, the flow path switching valve 23 opens the connection ports 23a and 23c to open the second flow path 26, and closes the first flow path 25 by closing the connection port 23b. The direction switching valve 24 passes the heat medium between the connection ports 24a and 24c and between the connection ports 24b and 24d, thereby changing the flow direction of the heat medium from the heat source unit 1 to the outdoor air heater 49 to return to the heat source unit 1 through the radiator 2. The flow direction of the heat medium in the heat medium circulation circuit unit 22 in Fig. 7 is opposite to that shown in Fig. 6.

[0103] Fig. 8 is a flowchart showing the procedure of the operation of the ventilation air-conditioning system 101 according to Embodiment 2. A program for realizing the procedure shown in Fig. 8 is stored in the control device 5.

[0104] In step S11, the ventilation air-conditioning system 101 starts operation of the ventilation device 3. If the heat source unit 1 is not in a powered state at the time of step S11, the ventilation air-conditioning system 101 brings the heat source unit 1 into a powered state.

[0105] In step S12, the control device 5 acquires the value of the outside air temperature. The outside air temperature detector 52 detects the outside air temperature, which is the temperature of the air outside the room, when the heat source unit 1 is in an energized state. The outside air temperature detector 52 sends a signal indicating the detected outside air temperature to the control device 5. The control device 5 acquires the value of the outside air temperature from the outside air temperature detector 52 by receiving the signal sent from the outside air temperature detector 52.

[0106] In step S13, the control device 5 determines whether the outside air temperature is higher than the first temperature. If the control device 5 determines that the outside air temperature is higher than the first temperature (step S13, Yes), the control device 5 sends a control signal to the flow path switching valve 23 to instruct the flow path switching valve 23 to open the first flow path 25 and close the second flow path 26. In step S14, the flow path switching valve 23 opens the first flow path 25 and closes the second flow path 26 in accordance with the instruction from the control device 5. In this way, when the temperature detected by the outside air temperature detector 52 is higher than the first temperature, the heat medium circulation circuit unit 22 enters a first state in which the transport of the heat medium to the outside air heater 49 is stopped.

[0107] Following step S14, the control device 5 sends a control signal to the directional switching valve 24, instructing the directional switching valve 24 to pass the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. In accordance with the instruction from the control device 5, the directional switching valve 24 passes the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. As a result, in step S15, the directional switching valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the radiator 2 returns to the heat source unit 1 through the connection point 27. When the heat source unit 1 is operating, the heat medium flows through the heat medium circulation circuit unit 22 and is transported to the radiator 2, as shown in FIG. 5 .

[0108] When the control device 5 determines that the outside air temperature is not higher than the first temperature (No in step S13), that is, when the control device 5 determines that the outside air temperature is equal to or lower than the first temperature, the control device 5 sends a control signal to the flow path switching valve 23 to instruct the flow path switching valve 23 to close the first flow path 25 and open the second flow path 26. In step S16, the flow path switching valve 23 closes the first flow path 25 and opens the second flow path 26 in accordance with the instruction from the control device 5.

[0109] In step S17, the control device 5 acquires the value of the temperature of the heated air. The outside air temperature detector 51 detects the temperature of the air heated by the outside air heater 49. The outside air temperature detector 51 sends a signal indicating the detected temperature to the control device 5. The control device 5 receives the signal sent from the outside air temperature detector 51 and acquires the value of the temperature of the heated air from the outside air temperature detector 51.

[0110] Following step S17, the control device 5 determines in step S18 whether the temperature of the heated air is higher than the first temperature. If the control device 5 determines that the temperature of the heated air is higher than the first temperature (step S18, Yes), the control device 5 sends a control signal to the directional switching valve 24 to instruct the directional switching valve 24 to pass the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. In accordance with the instruction from the control device 5, the directional switching valve 24 passes the heat medium between the connection ports 24a and 24b and between the connection ports 24c and 24d. As a result, in step S19, the directional switching valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that flows from the heat source unit 1 to the radiator 2 passes through the outdoor air heater 49 and returns to the heat source unit 1. When the heat source unit 1 is in operation, the heat medium flows through the heat medium circulation circuit unit 22 as shown in FIG. 6 and is transported to the radiator 2 and the outdoor air heater 49 .

[0111] If the control device 5 determines that the temperature of the heated air is not higher than the first temperature (No in step S18), that is, if the control device 5 determines that the temperature of the heated air is equal to or lower than the first temperature, the control device 5 sends a control signal to the directional switching valve 24 to instruct the directional switching valve 24 to pass the heat medium between the connection ports 24a and 24c and between the connection ports 24b and 24d. In accordance with the instruction from the control device 5, the directional switching valve 24 passes the heat medium between the connection ports 24a and 24c and passes the heat medium between the connection ports 24b and 24d. As a result, in step S20, the directional switching valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the outdoor air heater 49 passes through the radiator 2 and returns to the heat source unit 1. When the heat source unit 1 is in operation, the heat medium flows through the heat medium circulation circuit unit 22 as shown in FIG. 7 and is transported to the outdoor air heater 49 and the radiator 2 .

[0112] Thus, the ventilation and air-conditioning system 101 ends the operation according to the procedure shown in Fig. 8. While the operation of the ventilation device 3 continues, the ventilation and air-conditioning system 101 periodically acquires the outside air temperature value and the temperature value of the heated air using the control device 5, and repeats the operation from step S12 to step S15, step S19, or step S20.

[0113] In the above description, the flow path switching valve 23 switches the heat medium circulation circuit unit 22 to the second state when the outside air temperature matches the first temperature, but this is not limited to this. The flow path switching valve 23 may switch the heat medium circulation circuit unit 22 to the first state when the outside air temperature matches the first temperature. The flow path switching valve 23 may at least switch the heat medium circulation circuit unit 22 to the first state when the outside air temperature is higher than the first temperature, and switch the heat medium circulation circuit unit 22 to the second state when the outside air temperature is lower than the first temperature.

[0114] In the above description, the directional switching valve 24 changes the flow direction of the heat medium from the heat source unit 1 to the outdoor air heater 49 to return to the heat source unit 1 through the radiator 2 when the temperature of the heated air matches the first temperature, but this is not limited to this. When the temperature of the heated air matches the first temperature, the directional switching valve 24 may change the flow direction of the heat medium from the heat source unit 1 to the radiator 2 to return to the heat source unit 1 through the outdoor air heater 49. The directional switching valve 24 may at least change the flow direction of the heat medium from the heat source unit 1 to the radiator 2 to return to the heat source unit 1 through the outdoor air heater 49 when the temperature of the heated air is higher than the first temperature, and change the flow direction of the heat medium from the heat source unit 1 to the outdoor air heater 49 to return to the heat source unit 1 through the radiator 2 when the temperature of the heated air is lower than the first temperature.

[0115] When the outdoor air temperature is higher than the first temperature, the possibility of freezing in the heat exchanger 31 is low even if heating is not performed by the outdoor air heater 49. When the temperature detected by the outdoor air temperature detector 52 is higher than the first temperature, the flow path switching valve 23 sets the heat medium circulation circuit unit 22 to a first state in which the delivery of heat medium to the outdoor air heater 49 is stopped. When the outdoor air temperature is higher than the first temperature, the ventilation air-conditioning system 101 can prevent a decrease in ventilation air volume due to freezing in the heat exchanger 31 even if the delivery of heat medium to the outdoor air heater 49 is stopped. Furthermore, by stopping the delivery of heat medium to the outdoor air heater 49, the ventilation air-conditioning system 101 can reduce the energy consumption of the heat source unit 1.

[0116] When the outside air temperature is lower than the first temperature, the possibility of freezing in the heat exchanger 31 increases unless heating is performed by the outside air heater 49. When the temperature detected by the outside air temperature detector 52 is lower than the first temperature, the flow path switching valve 23 sets the heat medium circulation circuit unit 22 to a second state in which the heat medium is transported to the outside air heater 49. When the temperature detected by the outside air temperature detector 52 is lower than the first temperature, the ventilation air-conditioning system 101 transports the heat medium to the outside air heater 49, thereby reducing freezing in the heat exchanger 31. By reducing freezing in the heat exchanger 31, the ventilation air-conditioning system 101 can prevent a decrease in ventilation air volume due to freezing in the heat exchanger 31.

[0117] When the temperature of the air heated by the outdoor air heater 49 is higher than the first temperature, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium that has flowed from the heat source unit 1 to the radiator 2 passes through the outdoor air heater 49 and returns to the heat source unit 1. In this case, the heat medium leaving the heat source unit 1 is transported to the radiator 2 before the outdoor air heater 49. By transporting the heat medium that has undergone heat dissipation in the radiator 2 to the outdoor air heater 49, the ventilation and air-conditioning system 101 can efficiently use the thermal energy generated in the heat source unit 1 to heat the air passing through the outdoor air duct 45.

[0118] When the temperature of the air heated by the outdoor air heater 49 is lower than the first temperature, the directional control valve 24 changes the flow direction of the heat medium in the heat medium circulation circuit unit 22 so that the heat medium flowing from the heat source unit 1 to the outdoor air heater 49 passes through the radiator 2 and returns to the heat source unit 1. In this case, the heat medium leaving the heat source unit 1 is transported to the outdoor air heater 49 before being transported to the radiator 2. The ventilation and air-conditioning system 101 can secure a large amount of thermal energy to be released in the outdoor air duct 45 regardless of the indoor heating load. The ventilation and air-conditioning system 101 can reliably heat the air by the outdoor air heater 49 to a temperature that reduces freezing in the heat exchanger 31. The ventilation and air-conditioning system 101 can reduce freezing in the heat exchanger 31 when the outdoor air temperature drops significantly. By reducing freezing in the heat exchanger 31, the ventilation and air-conditioning system 101 can prevent a decrease in ventilation air volume due to freezing in the heat exchanger 31.

[0119] According to the second embodiment, the ventilation air-conditioning system 101 includes an outdoor air heater 49 that uses a heat medium to heat air taken in from outside before it is introduced into the heat exchanger 31, and a heat medium circulation circuit unit 22 that forms a flow path for the heat medium that is transported from the heat source unit 1 to the radiator 2 and the outdoor air heater 49 and then returned to the heat source unit 1. By heating the air using the outdoor air heater 49, the ventilation air-conditioning system 101 can prevent a decrease in ventilation air volume due to freezing in the heat exchanger 31. The ventilation air-conditioning system 101 can ensure a sufficient indoor supply air volume because it continues to supply air by the ventilation device 3 regardless of the outdoor temperature conditions. The ventilation air-conditioning system 101 can reduce the heating load compared to when type 3 ventilation is performed because it continues to supply air with heat exchange by the ventilation device 3. As described above, the ventilation air-conditioning system 101 has the effect of preventing a decrease in ventilation air volume due to freezing in the heat exchanger 31 and reducing the heating load.

[0120] In the first and second embodiments, the ventilating air-conditioning systems 100, 101 are configured to include one radiator 2 and one ventilation device 3. The ventilating air-conditioning systems 100, 101 may be configured to include one radiator 2 and multiple ventilation devices 3, multiple radiators 2 and one ventilation device 3, or multiple radiators 2 and multiple ventilation devices 3.

[0121] When the outside temperature drops significantly, the ventilation air-conditioning systems 100, 101 can effectively prevent a decrease in ventilation air volume due to freezing in the heat exchanger 31. The ventilation air-conditioning systems 100, 101 are applied, for example, to indoor ventilation and indoor air conditioning in cold regions.

[0122] Next, a hardware configuration for realizing the control device 5 according to the first or second embodiment will be described. The control device 5 is realized by a processing circuit. The processing circuit may be a circuit in which a processor executes software, or may be a dedicated circuit.

[0123] When the processing circuit is realized by software, the processing circuit is, for example, a control circuit 60 shown in FIG. 9. FIG. 9 is a diagram showing an example configuration of the control circuit 60 according to the first or second embodiment. The control circuit 60 includes an input unit 61, a processor 62, a memory 63, and an output unit 64. The input unit 61 is an interface circuit that receives data input from outside the control circuit 60 and provides the data to the processor 62. The output unit 64 is an interface circuit that sends data from the processor 62 or the memory 63 to outside the control circuit 60.

[0124] The processor 62 is a CPU (Central Processing Unit). The processor 62 may be a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor). The memory 63 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, or a DVD (Digital Versatile Disc).

[0125] 9 shows an example of hardware in which the functions of the control device 5 are realized by a general-purpose processor 62 and memory 63, but the functions of the control device 5 may also be realized by a dedicated hardware circuit. Fig. 10 is a diagram showing an example of the configuration of a dedicated hardware circuit 65 according to the first or second embodiment.

[0126] The dedicated hardware circuit 65 includes an input unit 61, an output unit 64, and a processing circuit 66. The processing circuit 66 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The control device 5 may be realized by the processing circuit 66 for each function, or the functions of the control device 5 may be realized collectively by the processing circuit 66. The control device 5 may also be realized by combining the control circuit 60 and the hardware circuit 65.

[0127] The configurations shown in the above embodiments are examples of the contents of the present disclosure. The configurations of each embodiment can be combined with other known technologies. The configurations of each embodiment can also be combined as appropriate. Part of the configuration of each embodiment can be omitted or modified without departing from the gist of the present disclosure.

[0128] REFERENCE SIGNS LIST 1 Heat source machine, 2 Radiator, 3 Ventilation device, 4 Building, 5 Control device, 11 Hot water generator, 12 Heat pump unit, 21, 114 Heat medium circuit section, 21a, 21b, 23a, 23b, 23c, 24a, 24b, 24c, 24d, 36a, 36b, 49a, 49b, 114a, 114b Connection port, 22 Heat medium circulation circuit section, 23 Flow path switching valve, 24 Direction switching valve, 25 First flow path, 26 Second flow path, 27 Connection point, 30 Housing, 31, 111 Heat exchanger, 32 Outdoor air duct, 33 Exhaust air duct, 34 Supply air duct, 35 Return air duct, 36, 49 Outdoor air heater, 41 Outdoor intake port, 42 Outdoor outlet, 43 Indoor outlet, 44 Indoor intake port, 45 outdoor air duct, 46 exhaust duct, 47 supply air duct, 48 return air duct, 51, 52 outdoor air temperature detector, 60 control circuit, 61 input unit, 62 processor, 63 memory, 64 output unit, 65 hardware circuit, 66 processing circuit, 100, 101 ventilation air conditioning system, 112 transfer pump, 113 heat medium tank, 121 refrigerant circulation circuit unit.

Claims

1. A ventilation and air conditioning system comprising: a heat source unit that heats a heat medium; a radiator that releases heat from the heat medium in a space to be heated; a ventilation device having a heat exchanger that exchanges heat between air supplied from outside to the room and air exhausted from the room to the outside, and that supplies air to the room and exhausts air from the room; an outdoor air heater that uses the heat medium to heat air that is taken in from outside and before it is introduced into the heat exchanger; and a heat medium circulation circuit section that forms a flow path for the heat medium that is transported from the heat source unit to each of the radiator and the outdoor air heater and returned to the heat source unit.

2. The ventilation and air conditioning system of claim 1, further comprising: an outdoor air temperature detector that detects the temperature of the air outside the room; and a switching unit that switches the heat medium circulation circuit unit between a first state in which the transport of the heat medium to the outdoor air heater is stopped and a second state in which the heat medium is transported to the outdoor air heater based on the detection result by the outdoor air temperature detector.

3. The ventilation and air conditioning system of claim 2, characterized in that when the temperature detected by the outside air temperature detector is higher than a predetermined first temperature, the switching unit switches the heat medium circulation circuit unit to the first state, and when the temperature detected by the outside air temperature detector is lower than the first temperature, the switching unit switches the heat medium circulation circuit unit to the second state.

4. The ventilation and air conditioning system described in claim 3, characterized in that the heat medium circulation circuit unit has a first flow path through which the heat medium that has passed through the radiator returns to the heat source unit in the first state, and a second flow path that transports the heat medium to the outdoor air heater in the second state, and the switching unit is a first valve that switches the flow path of the heat medium between the first flow path and the second flow path, and when the temperature detected by the outdoor air temperature detector is higher than the first temperature, the first valve opens the first flow path and closes the second flow path, and when the temperature detected by the outdoor air temperature detector is lower than the first temperature, the first valve closes the first flow path and opens the second flow path.

5. The ventilation and air conditioning system of claim 4, further comprising a second valve which switches the flow direction of the heat medium in the heat medium circulation circuit section, wherein when the temperature detected by the outdoor air temperature detector is lower than the first temperature and higher than a predetermined second temperature, the second valve changes the flow direction of the heat medium so that the heat medium that has flowed from the heat source unit to the radiator passes through the outdoor air heater and returns to the heat source unit, and when the temperature detected by the outdoor air temperature detector is lower than the second temperature, the second valve changes the flow direction of the heat medium so that the heat medium that has flowed from the heat source unit to the outdoor air heater passes through the radiator and returns to the heat source unit.

6. The ventilation and air conditioning system according to any one of claims 1 to 5, characterized in that the ventilation device has an outside air duct which is an air path through which air flowing into the ventilation device from outside the room passes until it reaches the heat exchanger, and the outside air heater heats the air passing through the outside air duct.

7. A ventilation and air conditioning system as described in any one of claims 1 to 5, characterized in that the outdoor air heater heats air in an outdoor air duct through which air passes to be taken into the ventilation device from outside the room.

8. The ventilation and air conditioning system described in any one of claims 2 to 5, characterized in that the ventilation device has an outside air duct which is an air passage through which air flowing into the ventilation device from outside the room reaches the heat exchanger, the outside air temperature detector detects the temperature of the air outside the room by detecting the temperature of the air passing through the outside air duct, and the outside air heater heats the air at a position in the outside air duct that is downwind from the position where the outside air temperature detector detects the air temperature.

9. The ventilation and air conditioning system of claim 4, further comprising a second valve which switches the flow direction of the heat medium in the heat medium circulation circuit section, wherein when the temperature of the air heated by the outdoor air heater is higher than the first temperature, the second valve changes the flow direction of the heat medium so that the heat medium that has flowed from the heat source unit to the radiator passes through the outdoor air heater and returns to the heat source unit, and when the temperature of the air heated by the outdoor air heater is lower than the first temperature, the second valve changes the flow direction of the heat medium so that the heat medium that has flowed from the heat source unit to the outdoor air heater passes through the radiator and returns to the heat source unit.

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