Displacement air conditioning system

Abstract

To solve the problem that it is difficult to control a ventilation amount in an optimal operation state from the viewpoint of energy saving since energy consumption is not considered in conventional control of the ventilation amount.SOLUTION: The replacement air conditioning system 100 forms concentration stratification in the target space SP. In the replacement air conditioning system 100, the indoor-air conditioner 50 sends circulating air to the lower side of the target space SP. The outside air conditioner 10 sends outside air to the lower side of the target space SP. The carbon dioxide concentration sensor 95 acquires a carbon dioxide concentration at a first height of the target space SP. In accordance with the carbon dioxide concentration, the control unit 90 performs control to change the ratio between the circulation air amount Qr and the outside air introduction amount Qo while keeping the total amount of the circulation air amount Qr, which is the amount of circulation air sucked into the indoor-air conditioner 50 from above the target space SP and returned from the indoor-air conditioner 50 to the target space SP, and the outside air introduction amount Qo, which is the amount of outside air supplied from the outdoor-air conditioner 10 to the target space SP, at a predetermined level.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Regarding displacement air conditioning systems. [Background technology]

[0002] In order to keep the carbon dioxide concentration in a room below a standard, there has long been a system that calculates a set ventilation volume from information from a carbon dioxide sensor attached to a ventilation device and controls the ventilation volume by correcting the set ventilation volume (Patent Document 1 (Patent Publication No. 6415720)). Summary of the Invention [Problem to be solved by the invention]

[0003] However, conventional ventilation volume control does not take energy consumption into consideration, and there is a problem in that it can be difficult to control the ventilation volume under the optimal operating conditions from the viewpoint of energy conservation. [Means for solving the problem]

[0004] A displacement air conditioning system of a first aspect is a displacement air conditioning system that forms concentration stratification in a target space, and includes an air conditioner, a ventilation device, a first sensor, and a controller. The air conditioner sends circulating air to a lower portion of the target space. The ventilation device sends outside air to a lower portion of the target space. The first sensor acquires a contaminant concentration at a first height in the target space. The controller controls, according to the contaminant concentration, to change the ratio between the circulating air volume and the outside air introduction volume, while maintaining a predetermined level the total volume of the circulating air volume, which is the volume of circulating air drawn into the air conditioner from above the target space and returned to the target space from the air conditioner, and the outside air introduction volume, which is the volume of outside air supplied to the target space from the ventilation device.

[0005] This displacement air conditioning system can control the concentration of contaminants in a target space while maintaining the total amount of circulating air and introducing outside air at a predetermined level.

[0006] A displacement air conditioning system of a second aspect is the system of the first aspect, wherein the control unit performs a first control to reduce the amount of outside air introduced and increase the amount of circulating air when the contaminant concentration at a first height is lower than a first target concentration.

[0007] In this displacement air conditioning system, when the contaminant concentration is low, the amount of circulating air and the amount of outside air introduced can be controlled so that the total amount of circulating air and the amount of outside air introduced is at a predetermined level.

[0008] A displacement air conditioning system according to a third aspect is the system according to the second aspect, wherein the control unit evaluates the energy-saving effect of the first control and determines whether to perform the first control based on the evaluation result.

[0009] In this displacement air conditioning system, the amount of circulating air and the amount of outside air introduced can be controlled based on the evaluation results of the energy saving effect so that the total amount of circulating air and the amount of outside air introduced is at a predetermined level.

[0010] A displacement air conditioning system according to a fourth aspect is the system according to the third aspect, in which the control unit calculates the energy saving effect based on the reduction in external load processing energy required to process the outside air load of the ventilation device and the increase in air transport energy required to transport air in the air conditioning device and the ventilation device.

[0011] In this displacement air conditioning system, the energy saving effect can be calculated by taking into account the external load processing energy and the air transport energy. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating air flow in a displacement air conditioning system. [Figure 2] FIG. 1 is a schematic diagram of a displacement air conditioning system. [Figure 3] FIG. 1 is a schematic diagram illustrating a configuration of an outdoor air conditioner. [Figure 4] 1 is a schematic diagram illustrating an outline of a configuration of an air conditioner. [Figure 5]2 is a block diagram schematically illustrating an air volume control unit and each unit connected to the air volume control unit. FIG. [Figure 6A] FIG. 10 is a diagram for explaining the layer height. [Figure 6B] FIG. 10 is a diagram for explaining the layer height. [Figure 7] 1 is a flow chart of a displacement air conditioning system. [Figure 8] FIG. 10 is a diagram showing an example of contaminant concentration and interface height. [Figure 9] FIG. 10 is a diagram showing the air flow in a displacement air conditioning system of Modification 1A. [Figure 10] 10 is a flowchart of a displacement air conditioning system according to Modification 1B. [Figure 11A] FIG. 10 is a diagram illustrating an example of air volume conditions. [Figure 11B] FIG. 10 is a diagram for explaining energy saving. [Figure 12A] FIG. 10 is a diagram illustrating an example of air volume conditions. [Figure 12B] FIG. 10 is a diagram for explaining energy saving. [Figure 13] FIG. 10 is a diagram showing the air flow in a displacement air conditioning system of Modification 1C. [Figure 14] 10 is a flowchart of a displacement air conditioning system according to Modification 1C. [Figure 15] FIG. 10 is a diagram showing an example of contaminant concentration and interface height. [Figure 16] FIG. 10 is a diagram showing the relationship between tap information and the amount of circulating air. [Figure 17] FIG. 10 is a diagram showing the air flow in a displacement air conditioning system of Modification 1D. [Figure 18] 10 is a flowchart of a displacement air conditioning system according to Modification 1D. [Figure 19] FIG. 10 is a diagram showing the relationship between tap information and air volume. DETAILED DESCRIPTION OF THE INVENTION

[0013] (1) Overview of the Displacement Air Conditioning System 100 A schematic configuration diagram of a replacement air conditioning system 100 of this embodiment is shown in Figure 2. The replacement air conditioning system 100 is a system that realizes replacement air conditioning in a target space (indoor space) SP contained within a structure such as a house, building, factory, or public facility. The replacement air conditioning system 100 forms concentration stratification in the target space SP. In this embodiment, the replacement air conditioning system 100 is applied to a building BL that contains the target space SP.

[0014] The replacement air conditioning system 100 has an outdoor air conditioner (outdoor conditioning unit) 10, which is an example of a "ventilation device," an air conditioner (air conditioner) 50, which is an example of an "air conditioning device," a control unit 90, and a carbon dioxide concentration sensor 95, which is an example of a "first sensor." In other words, the replacement air conditioning system 100 includes a blower, a control unit 90, and a carbon dioxide concentration sensor 95.

[0015] The displacement air conditioning system 100 performs air conditioning such as cooling, heating, ventilation, dehumidification, and / or humidification in the target space SP by taking in outside air OA using the outside air conditioner 10, conditioning it, and supplying it to the target space SP. The outside air OA is air outside the target space SP, and in this embodiment is outdoor air (see FIG. 2).

[0016] Furthermore, the displacement air conditioning system 100 performs air conditioning such as cooling, heating, and / or dehumidification in the target space SP by taking in and conditioning the inside air IA using the air conditioner 50 and supplying it to the target space SP. The inside air IA is the air within the target space SP.

[0017] The blower sends air to the target space SP. The blower includes the indoor fan 38 of the outdoor-air conditioner 10, the indoor fan 75 of the air conditioner 50, and air outlets 81 and 82 (see FIGS. 1 and 2).

[0018] The carbon dioxide concentration sensor 95 is installed in the target space SP. In this embodiment, the contaminant is carbon dioxide. The carbon dioxide concentration sensor 95 measures the carbon dioxide concentration in the living area SP1. In this embodiment, the carbon dioxide concentration sensor 95 acquires the carbon dioxide concentration at a first height in the target space SP.

[0019] In the air conditioner 50, the indoor fan 75 (blower) draws in air from the top of the target space SP and returns the air to the target space SP from the bottom of the living area SP1. In the outdoor air conditioner 10, the indoor fan 38 (blower) supplies outside air OA to the target space SP from the bottom of the living area SP1. In other words, the air conditioner 50 sends circulating air from above the target space SP to below the target space SP. In addition, the outdoor air conditioner 10 sends outside air below the target space SP.

[0020] The air flow in the displacement air conditioning system 100 is shown in Figure 1. The target space SP includes an occupied area SP1 and an under-ceiling space SP4. The occupied area SP1 refers to the area in the target space SP where people, who are heat-generating entities, are present. The occupied area SP1 includes a breathing area SP2. The breathing area SP2 refers to the area in the target space SP between 75 mm and 1800 mm above the floor.

[0021] The displacement air conditioning system 100 supplies air to the lower part of the occupied space SP1 of the target space SP that includes the occupied space SP1. In other words, as shown in Fig. 1 , the indoor air IA within the target space SP flows into the under-ceiling space SP4. The return air RA, which is the air that flows from the target space SP through the air vent 88 and above the ceiling CL, is partially discharged to the outdoors from the exhaust device 86 as exhaust air EA. In addition, part of the return air RA is sent from the return air port 85 to the indoor unit 70 of the air conditioner 50.

[0022] In addition, outdoor air OA is taken in from outdoors into the air handling unit 30 of the outdoor air conditioner 10. The return air RA sent to the indoor unit of the air conditioner 50 is mixed with the outdoor air OA, and supply air SA is supplied into the room from under the floor of the target space SP through the air outlets 81 and 82.

[0023] In the displacement air conditioning system 100, highly purified air is supplied to the floor surface at a low velocity, creating temperature stratification in the room, and the stratified area is filled with clean air (similar to the cleanliness of the supply air). In addition, the contaminant concentration in the mixing area is similar to that of a mixing method that makes the air quality uniform throughout the room.

[0024] The stratification height in the indoor space (target space) SP is the height of the boundary surface (hereinafter also referred to as the boundary surface height) between the stratification zone, which is an area where temperature stratification is formed by the flow of air rising from the heating element in the living area SP1, and the mixing zone, which is an area where the air above the living area SP1 in the indoor space SP and the air rising from the heating element mix.

[0025] 6A and 6B are diagrams for explaining the layer height. As shown in Fig. 6A and 6B, the heat generating elements He1 to He4 are occupants of the target space SP.

[0026] 6A, the rising plume from the heating element rises while drawing in surrounding air until the sum (Qh1+Qh2) of the amount of the rising plume from heating element He1, Qh1, and the amount of the rising plume from heating element He2, Qh2, reaches the amount of air supplied (exhausted), Qs1. The rising plume draws in more and more surrounding air as it rises.

[0027] In the region above the height where the supply volume Qs1 and the total volume of the rising plumes from the heating elements He1 and He2 (Qh1 + Qh2) are balanced, the rising plumes from the heating elements He1 and He2 accumulate and mix. A boundary surface is formed at the position where the volume of the rising plume (Qh1 + Qh2) and the supply volume (exhaust volume) Qs1 are balanced. As shown in Figures 6A and 6B, the heights at the centers of the boundary surfaces are called the stratification heights (boundary surface heights) h1 and h2.

[0028] As shown in Figures 6A and 6B, in replacement-type air conditioning, low-temperature air is supplied at a low speed so as not to disturb the area below the boundary surface, so the vertical temperature distribution forms a temperature stratification below the boundary surface, and uniform temperatures t2 and t4 are obtained above the boundary surface. Also, the vertical concentration distribution (vertical contaminant distribution) below the boundary surface is C1 and C3, which are close to the supply air concentrations, because contaminants from the heating elements He1 to He4 are not mixed, and above the boundary surface, the concentrations are C2 and C4, which are the same as the contaminant concentrations in mixing-type air conditioning (complete mixing).

[0029] The supply amount Qs2 in Fig. 6B is reduced compared to the supply amount Qs1 in Fig. 6A. As shown in Fig. 6B, the reduction in the supply amount results in a lower boundary surface height h2 than the boundary surface height h1 in the case of the supply amount Qs1 in Fig. 6A. While Figs. 6A and 6B have been described with reference to a case where there are two heat-generating elements present, for example, if the number of heat-generating elements in the target space SP increases, the boundary surface height will decrease.

[0030] (2) Details of the Displacement Air Conditioning System 100 (2-1) Outdoor air conditioner 10 (ventilation device) 3 is a schematic diagram showing an outline of the configuration of outdoor air conditioner 10. Outdoor air conditioner 10 mainly comprises a chiller unit 20, an air handling unit (hereinafter referred to as "air handling unit") 30, an intake air duct 48, and an outdoor air conditioner control unit 49. During operation, outdoor air conditioner 10 takes in outside air OA in air handling unit 30, cools or heats, or dehumidifies or humidifies the air, and supplies it to target space SP as intake air SA via intake air duct 48.

[0031] In the outdoor-air conditioner 10, the heat medium circuit C1 and the outdoor-air-conditioner refrigerant circuit C2 are configured independently of each other.

[0032] The heat medium circuit C1 is a circuit through which a heat medium (water) circulates to exchange heat with the outside air OA. The heat medium circuit C1 is configured across the chiller unit 20 and the air handling unit 30. The heat medium circuit C1 is mainly configured by connecting the outside air heat exchanger 33 arranged in the air handling unit 30 with the heat medium heat exchanger 22 and heat medium pump Pa arranged in the chiller unit 20 via a first pipe P1. In the heat medium circuit C1, the heat medium flows in a predetermined direction (the direction indicated by the two-dot chain arrow d1 in FIG. 3).

[0033] The outdoor air-conditioning unit refrigerant circuit C2 is a circuit through which refrigerant circulates, serving as a cooling or heating source for the heat medium in the heat medium circuit C1. The outdoor air-conditioning unit refrigerant circuit C2 is configured within the chiller unit 20. The outdoor air-conditioning unit refrigerant circuit C2 is mainly configured by connecting a refrigerant compressor 21, a heat medium heat exchanger 22, a refrigerant expansion valve 23, a refrigerant heat exchanger 24, and a flow path switching valve 25, which are all arranged in the chiller unit 20, via a second pipe P2. In the outdoor air-conditioning unit refrigerant circuit C2, refrigerant flows in a predetermined direction (the direction indicated by the two-dot chain arrow d2 in FIG. 3 during forward cycle operation, and the direction opposite to d2 during reverse cycle operation), and a vapor compression refrigeration cycle is performed.

[0034] (2-1-1) Chiller unit 20 (heat medium adjustment unit) The chiller unit 20 cools the heat medium in the heat medium circuit C1 by performing a refrigeration cycle in the outdoor-air-conditioning refrigerant circuit C2. The chiller unit 20 mainly includes a refrigerant compressor 21, a heat medium heat exchanger 22, a refrigerant expansion valve 23, a refrigerant heat exchanger 24, a flow path switching valve 25, a chiller fan 26, and a heat medium pump Pa.

[0035] The heat medium heat exchanger 22 is a heat exchanger that exchanges heat between the heat medium in the heat medium circuit C1 and the low-pressure refrigerant in the outdoor-air-conditioning unit refrigerant circuit C2, thereby cooling the heat medium. The heat medium heat exchanger 22 has a heat medium flow path that communicates with the heat medium circuit C1 and a refrigerant flow path that communicates with the outdoor-air-conditioning unit refrigerant circuit C2, and is configured to allow heat exchange between the heat medium in the heat medium flow path and the refrigerant in the refrigerant flow path. The heat medium heat exchanger 22 functions as an evaporator or heater for the low-pressure refrigerant during forward cycle operation (cooling operation or dehumidification operation), and as a condenser or radiator for the high-pressure refrigerant during reverse cycle operation (heating operation).

[0036] The refrigerant heat exchanger 24 is a heat exchanger that exchanges heat between the refrigerant in the outdoor-air-conditioning unit refrigerant circuit C2 and the air passing through it. The refrigerant heat exchanger 24 has heat transfer tubes and heat transfer fins that communicate with the outdoor-air-conditioning unit refrigerant circuit C2. In the refrigerant heat exchanger 24, heat is exchanged between the air passing around the heat transfer tubes and heat transfer fins (airflow generated by the chiller fan 26) and the refrigerant passing through the heat transfer tubes. The refrigerant heat exchanger 24 functions as a condenser or radiator for high-pressure refrigerant during forward cycle operation and as an evaporator or heater for low-pressure refrigerant during reverse cycle operation.

[0037] Chiller fan 26 is a blower that generates an airflow that flows into chiller unit 20, passes through refrigerant heat exchanger 24, and flows out of chiller unit 20. The airflow generated by chiller fan 26 is a cooling source for the refrigerant in refrigerant heat exchanger 24 during forward cycle operation (cooling operation or dehumidifying operation), and is a heating source for the refrigerant in refrigerant heat exchanger 24 during reverse cycle operation (heating operation). Chiller fan 26 includes a fan motor, and its rotation speed is adjusted by inverter control of the fan motor. In other words, the airflow of chiller fan 26 is variable.

[0038] (2-1-2) Air Conditioning Unit 30 (Outdoor Air Conditioning Unit) The air handling unit 30 cools, dehumidifies, heats, and / or humidifies the outside air OA. The air handling unit 30 mainly includes an outside air heat exchanger 33, a filter 34, a humidifier 35, and an air supply fan 38.

[0039] The outdoor air heat exchanger 33 (outdoor air conditioning heat exchanger) is a heat exchanger that functions as a cooler for outdoor air OA. The outdoor air heat exchanger 33 is arranged in the heat medium circuit C1. The outdoor air heat exchanger 33 has heat transfer tubes and heat transfer fins that communicate with the heat medium circuit C1. In the outdoor air heat exchanger 33, heat exchange occurs between the outdoor air OA that passes around the heat transfer tubes and heat transfer fins and the heat medium that passes through the heat transfer tubes.

[0040] The humidifier 35 is a device for humidifying the outdoor air OA that has passed through the outdoor air heat exchanger 33. There are no particular limitations on the method or model of the humidifier 35, but a general natural evaporation type humidifier is used here.

[0041] The intake fan 38 is a blower that takes in outside air OA into the air handling unit 30 and sends it to the intake air duct 48. There are no particular limitations on the type of intake fan 38, but in this embodiment, a sirocco fan is used as the intake fan 38. Here, in the air handling unit 30, an outside air flow path FP is formed through which the outside air OA flows (see the dashed arrow "FP" in FIG. 3), and when the intake fan 38 is in operation, the outside air OA flows along the outside air flow path FP. The intake fan 38 includes a fan motor, and its rotation speed is adjusted by inverter control. In other words, the intake fan 38 has a variable airflow rate.

[0042] In air handling unit 30, a filter 34, an outdoor air heat exchanger 33, a humidifier 35, and an air supply fan 38 are arranged in this order from the upwind side to the downwind side of outdoor air flow path FP. The downwind end of outdoor air flow path FP is connected to an air supply duct 48.

[0043] (2-1-3) Air Intake Duct 48 The air supply duct 48 includes a first air supply duct 48a and a second air supply duct 48b.

[0044] The first air supply duct 48a is a component that mainly forms a flow path for outside air OA. The first air supply duct 48 is connected to the air handling unit 30 so that outside air OA flows in when the air supply fan 38 is driven. The first air supply duct 48a has a first damper 401 between the outdoors and the intake port 41 of the air handling unit 30. The first air supply duct 48a also communicates with the target space SP. The first air supply duct 48a is connected to the air outlet 42 of the air handling unit 30 and an air outlet 81 formed under the floor of the target space SP (see FIGS. 1 and 2).

[0045] The second supply air duct 48b is a component that mainly forms a flow path for the return air RA. The second supply air duct 48b is connected to the indoor unit 70 so that the return air RA flows in when the indoor fan 72 is driven. The second supply air duct 48b has a second damper 402 between the return air port 85 and the intake port 43 of the indoor unit 70. The second supply air duct 48b also extends from the outlet 44 of the indoor unit 70 and is connected to the first supply air duct 48a between the outlet 42 of the air handling unit 30 and an outlet 81 formed under the floor of the target space SP. As a result, the outside air OA sent from the first supply air duct 48a and the return air RA sent from the second supply air duct 48b merge, and the resulting air is supplied as supply air SA from under the floor of the target space SP through the outlets 81 and 82 to the target space SP (see FIGS. 1 and 2).

[0046] (2-1-4) Outside air conditioner control section 49 The outdoor-conditioning unit control unit 49 is a functional unit that controls the operation of each unit included in the outdoor-air conditioner 10. The outdoor-conditioning unit control unit 49 is composed of a CPU, memory, various electrical components, etc. The outdoor-conditioning unit control unit 49 is connected to each device included in the outdoor-air conditioner 10 via wiring. In addition, the outdoor-conditioning unit control unit 49 is electrically connected to the control unit 90 via a communication line.

[0047] In this embodiment, the outdoor air-conditioning unit control unit 49 is configured by electrically connecting the microcomputers and electrical components disposed in the chiller unit 20 and the air handling unit 30 to each other.

[0048] When cooling is performed by supplying outside air OA without treating the sensible heat (when outside air cooling operation is performed), the outdoor air conditioning unit control unit 49 pauses or stops the operation of each part in the chiller unit 20 and the air handling unit 30.

[0049] (2-1-5) Flow of heat medium, refrigerant, cooling water, and air during operation of the outdoor air conditioner 10 When the outdoor-air conditioner 10 is operating, the heat medium pump Pa is normally driven, causing the heat medium (water) to circulate in the heat medium circuit C1. Also, the refrigerant compressor 21 is driven, causing the refrigerant to circulate in the outdoor-air-conditioner refrigerant circuit C2.

[0050] During operation, in the heat medium circuit C1, the heat medium is cooled or heated by heat exchange with the refrigerant flowing in the outdoor-air-conditioning unit refrigerant circuit C2 in the heat medium heat exchanger 22. In the heat medium heat exchanger 22, the heat medium is cooled during forward cycle operation and heated during reverse cycle operation. The heat medium cooled or heated in the heat medium heat exchanger 22 flows into the outdoor air heat exchanger 33 and is heated or cooled by heat exchange with the outdoor air OA taken in by the air handling unit 30.

[0051] In the outdoor air heat exchanger 33, the heat medium is heated during forward cycle operation and cooled during reverse cycle operation. The heat medium that has passed through the outdoor air heat exchanger 33 flows into the heat medium heat exchanger 22 again.

[0052] In the outdoor-air-conditioning refrigerant circuit C2, during operation, the refrigerant is compressed in the refrigerant compressor 21 and discharged as high-pressure refrigerant. During forward cycle operation, the high-pressure refrigerant discharged from the refrigerant compressor 21 condenses or releases heat by exchanging heat with the airflow generated by the chiller fan 26 in the refrigerant heat exchanger 24. During reverse cycle operation, the high-pressure refrigerant discharged from the refrigerant compressor 21 condenses or releases heat by exchanging heat with the heat medium in the heat medium circuit C1 in the heat medium heat exchanger 22. The refrigerant that condenses or releases heat in either the refrigerant heat exchanger 24 or the heat medium heat exchanger 22 is decompressed in the refrigerant expansion valve 23 to become low-pressure refrigerant and then flows into the other heat exchanger. There, the refrigerant is evaporated or heated by exchanging heat with the heat medium or airflow. The refrigerant is then drawn back into the refrigerant compressor 21.

[0053] In the outdoor air heat exchanger 33, the outdoor air OA exchanges heat with the heat medium. In the outdoor air heat exchanger 33, the outdoor air OA is cooled (or dehumidified) during cooling operation, and heated during heating operation. The outdoor air OA that has passed through the outdoor air heat exchanger 33 is sent to the supply air duct 48 (target space SP). When the humidifier 35 is in operation, the air that has been heated by exchanging heat with the heat medium in the outdoor air heat exchanger 33 is humidified by the humidifier 35 and then sent to the supply air duct 48.

[0054] (2-2) Air conditioner 50 (air conditioning device) 4 is a schematic diagram showing an outline of the configuration of an air conditioner 50. The air conditioner 50 includes a refrigerant circuit RC, and performs air conditioning such as cooling, dehumidification, or heating of a target space SP by circulating a refrigerant in the refrigerant circuit RC to perform a vapor compression refrigeration cycle. The air conditioner 50 has multiple operating modes and operates according to the operating mode. Specifically, the air conditioner 50 performs operations such as cooling operation for cooling, dehumidification operation for dehumidifying, and heating operation for heating.

[0055] The air conditioner 50 mainly has one outdoor unit 60 as a heat source unit, one indoor unit 70 as a utilization unit, and an air conditioner control unit 79. In the air conditioner 50, the outdoor unit 60 and each indoor unit 70 are connected via a liquid-side refrigerant communication pipe LP1 and a gas-side refrigerant communication pipe GP1 to form a refrigerant circuit RC. The refrigerant sealed in the refrigerant circuit RC is not particularly limited, but is typically filled with an HFC refrigerant such as R32 or R410A.

[0056] (2-2-1) Outdoor unit 60 (refrigerant adjustment unit) The outdoor unit 60 is disposed outside the target space SP. In this embodiment, the outdoor unit 60 is disposed outdoors.

[0057] The outdoor unit 60 is connected to the indoor unit 70 via a liquid-side refrigerant communication pipe LP1 and a gas-side refrigerant communication pipe GP1, and constitutes part of the refrigerant circuit RC. The outdoor unit 60 mainly includes a compressor 61, a four-way switching valve 62, an outdoor heat exchanger 63, and an outdoor fan 68.

[0058] The outdoor unit 60 also has a plurality of refrigerant pipes RP (first refrigerant pipe RP1 to fifth refrigerant pipe RP5). The first refrigerant pipe RP1 connects the gas side refrigerant communication pipe GP1 and the four-way switching valve 62. The second refrigerant pipe RP2 connects the four-way switching valve 62 and the suction side of the compressor 61. The third refrigerant pipe RP3 connects the discharge side of the compressor 61 and the four-way switching valve 62. The fourth refrigerant pipe RP4 connects the four-way switching valve 62 and a gas side inlet / outlet of the outdoor heat exchanger 63. The fifth refrigerant pipe RP5 connects the liquid side inlet / outlet of the outdoor heat exchanger 63 and the liquid side refrigerant communication pipe LP1.

[0059] The outdoor heat exchanger 63 is a heat exchanger that exchanges heat between the passing airflow (outdoor airflow generated by the outdoor fan 68) and the refrigerant. The outdoor heat exchanger 63 functions as a refrigerant condenser or radiator during forward cycle operation (cooling operation or dehumidifying operation). The outdoor heat exchanger 63 functions as a refrigerant evaporator or heater during reverse cycle operation (heating operation).

[0060] The outdoor fan 68 is a blower that generates an outdoor airflow. The outdoor airflow is a flow of outside air OA that flows into the outdoor unit 60, passes through the outdoor heat exchanger 63, and flows out of the outdoor unit 60. The outdoor airflow is a cooling source for the refrigerant in the outdoor heat exchanger 63 during forward cycle operation, and is a heating source for the refrigerant in the outdoor heat exchanger 63 during reverse cycle operation. The outdoor fan 68 includes a fan motor, and its rotation speed is adjusted by inverter control of the fan motor. In other words, the outdoor fan 68 has variable airflow.

[0061] (2-2-2) Indoor unit 70 The indoor units 70 are arranged outside the target space SP. In this embodiment, each indoor unit 70 is a floor-standing air conditioning indoor unit installed outside the target space SP in the building BL. The indoor units 70 are installed so that the air inlet 43 and the air outlet 44 are connected to the second air supply duct 48b (see FIGS. 1 and 2).

[0062] The indoor unit 70 is connected to the outdoor unit 60 via a liquid-side refrigerant communication pipe LP1 and a gas-side refrigerant communication pipe GP1, and constitutes part of the refrigerant circuit RC. In this embodiment, one indoor unit 70 is connected to one outdoor unit 60.

[0063] The indoor unit 70 has an expansion valve 71 and an indoor heat exchanger 72. The indoor unit 70 also has a sixth refrigerant pipe RP6 that connects the liquid side inlet / outlet of the indoor heat exchanger 72 to the liquid side refrigerant connection pipe LP1, and a seventh refrigerant pipe RP7 that connects the gas side inlet / outlet of the indoor heat exchanger 72 to the gas side refrigerant connection pipe GP1.

[0064] The indoor heat exchanger 72 (air conditioning heat exchanger) is a heat exchanger that exchanges heat between the passing airflow (indoor airflow generated by the indoor fan 75) and the refrigerant. The indoor heat exchanger 72 functions as an evaporator or heater of the refrigerant during forward cycle operation. The outdoor heat exchanger 63 functions as a condenser or radiator of the refrigerant during reverse cycle operation.

[0065] The indoor fan 75 is a blower that generates an indoor air flow. The indoor air flow is a flow of indoor air IA that flows into the indoor unit 70, passes through the indoor heat exchanger 72, and flows out of the indoor unit 70. The indoor air flow is a heating source for the refrigerant in the indoor heat exchanger 72 during forward cycle operation, and is a cooling source for the refrigerant in the indoor heat exchanger 72 during reverse cycle operation. The indoor fan 75 includes a fan motor, and its rotation speed is adjusted by inverter control of the fan motor. In other words, the airflow of the indoor fan 75 is variable.

[0066] (2-2-3) Air conditioner control unit 79 The air conditioner control unit 79 is a functional unit that controls the operation of each unit included in the air conditioner 50. The air conditioner control unit 79 is composed of a CPU, memory, various electrical components, etc. The air conditioner control unit 79 is connected to each device included in the air conditioner 50 via wiring. The air conditioner control unit 79 is also electrically connected to various sensors (not shown) arranged in the indoor unit 70. The air conditioner control unit 79 is also electrically connected to an air volume control unit (control unit) 90 via a communication line.

[0067] (2-2-4) Refrigerant flow in the refrigerant circuit RC The flow of refrigerant in the refrigerant circuit RC will be explained separately for forward cycle operation and reverse cycle operation.

[0068] <Forward cycle operation> In the air conditioner 50, during forward cycle operation (cooling operation / dehumidifying operation), the four-way switching valve 62 is controlled to the first state, and the refrigerant filled in the refrigerant circuit RC circulates primarily through the compressor 61, the outdoor heat exchanger 63, the expansion valve 71 of the indoor unit 70 in operation, and the indoor heat exchanger 72 of the indoor unit 70 in operation (the refrigerant circulates in a forward cycle).

[0069] <During reverse cycle operation> In the air conditioner 50, during reverse cycle operation (heating operation), the four-way switching valve 62 is controlled to the second state, and the refrigerant filled in the refrigerant circuit RC circulates primarily through the compressor 61, the indoor heat exchanger 72 of the indoor unit 70 in operation, the expansion valve 71 of the indoor unit 70 in operation, and the outdoor heat exchanger 63 (the refrigerant circulates in a reverse cycle).

[0070] (2-3) Control unit 90 FIG. 5 is a block diagram showing a schematic diagram of the control unit 90 and each unit connected to the control unit 90. The control unit 90 is realized by a computer. The control unit 90 includes a control arithmetic unit and a storage device (not shown). A processor such as a CPU or GPU can be used as the control arithmetic unit. The control arithmetic unit reads a program stored in the storage device and performs predetermined arithmetic processing in accordance with the program. Furthermore, the control arithmetic unit can write the results of calculations to the storage device and read information stored in the storage device in accordance with the program. FIG. 5 shows various functional blocks realized by the control arithmetic unit. The storage device can be used as a database.

[0071] The control unit 90 is electrically connected to the outdoor-conditioning unit control unit 49 and the air-conditioning unit control unit 79, and transmits and receives signals to and from them. The control unit 90 can control the operation of the outdoor-air conditioner 10 and the devices in the air conditioner 50 by transmitting predetermined signals to the outdoor-conditioning unit control unit 49 and the air-conditioning unit control unit 79. The control unit 90 can also acquire the measurement value of the carbon dioxide concentration sensor 95.

[0072] The control unit 90 controls the circulating air volume Qr (internal circulation volume) which is the volume of circulating air drawn into the air conditioner 50 and returned from the air conditioner 50 to the target space SP, and the outdoor air introduction volume Qo which is the volume of outdoor air supplied from the outdoor air conditioner 10 to the target space SP, to change the ratio between the circulating air volume Qr and the outdoor air introduction volume Qo in accordance with changes in carbon dioxide concentration, while keeping constant the total volume of the circulating air volume Qr and the outdoor air introduction volume Qo.

[0073] Furthermore, when the carbon dioxide concentration at the first height in the target space SP is lower than the first target concentration, the control unit 90 performs a first control to reduce the amount of outdoor air introduced Qo and increase the amount of circulating air Qr. In other words, the control unit 90 controls the supply air fan 38 of the outdoor-air conditioner 10, the indoor fan 75 of the air conditioner 50, and the air outlets 81 and 82 so that the carbon dioxide concentration in the target space SP falls within a predetermined range. For example, the control unit 90 may control the rotation speed of the indoor fan 38 of the outdoor-air conditioner 10 by controlling the fan motor of the indoor fan 38 of the outdoor-air conditioner 10, or may control the rotation speed of the indoor fan 75 of the air conditioner 50 by controlling the fan motor of the indoor fan 75 of the air conditioner 50. The control unit 90 may also control the airflow rates of the air outlets 81 and 82 by adjusting the opening degrees of the first damper 401 and the second damper 402. In addition, the control unit 90 may control the air volume of the air outlets 81, 82 by controlling the tap (not shown) of the indoor fan 75 of the air conditioner 50 or the tap (not shown) of the supply air fan 38 of the outdoor air conditioner 10.

[0074] (3) Overall operation of the displacement air conditioning system A flow chart of the displacement air conditioning system 100 is shown in FIG.

[0075] In step S1, operation of the air conditioner 50 and the outdoor-air conditioner 10 is started. In step S1, the control unit 90 sets the amount of air circulation Qr to an initial value. The control unit 90 also sets the amount of outdoor air introduction Qo to an initial value.

[0076] In step S2, the control unit 90 determines whether the carbon dioxide concentration C in the target space SP is equal to or less than the first target concentration Cp. In other words, in step S2, the control unit 90 determines whether the cleanliness of the air in the target space SP is ensured. If the carbon dioxide concentration C in the target space SP is equal to or less than the first target concentration Cp (Yes in step S2), the cleanliness of the air in the target space SP is ensured, and the process proceeds to step S3. If the carbon dioxide concentration C in the target space SP is greater than the first target concentration Cp (No in step S2), the cleanliness of the air in the target space SP is not ensured, and the process proceeds to step S4.

[0077] In step S4, the control unit 90 controls the ratio between the amount of circulating air Qr and the amount of introduced outside air Qo to be changed while maintaining the amount of supplied air Qs, which is the sum of the amount of circulating air Qr and the amount of introduced outside air Qo, constant. In step S4, the control unit 90 increases the amount of introduced outside air Qo and decreases the amount of circulating air Qr by an amount corresponding to the increase in the amount of introduced outside air Qo. Then, the process returns to step S2.

[0078] In step S3, the control unit 90 determines whether the carbon dioxide concentration C in the target space SP is equal to or greater than a second target concentration Cp-k, which is a concentration lower than the first target concentration Cp, where "k" is a target concentration range.

[0079] If the carbon dioxide concentration C in the target space SP is equal to or greater than the second target concentration Cp-k (Yes in step S3), the cleanliness of the air in the target space SP is ensured, and the process proceeds to step S5. In other words, if the carbon dioxide concentration C in the target space SP is in the range between the second target concentration Cp-k and the first target concentration Cp (Cp-k≦C≦Cp), the cleanliness of the air in the target space SP is ensured.

[0080] If the carbon dioxide concentration C in the target space SP is lower than the second target concentration Cp-k (No in step S3), proceed to step S6. In other words, if the carbon dioxide concentration C in the target space SP is lower than the second target concentration Cp-k, it is determined that the air cleanliness in the target space SP is excessive.

[0081] In step S6, the control unit 90 controls the total amount (supply amount) Qs of the circulating air amount Qr and the outdoor air introduction amount Qo to change the ratio between the circulating air amount Qr and the outdoor air introduction amount Qo while maintaining the total amount (supply amount) Qs of the circulating air amount Qr and the outdoor air introduction amount Qo constant. In step S6, the outdoor air introduction amount Qo is reduced, and the circulating air amount Qr is increased by an amount corresponding to the decrease in the outdoor air introduction amount Qo. This makes it possible to maintain the supply air amount Qs constant even when the outdoor air introduction amount Qo is reduced. Then, the process returns to step S3. In the present embodiment, the case where the control unit 90 maintains the total amount Qs of the circulating air amount Qr and the outdoor air introduction amount Qo constant in step S6 has been described. However, the total amount Qs of the circulating air amount Qr and the outdoor air introduction amount Qo may also be maintained at a predetermined level.

[0082] In step S5, the control unit 90 maintains the supply amount Qs, which is the total amount of the circulating air amount Qr and the outside air introduction amount Qo controlled in step S4, for a certain period of time, and after the certain period of time has elapsed, returns to step S2.

[0083] FIG. 8 is a diagram showing an example of the contaminant concentration and the interface height. As shown in FIG. 8, when the carbon dioxide concentration is higher than the first target concentration Cp, the control unit 90 increases the amount of outside air introduced Qo so that the carbon dioxide concentration becomes the target carbon dioxide concentration (Cp-k≦C≦Cp) and reduces the amount of circulating air Qr by the amount of the increase in the amount of outside air introduced Qo. On the other hand, when the carbon dioxide concentration is lower than the first target concentration Cp, the control unit 90 reduces the amount of outside air introduced Qo so that the carbon dioxide concentration becomes within the range of the target carbon dioxide concentration (Cp-k≦C≦Cp) and increases the amount of circulating air Qr by the amount of the decrease in the amount of outside air introduced Qo (first control). In this way, the carbon dioxide concentration is controlled while maintaining the interface height.

[0084] (4) Features (4-1) The displacement air conditioning system 100 according to this embodiment is a displacement air conditioning system that forms concentration stratification in a target space SP and includes an air conditioner 50, an outdoor air conditioner 10, a carbon dioxide concentration sensor 95, and a controller 90. The air conditioner 50 sends circulating air below the target space SP. The outdoor air conditioner 10 sends outside air below the target space SP. The carbon dioxide concentration sensor 95 acquires the carbon dioxide concentration at a first height in the target space SP. The controller 90 controls the ratio between the circulating air volume Qr, which is the volume of circulating air drawn into the air conditioner 50 from above the target space SP and returned from the air conditioner 50 to the target space SP, and the outside air introduction volume Qo, which is the volume of outside air supplied from the outdoor air conditioner 10 to the target space SP, to be changed according to the carbon dioxide concentration, while maintaining the total volume of the circulating air volume Qr and the outside air introduction volume Qo at a predetermined level.

[0085] Conventionally, ventilation volume control assuming a general ventilation method (mixing method) focuses on the difference between the carbon dioxide concentration (exhaust concentration) attached to the ventilation device and the carbon dioxide concentration in the occupied area, and determines the required ventilation volume by correcting the set ventilation volume. This is ventilation volume control that adds ventilation volume by taking into account negative ventilation unevenness, in other words, a ventilation state where the carbon dioxide concentration in the occupied area is higher than the exhaust concentration.

[0086] Due to the stratification effect (positive ventilation unevenness), a displacement air conditioning system can achieve the same carbon dioxide concentration in the target space SP as a mixing system with a smaller outdoor air intake volume Qo compared to a mixing system. However, because the stratification effect is determined by the supply volume Qs (the sum of the circulated air volume Qr and the outdoor air intake volume Qo), if the outdoor air intake volume Qo is actually reduced, in order to stabilize the stratification effect, it is necessary to increase the circulated air volume Qr and keep the supply volume Qs constant. If the carbon dioxide concentration in the target space SP is lower than the target carbon dioxide concentration and the outdoor air intake volume Qo can be reduced, simply reducing the outdoor air intake volume Qo in displacement air conditioning will reduce the supply volume Qs, which will cause the boundary surface height to become unstable. Therefore, the supply volume Qs must be kept constant.

[0087] In this replacement air conditioning system 100, the carbon dioxide concentration in the target space SP can be controlled while maintaining the total amount of circulating air Qr and the amount of introduced outside air Qo at a predetermined level.

[0088] (4-2) In the replacement air conditioning system 100 according to this embodiment, when the carbon dioxide concentration at the first height is lower than the first target concentration, the control unit 90 performs a first control to reduce the amount of outside air introduced Qo and increase the amount of circulating air Qr.

[0089] In this replacement air conditioning system 100, when the carbon dioxide concentration is low, the amount of circulating air Qr and the amount of introduced outside air Qo can be controlled so that the total amount of the circulating air Qr and the amount of introduced outside air Qo is at a predetermined level.

[0090] (5) Variations (5-1) Variation 1A In this embodiment, a case has been described in which air is supplied from under the floor of the target space SP, but air may be supplied from below the wall surface of the target space SP.

[0091] The air flow in the displacement air conditioning system 101 of variant 1A is shown in Figure 9. As shown in Figure 9, indoor air IA, which is the air in the target space SP, flows into the space under the ceiling. Part of the return air RA, which is the air that flows from the target space SP above the ceiling CL, is discharged outdoors from the exhaust device 86 as exhaust air EA. Part of the return air RA is also sent to the indoor unit 70 of the air conditioner 50.

[0092] In addition, outdoor air OA is taken in from outdoors into the air handling unit 30 of the outdoor air conditioner 10. The return air RA sent to the indoor unit 70 of the air conditioner 50 is mixed with the outdoor air OA, and supply air SA is supplied into the room from an air outlet 83 near the floor of the target space SP.

[0093] (5-2) Variation 1B The displacement air conditioning system 100 shown in Figure 2 further includes a temperature adjustment unit that is built into at least the air conditioner 50 of the air conditioner 50 and outdoor air conditioner 10, and adjusts the temperature of at least the circulating air of the circulating air and outdoor air. The temperature adjustment unit adjusts the temperature of air that includes at least the air RA, of the air RA that is drawn in from the top of the target space SP and returned to the bottom of the occupied area SP1, and the outdoor air OA that is supplied to the bottom of the occupied area SP1. The temperature adjustment unit includes a heat medium circuit C1 and outdoor air conditioner refrigerant circuit C2 of the outdoor air conditioner 10, and a refrigerant circuit RC of the air conditioner 50 (see Figures 3 and 4).

[0094] The control unit 90 evaluates the energy-saving effect of the first control that reduces the amount of outdoor air introduced Qo and increases the amount of circulating air Qr, and determines based on the evaluation result whether to perform the first control that reduces the amount of outdoor air introduced Qo and increases the amount of circulating air Qr. The control unit 90 calculates the energy-saving effect based on the amount of reduction in external load processing energy required to process the outdoor air load of the outdoor air conditioner 10 and the amount of increase in air transport energy required to transport air by the air conditioner 50 and the outdoor air conditioner 10.

[0095] A flowchart of the displacement air conditioning system of Modification 1B is shown in FIG.

[0096] In step S11, operation of the air conditioner 50 and the outdoor-air conditioner 10 is started. In step S11, the control unit 90 sets the amount of circulation air Qr to an initial value. The control unit 90 also sets the amount of outdoor air introduced Qo to an initial value.

[0097] In step S12, the control unit 90 determines whether the carbon dioxide concentration C in the target space SP is equal to or less than the first target concentration Cp. In other words, in step S12, it determines whether the cleanliness of the air in the target space SP is ensured. If the carbon dioxide concentration C in the target space SP is equal to or less than the first target concentration Cp (Yes in step S12), the cleanliness of the air in the target space SP is ensured, and the process proceeds to step S13.

[0098] In step S13, the control unit 90 determines whether the outdoor air load processing energy reduced when the outdoor air introduction amount Qo is reduced by one tap is greater than the air conveying energy increased by increasing the circulating air volume Qr by an amount equivalent to the reduced outdoor air introduction amount Qo. The control unit 90 can, for example, control the motor of the indoor fan 38 of the outdoor air conditioner 10 to increase the rotation speed in the order of weak tap, which has the lowest rotation speed, strong tap, and fast tap. In Modification 1B, the outdoor air introduction amount Qo reduced when the motor of the indoor fan 38 of the outdoor air conditioner 10 is controlled to change the setting from the strong tap to the weak tap is set to the outdoor air introduction amount Qo for one tap.

[0099] If the carbon dioxide concentration C in the target space SP is greater than the first target concentration Cp (No in step S12), the cleanliness of the air in the target space SP is not ensured, and the process proceeds to step S14.

[0100] In step S14, the control unit 90 controls the ratio between the circulating air amount Qr and the outside air introduction amount Qo to be changed while maintaining the supply amount Qs, which is the sum of the circulating air amount Qr and the outside air introduction amount Qo, constant. In step S14, the outside air introduction amount Qo is increased and the circulating air amount Qr is reduced by an amount corresponding to the increase in the outside air introduction amount Qo. Then, the process returns to step S12. If the outdoor air load processing energy reduced when reducing the outdoor air intake amount Qo by one tap is greater than the air transport energy increased by increasing the circulating air amount Qr by the same amount as the reduced outdoor air intake amount Qo (Yes in step S13), proceed to step S15.

[0101] If the outdoor air load processing energy reduced when reducing the outdoor air introduction amount Qo by one tap is equal to or less than the air conveying energy increased by increasing the circulating air amount Qr by an amount equivalent to the reduced outdoor air introduction amount Qo (No in step S13), the process proceeds to step S17. In other words, if the reduced outdoor air load processing energy is smaller than the increased air conveying energy, the control unit 90 determines that there is no benefit to reducing the outdoor air introduction amount Qo.

[0102] In step S15, the control unit 90 controls the ratio between the circulating air amount Qr and the outside air introduction amount Qo to change while maintaining the supply amount Qs, which is the sum of the circulating air amount Qr and the outside air introduction amount Qo, constant. In step S15, the outside air introduction amount Qo is reduced and the circulating air amount Qr is increased by an amount corresponding to the decrease in the outside air introduction amount Qo. Then, the process proceeds to step S16.

[0103] In step S16, the control unit 90 determines whether the carbon dioxide concentration C in the target space SP is equal to or less than the first target concentration Cp. If the carbon dioxide concentration C in the target space SP is equal to or less than the first target concentration Cp (Yes in step S16), the process proceeds to step S17.

[0104] If the carbon dioxide concentration C in the target space SP is greater than the first target concentration Cp (No in step S16), the process returns to step S15.

[0105] In step S17, the supply amount Qs is maintained for a certain period of time, and after the certain period of time has elapsed, the process returns to step S12.

[0106] An example of the operation of the air conditioner 50 and the outdoor air conditioner 10 will be described with reference to FIGS. 11A and 11B. 2 Assume that the number of people present in the target space SP is 60, and the ventilation rate per person is 30 CMH. The target space SP is an office (see FIG. 9) where supply air SA is blown out from the bottom of the wall. The power consumption of the outdoor air conditioner 10 and the air conditioner 50 under the first and second conditions is compared. The first condition is a condition when the air in the target space SP is excessively clean. The second condition is a condition when the amount of outdoor air introduced into the target space SP is adjusted. In FIGS. 11A and 11B, the first condition is a condition when the carbon dioxide concentration C of the target air SP is lower than the first target concentration Cp, resulting in excessive air cleanliness. The second condition is a condition when adjustment is made to reduce the amount of outdoor air introduced into the target space SP.

[0107] The first condition is an outdoor air condition in which the outdoor air temperature is 34° C. and the humidity is 50%.

[0108] Examples of air volume conditions are shown in FIG. 11A. As shown in FIG. 11A, the amount of outside air introduced Qo under the first condition is 1800 CMH, and the amount of outside air introduced Qo under the second condition is 1500 CMH. The amount of circulated air (internal circulation amount) Qr under the first condition is 1800 CMH, and the amount of circulated air Qr under the second condition is 2100 CMH. The supply amount Qs under the first condition is 3600 CMH, and the supply amount Qs under the second condition is 3600 CMH. The supply amount Qs is the sum of the amount of circulated air Qr and the amount of outside air introduced Qo. The total power consumption under the first condition is 17582 W, and the total power consumption under the second condition is 16814 W. The ratio of the total power consumption under the first condition to the total power consumption under the second condition is 95.4% when the first condition is 100%.

[0109] Fig. 11B is a diagram for explaining energy saving. As shown in Fig. 11B, the power consumption (indoor load) of the air conditioner 50 is approximately 9000 W under the first condition in which the air cleanliness of the target space SP is excessive, and under the second condition in which adjustment is made to reduce the amount of outside air introduced Qo. The indoor load is the indoor load processing energy processed by the air conditioner 50. The indoor load processing energy is approximately the same under the first condition and the second condition, and does not change.

[0110] Furthermore, the power consumption (outdoor air load) of the outdoor air conditioner 10 is approximately 5500 W under the first condition and approximately 4500 W under the second condition. The outdoor air load is the outdoor air load processing energy processed by the outdoor air conditioner 10. The outdoor air load processing energy is smaller under the second condition than under the first condition because the amount of outdoor air introduced Qo is reduced. The reduction in outdoor air load processing energy (power consumption) when changing from the first condition to the second condition is approximately 1000 W.

[0111] Furthermore, the power consumption (air conveying energy) of the blower (blowing unit) is approximately 3000 W under the first condition and approximately 3500 W under the second condition. The air conveying energy is handled by the blower of the air conditioner 50 and the blower of the outdoor air conditioner 30. The blowers include at least the supply air fan 38 of the outdoor air conditioner 10 and the indoor fan 75 of the air conditioner 10. When changing from the first condition to the second condition, the air conveying energy increases because the supply volume Qs, which is the sum of the air circulation volume Qr and the outdoor air introduction volume Qo, increases. The increase in air conveying energy (power consumption) when changing from the first condition to the second condition is approximately 500 W.

[0112] 11B, when the first condition, in which the air in the target space SP is excessively clean, is changed to the second condition, in which the amount of outside air introduced Qo is reduced, the reduction in the amount of outside air load processing energy is greater than the increase in the amount of air transport energy. Therefore, to achieve the second condition, the amount of outside air introduced Qo is reduced and the amount of air circulation Qr is increased by the same amount as the reduction in the amount of outside air introduced Qo.

[0113] Another example of the operation of the air conditioner 50 and the outdoor air conditioner 10 will be described with reference to Figs. 12A and 12B. 2 Assume that the number of people present in the target space SP is 60, and the ventilation rate per person is 30 CMH. The target space SP is an office (see FIG. 9) where supply air SA is blown out from the bottom of the wall. The power consumption of the outdoor-air conditioner 10 and the air conditioner 50 under the first and second conditions will be compared. The example shown in FIGS. 12A and 12B differs from the example shown in FIGS. 11A and 11B in that the filter of the outdoor-air conditioner 10 is clogged.

[0114] The first condition is an outdoor air condition in which the outdoor air temperature is 34° C. and the humidity is 50%.

[0115] Examples of air volume conditions are shown in FIG. 12A. As shown in FIG. 12A, the outside air introduction amount Qo under the first condition is 1800 CMH, and the outside air introduction amount Qo under the second condition is 1500 CMH. The air circulation amount Qr under the first condition is 1800 CMH, and the air circulation amount Qr under the second condition is 2100 CMH. The supply amount Qs under the first condition is 3600 CMH, and the supply amount Qs under the second condition is 3600 CMH. The supply amount Qs is the sum of the air circulation amount Qr and the outside air introduction amount Qo. The total power consumption under the first condition is 17582 W, and the total power consumption under the second condition is 18071 W. The ratio of the total power consumption under the first condition to the total power consumption under the second condition is 103% when the first condition is 100%.

[0116] Fig. 12B is a diagram for explaining energy saving. As shown in Fig. 12B, the power consumption (indoor load) of the air conditioner 50 is approximately 9000 W under the first condition in which the air cleanliness of the target space SP is excessive, and under the second condition in which adjustment is made to reduce the amount of outside air introduced Qo. The indoor load is the indoor load processing energy processed by the air conditioner 50. The indoor load processing energy is approximately the same under the first condition and the second condition, and does not change.

[0117] Furthermore, the power consumption (outdoor air load) of the outdoor air conditioner 10 is approximately 5500 W under the first condition and approximately 4500 W under the second condition. The outdoor air load is the outdoor air load processing energy processed by the outdoor air conditioner 10. When changing from the first condition to the second condition, the outdoor air load processing energy decreases because the amount of outdoor air introduced Qo decreases. The reduction in outdoor air load processing energy (power consumption) when changing from the first condition to the second condition is approximately 1000 W.

[0118] Furthermore, the power consumption (air conveying energy) of the blower is approximately 3000 W under the first condition and approximately 4500 W under the second condition. The air conveying energy is handled by the blower of the air conditioner 50 and the blower of the outdoor air conditioner 30. When changing from the first condition to the second condition, the air conveying energy increases because the supply volume Qs, which is the sum of the circulating air volume Qr and the outdoor air intake volume Qo, increases. The increase in air conveying energy (power consumption) when changing from the first condition to the second condition is approximately 1500 W.

[0119] As shown in Figure 12B, because the filter of the outdoor-air conditioner 10 is clogged, when the first condition, in which the air in the target space SP is excessively clean, changes to the second condition, in which adjustment is made to reduce the amount of outdoor air introduced Qo, the increase in air conveyance energy is greater than the reduction in the amount of outdoor air processing load energy. Therefore, in the example shown in Figures 12A and 12B, no energy-saving effect is obtained, and the amount of outdoor air introduced is not reduced to achieve the second condition.

[0120] Conventional ventilation volume control does not take power consumption into account, making it impossible to derive the optimal operating state from the viewpoint of energy conservation.

[0121] In the displacement air conditioning system of Variation 1B, the amount of circulated air Qr and the amount of introduced outside air Qo can be controlled based on the evaluation results of the energy-saving effect so that the total amount of the circulated air Qr and the amount of introduced outside air Qo remains constant. The energy-saving effect can also be calculated by taking into account the external load processing energy and the air transport energy. Furthermore, by adjusting the temperature of at least the circulated air, it is possible to adjust the air temperature with less energy consumption than adjusting the temperature of the outside air.

[0122] (5-3) Variation 1C The air volume of the outside air OA may be adjusted by a variable air volume controller (VAV), and the outside air OA whose air volume has been adjusted by the VAV may be mixed with the inside air IA and supplied as the supply air SA.

[0123] The displacement air conditioning system 102 of Variation 1C has the functions of the air conditioner of this embodiment and the functions of an outdoor air conditioner. In the displacement air conditioning system 102 of Variation 1C, the blower unit includes a supply air fan 38a of the outdoor air conditioner 10a, an indoor fan 75a of the air conditioner 50a, a VAV 401, and one or more air outlets 83a. In the displacement air-head system of Variation 1C, the one or more air outlets 83a included in the air conditioner 50a and the outdoor air conditioner 10a are installed above the occupants in the target space SP and blow air toward the floor of the target space SP. In other words, the one or more air outlets 83a included in the blower unit are installed above the occupants in the target space SP and blow supply air toward the floor of the target space SP.

[0124] FIG. 13 shows the air flow in the displacement air conditioning system 102 of Modification 1C.

[0125] As shown in Fig. 13, the indoor air IA in the target space SP flows above the ceiling CL through the vent 88. A portion of the return air RA that flows from the target space SP above the ceiling CL is discharged to the outdoors as exhaust air EA from the exhaust device 86. In addition, a portion of the return air RA is taken in by the indoor unit 70a of the air conditioner 50a.

[0126] Furthermore, outside air is taken in from outdoors into the air handling unit 30a of the outdoor-air conditioner 10a. The outside air OA taken in by the air handling unit 30a passes through a variable air volume controller (VAV) 401. The return air RA and the outside air OA are mixed, and supply air SA is supplied from the air outlet 83a toward the floor from the ceiling CL of the target space SP. While FIG. 13 shows a case where there is one air outlet 83a, there may be two or more air outlets.

[0127] The air handling unit 30a of the outdoor-air conditioner 10a includes a temperature sensor 96a. The temperature sensor 96a acquires the temperature of the outdoor air OA taken into the outdoor-air conditioner 10a.

[0128] Furthermore, the carbon dioxide concentration sensor 95 acquires the carbon dioxide concentration at the first height in the target space SP.

[0129] The control unit 90 acquires information for controlling the air conditioner 50a and the outdoor air conditioner 10a as first information (acquired information). For example, the control unit 90 acquires the amount of outdoor air introduced Qo [m 3 / h]. The control unit 90 also obtains the circulating air volume Qr [m 3 / h]. The control unit 90 also acquires the carbon dioxide concentration (occupied zone concentration) C[-] of the target space SP, the carbon dioxide concentration Ce[-] of the exhaust, and the intake temperature (outdoor air temperature) To[°C] of the outdoor air conditioner 10a.

[0130] Furthermore, information for controlling the air conditioner 50a and the outdoor-air conditioner 10a is input to the control unit 90 as second information (input information). For example, the control unit 90 receives the target carbon dioxide (first target concentration) Cp[-] for the occupied area SP1, the target temperature Tp[°C] for the occupied area SP1, the estimated COP[-] of the outdoor-air conditioner 10a, the motor output Wrf[W] of the air conditioner 50a at the circulating air volume Qr' after the outdoor air introduction volume Qo has been reduced, the motor output Wof[W] of the heat exchanger 33a at the outdoor air introduction volume Qo' after the reduction, the motor efficiency η[-], the specific heat c[J / kg·K] of the air, the air density ρ, and the relationship between the tap information and the air volume.

[0131] A flowchart of the displacement air conditioning system 102 of Modification 1C is shown in FIG.

[0132] In step S21, the control unit 90 determines that the carbon dioxide concentration C in the target space SP is lower than the first target concentration Cp.

[0133] In step S22, the control unit 90 determines the maximum reduction amount (ΔQo) of the amount of outside air introduced Qo. In step S22, the control unit 90 determines the maximum reduction amount (ΔQo) of the amount of outside air introduced Qo by solving the simultaneous equations of the following equations (1) to (6). TIFF2026004111000002.tif11163TIFF2026004111000003.tif11163TIFF2026004111000004.tif9163TIFF2026004111000005.tif11163TIFF2026004111000006.tif11163TIFF2026004111000007.tif9163Cs: Intake air concentration Cs´: Intake air concentration after reducing the amount of outside air introduced Ce´: Exhaust gas concentration after reducing the amount of outside air intake M: Amount of indoor pollutants generated ΔC: Difference between supply air concentration and occupied area concentration

[0134] Next, the control unit 90 determines a candidate reduction amount for the outside air introduction amount Qo that is equal to or less than the maximum reduction amount ΔQo of the outside air introduction amount Qo that can be adjusted so that the supply amount (supply amount) Qs remains substantially constant.

[0135] The control unit 90 calculates the outdoor air load processing energy reduction candidate amount (ΔWo) when the outdoor air introduction amount Qo is reduced, using the following formula (7). TIFF2026004111000008.tif15163

[0136] Next, the control unit 90 calculates the proposed increase amount (ΔWf) of air conveying energy using the fan law according to the following formula (8): The first term of formula (8) is the conveying power when the proposed reduction amount is reduced, and the second term of formula (8) is the conveying power before reduction. TIFF2026004111000009.tif15163

[0137] In step S23, the control unit 90 determines whether the candidate amount of reduction in outdoor air load processing energy ΔWo is greater than the candidate amount of increase in air conveying energy ΔWf. If the candidate amount of reduction in outdoor air load processing energy ΔWo is greater than the candidate amount of increase in air conveying energy ΔWf (Yes in step S23), the process proceeds to step S24.

[0138] In step S24, the control unit 90 increases the airflow rate of the air conditioner 50a by an amount equivalent to the candidate reduction amount for the amount of outdoor air introduced Qo, using the tap of the air conditioner 50a. Furthermore, the control unit 90 reduces the airflow rate of the amount of outdoor air introduced Qo by the candidate reduction amount, using the VAV. Then, the process proceeds to step S25.

[0139] In order to adjust the air volume so that the boundary surface height does not decrease, it is preferable to first increase the circulating air volume Qr and then decrease the outside air intake volume Qo, or to adjust them simultaneously. In the case of an outdoor air conditioning unit whose air volume can be changed by tapping, an air conditioning system without a VAV may obtain the outdoor air intake amount Qo from tap information, and control may be performed so that the circulating air volume Qr is increased by tapping to an air volume close to the candidate reduction amount for the outdoor air intake amount Qo, and the outdoor air intake amount Qo is reduced by tapping to an air volume close to the candidate reduction amount.

[0140] If the outdoor air load processing energy reduction candidate amount ΔWo is equal to or less than the air conveying energy increase candidate amount ΔWf (No in step S23), the process proceeds to step S25.

[0141] In step S25, after a certain period of time has elapsed, the process returns to step S21.

[0142] FIG. 15 is a diagram showing an example of contaminant concentration and boundary surface height. When there is an air outlet at the top of the target space SP (see FIG. 13), the blown-out air reaches the occupied area while entraining the surrounding air, so the carbon dioxide concentration (occupied area concentration) C at the bottom of the target space SP is higher than the supply air concentration Cs. Analysis results show that the volume of air entrained before reaching the occupied area (entrained air volume) and the blown-out air volume are proportional to each other (not shown). Therefore, when there are multiple air outlets, even if the air volume for each outlet is changed, the entrained air volume will not change significantly if the total blown-out air volume is the same, and the difference ΔC between the supply air concentration and the occupied area concentration will be close to the value before and after air volume adjustment.

[0143] In variant 1C, as shown in Fig. 15, the target carbon dioxide concentration (first target concentration) Cp in the occupied area is higher than the supply air concentration Cs' after the amount of outside air introduced Qo is reduced. Furthermore, the difference between the supply air concentration Cs' after the amount of outside air introduced Qo is reduced and the target carbon dioxide concentration Cp in the occupied area is a value equivalent to the difference ΔC between the supply air concentration Cs and the occupied area concentration C.

[0144] 16 is a diagram showing the relationship between tap information and the amount of circulating air. As shown in FIG. 16, when the tap of the air conditioner 50a is turned on suddenly, the amount of circulating air Qr is 1740 [m 3 / h], and when the tap of the air conditioner 50a is strong, the amount of circulating air Qr is 1500 [m 3 / h], and when the tap of the air conditioner 50a is weak, the amount of circulating air Qr is 1320 [m 3 / h].

[0145] In the replacement air conditioning system 102 of variant example 1C, even if the air outlets 83a of the air conditioner 50 and the outdoor air conditioner 10 are installed above the target space SP, temperature stratification can be created in the target space SP by blowing air toward the floor surface of the target space SP, and the stratified area can be filled with highly purified air.

[0146] (5-4) Variation 1D The ventilation device may be configured to have a ventilation heat exchanger (total heat exchanger) and supply the outside air OA that has exchanged heat with the return air RA, and the return air RA sent to the air conditioner 50, as the supply air SA.

[0147] The displacement air conditioning system 103 of variant 1D has the functions of the air conditioner of this embodiment and also the functions of a ventilation device. In displacement air conditioning system 103 of variant 1D, the blower section includes supply air fan 75a of air conditioner 50a, an outlet (not shown) of ventilation device 10b, and outlets 83b and 83c. Outlets 83b and 83c included in the blower section are installed above the occupants in the target space SP, and blow supply air toward the floor surface of the target space SP.

[0148] In the displacement air conditioning system 103 of variation 1D, the ventilation device 10b has a ventilation heat exchanger 301. The ventilation heat exchanger 301 is a total heat exchanger that simultaneously exchanges sensible heat and latent heat between two air flows (here, return air RA and outdoor air OA), and is installed across the ventilation duct.

[0149] In the replacement air conditioning system 103, the carbon dioxide concentration sensor 95a acquires the carbon dioxide concentration at a first height in the target space SP. The temperature sensor 96b acquires the temperature of the outside air OA taken in by the ventilation device 10b, and the carbon dioxide concentration sensor 95b acquires the carbon dioxide concentration in the exhaust air EA discharged outdoors from the ventilation device 10b.

[0150] FIG. 17 shows the air flow in the displacement air conditioning system of variation 1D.

[0151] As shown in Fig. 17, the indoor air IA in the target space SP flows above the ceiling CL through the vent 88. A portion of the return air RA that flows from the target space SP to the ceiling CL is taken in by the indoor unit 70a of the air conditioner 50a, and supply air SA is supplied from the air outlet 83b from the ceiling CL of the target space SP toward the floor surface.

[0152] Furthermore, outside air OA is taken in from outdoors by the ventilation device 10b. A portion of the return air RA, which is air that flows from the target space SP above the ceiling CL, exchanges heat with the outside air OA in the total heat exchanger 301 of the ventilation device 10b and is discharged outdoors as exhaust air EA. The outside air OA that has exchanged heat with the return air RA is supplied as supply air SA from the air outlet 83c from the ceiling CL of the target space SP toward the floor surface.

[0153] In the displacement air conditioning system 103, the control unit 90 controls the circulating air volume Qr and the outdoor air introduction volume Qo using parameters including the assumed COP of the air conditioner 50a and the supply air concentration in the target space SP as further inputs. If the ventilation device 10b has a total heat exchanger 301, the parameters further include the assumed enthalpy exchange efficiency of the total heat exchanger 301.

[0154] The control unit 90 acquires information for controlling the air conditioner 50a and the ventilation device 10b as first information (acquired information). For example, the control unit 90 acquires the amount of outside air introduced Qo [m 3 / h]. The control unit 90 also obtains the circulating air volume Qr [m 3 / h]. The control unit 90 also acquires the carbon dioxide concentration C[-] in the target space SP, the carbon dioxide concentration Ce[-] in the exhaust air, and the intake temperature (outside air temperature) To[°C] on the outside air intake side of the total heat exchanger 301.

[0155] The control unit 90 also receives as input information information for controlling the air conditioner 50b and the outdoor-air conditioner 10b. For example, the control unit 90 receives as input information the target carbon dioxide Cp[-] for the occupied area SP1, the target temperature Tp[°C] for the occupied area, the estimated COP[-] for the outdoor-air conditioner 10b, the motor output Wrf[W] of the air conditioner 50a for the circulating air volume Qr' after the outdoor air introduction volume Qo has been reduced, the motor output Wof[W] of the ventilation heat exchanger 33b for the outdoor air introduction volume Qo' after the reduction, the motor efficiency ηf[-], the specific heat c[J / kg·K] of the air, the air density ρ, the relationship between the tap information and the air volume of the total heat exchanger 301 of the air conditioner 50b or the ventilation device 10b, and the enthalpy efficiency ηo of the total heat exchanger 301.

[0156] A flowchart of the replacement air conditioning system 103 of Modification 1D is shown in Figure 18. Steps S21, S23, and S25 are the same as those in the flowchart of the replacement air conditioning system of Modification 1C shown in Figure 14, so detailed explanations will be omitted.

[0157] In step S31, the control unit 90 determines the maximum reduction amount (ΔQo) of the amount of outside air introduced Qo. In step S31, the control unit 90 determines the maximum reduction amount (ΔQo) of the amount of outside air introduced Qo by solving the simultaneous equations of the following equations (1) to (6). TIFF2026004111000010.tif12160TIFF2026004111000011.tif10163TIFF2026004111000012.tif9163 TIFF2026004111000013.tif12163TIFF2026004111000014.tif12163TIFF2026004111000015.tif9163 Cs: supply air concentration Cs´: Intake air concentration after reducing the amount of outside air introduced Ce´: Exhaust gas concentration after reducing the amount of outside air intake M: Amount of indoor pollutants generated ΔC: Difference between supply air concentration and occupied area concentration

[0158] Next, the control unit 90 determines a candidate reduction amount for the outside air introduction amount Qo that is equal to or less than the maximum reduction amount ΔQo of the outside air introduction amount Qo that can be adjusted so that the supply amount (supply amount) Qs remains substantially constant.

[0159] The control unit 90 calculates the outdoor air load processing energy reduction candidate amount (ΔWo) when the outdoor air introduction amount Qo is reduced, using the following formula (9). TIFF2026004111000016.tif14163

[0160] Next, the control unit 90 calculates the proposed increase amount (ΔWf) of air conveying energy using the fan law according to the following formula (10): The first term of formula (10) is the conveying power when the proposed reduction amount is reduced, and the second term of formula (10) is the conveying power before reduction. TIFF2026004111000017.tif17162

[0161] In step S32, the control unit 90 increases the airflow rate at the tap of the air conditioner 50a for the circulating air volume Qr by a value close to the candidate reduction amount for the outdoor air introduction volume Qo. The airflow rate close to the candidate reduction amount for the outdoor air introduction volume Qo may be an amount equivalent to the candidate reduction amount for the outdoor air introduction volume Qo. Furthermore, the control unit 90 reduces the airflow rate at the tap of the total heat exchanger 301 of the ventilation device 10b for the outdoor air introduction volume Qo by a candidate reduction amount.

[0162] The control unit 90 adjusts the air volume so that the boundary surface height does not decrease, and therefore adjusts the air volume by first increasing the circulation air volume Qr and then decreasing the outside air introduction volume Qo, or by adjusting both simultaneously.

[0163] Fig. 19 is a diagram showing the relationship between tap information and air volume. As shown in Fig. 19, when the tap is fast, the air volume of the air conditioner 50a is 1740 [m 3 / h] and when the tap is on high, the air volume is 1500 [m 3 / h] and when the tap is weak, the air volume is 1320 [m 3 / h].

[0164] The total heat exchanger 301 of the ventilation device 10b has an air volume of 1000 m when the tap is strong. 3 / h] and when the tap is on low, the air volume is 880 [m 3 / h].

[0165] In the replacement air conditioning system 103 of variant 1D, the ventilation device 10b has a total heat exchanger 301, so the amount of circulating air Qr and the amount of outdoor air introduced Qo can be controlled taking into account the estimated COP of the air conditioner 50a, the estimated enthalpy exchange efficiency of the total heat exchanger 301, etc.

[0166] (5-5) Variation 1E In the displacement air conditioning system 100 shown in Fig. 2, the control unit 90 controls the circulating air volume Qr and the outdoor air introduction volume Qo using as input parameters including the desired indoor temperature of the target space SP, the desired carbon dioxide concentration of the target space SP, the outdoor air temperature, the outdoor air introduction volume Qo, the circulating air volume Qr, the carbon dioxide concentration of the target space SP, the exhaust concentration of the target space SP, and air transport energy data required for air transport by the air conditioner 50 and the outdoor air conditioner 10. When the ventilation device is an outdoor air conditioner (outdoor air conditioner) 10 that adjusts the temperature of the outdoor air, the parameters further include an expected COP of the outdoor air conditioner 10.

[0167] In the displacement air conditioning system of variation 1E, the amount of circulating air Qr and the amount of outside air introduced Qo can be controlled taking into account the indoor temperature conditions of the target space SP, etc.

[0168] (5-6) Variation 1F In this embodiment, the contaminant is carbon dioxide, but the present invention is not limited to this. The contaminant may be odorous substances, droplet nuclei, viruses, or PM2.5. The contaminant may include at least one of carbon dioxide, odorous substances, droplet nuclei, viruses, or PM2.5, and may include two or more of them.

[0169] (5-7) Variation 1G In this embodiment, a case has been described in which water is also used as a heat medium in the outdoor-air conditioner 10. However, the heat medium used in the outdoor-air conditioner 10 is not necessarily limited to water, and may be another fluid. For example, in the outdoor-air conditioner 10, a refrigerant may be used as a heat medium.

[0170] (5-8) Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims. [Explanation of symbols]

[0171] 10, 10a: Outdoor air conditioner (ventilation device) 10b: Ventilation equipment 20: Chiller unit (heat medium adjustment section) 21: Refrigerant compressor 22: Heat medium heat exchanger 23: Refrigerant expansion valve 24: Refrigerant heat exchanger 25: Flow path switching valve 26: Chiller fan 30, 30a: Air conditioning unit (outdoor air conditioning unit) 33: Outside air heat exchanger (external heat exchanger) 301: Ventilation heat exchanger (total heat exchanger) 34: Filter 35: Humidifier 38, 38a: Air supply fan 48, 48a, 48b: Air supply duct (duct) 49:Outdoor conditioning machine control section 50, 50a: Air conditioner (air conditioning unit) 60: Outdoor unit (refrigerant adjustment section) 61: Compressor 62: Four-way switching valve 63:Outdoor heat exchanger 68: Outdoor fan 70, 70a: Indoor unit 71: Expansion valve 72: Indoor heat exchanger (air conditioning heat exchanger) 75, 75a: Indoor fan 76: Filter 79: Air conditioner control unit 81, 82, 83, 84a, 84b, 84c: Air outlet 85:Return air port 86: Exhaust system 90: Control unit 95, 95a, 95b: Carbon dioxide concentration sensor 96a, 96b: Temperature sensors 100, 101, 102, 103: Displacement air conditioning system 401: Variable air volume control device BL: Building C1: Heat medium circuit C2: Outside air conditioner refrigerant circuit CL: Ceiling FP: Outside air flow path GP1: Gas side refrigerant connection pipe H1: Air intake IA: Shy LP1: Liquid side refrigerant connection pipe OA: Outside air P1-P3: 1st pipe - 3rd pipe Pa: Heat medium pump (heat medium adjustment section) Qo: Amount of outside air introduced Qr: Circulating air volume RC: Refrigerant circuit RP: Refrigerant piping RP1-RP7: 1st refrigerant piping - 7th refrigerant piping SA: Air supply SP: Target space SP1: Living area SP2:Respiratory area SP4: The Space Under the Ceiling [Preliminary Technology Documents] [License]

[0172] [License 1] Patent No. 6415720

Claims

1. A displacement air conditioning system that forms concentration stratification in a target space (SP), An air conditioning device (50, 50a) that sends circulating air below the target space; A ventilation device (10, 10a, 10b) that sends outside air below the target space; a first sensor (95, 95a, 95b) for acquiring a contaminant concentration at a first height in the target space; a control unit (90) that controls the ratio between a circulating air amount (Qr), which is the amount of circulating air drawn into the air conditioning device from above the target space and returned from the air conditioning device to the target space, and an outside air introduction amount (Qo), which is the amount of outside air supplied from the ventilation device to the target space, to be controlled to a predetermined level in accordance with the contaminant concentration; Equipped with Displacement air conditioning system (100, 101, 102, 103).

2. the control unit performs a first control of reducing the amount of outside air introduced and increasing the amount of circulating air when the contaminant concentration at the first height is lower than a first target concentration.

10. The displacement air conditioning system of claim 1.

3. The control unit evaluates an energy-saving effect of the first control and determines whether to perform the first control based on the evaluation result.

3. The displacement air conditioning system of claim 2.

4. The control unit calculates the energy-saving effect based on a reduction amount of external load processing energy required to process the outdoor air load of the ventilation device and an increase amount of air transport energy required to transport air in the air conditioner and the ventilation device.

4. The displacement air conditioning system of claim 3.

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