JP3688694B2 - Air conditioning system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air conditioning system for cooling and heating a building or the like by supplying heat source water generated by a heat source device such as a refrigerator to a load side device such as an air conditioner.
[0002]
[Prior art]
An example of this type of air conditioning system is shown in FIG. As shown in the figure, this air conditioning system uses a load side system 50 in which a load side device 51 such as an air conditioner for processing an air conditioning load is installed, and heat source water of a predetermined temperature (for example, 7 ° C. cold water). A heat source side system 60 in which a heat source device 61 such as a refrigerator to be generated is installed, and a load side pipe 52 of the load side system 50 and a heat source side pipe 62 of the heat source side system 60 are connected to the forward header SH and the return. They are connected to each other via a header RH.
[0003]
The load side piping 52 of the load side system 50 is provided with a two-way valve 53 that adjusts the supply amount of the heat source water to the load side device 51 according to the air conditioning load, and the heat source side piping of the heat source side system 60. 62 is provided with a primary pump 63 for sending heat source water from the return header RH to the outgoing header SH via the heat source device 61.
[0004]
Further, the load side system 50 includes a secondary pump 55 that sends the heat source water introduced into the forward header SH by the heat source side system 60 to the load side device 51 via the load side forward header 54. Even when the water supply amount to the load-side device 51 is changed by opening and closing the two-way valve 53 according to the load, the water supply differential pressure, that is, the differential pressure between the load-side forward header 54 and the forward header SH is reduced. The secondary pump 55 can change the rotational speed of the secondary pump 55 by an inverter so as to be maintained at the set differential pressure.
[0005]
On the other hand, since the primary pump 63 of the heat source side system 60 sends the heat source water of a predetermined flow rate to the forward header SH, when the amount of water supplied to the load side device 51 in the load side system 50 decreases, the heat source side system 60. The return header SH and the return header RH are connected by the bypass pipe BP so that the excess heat source water introduced to the return header SH is directly returned to the return header RH.
[0006]
Further, as described above, in such an air conditioning system in which the rotation speed of the secondary pump 55 is controlled so that the differential pressure between the load side forward header 54 and the forward header SH becomes the set differential pressure, Even if the two-way valve 53 of the load side system 50 is fully closed, the secondary pump 55 continues to rotate in order to ensure the differential pressure between the load side forward header 54 and the forward header SH. When the two-way valve 53 of the load side system 50 is fully closed, the water supply amount becomes 0 and the secondary pump 55 performs a shut-off operation. As a result, the heat source water in the secondary pump 55 boils. There is a problem such as.
[0007]
Therefore, in such an air conditioning system, as shown in the figure, the bypass pipe 56 for returning the heat source water introduced into the load-side outgoing header 54 by the secondary pump 55 to the outgoing header SH is provided with the load-side outgoing header 54. And a bypass valve 57 that adjusts the bypass flow rate of the heat source water returned from the load-side forward header 54 to the forward header SH, and is connected to the forward header SH. Even if the inverter that controls the rotational speed of 55 reduces the rotational speed of the secondary pump 55 to a preset minimum rotational speed, the differential pressure between the load-side forward header 54 and the forward header SH Is not maintained at the set differential pressure, the bypass valve 57 is opened, and the heat source water introduced into the load-side outgoing header 54 by the secondary pump 55 is sent to the outgoing header S. By returning to, by maintaining the set differential pressure of the pressure differential between the header SH outward and the load side forward header 54, so as to prevent the discharge operation of secondary pump 55.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-241735
[Problems to be solved by the invention]
By the way, when the rotational speed of the secondary pump 55 is reduced, the pump characteristic (flow rate-lift characteristic) becomes flat accordingly, that is, the change in the lift with respect to the change in the flow rate becomes small. The valve is opened so that the change in the differential pressure between the load-side forward header 54 and the forward header SH with respect to the change in the water supply amount becomes small and the differential pressure between the load-side forward header 54 and the forward header SH becomes the set differential pressure. There is a problem that the controllability of the bypass valve 57 which is adjusting the degree is lowered.
[0010]
In particular, in pursuit of an energy saving effect, when the minimum rotational speed of the secondary pump 55 is set low, the bypass valve 57 is fully closed by a very small differential pressure fluctuation between the load side forward header 54 and the forward header SH. Therefore, there is a possibility that the bypass valve 57 does not open when necessary, and there is a problem that the shut-off operation of the secondary pump 55 cannot be reliably prevented.
[0011]
On the other hand, if the minimum rotational speed of the secondary pump 55 is set higher in order to reliably prevent the shutoff operation of the secondary pump 55, the bypass flow rate becomes larger than necessary, which is contrary to energy saving.
[0012]
Further, in order to set the minimum rotation speed of the secondary pump 55, that is, the minimum frequency of the motor output to the inverter, the load-side forward header 54 and the forward header are stopped while water supply to the load-side device 51 is stopped. The rotational speed of the secondary pump 55 is reduced by the inverter so that the differential pressure with the SH is slightly higher (for example, about 2 mAq) than the set differential pressure, and the motor frequency at that time is set to the minimum frequency. It is necessary to perform troublesome work such as setting.
[0013]
Accordingly, an object of the present invention is to provide an air conditioning system capable of reliably preventing the closing operation of the secondary pump while maximizing the energy saving effect and easily performing the adjustment work during the trial operation. Is to provide.
[0014]
[Means for solving the problems and effects thereof]
In order to solve the above problems, the present invention provides a load-side system including a load-side device that processes an air-conditioning load, and a heat-source-side system that supplies heat-source water to the load-side device, and includes a forward header and a return header. Are connected to each other, and the load side system supplies the heat source water introduced to the forward header by the heat source side system to the load side device via the load side forward header. A secondary pump to be sent out, a bypass pipe connecting the load side forward header and the forward header or the return header, and from the load side forward header to the forward header or the return header via the bypass pipe A bypass valve installed in the bypass pipe for adjusting a bypass flow rate of the heat source water to be returned, and a load side flow of the heat source water sent from the load side forward header to the load side device The secondary pump is configured such that its rotational speed is adjusted so that the water supply differential pressure to the load side system becomes a set differential pressure. When the detected load-side flow rate falls below the pump minimum flow rate set for the secondary pump, the bypass valve opens, and the sum of the load-side flow rate and the bypass flow rate is the pump minimum flow rate. Thus, the opening degree of the bypass valve is adjusted so as to provide an air conditioning system. Here, “the opening degree of the bypass valve is adjusted so that the sum of the load-side flow rate and the bypass flow rate becomes the minimum pump flow rate” means the sum of the load-side flow rate and the bypass flow rate Needs to substantially match the pump minimum flow rate, and the sum of the load side flow rate and the bypass flow rate does not need to completely match the pump minimum flow rate. In addition, the “bypass pipe connecting the load-side forward header and the forward header or the return header” here does not necessarily have to be directly connected to various headers, but via the load-side piping. The case where it is connected to various headers is also included.
[0015]
As described above, in this air conditioning system, in order to secure the minimum pump flow rate of the secondary pump, the open / close control of the bypass valve is directly performed based on the load side flow rate. Due to the influence of pump characteristics, the controllability of the bypass valve may be reduced, as in the conventional air conditioning system that controls the opening and closing of the bypass valve based on the differential water supply pressure that changes secondaryly. Absent.
[0016]
Therefore, even if the amount of water supplied to the load-side device is extremely reduced, that is, even if the rotational speed of the secondary pump is extremely reduced, the bypass valve is surely opened, and the minimum pump flow rate of the secondary pump. As a result, it is possible to reliably prevent the secondary pump from shutting down and to minimize the pump minimum flow rate, so that the energy saving effect can be maximized. .
[0017]
Moreover, in this air conditioning system, the rotational speed control of the secondary pump is not limited as in the conventional air conditioning system that controls the opening and closing of the bypass valve based on the water supply differential pressure of the load side system. Therefore, there is no need to perform troublesome work for obtaining the minimum rotation speed (minimum frequency of the motor) of the secondary pump, and there is an advantage that the trial run adjustment can be performed efficiently.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments will be described with reference to the drawings. As shown in FIG. 1, the air conditioning system 1 includes a heat source side system 10 including heat source devices 11A and 11B such as a refrigerator that generates heat source water at a predetermined temperature (for example, 7 ° C.), and each heat source device 11A. The load-side system 20 including the load-side devices 21A and 21B such as an air conditioner that processes the air-conditioning load using the heat source water having a predetermined temperature generated by the 11B is mutually connected via the forward header 31 and the return header 32. The forward header 31 and the return header 32 are connected to each other via a bypass pipe 33.
[0019]
The heat source side system 10 is installed on the upstream side of the heat source equipment 11A, 11B in the heat source side pipes 12A, 12B, and the heat source side pipes 12A, 12B connecting the heat source equipment 11A, 11B to the forward header 31 and the return header 32. Secondary pumps 13A and 13B are provided, and heat source water at a predetermined temperature generated by the heat source devices 11A and 11B is sent to the forward header 31 by the primary pumps 13A and 13B.
[0020]
The load-side system 20 includes a load-side forward header connected to the forward header 31 via load-side forward piping 24a, 24b where the secondary pumps 26a, 26b are installed and a load-side bypass piping 24c where the bypass valve 27 is installed. 22 and a load-side return header 23 connected to the return header 32 via a load-side return pipe 24d provided with a flow meter 43, and the load-side devices 21A and 21B are connected to the load-side end pipe 25A, It is connected to the load side forward header 22 and the load side return header 23 via 25B.
[0021]
Two-way valves 28A and 28B are installed on the upstream side of the load-side devices 21A and 21B in the load-side end pipes 25A and 25B, respectively, and the two-way valves 28A and 28B are opened and closed according to the air conditioning load. The supply amount of the heat source water to the load side devices 21A and 21B is adjusted.
[0022]
Further, the secondary pumps 26a and 26b can adjust the water supply amount by changing the rotation speed by an inverter, and the two-way valves 28A and 28B open and close according to the air conditioning load. Thus, even when the amount of water supplied to the load side devices 21A and 21B changes, the water supply differential pressure to the load side system 20, that is, the load side forward header 22 and the forward header 31 detected by the differential pressure transmitter 42 are detected. The programmable logic controller 41 controls the rotational speeds of the secondary pumps 26a and 26b so that the differential pressure between them becomes the set differential pressure.
[0023]
However, when the two-way valves 28A, 28B of the load side system 20 are fully closed or close to full close, the secondary pumps 26a, 26b perform a deadline operation or an operation close thereto, so the load side devices 21A, When the amount of water supplied to 21B decreases, the bypass valve 27 is opened, and the heat source water introduced into the load-side outgoing header 22 by the secondary pumps 26a, 26b passes through the load-side bypass piping 24c. It is returned to the header 31.
[0024]
Specifically, the minimum pump flow rate that must be secured for the secondary pumps 26a and 26b is registered in advance in the programmable logic controller 41, and is detected by the flow meter 43 as shown in FIG. When the load side flow rate falls below the minimum pump flow rate, the bypass valve 27 starts to open, and when the load side flow rate becomes zero, the programmable logic controller 41 is fully opened. However, the opening / closing operation of the bypass valve 27 is proportionally controlled. When the differential pressure between the load-side forward header 22 and the forward header 31 is maintained at the set differential pressure, when the bypass valve 27 is fully opened, the heat source water with the minimum pump flow rate is transferred to the load-side forward header 22. Therefore, the pipe resistance of the load side bypass pipe 24c is adjusted so as to be returned to the forward header 31 via the load side bypass pipe 24c.
[0025]
Furthermore, the programmable logic controller 41 is based on the load side flow rate detected by the flow meter 43 and the water supply temperature difference in the load side system 20, that is, the temperature difference between the forward header 31 and the return header 32. The air conditioning load is calculated, and the programmable logic controller 41 performs start / stop control of each of the heat source devices 11A and 11B and the primary pumps 13A and 13B according to the calculated air conditioning load. ing.
[0026]
In this air conditioning system 1, the load side system 20 adjusts the amount of water supplied according to the air conditioning load, and the heat source side system 10 controls the number of the heat source devices 11A and 11B and the primary pumps 13A and 13B. However, since the primary pumps 13A and 13B are constant flow rate pumps, when the amount of water supplied from the heat source side system 10 exceeds the amount of water supplied from the load side system 20, the surplus amount passes through the bypass pipe 33 and goes to the forward header 31. Is returned to the return header 32.
[0027]
As described above, in this air conditioning system 1, in order to secure the minimum pump flow rate of the secondary pumps 26a and 26b, the opening and closing control of the bypass valve 27 is performed based on the load-side flow rate detected by the flow meter 43. As with the secondary pump speed control, the bypass valve opening / closing control is performed based on the water supply differential pressure (header differential pressure) that changes secondary with the load-side flow rate change. Unlike conventional air conditioning systems that are used, the controllability of the bypass valve does not deteriorate due to the influence of the pump characteristics.
[0028]
Therefore, when the amount of water supplied to the load side devices 21A and 21B falls below the pump minimum flow rate set for the secondary pumps 26a and 26b, the bypass valve 27 is reliably opened to ensure the pump minimum flow rate. In addition, since the minimum pump flow rate can be minimized, the shutoff operation of the secondary pumps 26a and 26b can be reliably prevented while maximizing the energy saving effect.
[0029]
Further, in this air conditioning system 1, a limitation is imposed on the rotational speed control of the secondary pump as in the conventional air conditioning system that controls the opening and closing of the bypass valve based on the water supply differential pressure of the load side system. Therefore, it is not necessary to perform a troublesome operation for obtaining the minimum rotation speed (minimum motor frequency) of the secondary pump, and the water supply differential pressure that is a reference for the rotation speed control of the secondary pumps 26a and 26b is reduced. Even if the setting is changed, there is no need for readjustment, so the trial run adjustment can be performed efficiently.
[0030]
In the above-described embodiment, the air conditioning system 1 that controls the number of the two heat source devices 11A and 11B and the constant flow primary pumps 13A and 13B has been described. However, the present invention is not limited to this. It goes without saying that the present invention can also be applied to an air conditioning system that controls the number of heat source devices and primary pumps as described above, and an air conditioning system in which the heat source side system includes one heat source device and a primary pump.
[0031]
In the above-described embodiment, the air conditioning system 1 including the two secondary pumps 26a and 26b has been described. However, the present invention is not limited to this, and one or three or more secondary pumps are included. Needless to say, the present invention can also be applied to an air conditioning system.
[0032]
In the above-described embodiment, the two secondary pumps 26a and 26b are operated simultaneously. However, the present invention is not limited to this, and the number control of the two secondary pumps 26a and 26b is performed. It is also possible to do this.
[0033]
In the above-described embodiment, the load-side bypass pipe 24c is connected to the load-side forward header 22 and the forward header 31. However, the present invention is not limited to this, and is connected to the load-side forward header 22, for example. The load side bypass pipe can be connected to the return header 32 instead of the forward header 31 or can be connected to the downstream side of the flow meter 43 in the load side return pipe 24d.
[0034]
In the above-described embodiment, the bypass pipe 33 is directly connected to the forward header 31 and the return header 32. However, the present invention is not limited to this. For example, the bypass pipe connected to the forward header 31 is returned to the return pipe 31. Instead of the header 32, it is also possible to connect to the downstream side of the flow meter 43 in the load side return pipe 24d.
[0035]
Moreover, in embodiment mentioned above, although the common bypass pipe 33 is provided with respect to each heat source apparatus 11A, 11B, it is not limited to this, For example, each heat source apparatus 11A, 11B is bypassed separately. Thus, it is also possible to provide a bypass pipe in each of the heat source side pipes 12A and 12B.
[0036]
In the above-described embodiment, the air source system 10 includes the air conditioning system 1 including the constant flow type heat source devices 11A and 11B and the constant flow primary pumps 13A and 13B. However, the present invention is not limited thereto. Instead, the present invention can be applied to an air conditioning system in which the heat source side system includes a variable flow type heat source device or a variable flow primary pump.
[0037]
Moreover, although embodiment mentioned above demonstrated the air-conditioning system 1 by which the heat source water of the predetermined temperature produced | generated by heat-source equipment 11A, 11B was directly sent to the load side system | strain 20, it is not limited to this, A heat source It goes without saying that the present invention can also be applied to an air conditioning system in which the amount of heat held in a heat source water at a predetermined temperature once stored in a heat storage tank by an apparatus is supplied to a load side system via a heat exchanger. Nor.
[0038]
In the above-described embodiment, the programmable logic controller 41 performs the rotational speed control of the secondary pumps 26a and 26b and the open / close control of the bypass valve 27. However, the present invention is not limited to this. For example, It is also possible to use various control means such as a differential pressure regulator in combination.
[0039]
Moreover, although embodiment mentioned above demonstrated the air conditioning system 1 which employ | adopted the normal header differential pressure control which hold | maintains the water supply differential pressure of the load side system | strain 20 to a fixed setting differential pressure, it is not limited to this. This is also true for air conditioning systems that employ terminal differential pressure control that maintains the differential pressure across the load side device at a fixed set differential pressure, or estimated terminal differential pressure control that changes the set differential pressure according to the air conditioning load. The invention can be applied. When performing the estimated terminal differential pressure control, the water supply differential pressure (set differential pressure) is usually reduced when the amount of water supplied to the load-side device decreases, compared to when performing normal differential pressure control. Since the rotational speed of the secondary pump is greatly reduced and the pump characteristics tend to be flat, the air conditioning system of the present invention is particularly effective when adopting the estimated terminal differential pressure control.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of an air conditioning system according to the present invention.
FIG. 2 is a diagram showing an opening / closing operation of a bypass valve in the air conditioning system same as above.
FIG. 3 is a schematic configuration diagram showing a conventional air conditioning system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Air conditioning system 10 Heat source side system | strain 11A, 11B Heat source apparatus 12A, 12B Heat source side piping 13A, 13B Primary pump 20 Load side system | strain 21A, 21B Load side apparatus 22 Load side return header 23 Load side return header 24a, 24b Load side return Piping 24c Load-side bypass piping 24d Load-side return piping 25A, 25B Load-side end piping 26a, 26b Secondary pump 27 Bypass valve 28A, 28B Two-way valve 31 Forward header 32 Return header 33 Bypass pipe 41 Programmable logic controller 42 Difference Pressure transmitter 43 Flow meter

Claims (1)

An air conditioning system in which a load side system including a load side device that processes an air conditioning load and a heat source side system that supplies heat source water to the load side device are connected to each other via a forward header and a return header. There,
The load side system is:
A secondary pump for sending the heat source water introduced into the forward header by the heat source side system to the load side device via the load side forward header;
A bypass pipe connecting the load side forward header and the forward header or the return header;
A bypass valve installed in the bypass pipe for adjusting a bypass flow rate of heat source water returned to the forward header or the return header from the load side forward header through the bypass pipe;
A flow meter for detecting a load-side flow rate of heat source water sent from the load-side forward header to the load-side device;
The rotation speed of the secondary pump is adjusted so that the water supply differential pressure to the load side system becomes a set differential pressure,
When the load side flow rate detected by the flow meter falls below the pump minimum flow rate set for the secondary pump, the bypass valve is opened, and the sum of the load side flow rate and the bypass flow rate is The air conditioning system is characterized in that the opening degree of the bypass valve is adjusted so that the pump has a minimum flow rate.

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