Ventilation device

Abstract

This ventilation device comprises: an air supply blower which forms a flow of air passing through an air supply air passage; an exhaust air blower which forms a flow of air passing through an exhaust air passage; a heat exchanger which is installed in a casing across the air supply air passage and the exhaust air passage, and performs heat exchange between the air passing through the air supply air passage and the air passing through the exhaust air passage; a direct expansion coil which is installed in the air supply air passage and comprises a refrigerant circuit for heating or cooling the air passing through the air supply air passage; a refrigerant detection sensor which is installed in the air supply air passage and detects a refrigerant leaked from the refrigerant circuit to the air supply air passage; and a control unit which controls operation of the air supply blower and the exhaust air blower, and which, when the refrigerant concentration detected by the refrigerant detection sensor is equal to or greater than a predetermined reference value, stops the air supply blower and operates only the exhaust air blower.

Description

ventilation equipment

[0001] The present disclosure relates to ventilation devices.

[0002] A conventional air conditioning system includes an air conditioner, a refrigerant sensor, a ventilation device, and a controller. The ventilation device includes a total heat exchanger, a first intake air duct and a first exhaust air duct that connect the inside and outside of the air-conditioned space via the total heat exchanger, a second intake air duct that connects the inside and outside of the air-conditioned space without passing through the total heat exchanger, a supply air fan that supplies air from outside the air-conditioned space into the air-conditioned space via the first intake air duct and the second intake air duct, an exhaust fan that exhausts air from inside the air-conditioned space to outside the air-conditioned space via the first exhaust air duct, and an intake air opening / closing mechanism that switches between opening and closing the first intake air duct and the second intake air duct. The controller controls the intake air opening / closing mechanism to open the second intake air duct when the refrigerant sensor detects a refrigerant leak (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-186820

[0004] However, in conventional air conditioning systems, the air conditioner and the ventilation device are installed separately, so if a refrigerant leak occurs from the direct expansion coil installed in the ventilation device, the leaked refrigerant mixes with the intake air flow and is supplied to the space to be air-conditioned.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a ventilation device that prevents leaked refrigerant from being supplied to the space to be air-conditioned, even if refrigerant leaks from a direct expansion coil that exchanges heat with the refrigerant.

[0006] The ventilation device according to the present disclosure includes a casing provided with an air intake port that takes in outdoor air, an air intake outlet that supplies outdoor air indoors, an exhaust air intake port that draws in indoor air, an exhaust outlet that discharges indoor air to the outside, an air intake duct connecting the air intake port and the air intake outlet, and an exhaust duct connecting the exhaust air intake port and the exhaust outlet, an air intake fan installed in the air intake duct and forming an air flow passing through the air intake duct, an exhaust fan installed in the exhaust duct and forming an air flow passing through the exhaust duct, and a casing extending across the air intake duct and the exhaust duct. the intake air passage and the exhaust air passage; a direct expansion coil equipped with a refrigerant circuit installed in the intake air passage for heating or cooling the air passing through the intake air passage; a refrigerant detection sensor installed in the intake air passage for detecting refrigerant leaking from the refrigerant circuit into the intake air passage; and a control unit that controls the operation of the intake air blower and the exhaust air blower and stops the intake air blower and operates only the exhaust air blower when the refrigerant concentration detected by the refrigerant detection sensor is equal to or higher than a predetermined reference value.

[0007] According to the ventilation device disclosed herein, when a refrigerant leak from the direct expansion coil to the supply air duct is detected, the supply air blower is stopped, thereby preventing the leaked refrigerant from flowing along with the supply airflow through the supply air duct into the room, which is the air-conditioned space. When a refrigerant leak from the direct expansion coil to the supply air duct is detected, the ventilation device continues operating the exhaust air blower, creating a negative pressure in the exhaust air duct compared to the supply air duct, allowing the refrigerant leaked into the supply air duct to flow into the exhaust air duct through gaps created within the ventilation device and be discharged outdoors. According to the ventilation device disclosed herein, when changing to a refrigerant that requires safety measures in the event of a refrigerant leak, this can be achieved by simply adding a refrigerant detection sensor and changing the control method for the supply air blower and the exhaust air blower, without significantly modifying the ventilation device's structure.

[0008] FIG. 1 is a schematic diagram of a ventilation device according to embodiment 1, showing a state during normal operation when no refrigerant is leaking; FIG. 2 is a schematic diagram of a ventilation device according to embodiment 1, showing a state when a refrigerant is leaking; FIG. 3 is a flowchart showing a control method for heat exchange ventilation operation according to embodiment 1; and FIG. 4 is a flowchart showing a control method for heat exchange ventilation operation according to embodiment 2.

[0009] Hereinafter, a ventilation device according to an embodiment will be described in detail with reference to the drawings. However, the present disclosure is not limited to the embodiment.

[0010] Embodiment 1. FIG. 1 is a schematic diagram of a ventilation device according to embodiment 1, illustrating a state during normal operation when no refrigerant is leaking. Note that the symbol OA denotes outdoor air, the symbol SA denotes supply air, the symbol RA denotes return air, and the symbol EA denotes exhaust air. FIG. 2 is a schematic diagram of a ventilation device according to embodiment 1, illustrating a state when a refrigerant leak occurs. The ventilation device 100 has a casing 1 with a box structure that is installed in a building and provided above the ceiling in a room. The casing 1 has an intake air inlet 9 and an exhaust air outlet 12 on its outdoor side 1a, and an intake air outlet 10 and an exhaust air inlet 11 on its indoor side 1b. In the casing 1, an air intake duct 13 is formed by connecting the air intake port 9 and the air intake outlet 10 to supply outdoor air into the room, and an exhaust duct 14 is formed by connecting the exhaust intake port 11 and the exhaust outlet 12 to exhaust indoor air outdoors.

[0011] The ventilation device 100 includes a heat exchanger 6 where an intake air duct 13 and an exhaust air duct 14 intersect, and where heat is exchanged between air flowing through the intake air duct 13 (the intake air flow) and air flowing through the exhaust air duct 14 (the exhaust air flow). The intake air duct 13 is formed by an upstream intake air duct 13a from the intake air inlet 9 to the heat exchanger 6, a downstream intake air duct 13b from the heat exchanger 6 to the intake air outlet 10, and a heat exchange intake air duct 13c that passes through the heat exchanger 6. Meanwhile, the exhaust air duct 14 is formed by a common air duct for the upstream exhaust air duct 14a from the exhaust air inlet 11 to the heat exchanger 6 and a downstream exhaust air duct 14b from the heat exchanger 6 to the exhaust air outlet 12, and is also formed by a common air duct for either a heat exchange exhaust air duct 14c that passes through the heat exchanger 6 or a bypass exhaust air duct 14d that bypasses the heat exchanger 6. The ventilation device 100 includes a damper 15 at a location where the heat exchange exhaust air duct 14c and the bypass exhaust air duct 14d branch off, in order to switch between the heat exchange exhaust air duct 14c and the bypass exhaust air duct 14d.

[0012] Ventilation device 100 is provided with supply air blower 3 between supply air inlet 9 and supply air outlet 10, which form supply air passage 13, and exhaust air blower 5 between exhaust air inlet 11 and exhaust air outlet 12, which form exhaust air passage 14. Supply air blower 3 has an supply air motor 2 therein for driving supply air blower 3. Exhaust air blower 5 has an exhaust motor 4 therein for driving exhaust blower 5. Furthermore, ventilation device 100 is provided with a direct expansion coil 7, downstream of heat exchanger 6 in supply air passage 13, which has a refrigerant circuit for heating or cooling air supplied from outdoors.

[0013] The direct expansion coil 7 exchanges heat between the refrigerant inside the coil and the supply air flow passing over the coil surface, cooling and dehumidifying the air supplied from outdoors in summer, and heating the air supplied from outdoors in winter. In winter, the air heated by the direct expansion coil 7 is further humidified by a humidifier 8 installed downstream of the direct expansion coil 7, thereby supplying air with adjusted temperature and humidity to the room.

[0014] An outdoor air temperature and humidity sensor 21 is mounted in the upstream intake air duct 13a, and an indoor air temperature and humidity sensor 22 is mounted in the upstream exhaust air duct 14a. The outdoor air temperature and humidity sensor 21 and the indoor air temperature and humidity sensor 22 are used to adjust the cooling or heating capacity of the direct expansion coil 7. A removable intake air filter 16 is also mounted in the upstream intake air duct 13a to remove dust from the outdoor air being drawn into the heat exchanger 6, preventing performance degradation of the heat exchanger 6 due to clogging caused by dust contained in the outdoor air. A removable exhaust air filter 17 is also mounted in the upstream exhaust air duct 14a to remove dust from the indoor air being drawn into the heat exchanger 6, preventing performance degradation of the heat exchanger 6 due to clogging caused by dust contained in the indoor air.

[0015] A refrigerant detection sensor 18 that detects refrigerant leakage is provided near the direct expansion coil 7. The refrigerant detection sensor 18 is arranged in the supply air duct 13 from downstream of the direct expansion coil 7 to the supply air outlet 10 so that refrigerant leakage can be detected even when the supply air blower 3 is operating. Furthermore, when the supply air blower 3 is stopped, leaking refrigerant is heavier than air and therefore accumulates below the direct expansion coil 7. For this reason, the refrigerant detection sensor 18 is arranged as low as possible in the supply air duct 13, at or near the bottom of the supply air duct 13.

[0016] The refrigerant detection sensor 18 is a semiconductor-type sensor that primarily uses a semiconductor as a gas-sensing element. The refrigerant detection sensor 18 utilizes the properties of a metal oxide semiconductor. When the refrigerant to be measured comes into contact with the metal oxide semiconductor, oxygen in the metal oxide binds with a component of the refrigerant, changing the resistance of the metal oxide to detect the gas concentration. Note that the refrigerant detection sensor 18 is not limited to a semiconductor-type sensor as long as it can detect the refrigerant concentration. For example, an infrared sensor using non-dispersive infrared absorption (NDIR) may also be used.

[0017] The control unit 19 determines the operating state of the ventilation device 100 based on the user's operation of the controller 20, and controls the following: starting and stopping the supply air blower 3, setting the air speed of the supply air blower 3, starting and stopping the exhaust air blower 5, setting the air speed of the exhaust air blower 5, operating the damper 15, switching between heating and cooling the direct expansion coil 7, adjusting the capacity of the direct expansion coil 7, and supplying and draining water to and from the humidifier 8. A refrigerant detection sensor 18 is also connected to the control unit 19. When the refrigerant detection sensor 18 detects a refrigerant leak from the direct expansion coil 7, the control unit 19 controls the supply air blower 3 and the exhaust air blower 5 to discharge the leaked refrigerant outdoors.

[0018] Next, the operation of the ventilation device 100 configured as described above when a refrigerant leak is detected will be described.

[0019] When a user operates the controller 20 to select the start of the "ventilation" operation, the heat exchange ventilation operation is initiated in the ventilation device 100. When the control unit 19 starts the operation of the intake air blower 3, the exhaust air blower 5, and the direct expansion coil 7, outdoor air is drawn in through the intake air inlet 9 by the intake air blower 3, and indoor air is drawn in through the exhaust air inlet 11 by the exhaust air blower 5. The outdoor air drawn in through the intake air inlet 9 exchanges heat with indoor air drawn in through the exhaust air inlet 11 by the exhaust air blower 5 in the heat exchanger 6. The air that has exchanged heat in the heat exchanger 6 then passes through the direct expansion coil 7, where it exchanges heat with the refrigerant flowing inside the direct expansion coil 7, and is then blown out as an intake airflow from the intake air outlet 10 into the room, which is the space to be air-conditioned. Meanwhile, the indoor air drawn in through the exhaust air inlet 11 by the exhaust air blower 5 exchanges heat in the heat exchanger 6, and is then discharged to the outdoors through the exhaust air outlet 12.

[0020] The control unit 19 also compares the indoor humidity detected by the indoor temperature and humidity sensor 22 with the target humidity set in the controller 20, and adjusts the capacity of the direct expansion coil 7 to control the supply air blowing state, which is the state of the supply airflow blown out as a supply airflow from the supply air outlet 10 into the room, which is the space to be air-conditioned. At this time, if the indoor humidity is below the target humidity, the control unit 19 controls the direct expansion coil 7 to perform cooling or heating at 100% capacity operation, and further controls the supply air blowing state by supplying or draining water to the humidifier 8 to achieve the target humidity. If the indoor humidity has achieved the target humidity, i.e., if the indoor humidity is equal to or higher than the target humidity, the control unit 19 detects the temperature and humidity of the outdoor air with the outdoor air temperature and humidity sensor 21, and adjusts the cooling or heating capacity of the direct expansion coil 7 to control the supply air blowing state so that the indoor humidity is maintained at the target humidity. At this time, the damper 15 switches the exhaust air duct 14 to a heat exchange exhaust air duct 14c through which the exhaust flow passes through the heat exchanger 6 in order to exchange heat between the air sucked from outdoors and the air sucked from indoors.

[0021] As described above, Fig. 2 is a schematic diagram of the ventilation device according to embodiment 1, showing the airflow when a refrigerant leak is detected. Fig. 3 is a flowchart showing a control method for the heat exchange ventilation operation according to embodiment 1. In the flowchart shown in Fig. 3, the control unit 19 performs the judgment and control.

[0022] When the user operates the controller 20 to select the start of "ventilation" operation and the ventilation device 100 starts operation, heat exchange ventilation is performed in step S1. In step S2, the control unit 19 switches the damper 15 to a position where heat exchange exhaust is performed, i.e., a position where the exhaust air duct 14 becomes the heat exchange exhaust air duct 14c through which the heat exchanger 6 passes, and operates the exhaust blower 5 at a preset air volume and the intake air blower 3 at a preset air volume. This position of the damper 15 can be said to be the heat exchange ventilation position.

[0023] In step S3, if the refrigerant concentration detected by the refrigerant detection sensor 18 is equal to or greater than a predetermined reference value, the answer to step S3 becomes Yes, and the control unit 19 determines that refrigerant is leaking from the direct expansion coil 7, and proceeds to step S4.

[0024] In step S4, the control unit 19 switches the damper 15 to a position where bypass exhaust is performed, i.e., a position where the exhaust air duct 14 becomes a bypass exhaust air duct 14d that bypasses the heat exchanger 6, stops the supply air blower 3, and allows only the exhaust air blower 5 to continue operating.

[0025] If the refrigerant concentration detected by the refrigerant detection sensor 18 is less than the reference value in step S3, the result in step S3 is No, and the control unit 19 returns to step S2 to continue the heat exchange ventilation operation.

[0026] In step S4, control unit 19 stops supply air duct 3, preventing refrigerant leaked into supply air duct 13 from being supplied indoors. At the same time, exhaust air duct 5 is operating at a set airflow rate, creating a negative pressure in exhaust air duct 14 relative to supply air duct 13. Ventilation device 100, which includes supply air duct 13 and exhaust air duct 14 and functions to exchange heat between the air flowing through supply air duct 13 and the air flowing through exhaust air duct 14, includes heat exchanger 6 that crosses supply air duct 13 and exhaust air duct 14. Because supply air duct 13 and exhaust air duct 14 are adjacent to each other, it is difficult to completely separate supply air duct 13 and exhaust air duct 14. Therefore, a small gap is created around heat exchanger 6 and between supply air duct 13 and exhaust air duct 14. This gap creates communication between supply air duct 13 and exhaust air duct 14, creating a leakage airflow in which air leaks between supply air duct 13 and exhaust air duct 14.

[0027] Normally, when the intake air blower 3 and the exhaust air blower 5 are operating at the same air volume, the pressure inside the intake air duct 13 and the pressure inside the exhaust air duct 14 are almost the same, and the amount of leakage airflow between the intake air duct 13 and the exhaust air duct 14 is extremely small.

[0028] On the other hand, when refrigerant detection sensor 18 detects a refrigerant concentration equal to or higher than the reference value, ventilation device 100 stops supply air blower 3 and operates exhaust air blower 5, which creates a difference in pressure between supply air duct 13 and exhaust air duct 14, increasing the amount of leakage airflow. Because exhaust air duct 14 is at a lower pressure than supply air duct 13, a refrigerant discharge air duct 31 is formed, as shown in Figure 2, through which air from supply air duct 13 flows from supply air duct 13 to exhaust air duct 14 through the periphery of heat exchanger 6 and the gap between supply air duct 13 and exhaust air duct 14. As a result, refrigerant leaking into supply air duct 13 is discharged through refrigerant discharge air duct 31 to the outdoors through exhaust air outlet 12.

[0029] 2, damper 15 is disposed at a position where exhaust air duct 14 bypasses heat exchanger 6 and passes through bypass exhaust air duct 14d. This is because, as described above, when refrigerant leaked into supply air duct 13 is discharged, supply air blower 3 is stopped, and therefore heat exchange between the supply air flow and the exhaust air flow is not necessary, so the exhaust air flow passes through bypass exhaust air duct 14d. In this case, heat exchange does not occur between the supply air flow and the exhaust air flow, but damper 15 can be left in the heat exchange ventilation position where the exhaust air flow passes through heat exchanger 6 without causing any problems.

[0030] The ventilation device 100 shown in embodiment 1 has the advantage that refrigerant leaking from the direct expansion coil 7 does not mix with the intake air flow and is supplied to the air-conditioned space, but rather the refrigerant passes through the exhaust air duct 14 and is discharged outdoors from the exhaust outlet 12. Furthermore, the ventilation device 100 shown in embodiment 1 can be adapted to a configuration that achieves the above-mentioned effects, without requiring major changes to the structure of an existing ventilation device, simply by adding a refrigerant detection sensor 18 and a control method for when a refrigerant leak is detected.

[0031] In recent years, there has been a trend toward replacing non-flammable refrigerants with low global warming potentials (GWPs) and mildly flammable refrigerants with low GWPs (flammable refrigerants), and safety measures are required when using mildly flammable refrigerants or mildly flammable refrigerants. The ventilation device 100 shown in the first embodiment also has the advantage of enabling replacement of a non-flammable refrigerant with a mildly flammable refrigerant or mildly flammable refrigerant without replacing the ventilation device 100.

[0032] Embodiment 2. Fig. 4 is a flowchart showing a method for controlling heat exchange ventilation operation according to embodiment 2. Comparing Fig. 4 with Fig. 3, embodiment 2 differs from embodiment 1 in that, when the refrigerant concentration is equal to or higher than a reference value, in step S14, the exhaust fan 5 is operated at the maximum airflow rate. That is, in step S11 shown in Fig. 4, the same process as step S1 shown in Fig. 3 is performed. In step S12 shown in Fig. 4, the same process as step S2 shown in Fig. 3 is performed. In step S13 shown in Fig. 4, the same process as step S3 shown in Fig. 3 is performed.

[0033] In step S14, by operating exhaust fan 5 at maximum airflow rate and stopping air supply fan 3, the pressure difference between the pressure inside exhaust airflow duct 14 and the pressure inside air supply airflow duct 13 becomes even larger than in embodiment 1, and the leakage airflow rate of the leakage airflow flowing through refrigerant discharge airflow duct 31 formed from air supply airflow duct 13 toward exhaust airflow duct 14 increases. If the leakage airflow rate of the leakage airflow flowing through refrigerant discharge airflow duct 31 increases, refrigerant leaking into air supply airflow duct 13 can be moved more quickly and in a shorter time to exhaust airflow duct 14, and the refrigerant can be discharged to the outdoors through exhaust outlet 12.

[0034] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention.

[0035] DESCRIPTION OF SYMBOLS 1 Casing, 1a, 1b Side, 2 Air intake motor, 3 Air intake blower, 4 Exhaust motor, 5 Exhaust blower, 6 Heat exchanger, 7 Direct expansion coil, 8 Humidifier, 9 Air intake inlet, 10 Air intake outlet, 11 Exhaust intake port, 12 Exhaust outlet, 13 Air intake duct, 13a Upstream air intake duct, 13b Downstream air intake duct, 13c Heat exchange air intake duct, 14 Exhaust duct, 14a Upstream exhaust duct, 14b Downstream exhaust duct, 14c Heat exchange exhaust duct, 14d Bypass exhaust duct, 15 Damper, 16 Air intake filter, 17 Exhaust air filter, 18 Refrigerant detection sensor, 19 Control unit, 20 Controller, 21 Outdoor air temperature and humidity sensor, 22 Indoor air temperature and humidity sensor, 31 Refrigerant exhaust duct, 100 Ventilation equipment.

Claims

[Claim 1] A casing provided with an air intake port for taking in outdoor air, an air outlet for supplying outdoor air to the interior, an exhaust intake port for drawing in indoor air, an exhaust outlet for discharging indoor air to the outside, an air intake passage connecting the air intake port and the air outlet, and an exhaust passage connecting the exhaust intake port and the exhaust outlet, An air supply fan installed in the aforementioned air supply duct and forming the airflow through the aforementioned air supply duct, An exhaust fan installed in the exhaust air passage and forming the airflow through the exhaust air passage, A heat exchanger is installed within the casing, spanning the air intake passage and the exhaust passage, and performs heat exchange between the air passing through the air intake passage and the air passing through the exhaust passage. A direct expansion coil is installed in the air intake duct and is equipped with a refrigerant circuit for heating or cooling the air passing through the air intake duct, A refrigerant detection sensor is installed in the air supply passage and detects refrigerant leaking from the refrigerant circuit into the air supply passage. A control unit that controls the operation of the supply air blower and the exhaust air blower, and when the refrigerant concentration detected by the refrigerant detection sensor is above a predetermined standard value, stops the supply air blower and operates only the exhaust air blower, Equipped with, The control unit, when the refrigerant concentration detected by the refrigerant detection sensor is above a predetermined standard value, stops the supply air blower, operates the exhaust air blower at maximum airflow, and creates a negative pressure state in the exhaust air passage compared to the supply air passage, thereby causing the refrigerant that has leaked into the supply air passage to flow through the gaps created inside the ventilation device into the exhaust air passage and be discharged outdoors. A ventilation system characterized by the following.