JP2018017458A - Freezing prevention system for air conditioner and control device for air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a freezing prevention system for an air conditioner capable of preventing cold water freezing more surely than a conventional one, and a control device for an air conditioner.SOLUTION: A control device 12 calculates a first opening A1 corresponding to a cold water temperature acquired from a water temperature sensor 32 from a temperature-opening map obtained by associating the cold water temperature with the opening of the control valve 30 when the cold water temperature is less than a prescribed freezing prevention threshold temperature. Further, the control device calculates a first cold water flow amount Q1 corresponding to the cold water temperature acquired from the water temperature sensor 32 from the temperature-flow rate map obtained by associating the cold water temperature with a cold water flow rate. Then, the control device calculates a second opening A2 corresponding to the first cold water flow rate Q1 from a flow rate-opening map obtained by associating the cold water flow rate with the opening of the control valve. The control device 12 sets a larger opening between the first and second openings A1, A2 to an opening command value A* of the control valve 30.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a freeze prevention system for an air conditioner and a control device for the air conditioner.

  For example, an air conditioner (air conditioner) is provided in a central air conditioning facility. The 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 air-conditioned such as a tenant or office space.

  When the outside air is cooled, the air conditioner is provided with a cold water coil to which cold water is supplied. In addition, when heating 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, each device is arranged in the order of outside air introduction port → cold water coil → hot water coil → air supply fan. The outside air introduced into the air conditioner (introduced outside air) is cooled or heated by passing through each coil.

  For example, when it is not necessary to heat and cool the introduced outside air exclusively during winter, the cold water supply to the cold water coil is stopped. Thereby, cold water stays in the cold water coil. When the introduced outside air passes through the cold water coil, for example, when a cold wave passes in a cold region, the cold water staying in the cold water coil may be frozen and expanded, leading to damage to the cold water coil.

  Therefore, for example, in Patent Document 1, the temperature of the cold water circulating in the cold water coil is monitored, and the flow rate of the circulating water is adjusted according to the temperature. Moreover, in patent document 2, the opening degree of the control valve of the chilled water pipe is set so that the chilled water temperature flowing through the chilled water coil becomes the freeze prevention set temperature, for example, approximately equal to the chilled water temperature at the time of being sent from the heat source equipment. It is adjusted.

Japanese Utility Model Publication No. 1-100044 JP 2009-216321 A

  By the way, when only the flow rate is used as a control parameter for preventing freezing of cold water, for example, when performing anti-freezing control based only on whether or not the cold water flow rate has reached the target flow rate, for example, the discharge pressure of a pump for supplying cold water If it is high, the flow rate may reach the target flow rate even if the opening of the control valve is small. In such a case, since the opening degree of the control valve is small, the flow of cold water in the piping is stagnated, and there is a possibility that freezing occurs at the staying location.

  Further, when only the opening degree of the control valve is used as a control parameter for preventing freezing of cold water, for example, when anti-freezing control is performed based only on whether the opening degree of the control valve has reached the target opening degree, for example, cold water If the discharge pressure of the pump that supplies the pressure is low, a sufficient flow rate cannot be obtained even if the opening of the control valve is large, and the flow of cold water may become slow and may freeze.

  In view of the above problems, an object of the present invention is to provide an anti-freezing system for an air conditioner and a control device for the air conditioner that can prevent cold water freezing more reliably than in the past.

  The present invention relates to an antifreezing system for an air conditioner. The system is provided in a chilled water coil in which chilled water is supplied from a water supply pipe and heat is exchanged with the air passing through the chilled water, and a return water pipe to which chilled water returned from the chilled water coil is sent. And a control device that generates an opening degree command of the control valve based on a cold water temperature acquired from the water temperature sensor. The control device, when the cold water temperature is less than a predetermined antifreezing threshold temperature, the cold water temperature acquired from the water temperature sensor from a temperature-opening map in which the cold water temperature and the opening of the control valve are associated A first opening corresponding to is obtained. Moreover, the said control apparatus calculates | requires the 1st cold water flow rate corresponding to the cold water temperature acquired from the said water temperature sensor from the temperature-flow rate map with which the cold water temperature and the cold water flow rate were linked | related. Moreover, the said control apparatus calculates | requires the 2nd opening degree corresponding to a said 1st cold water flow rate from the flow volume-opening degree map with which the cold water flow rate and the opening degree of the said control valve were linked | related. Moreover, the said control apparatus sets the larger opening degree among the said 1st and 2nd opening degree to the opening degree command of the said control valve.

  The present invention also relates to a control device for an air conditioner. The air conditioner is provided in a cold water coil in which cold water is supplied from a water supply pipe and heat exchange is performed with air passing through the air conditioner, and a return water pipe in which the return cold water from the cold water coil is sent. A control valve for adjusting the flow rate, and a water temperature sensor provided in the return water pipe. A control apparatus produces | generates the opening degree command of the said control valve based on the cold water temperature acquired from the said water temperature sensor. The control device, when the cold water temperature is less than a predetermined antifreezing threshold temperature, the cold water temperature acquired from the water temperature sensor from a temperature-opening map in which the cold water temperature and the opening of the control valve are associated When the cold water temperature acquired by the water temperature sensor is less than a predetermined freezing prevention threshold temperature, the cold water temperature and the cold water flow rate are associated with each other. A temperature-based flow rate calculation unit that obtains a first chilled water flow rate corresponding to the chilled water temperature acquired from the water temperature sensor from a temperature-flow rate map, and a flow rate-opening amount associated with the chilled water flow rate and the opening degree of the control valve. From the map, a flow rate base opening degree calculation unit for obtaining a second opening degree corresponding to the first cold water flow rate, and a larger opening degree among the first opening degree and the second opening degree is set to open the control valve. Opening set in degree command It includes a tough, a.

  According to the present invention, since both the flow rate and the opening degree of the control valve are used as the control parameters for preventing freezing of cold water, it becomes possible to prevent freezing of cold water more reliably as compared with the case where either one is used. .

The freeze prevention system of the air conditioner concerning this embodiment is included. It is a figure which illustrates the composition of an air-conditioning system. It is a figure which illustrates the functional block of a controller. It is a figure which illustrates a temperature-opening degree map (TA map). It is a figure which illustrates a temperature-flow rate map (TQ map). It is a figure which illustrates a flow-opening degree map (QA map). It is a figure which illustrates the opening degree setting flow of a control valve based on this embodiment.

  FIG. 1 illustrates a freeze prevention system for an air conditioner according to the present embodiment. This system includes an air conditioner 10 and a controller 12 (control device). The signal line is indicated by a one-dot chain line. In addition, illustrations are omitted as appropriate for devices such as a filter, a micro differential pressure switch that detects filter clogging, and a humidification mechanism that are not related to freezing prevention of the cold water coil 14.

  The air conditioner 10 introduces outside air to generate conditioned air, and supplies the conditioned air to an air-conditioning target space such as a tenant or office space. The air conditioner 10 includes a damper 16, a damper motor 18, 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 adjusting damper (VD) that adjusts the amount of outside air (OA) introduced by adjusting the opening of the outside air duct 24. The damper 16 is composed of a plate member, for example. The damper motor 18 adjusts the opening degree of the outside air duct 24 by driving the damper 16. The damper motor 18 is composed of, for example, a pulse motor.

  In the cold water coil 14, heat exchange is performed with air (outside air) introduced from the outside air duct 24 and passing through the outside. In the embodiment shown in FIG. 1, the air exchanged with the cold water coil 14 includes a part of the return air returned from the air-conditioning target space in addition to the outside air. The cold water coil 14 is connected to a water supply pipe 26 and receives cold water from a heat source facility (not shown). The cold water that has passed through the cold water coil 14 is returned to the heat source facility from the return water pipe 28.

  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. It is done. As will be described later, the controller 12 adjusts the opening degree 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 in the cold water coil 14 from freezing.

  As with the cold water coil 14, the hot water coil 20 exchanges heat with air (outside air) introduced from the outside air duct 24 and passing through itself and a part of the return air. The hot water coil 20 is connected to a water supply pipe 36 and receives supply of hot water from a heat source facility (not shown). The hot water that has passed through the hot water coil 20 is returned to the heat source facility from 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 warm water flowing through the return water pipe 38.

  Only one of the cold water coil 14 and the hot water coil 20 is basically used. For example, when the outside air is cooled, cold water is supplied to the cold water coil 14 while supply of hot water to the hot water coil 20 is stopped (control valve 40 is closed). Further, when heating (heating) the outside air, hot water is supplied to the hot water coil 20 while supply of cold water 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 executed 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 to each air conditioning target space via the air supply duct 42.

  The controller 12 is composed of, for example, a PLC (programmable logic computer). The controller 12 may be compliant with BACnet (Building Automation and Control Network), which is a communication protocol, in order to be compatible with, for example, BA (Building Automation). In accordance with 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. The controller 12 can control various devices connected to the internal bus.

  The controller 12 includes a CPU 44, a memory 46, a user interface 48 (UI), and an external interface 50. The user interface 48 is used when inputting user information, and is also used when displaying information.

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

  The memory 46 includes nonvolatile and volatile memories such as a ROM, a RAM, and a hard disk drive (HDD). The memory 46 includes a program for configuring the CPU 44 into functional blocks described later, a program for executing an opening setting flow of the control valve 30 described later, a temperature-opening map (TA map) described later, and temperature. A flow rate map (TQ map), a flow rate-opening map (QA map), and the like are stored.

  The CPU 44 executes the opening setting flow stored in the memory 46 and sets the opening of the control valve 30. The set opening degree is sent to the control valve 30 via the external interface 50. Further, an opening degree command is sent from the CPU 44 to the control valve 40 provided in the warm water return water pipe 38 via the external interface 50. Further, an opening degree command for the outside air duct 24 is sent from the CPU 44 to the damper motor 18 via the external interface 50.

  FIG. 2 illustrates a functional block diagram of the controller 12. The controller 12 includes a temperature base opening calculation unit 54, a temperature base flow rate calculation unit 56, a flow rate base opening calculation unit 58, and an opening setting unit 60.

  The temperature base opening calculation unit 54 has a temperature-opening map (TA map) illustrated in FIG. In the temperature-opening map, the horizontal axis represents the cold water temperature, the vertical axis represents the target opening of the control valve 30, and the cold water temperature and the opening of the control valve 30 are associated with each other. The temperature-opening degree map is created in order to prevent freezing of the cold water in the cold water coil 14, and for example, from the past data, the opening degree of the control valve 30 that can avoid freezing is plotted for each return cold water temperature. Yes. The temperature base opening calculation unit 54 plots the return chilled water temperature T1 (Tm = T1) acquired from the water temperature sensor 32 in a temperature-opening map, and sets the target opening A1 (first first) of the control valve corresponding to the temperature T1. Opening degree).

  The temperature-based flow rate calculation unit 56 has 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, the vertical axis represents the target flow rate of the returned chilled water passing through the control valve 30, and the chilled water temperature and the chilled water flow rate are associated with each other. The temperature-flow rate map is created in order to prevent cold water freezing in the cold water coil 14, and for example, from the past data, the flow rate of the returning cold water that can avoid freezing is plotted for each temperature of the returning cold water. The temperature-based flow rate calculation unit 56 plots the return chilled water temperature T1 acquired from the water temperature sensor 32 in a temperature-flow rate map, and obtains the return chilled water flow rate Q1 (first chilled water flow rate) corresponding to the temperature T1.

  The flow rate base opening degree calculation unit 58 has a flow rate-opening degree map (QA map) illustrated in FIG. In the flow rate-opening degree map, the horizontal axis represents the flow rate of cold water, the vertical axis represents the target opening degree of the control valve 30, and the cold water flow rate and the opening degree of the control valve 30 are associated with each other. In the flow rate-opening degree map, for example, the opening degree of the control valve 30 corresponding to an arbitrary flow rate is plotted from past data.

  For example, the discharge pressure of cold water to the water supply pipe 26 varies depending on the operation status of the heat source facility and the operation status of other air conditioners 10 sharing the heat source facility, and the flow rate and the opening degree are changed accordingly. Correspondence also varies. In the present embodiment, for example, from the past results, the most frequent opening is extracted as the opening corresponding to the predetermined flow rate, and this is plotted in a flow rate-opening map (QA map). The flow rate base opening degree calculation unit 58 plots the target flow rate Q1 obtained by the temperature base flow rate calculation unit 56 on the flow rate-opening degree map, and the target opening degree A2 (second opening degree) of the control valve 30 corresponding to the flow rate Q1. )

  In the opening setting unit 60, the opening A1 (first opening) obtained by the temperature base opening calculation unit 54 and the opening A2 obtained by the flow rate base opening calculation unit 58 via the temperature base flow rate calculation unit 56. (Second opening) is compared, and a higher value (larger opening) is set as an opening setting value A * (opening command) of the control valve 30.

  Thus, only the opening degree is set by setting the opening degree so as to satisfy both of the opening degree A1 obtained from the relationship between the temperature and the opening degree and the opening degree A2 in consideration of the flow rate. Compared with the opening setting based on the above and the opening setting based only on the flow rate, it is possible to prevent the cold water freezing in the cold water coil 14 more reliably.

<Anti-freezing flow>
FIG. 6 illustrates an opening setting flow by the controller 12. 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 return chilled water temperature Tm is lower than a predetermined threshold temperature (lower than the freeze prevention threshold temperature) (S12). The threshold temperature is a temperature at which cold water does not freeze in the cold water coil 14 even when the control valve 30 is fully closed, for example, −10 ° C.

  When the return chilled water temperature Tm is equal to or higher than the threshold temperature, the process proceeds to the end (Return) of the flow and returns to the start point (Start) of the flow again. When the return chilled water temperature Tm is less than the threshold temperature (less than the freeze prevention threshold temperature), the controller 12 acquires the flow rate Qm of the return chilled water flowing through the return water pipe 28 (S14). Subsequently, the controller 12 determines whether or not the return chilled water flow rate Qm is less than a predetermined threshold flow rate (S16). The threshold flow rate is a flow rate at which freezing does not occur even at the lowest temperature set in the temperature-flow rate map (FIG. 4), for example. When the return chilled water flow rate Qm is equal to or higher than the threshold flow rate, the controller 12 proceeds to the end of this flow (Return) and returns to the starting point of the flow again.

  On the other hand, when the return chilled water flow rate Qm is less than the threshold flow rate, the controller 12 sets the opening degree of the control valve 30 to prevent freezing. First, the temperature base opening calculation part 54 calculates | requires target opening A1 (1st opening) based on return cold water temperature Tm and TA map (FIG. 3) (S18). In parallel with this, the temperature-based flow rate calculation unit 56 obtains the target flow rate Q1 (first flow rate) based on the return chilled water temperature Tm and the TQ map (FIG. 4) (S20). Further, the flow rate base opening calculation unit 58 obtains the target opening A2 (second opening) based on the target flow Q1 and the QA map (FIG. 5) (S22). The opening setting unit 60 sets a larger opening of the target opening A1, A2 to the opening command value A * of the control valve 30 (S24).

  In the above-described embodiment, the opening degree of the control valve 30 is adjusted for the purpose of preventing freezing of the cold water in the cold water coil 14, but this is not a limitation. 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 also in the warm water return water pipe 38, and the opening setting flow in FIG. 6 may be executed for the control valve 40 of the return water pipe 38.

  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 rate sensor, 42 Air supply duct, 52 Air supply temperature sensor, 54 Temperature base opening calculation unit, 56 Temperature base flow rate calculation unit, 58 Flow rate base opening calculation unit, 60 Opening setting unit

Claims (2)

A cold water coil in which cold water is supplied from a water supply pipe and heat exchange is performed with air passing through the pipe;
A control valve that is provided in a return water pipe through which the return cold water from the cold water coil is sent, and adjusts the flow rate of the return cold water;
A water temperature sensor provided in the return water pipe;
Based on the cold water temperature acquired from the water temperature sensor, a control device that generates an opening degree command of the control valve;
An anti-freezing system for an air conditioner comprising:
The control device, when the cold water temperature is less than a predetermined freezing prevention threshold temperature,
From a temperature-opening map in which the cold water temperature and the opening degree of the control valve are associated, a first opening degree corresponding to the cold water temperature acquired from the water temperature sensor is obtained,
From the temperature-flow rate map in which the chilled water temperature and the chilled water flow rate are associated, a first chilled water flow rate corresponding to the chilled water temperature acquired from the water temperature sensor is obtained,
A second opening degree corresponding to the first cold water flow rate is obtained from a flow rate-opening degree map in which the cold water flow rate and the opening degree of the control valve are associated with each other.
Of the first and second openings, a larger opening is set in the opening instruction of the control valve.
An antifreezing system for an air conditioner characterized by the above. A cold water coil in which cold water is supplied from a water supply pipe and heat exchange is performed with air passing through the pipe;
A control valve that is provided in a return water pipe through which the return cold water from the cold water coil is sent, and adjusts the flow rate of the return cold water;
A water temperature sensor provided in the return water pipe;
A control device for an air conditioner that generates an opening degree command of the control valve based on a cold water temperature acquired from the water temperature sensor,
When the cold water temperature is lower than a predetermined freeze prevention threshold temperature, the first corresponding to the cold water temperature acquired from the water temperature sensor from the temperature-opening map in which the cold water temperature and the opening degree of the control valve are associated with each other. A temperature-based opening calculation unit for calculating the opening of
When the chilled water temperature acquired by the water temperature sensor is less than a predetermined freezing prevention threshold temperature, the first corresponding to the chilled water temperature acquired from the water temperature sensor from the temperature-flow rate map in which the chilled water temperature and the chilled water flow rate are associated with each other. A temperature-based flow rate calculation unit for obtaining the cold water flow rate of
A flow rate-based opening degree calculation unit for obtaining a second opening degree corresponding to the first cold water flow rate from a flow rate-opening degree map in which the cold water flow rate and the opening degree of the control valve are associated;
An opening setting unit for setting a larger opening of the first and second opening to the opening command of the control valve;
A control device for an air conditioner, comprising:

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