JP2022189288A - Air conditioner freeze prevention system and air conditioner control device - Google Patents

Abstract

To secure a sufficient flow rate necessary for freeze prevention even when cold-water coil inlet pressure deviates from a value at the introduction of equipment due to disturbance, deterioration or the like.SOLUTION: When a detected cold water temperature Tm is lower than a prescribed freeze prevention threshold temperature, a controller 12 determines an opening command value A* corresponding to the detected cold water temperature Tm from a temperature-opening map in which cold water temperatures and degrees of opening of a control valve 30 are associated with each other. The controller 12 also determines a target flow rate Q* corresponding to the detected cold water temperature Tm from a temperature-flow rate map in which cold water temperatures and cold water flow rates are associated with each other. The controller 12 also determines a difference flow rate ΔQ, which is an actual measurement flow rate Qm of water backflow piping 28 after setting the opening of the control valve 30 to the opening command value A* minus the target flow rate Q*. When the difference flow rate ΔQ is a positive value, the controller 12 resets the opening command value A* to an increasing direction. When the difference flow rate ΔQ is equal to or smaller than zero, the controller maintains the opening command value A*.SELECTED DRAWING: Figure 2

Description

Disclosed herein is an antifreeze system for an air conditioner and a controller for an air conditioner.

For example, a central air conditioner is provided with an air conditioner (air conditioner). An air conditioner takes outside air, heats (warms) or cools it, and dehumidifies or humidifies it as necessary to generate conditioned air, which is supplied to a space to be conditioned such as a tenant or office space.

In order to cool the outside air, the air conditioner is provided with a cold water coil to which cold water is supplied. In addition, in order to heat the outside air, the air conditioner is provided with a hot water coil to which hot water is supplied. These coils are provided between the outside air inlet of the air conditioner and the air supply fan. For example, the devices are arranged in the order of outside air inlet→cold water coil→hot water coil→air supply fan. Outside air (introduced outside air) introduced into the air conditioner is cooled or heated by passing through each coil.

For example, when it is not necessary to exclusively heat the introduced outside air and cool it, such as in winter, the cold water supply to the cold water coil is stopped. This causes cold water to stay in the cold water coil. When a cold wave passes through a cold region, the introduced outside air passes through the cold water coil, causing the cold water remaining in the cold water coil to freeze and expand, which may lead to breakage of the cold water coil.

Therefore, cold water is supplied (moved) at a predetermined flow rate from the viewpoint of freezing prevention even in the so-called winter season when air conditioning is not required. For example, when the discharge pressure of the cold water pump is constant, the pressure at the cold water coil inlet is constant, and since the opening of the control valve and the flow rate are in a proportional relationship, it is possible to control the flow rate by adjusting the opening.

As an anti-freezing means for such an air conditioner, for example, in Patent Document 1, when the temperature of the cold water circulating in the cold water coil falls below a predetermined specific temperature, part of the hot water flowing through the hot water circulation path is converted into cold water containing the cold water coil. supplied to the circuit. Further, in Patent Document 2, in the anti-freezing operation, by adjusting the amount of anti-freezing water flowing through the water passage of the cooling heat exchanger, the temperature of the anti-freezing water at the outlet of the water passage of the cooling heat exchanger is adjusted to the set freeze protection temperature. Furthermore, in Patent Document 3, when the outside air temperature becomes equal to or lower than a preset set temperature, the flow control valve is fully opened to prevent freezing.

JP 2019-78501 A JP 2012-154543 A JP-A-5-215382

By the way, due to pump deterioration, cold water pipe rust, etc., the actual cold water coil inlet pressure may be lower than the value at the time of installation even if the set value of the discharge pressure for the pump is constant. In addition, when the cold water pipe is branched and supplied to other air conditioners, the actual cold water coil inlet pressure may deviate from the value at the time of installation even if the control valve of the other air conditioner is suddenly opened or closed. There is a risk of

Therefore, in this specification, even if the cold water coil inlet pressure deviates from the value at the time of installation due to disturbance, deterioration, etc., it is possible to secure the necessary and sufficient flow rate for freezing prevention. A control device for an antifreeze system and an air conditioner is disclosed.

Disclosed herein is an anti-freeze system for an air conditioner. The system includes a chilled water coil, a control valve, a water temperature sensor, a flow sensor, and a controller. Cold water is supplied to the cold water coil from the water supply pipe by a pump, and heat exchange with the air passing through the coil is performed. The control valve is provided in the return water pipe to which return cold water from the cold water coil is sent, and adjusts the flow rate of the return cold water. A water temperature sensor and a flow rate sensor are provided in the return water pipe. The control device generates an opening command for the control valve based on the cold water temperature detected by the water temperature sensor. Further, when the detected chilled water temperature is less than the predetermined antifreeze threshold temperature, the control device outputs an opening command corresponding to the detected chilled water temperature from the temperature-opening map in which the chilled water temperature and the opening of the control valve are associated. find the value. The control device also obtains the target flow rate corresponding to the detected cold water temperature from the temperature-flow rate map in which the cold water temperature and the cold water flow rate are associated. Further, the control device obtains a differential flow rate by subtracting the measured flow rate of the return water pipe after setting the opening degree command value of the control valve from the target flow rate. Furthermore, the control device resets the opening command value in an increasing direction when the differential flow rate is a positive value, while maintaining the opening command value when the differential flow rate is a value of zero or less.

According to the above configuration, when the differential flow rate takes a positive value, that is, when the measured flow rate has not reached the target flow rate, the opening degree command value is adjusted to increase. On the other hand, if the differential flow rate is less than zero, that is, if the measured flow rate is greater than or equal to the target flow rate, the opening command value is maintained from the viewpoint that sufficient flow rate is secured to prevent freezing. be.

Also disclosed herein is a controller for an air conditioner. The air conditioner includes a cold water coil, a control valve, a water temperature sensor and a flow rate sensor in addition to the control device. Cold water is supplied to the cold water coil from the water supply pipe by a pump, and heat exchange with the air passing through the coil is performed. The control valve is provided in the return water pipe to which return cold water from the cold water coil is sent, and adjusts the flow rate of the return cold water. A water temperature sensor and a flow rate sensor are provided in the return water pipe. The control device generates an opening command for the control valve based on the cold water temperature detected by the water temperature sensor. The control device includes a temperature-based opening calculation section, a temperature-based flow rate calculation section, and an opening adjustment section. When the detected cold water temperature is less than the predetermined antifreeze threshold temperature, the temperature-based opening calculation unit calculates the detected cold water temperature from the temperature-opening map in which the cold water temperature and the opening of the control valve are associated. Find the opening command value. The temperature-based flow rate calculator obtains a target flow rate corresponding to the detected cold water temperature from a temperature-flow rate map in which cold water temperatures and cold water flow rates are associated. The opening adjustment unit obtains a differential flow rate by subtracting the measured flow rate of the return water pipe after setting the opening command value of the control valve opening from the target flow rate, and when the differential flow rate is a positive value, While resetting the opening degree command value in the increasing direction, the opening degree command value is maintained when the differential flow rate is a value of zero or less.

According to the air conditioner antifreeze system and the air conditioner control device disclosed in the present specification, even if the cold water coil inlet pressure deviates from the value at the time of installation due to disturbance, deterioration, etc. , it becomes possible to ensure a necessary and sufficient flow rate to prevent freezing.

It includes an anti-freezing system for an air conditioner according to the present embodiment. It is a figure which illustrates the structure of an air-conditioning system. FIG. 4 is a diagram illustrating functional blocks of a controller; FIG. 4 is a diagram illustrating a temperature-opening degree map (TA map); FIG. 4 illustrates a temperature-flow map (TQ map); It is a figure which illustrates an opening adjustment map. It is a figure which illustrates the opening degree setting flow of a control valve which concerns on this embodiment.

FIG. 1 illustrates an anti-freezing system for an air conditioner according to this embodiment. This system includes an air conditioner 10 and a controller 12 (control device). A signal line is indicated by a dashed line. In addition, the illustration of devices that are less relevant to the prevention of freezing of the cold water coil 14, such as a filter, a slight differential pressure switch for detecting filter clogging, and a humidification mechanism, is omitted as appropriate.

The air conditioner 10 introduces outside air, generates conditioned air, and supplies the conditioned air to spaces to be air-conditioned, such as tenants and office spaces. A damper 16 and a damper motor 18 are provided on the outside air side of the air conditioner 10 . The air conditioner 10 includes a cold water coil 14, a hot water coil 20, and an air supply fan 22 in order from the outside air side.

The damper 16 is a so-called air volume adjustment damper (VD) that adjusts the amount of outside air (OA) introduced by adjusting the opening degree of the outside air duct 24 . The damper 16 is composed of, for example, a plate member. A damper motor 18 drives the damper 16 to adjust the opening of the outside air duct 24 . The damper motor 18 is composed of, for example, a pulse motor.

The upstream end of the cold water coil 14 is connected to a water supply pipe 26 for cold water. A downstream end of the cold water coil 14 is connected to a return water pipe 28 . Cold water is supplied to the cold water coil 14 from the water supply pipe 26 by the pump 60 . The chilled water coil 14 exchanges heat with air (outside air) introduced from the outside air duct 24 and passing through itself. In the embodiment shown in FIG. 1, the air that exchanges heat with the chilled water coil 14 includes, in addition to the outside air, part of the return air returned from the air-conditioned space.

A refrigerator 62 is connected to the upstream end of the water supply pipe 26 and the downstream end of the return water pipe 28 . Cold water that has passed through the cold water coil 14 is returned to the refrigerator 62 from the return water pipe 28 . A pump 60 is provided in the return water pipe 28 . By driving the pump 60 , cold water circulates through the flow path of pump 60 →refrigerator 62 →water supply pipe 26 →cold water coil 14 →return water pipe 28 →pump 60 .

Although not shown in FIG. 1, a plurality of water supply pipes 26 and a plurality of water return pipes 28 are branched from the refrigerator 62 so that cold water can be supplied from the refrigerator 62 to a plurality of air conditioners. .

The return water pipe 28 is provided with a control valve 30 for adjusting the flow rate of the return cold water flowing through the return water pipe 28, a water temperature sensor 32 for measuring the temperature of the return cold water, and a flow rate sensor 34 for measuring the flow rate of the return cold water. be provided. As will be described later, the controller 12 adjusts the degree of opening of the control valve 30 based on the measured values of the water temperature sensor 32 and the flow rate sensor 34 to prevent the cold water inside the cold water coil 14 from freezing.

As with the cold water coil 14, the hot water coil 20 exchanges heat with the air introduced from the outside air duct 24 and passing through itself (outside air) and part of the return air. The hot water coil 20 is connected to the water supply pipe 36 . A boiler 72 is provided at the upstream end of the water supply pipe 36 . Hot water that has passed through the hot water coil 20 is returned to the boiler 72 through the return water pipe 38 .

The return water pipe 38 is provided with a control valve 40 for adjusting the flow rate of the return hot water flowing through the return water pipe 38 . Furthermore, a pump 70 is provided in the return water pipe 38 . By driving the pump 70 , hot water circulates through the flow path of the pump 70 →boiler 72 →water supply pipe 36 →hot water coil 20 →return water pipe 38 →pump 70 .

Although not shown in FIG. 1, a plurality of water supply pipes 36 and return water pipes 38 are branched from the boiler 72 so that hot water can be supplied from the boiler 72 to a plurality of air conditioners.

Basically, only one of the cold water coil 14 and the hot water coil 20 is used. For example, when cooling the outside air, cold water is supplied to the cold water coil 14, while hot water supply to the hot water coil 20 is stopped (control valve 40 is closed). Further, when the outside air is heated (heated), hot water is supplied to the hot water coil 20, while cold water supply to the cold water coil 14 is stopped (control valve 30 is closed).

In the so-called dry operation, in which the introduced outside air is dehumidified, reheat control may be performed in which the outside air is cooled (supercooled) to a temperature lower than the target temperature and then heated. In such a case, cold water and hot water are supplied to the cold water coil 14 and the hot water coil 20, respectively. The conditioned air that has been cooled, heated, dehumidified, or humidified as necessary is sent from the air supply fan 22 through the air supply duct 42 to each air-conditioned space.

A controller 12, which is a control device for the air conditioner 10, is composed of, for example, a PLC (Programmable Logic Computer). The controller 12 may comply with BACnet (Building Automation and Control Network), which is a communication protocol, so as to be compatible with BA (Building Automation), for example. Based on this BACnet, the controller 12 can communicate with a central monitoring device (not shown).

FIG. 1 illustrates a hardware configuration diagram of the controller 12. As shown in FIG. The controller 12 can control various devices connected to the internal bus.

The controller 12 includes a CPU 44 , RAM 46 , ROM 47 , user interface 48 (UI), and external interface 50 . The user interface 48 is used to input user information and to display information.

The external interface 50 is used for connection with external devices and data communication. Specifically, the water temperature sensor 32 sends a detected cold water temperature Tm, which is the detected temperature of the return cold water flowing through the return water pipe 28 . Also, from the flow rate sensor 34, a measured flow rate Qm of the return cold water flow rate flowing through the return water pipe 28 is sent. Also, the measured value of the temperature of the supplied air is sent from the supplied air temperature sensor 52 of the supplied air duct 42 .

The ROM 47 includes a non-volatile memory such as a hard disk drive (HDD) or solid state drive (SSD). The ROM 47 stores a program for configuring the controller 12 into functional blocks (see FIG. 2), which will be described later. Furthermore, the ROM 47 stores a temperature-opening map (TA map), a temperature-flow rate map (TQ map), an opening adjustment map, and the like, which will be described later.

The controller 12 executes the opening degree setting flow illustrated in FIG. 6 to set the opening degree of the control valve 30 . The set opening is sent to the control valve 30 via the external interface 50 . Further, an opening command is sent from the controller 12 via the external interface 50 to the control valve 40 provided in the hot water return pipe 38 . Further, an opening command for the outside air duct 24 is sent from the controller 12 to the damper motor 18 via the external interface 50 .

A functional block diagram of the controller 12 is illustrated in FIG. This functional block diagram is configured by the CPU 44 executing a program capable of executing the opening degree setting flow illustrated in FIG. Also, this program is stored in the ROM 47 or stored in a non-transitory computer-readable storage medium such as a DVD.

The controller 12 includes a temperature-based opening calculator 54 , a temperature-based flow rate calculator 56 , and an opening adjuster 58 .

A temperature-opening degree map (TA map) illustrated in FIG. 3 is stored in the temperature-based opening degree calculating section 54 . In the temperature-opening degree map, the horizontal axis is the temperature of the chilled water, and the vertical axis is the opening command value of the control valve 30. A characteristic line L1 is defined in which the chilled water temperature and the opening degree of the control valve 30 are associated. there is

The temperature-opening degree map is created to prevent cold water freezing in the cold water coil 14. For example, based on past data, the opening degree of the control valve 30 that can avoid freezing is plotted for each return cold water temperature. It is

For example, when the discharge pressure of a pump having a rated output equivalent to that of the pump 60 is a constant value, the data set of the temperature of the return cold water, the degree of opening of the control valve 30, and the presence or absence of freezing of the return water pipe 28 at that time is Multiple points are obtained from past achievements. The chilled water temperature detected by the water temperature sensor 32 is acquired as the temperature of the returned chilled water.

A plurality of data sets based on past results are plotted on a temperature-opening degree map, and a characteristic line L1 is defined so as to pass through the plot in which the return water pipe 28 was not frozen. For example, a characteristic line L1 is defined as a boundary line between a plot group in which the return water pipe 28 is frozen (frozen plot group) and a plot group in which the return water pipe 28 is not frozen (freeze avoidance plot group). Alternatively, the characteristic line L1 is defined in an area closer to the freeze avoidance plot group than the boundary line.

Although a straight line is shown as the characteristic line L1 in FIG. 3, the shape of the characteristic line L1 is determined according to the distribution of the two plot groups. However, qualitatively, the higher the detected cold water temperature Tm, the smaller the opening degree command value A* of the control valve 30 necessary for anti-freezing. That is, the characteristic line L1 has a downward sloping shape as a whole.

The temperature-based opening calculator 54 plots the chilled water temperature Tm detected by the water temperature sensor 32 on a temperature-opening map, and obtains the control valve opening command value A* corresponding to the detected chilled water temperature Tm.

The temperature-based flow rate calculator 56 stores a temperature-flow rate map (TQ map) illustrated in FIG. In the temperature-flow rate map, the horizontal axis represents the temperature of the return chilled water, and the vertical axis represents the target flow rate of the returned chilled water passing through the control valve 30. A characteristic line L2 is defined in which the chilled water temperature and the chilled water flow rate are associated.

The temperature-flow rate map is created to prevent freezing of cold water in the cold water coil 14. For example, based on past data, the flow rate of cold water that can avoid freezing is plotted for each return cold water temperature.

For example, when the discharge pressure of a pump having a rated output equivalent to that of the pump 60 is a constant value, the data set of the temperature of the return cold water, the flow rate of the return cold water, and the presence or absence of freezing of the return water pipe 28 at that time are past data sets. Multiple points are obtained from achievements.

This historical data set is plotted on a temperature-flow map. A characteristic line L2 is defined so as to pass through the plot in which the return water pipe 28 was not frozen. For example, a characteristic line L2 is defined as a boundary line between a plot group in which the return water pipe 28 is frozen (frozen plot group) and a plot group in which the return water pipe 28 is not frozen (freeze avoidance plot group). Alternatively, the characteristic line L2 is defined in an area closer to the freeze avoidance plot group than the boundary line.

Although a straight line is shown as the characteristic line L2 in FIG. 4, the shape of the characteristic line L2 is determined according to the distribution of the two plot groups. However, qualitatively, the higher the detected cold water temperature Tm, the smaller the target flow rate Q* of cold water required for freezing prevention. That is, the characteristic line L2 has a downward sloping shape as a whole.

The temperature-based flow rate calculator 56 plots the detected chilled water temperature Tm obtained from the water temperature sensor 32 on a temperature-flow rate map, and obtains the target flow rate Q* of the return chilled water corresponding to the temperature Tm.

In addition, considering that the main factor for suppressing freezing of the return cold water flowing in the return water pipe 28 is theoretically the flow velocity of the return cold water, instead of the temperature-flow rate map (TQ map) , a temperature-velocity map (TV map) may be used.

For example, the flow velocity V is obtained based on the inner diameter of each pipe for the data group based on the past performance used in creating the temperature-flow rate map of FIG. Furthermore, on the plane with the horizontal axis of FIG. A data set of the flow rate and the presence or absence of freezing of the return water pipe 28 at that time is plotted.

Further, the characteristic line L2' is determined so as to pass through the plots in which the return water pipe 28 was not frozen among the above plot groups. For example, a characteristic line L2' is defined as a boundary line between a plot group in which the return water pipe 28 is frozen (frozen plot group) and a plot group in which the return water pipe 28 is not frozen (freeze avoidance plot group). Alternatively, a characteristic line L2' is defined in an area closer to the freeze avoidance plot group than the boundary line.

In this case, the temperature-based flow rate calculator 56 plots the return chilled water temperature Tm acquired from the water temperature sensor 32 on a temperature-flow velocity map, and obtains the target flow velocity V* of the return chilled water corresponding to the temperature Tm. Furthermore, the temperature-based flow rate calculator 56 obtains the target flow rate Q* based on the target flow velocity V* and the inner diameter φ of the return water pipe 28 .

The opening adjustment unit 58 sets the opening command value A* obtained by the temperature-based opening calculation unit 54 to the set opening of the control valve 30, and the measured flow Qm obtained by the temperature-based flow calculation unit 56. The opening degree adjustment value ΔA for the control valve 30 is obtained based on the difference from the target flow rate Q*.

An opening adjustment map illustrated in FIG. 5 is stored in the opening adjustment unit 58 . In the opening adjustment map, the horizontal axis indicates the differential flow rate ΔQ obtained by subtracting the measured flow rate Qm from the target flow rate Q*, the vertical axis indicates the opening adjustment value ΔA to the control valve 30, and the differential flow rate ΔQ and the opening adjustment are shown. A characteristic line L3 associated with the value ΔA is defined.

The opening degree adjustment map is created to ensure a necessary and sufficient flow rate of cold water for freezing the cold water in the cold water coil 14, and is obtained from past data, for example. When the measured flow rate Qm does not reach the target flow rate Q* even though the set opening of the control valve 30 is set to the opening command value A*, that is, when ΔQ>0, the pump 60 and the control valve 30 are included. The water supply pressure in the cold water circuit may be low. For example, deterioration of the pump 60, deterioration of piping, or rapid opening and closing of control valves of other air conditioners branching from the refrigerator 62 can reduce the water supply pressure.

Even in such a case, the characteristic line L3 is determined in order to ensure a necessary and sufficient flow rate for preventing the cold water coil 14 from freezing. Qualitatively, the characteristic line L3 has such a shape that the opening degree adjustment value ΔA increases as the differential flow rate ΔQ increases. For example, the characteristic line L3 is represented by a linear function with a positive slope starting from the origin (ΔQ=0, ΔA=0).

When ΔQ takes a value of zero or less (ΔQ≦0), that is, when the measured flow rate Qm is equal to or greater than the target flow rate Q*, the necessary and sufficient flow rate to prevent freezing of the cold water coil 14 is ensured. , the once set opening degree A* is maintained. That is, the characteristic line L3 takes a value of ΔA=0 in the region of ΔQ≦0.

<Freezing prevention flow>
FIG. 6 illustrates an opening degree setting flow by the controller 12, which is a control device. The controller 12 acquires the temperature Tm of the return cold water flowing through the return water pipe 28 from the water temperature sensor 32 (S10). Subsequently, the controller 12 determines whether or not the detected cold water temperature Tm is less than a predetermined threshold temperature (less than the anti-freezing threshold temperature) (S12). The threshold temperature is a temperature at which cold water does not freeze in the cold water coil 14 even if the control valve 30 is fully closed, for example +5°C.

If the detected cold water temperature Tm is equal to or higher than the threshold temperature, after waiting for a predetermined period (S30), the process proceeds to the end (Return) of this flow and returns to the starting point (Start) of the flow again. When the detected cold water temperature Tm is less than the threshold temperature (less than the anti-freezing threshold temperature), the controller 12 acquires the flow rate Qm0 of the return cold water flowing through the return water pipe 28 (S14).

Subsequently, the controller 12 sets the opening degree of the control valve 30 to prevent freezing. Furthermore, the temperature-based opening calculation unit 54 refers to the characteristic line L1 of the TA map (FIG. 3) to obtain the opening command value A* corresponding to the detected cold water temperature Tm acquired in step S10 ( S20). The obtained opening degree command value A* becomes the set opening degree of the control valve 30 (S22), and the control valve 30 opens until reaching the opening degree command value A*. After the set opening of the control valve 30 is set to the opening command value A*, for example, one minute after the setting, the opening adjuster 58 acquires the measured return cold water flow rate Qm1 from the flow sensor 34 (S24 ).

Here, in parallel with the process of obtaining the opening command value A* in step S20, the target flow rate Q* is obtained (S18). The temperature-based flow rate calculator 56 obtains the target flow rate Q* corresponding to the detected cold water temperature Tm obtained in step S10 by referring to the characteristic line L2 of the TQ map.

The opening adjustment unit 58 obtains a difference flow rate ΔQ by subtracting the measured flow rate Qm1 of the return cold water obtained in step S24 from the target flow rate Q*. Further, the opening degree adjustment unit 58 refers to the characteristic line L3 of the opening degree adjustment map of FIG. 5 to obtain the opening degree adjustment value ΔA corresponding to the differential flow rate ΔQ (S26). As described above, ΔA=0 when the differential flow rate ΔQ≦0.

Further, the controller 12 resets the degree of opening of the control valve 30 to increase by ΔA (S28). For example, the controller 12 resets the set opening degree of the control valve 30 to a value (A*+ΔA) obtained by adding the opening degree adjustment value ΔA to the already set opening degree command value A*. When ΔA=0, the set opening is maintained at the opening command value A*. After waiting for a predetermined period of time (S30), the flow in FIG. 6 is returned to the starting point (Start).

In the above-described embodiment, the opening degree of the control valve 30 is adjusted for the purpose of preventing the cold water in the cold water coil 14 from freezing. is not limited to this form. For example, when the hot water supply in the hot water coil 20 is stopped, the hot water staying in the hot water coil 20 may be frozen by the outside air passing through the hot water coil 20 . Therefore, a water temperature sensor and a flow rate sensor may be provided in the return water pipe 38 of hot water, and the opening degree setting flow of FIG.

10 air conditioner, 12 controller (control device), 14 cold water coil, 16 damper, 18 damper motor, 20 hot water coil, 22 air supply fan, 24 outside air duct, 26 cold water supply pipe, 28 cold water return pipe, 30 control valve, 32 water temperature sensor, 34 flow sensor, 42 air duct, 52 air temperature sensor, 54 temperature-based opening calculator, 56 temperature-based flow calculator, 58 opening adjuster, 60, 70 pumps, 62 refrigerator , 72 boilers.

Claims (2)

a chilled water coil supplied with chilled water from a water pipe by a pump and heat exchanged with the air passing through the chilled water coil;
A control valve provided in a return water pipe to which cold water returned from the cold water coil is sent and for adjusting the flow rate of the returned cold water;
a water temperature sensor and a flow rate sensor provided in the return water pipe;
a control device that generates an opening command for the control valve based on the detected cold water temperature detected by the water temperature sensor;
An antifreeze system for an air conditioner, comprising:
When the detected cold water temperature is less than a predetermined antifreeze threshold temperature, the control device
obtaining an opening command value corresponding to the detected cold water temperature from a temperature-opening map in which the cold water temperature and the opening of the control valve are associated;
Obtaining a target flow rate corresponding to the detected cold water temperature from a temperature-flow rate map in which the cold water temperature and the cold water flow rate are associated,
Obtaining a differential flow rate by subtracting the measured flow rate of the return water pipe after setting the opening of the control valve to the opening command value from the target flow rate,
When the differential flow rate is a positive value, the opening command value is reset to increase, while when the differential flow rate is a value of zero or less, the opening command value is maintained.
Antifreeze system for air conditioners. a chilled water coil supplied with chilled water from a water pipe by a pump and heat exchanged with the air passing through the chilled water coil;
A control valve provided in a return water pipe to which cold water returned from the cold water coil is sent and for adjusting the flow rate of the returned cold water;
a water temperature sensor and a flow rate sensor provided in the return water pipe;
A control device for an air conditioner that is provided in an air conditioner comprising:
When the detected chilled water temperature is less than a predetermined freezing prevention threshold temperature, an opening command value corresponding to the detected chilled water temperature is determined from a temperature-opening map in which the chilled water temperature and the opening of the control valve are associated. a temperature-based opening calculation unit to obtain;
a temperature-based flow rate calculation unit that obtains a target flow rate corresponding to the detected cold water temperature from a temperature-flow rate map in which the cold water temperature and the cold water flow rate are associated;
A differential flow rate is obtained by subtracting the measured flow rate of the return water pipe after setting the opening of the control valve to the opening command value from the target flow rate, and when the differential flow rate is a positive value, an opening adjustment unit that resets the opening command value in an increasing direction and maintains the opening command value when the differential flow rate is a value of zero or less;
A control device for an air conditioner, comprising:

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