JP2005127586A - Primary pump type heat source variable flow rate control system and primary pump minimum flow rate securing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a minimum flow rate of the heat source water passing through a heat source machine without using a flowmeter. <P>SOLUTION: A bypass valve is fully opened and simultaneously a rotational frequency of a primary pump is maximized (step 203), when the deviation (ΔPpv-ΔPsp) from a set differential pressure ΔPs of a differential pressure between headers ΔPpv exceeds an allowable width ΔPw. Then the differential pressure constant control based on the rotational frequency of the primary pump is recovered (step 205), when a specific time (for example, 5 minutes) has passed (YES in step 204). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a primary pump type heat source variable flow rate control system for controlling the rotation speed of a primary pump so that the differential pressure of heat source water between a forward header and a return header is constant, and a fail-safe method in the system. Is.

  FIG. 4 shows an instrumentation diagram of a conventional primary pump type heat source variable flow rate control system (see, for example, Patent Document 1). In the figure, 1-1 to 1-N are heat source units that generate heat source water, 2-1 to 2-N are primary pumps that convey the heat source water generated by the heat source units 1-1 to 1-N, 3 -1 to 3-N are inverters attached to the primary pumps 2-1 to 2-N, 4 is a forward header that mixes heat source water from the heat source units 1-1 to 1-N, 5 is a forward pipeline, 6 is an external load that receives supply of heat source water sent from the forward header 4 via the forward water pipeline 5 (thermal load of district cooling / heating customers, air conditioners, fan coils, etc.), and 7 is a return water pipeline. is there. The external load 6 is provided with a valve 6-1 for adjusting the flow rate of supplied heat source water.

  Reference numeral 8 denotes a return header in which heat source water exchanged by the external load 6 is returned and the heat source water sent via the return water pipe 7 is returned. Reference numeral 9 denotes a bypass pipe for connecting the forward header 4 and the return header 8. Reference numeral 10 denotes a bypass pipe. 9 is a bypass valve, 11 is a differential pressure gauge for measuring the pressure difference ΔP of the heat source water between the forward header 4 and the return header 8 (inter-header differential pressure) ΔP, and 12 is a differential pressure gauge from the forward header 4 to the external load 6 A forward water temperature sensor that measures the temperature of the heat source water as the forward water temperature TS, 13 is a return water temperature sensor that measures the temperature of the heat source water returned to the return header 8 as the return water temperature TR, and 14 is returned to the return header 8. A flow meter that measures the flow rate of the heat source water (the flow rate of the heat source water supplied to the external load 6) as the load flow rate F, 15 is a control device, and 16-1 to 16-N are the heat source devices 1-1 to 1-N. A flow meter provided in the circulation path to the forward header 4 of the heat source water That.

  In this primary pump type heat source variable flow rate control system, the heat source water pumped by the primary pumps 2-1 to 2-N is cooled or heated by the heat source units 1-1 to 1-N and mixed in the forward header 4 Then, it is supplied to the external load 6 through the outgoing water pipeline 5. And it heat-exchanges in the external load 6, returns to the return header 8 via the return water pipe 7, is pumped again by the primary pumps 2-1 to 2-N, and circulates the above path. For example, when the heat source devices 1-1 to 1-N are refrigerators, the heat source water is cold water and circulates through the above-described path. When the heat source devices 1-1 to 1-N are heaters, the heat source water is warm water and circulates through the above-described path.

[Constant pressure control by primary pump speed]
The control device 15 monitors the inter-header differential pressure ΔP measured by the differential pressure gauge 11, and controls the rotational speeds of the primary pumps 2-1 to 2-N so that the inter-header differential pressure ΔP is constant. That is, the header differential pressure ΔPpv measured by the differential pressure gauge 11 is compared with the preset differential pressure ΔPsp, and the inverter output (0 to 0-3) is set so that ΔPpv = ΔPsp. ˜100%) to control the rotational speed of the primary pumps 2-1 to 2-N. This is called pressure constant control by the primary pump rotation speed. In the constant pressure control based on the primary pump rotation speed, a 0% bypass valve opening output is sent from the control device 15 to the bypass valve 10 to fully close the bypass valve 10.

  FIG. 5B shows changes in the inverter output and the bypass valve opening degree output when the flow rate required by the external load 6 decreases (when the opening degree of the valve 6-1 is reduced). 5A shows a change in flow rate required by the external load 6, and FIG. 5C shows a change in the inter-header differential pressure ΔPpv. As can be seen from this figure, when the flow rate required by the external load 6 decreases, the inverter output decreases due to the constant pressure control by the primary pump rotation speed.

[Control of the number of operating heat source units]
The control device 15 calculates F × (TR−TS) = Q from the incoming water temperature TS from the incoming water temperature sensor 12, the return water temperature TR from the return water temperature sensor 12, and the load flow rate F from the flow meter 14. The current load heat quantity Q is obtained, and the number of operating heat source devices 1-1 to 1-N is controlled according to the obtained current load heat quantity Q or the load flow rate F from the flow meter 14. For example, according to a predetermined operation order table, the heat source unit 1-1 of the designated rank 1 is operated until the load flow rate F reaches a predetermined value F1, and if the load flow rate F exceeds the predetermined value F1, the heat source unit In addition to 1-1, the operation of the heat source machine 1-2 of the designated rank 2 is started. In addition, if the driving | operation of the heat source machine 1-2 is started, the driving | operation of the primary pump 2-2 which is an auxiliary machine of this heat source machine 1-2 will also be started.

[Constant pressure control by bypass valve opening]
For example, when the flow rate of the heat source water required by the external load 6 decreases during operation of the two heat source devices 1-1 and 1-2, the header differential pressure ΔPpv increases, so that ΔPpv = ΔPsp. In addition, the control device 15 reduces the inverter output to the primary pump 2-2. Even if the inverter output to the primary pump 2-2 reaches the preset lower limit value, if the flow rate required by the external load 6 is still smaller, the control device 15 opens the bypass valve 10 and opens the space between the headers. The opening degree of the bypass valve 10 is controlled so as to keep the differential pressure ΔP constant (see FIG. 5: “Bypass valve opening degree output”). This is called constant pressure control based on the opening degree of the bypass valve. At this time, the inverter output to the primary pump 2-2 maintains the lower limit value as shown in FIG.

[Ensuring minimum flow rate]
In the constant pressure control based on the opening degree of the bypass valve, the inverter output to the primary pump 2 is a command value to the primary pump 2, and when this keeps the lower limit value, the discharge flow rate of the primary pump 2 is actually Whether or not is the lower limit is not certain. For example, when the actual discharge flow rate is less than the assumed flow rate, there is a possibility that problems such as freezing may occur when the heat source device 1 is a refrigerator. Therefore, conventionally, when the flow rate of the cold water passing through the heat source unit 1 is monitored by the flow rate f from the flow meter 16, and the flow rate of the cold water may fall below a preset minimum flow rate, the primary pump The output of the inverter is increased, and the discharge flow rate of the primary pump 2 is increased. In addition, when the flow rate of the cold water passing through the heat source unit 1 has decreased to the minimum flow rate, the water cutoff relay is activated by the function of the heat source unit 1 itself, and the operation of the heat source unit 1 is stopped.

JP 2002-98358 A

  However, in the conventional primary pump type heat source variable flow rate control system described above, the flow meter 16 is required to monitor the flow rate of the cold water passing through the heat source unit 1. In this case, the flow meter 16 is required for the number of the heat source units 1, and an initial cost is required. In addition, when it is provided in an existing system, there is a construction difficulty.

  The present invention has been made to solve such a problem, and the object of the present invention is to provide a primary flow rate that can ensure the minimum flow rate of heat source water passing through the heat source unit without using a flow meter. It is to provide a pump type heat source variable flow rate control system.

In order to achieve such an object, in the above-described primary pump type heat source variable flow rate control system, when the deviation from the set differential pressure of the header differential pressure exceeds the allowable range, for a predetermined time, Forcible control means is provided for fully opening the bypass valve and simultaneously maximizing the rotation speed of the primary pump.
In the primary pump type heat source variable flow rate control system, the discharge flow rate of the primary pump may greatly decrease due to a sudden rise in the differential pressure between headers. In the present invention, if the difference between the set differential pressures (ΔPpv−ΔPsp) exceeds the allowable width (ΔPw) ((ΔPpv−ΔPsp)> ΔPw), the flow rate of the heat source water is Judging that there is a risk of lowering the minimum flow rate, fully open the bypass valve and at the same time maximize the rotation speed of the primary pump and increase the discharge flow rate of the primary pump while supplying heat source water to the external load. Avoid falling below the flow rate. When the predetermined time has elapsed, the control returns to the constant differential pressure control based on the primary pump rotation speed, but the same operation is repeated each time the state of (ΔPpv−ΔPsp)> ΔPw is confirmed.

  According to the present invention, when the deviation of the differential pressure between the headers exceeds the allowable range, the bypass valve is fully opened for a predetermined time, and at the same time, the rotation speed of the primary pump is maximized. Since the discharge flow rate of the secondary pump is increased, even if the discharge flow rate of the primary pump is greatly reduced due to a sudden rise in the differential pressure between the headers, there is no possibility that the flow rate will fall below the minimum flow rate. The minimum flow rate of the heat source water that passes through can be secured.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an instrumentation diagram of a primary pump type heat source variable flow rate control system showing an embodiment of the present invention. 4, the same reference numerals as those in FIG. 4 denote the same or equivalent components as those described with reference to FIG. 4, and the description thereof will be omitted.

  In this embodiment, the circulation path from the heat source devices 1-1 to 1-N to the forward header 4 of the heat source water is required in the conventional primary pump heat source variable flow rate control system (FIG. 4). The flow meters 16-1 to 16-N are not provided. Instead, the control device 15A is provided with a minimum flow rate securing function as one of the characteristic functions. The control device 15A is realized by hardware including a processor and a storage device, and a program that realizes various functions in cooperation with the hardware.

  The minimum flow rate securing function of the control device 15A eliminates the need to install the flow meters 16-1 to 16-N in the circulation path from the heat source devices 1-1 to 1-N to the forward header 4 of the heat source water. Cost is reduced. Further, in the case of an existing system, it is only necessary to add a minimum flow rate securing function to the control device, and there is no construction difficulty.

[Constant pressure control by primary pump speed]
The control device 15A compares the inter-header differential pressure ΔPpv measured by the differential pressure gauge 11 with a preset set differential pressure ΔPsp, and inverts the inverters 3-1 to 3-N so that ΔPpv = ΔPsp. An output (0 to 100%) is sent to control the rotation speed of the primary pumps 2-1 to 2-N. In the constant pressure control using the primary pump rotation speed, the bypass valve 10 is fully closed by sending a bypass valve opening output of 0% from the control device 15A to the bypass valve 10 as in the prior art.

[Control of the number of operating heat source units]
The control device 15A determines that F × (TR−TS) = Q from the incoming water temperature TS from the incoming water temperature sensor 12, the return water temperature TR from the return water temperature sensor 12, and the load flow rate F from the flow meter 14. The current load heat quantity Q is obtained, and the number of operating heat source devices 1-1 to 1-N is controlled according to the obtained current load heat quantity Q or the load flow rate F from the flow meter 14. For example, according to a predetermined operation order table, the heat source unit 1-1 of the designated rank 1 is operated until the load flow rate F reaches a predetermined value F1, and if the load flow rate F exceeds the predetermined value F1, the heat source unit In addition to 1-1, the operation of the heat source machine 1-2 of the designated rank 2 is started. In addition, if the driving | operation of the heat source machine 1-2 is started, the driving | operation of the primary pump 2-2 which is an auxiliary machine of this heat source machine 1-2 will also be started.

[Constant pressure control by bypass valve opening]
For example, when the flow rate of the heat source water required by the external load 6 decreases during operation of the two heat source devices 1-1 and 1-2, the header differential pressure ΔPpv increases, so that ΔPpv = ΔPsp. In addition, the control device 15A reduces the inverter output to the primary pump 2-2. Even if the inverter output to the primary pump 2-2 reaches a preset lower limit value, if the flow rate required by the external load 6 is still smaller, the control device 15A opens the bypass valve 10 and opens the space between the headers. The opening degree of the bypass valve 10 is controlled so that the differential pressure ΔP is constant. At this time, the inverter output to the primary pump 2-2 maintains the state of the lower limit value.

[Ensuring minimum flow rate]

  In the primary pump type heat source variable flow rate control system, the discharge flow rate of the primary pump may greatly decrease due to a sudden rise in the differential pressure between headers. For example, immediately after the number of operating heat source units increases, the differential pressure between the headers may increase rapidly, and the discharge flow rate of the primary pump of the increased heat source unit may greatly decrease.

  In the present embodiment, for example, when the number of heat source devices 1 increases, a rapid rise in the header differential pressure ΔPpv is detected, and the deviation (ΔPpv−ΔPsp) from the set differential pressure ΔPsp has an allowable width (ΔPw). If exceeded ((ΔPpv−ΔPsp)> ΔPw), it is determined that the flow rate of the heat source water may be lower than the minimum flow rate, and the bypass valve 10 is fully opened and at the same time the rotation speed of the primary pump 2-2 is maximized, While supplying the heat source water to the external load 6, the discharge flow rate of the primary pump 2-2 is increased to avoid the lowering of the minimum flow rate. Then, after a predetermined time (for example, 5 minutes) has elapsed, the control is returned to the constant pressure differential control by the primary pump rotation speed, and the same operation is repeated every time the state of (ΔPpv−ΔPsp)> ΔPw is confirmed.

  FIG. 2 shows a flowchart of the minimum flow rate securing process executed by the control device 15A. The control device 15A periodically obtains a difference (ΔPpv−ΔPsp) between the set differential pressure ΔPsp and the inter-header differential pressure ΔPpv measured by the differential pressure gauge 11 (step 201). That is, the deviation (ΔPpv−ΔPsp) of the inter-header differential pressure ΔPpv from the set differential pressure ΔPsp is obtained. Then, the deviation (ΔPpv−ΔPsp) is compared with a predetermined allowable width ΔPw (step 202).

  For example, it is assumed that the constant pressure control is performed by the primary pump rotation speed during operation of one heat source device 1-1. When the heat source device 1-2 is activated due to an increase in the flow rate of the heat source water required by the external load 6, the header pressure difference ΔPpv increases (point t1 shown in FIG. 3A).

  Here, when the inter-header differential pressure ΔPpv suddenly increases and the deviation (ΔPpv−ΔPsp) of the inter-header differential pressure ΔPpv from the set differential pressure ΔPsp exceeds the allowable width ΔPw [(ΔPpv−ΔPsp)> ΔPw: step 202 YES, point t2 shown in FIG. 3A], the control device 15A forcibly sets the bypass valve opening output to the bypass valve 10 and the inverter output to the primary pump 2-2 to 100% (step). 203, point t2 shown in FIGS. 3B and 3C). As a result, the bypass valve 10 is fully opened, and at the same time, the rotation speed of the primary pump 2-2 is maximized, the discharge flow rate of the primary pump 2-2 increases, and there is no possibility that the flow rate falls below the minimum flow rate.

  The controller 15A forcibly sets the bypass valve opening output to the bypass valve 10 and the inverter output to the primary pump 2-2 to 100%, and then a certain time (for example, 5 minutes) elapses (step 204). YES), the control returns to the constant pressure differential control based on the primary pump speed (step 205). The controller 15A periodically repeats the check in step 202 even after returning to the differential pressure constant control by the primary pump rotation speed, and performs the same operation every time the state of (ΔPpv−ΔPsp)> ΔPw is confirmed. repeat.

  If the flow rate of the heat source water required by the external load 6 decreases and the load flow rate F falls below the first step-down threshold value having a hysteresis width with respect to the predetermined value F1 (first step-up threshold value), The operation of the heat source 1-2 and the primary pump 2-2 is stopped. The same operation is performed during operation of one heat source device 1-1. The same operation is performed during the operation of N heat sources 1-1 to 1-N.

It is an instrumentation diagram of a primary pump type heat source variable flow rate control system showing an embodiment of the present invention. It is a flowchart of the minimum flow volume ensuring process which the control apparatus in this primary pump system heat source variable flow control system performs. 7 is a time chart showing a situation where the inverter output and the bypass valve opening are forcibly set to 100% when the deviation (ΔPpv−ΔPsp) of the inter-header differential pressure ΔPpv from the set differential pressure ΔPsp exceeds the allowable width ΔPw. It is an instrumentation figure of the conventional primary pump system heat source variable flow control system. It is a time chart which shows the condition at the time of switching from the constant pressure control by primary pump rotation speed to the constant pressure control by bypass valve opening degree.

Explanation of symbols

1 (1-1 to 1-N) ... Heat source machine, 2 (2-1 to 2-N) ... Primary pump, 3 (3-1 to 3-N) ... Inverter, 4 ... Out header, 5 ... Out Water pipe, 6 ... external load, 7 ... return water pipe, 8 ... return header, 9 ... bypass pipe, 10 ... bypass valve, 11 ... differential pressure gauge, 12 ... outgoing water temperature sensor, 13 ... return water temperature sensor, 14 ... Flow meter, 15A ... Control device.

Claims (4)

A heat source machine for generating heat source water;
A primary pump for conveying heat source water generated by the heat source unit;
A forward header for receiving heat source water from the heat source machine;
An external load that receives the supply of heat source water via this forward header,
A return header to which the heat source water exchanged in the external load is returned;
A bypass conduit for communicating the forward header and the return header;
A bypass valve provided in the bypass line;
A primary pump system heat source comprising primary pump rotational speed control means for controlling the rotational speed of the primary pump so that the differential pressure of the heat source water between the forward header and the return header is a set differential pressure. In variable flow control system,
When the deviation of the differential pressure from the set differential pressure exceeds an allowable range, forcible control means for fully opening the bypass valve and simultaneously maximizing the rotation speed of the primary pump for a predetermined time is provided. A primary pump type heat source variable flow rate control system. First to Nth (N ≧ 2) heat source units for generating heat source water;
First to Nth primary pumps for conveying heat source water generated by the first to Nth heat source units;
A forward header for mixing heat source water from the first to Nth heat source units;
An external load that receives the supply of heat source water via this forward header,
A return header to which the heat source water exchanged in the external load is returned;
A bypass conduit for communicating the forward header and the return header;
A bypass valve provided in the bypass line;
A water temperature sensor that measures the temperature of the heat source water from the forward header to the external load as a forward water temperature;
A return water temperature sensor for measuring the temperature of the heat source water returned to the return header as a return water temperature;
A flow meter for measuring the flow rate of the heat source water returned to the return header as a load flow rate,
The current load calorie obtained from the water flow temperature measured by the water flow temperature sensor, the water return temperature measured by the water return temperature sensor and the load flow rate measured by the flow meter, or measured by the flow meter Number of operation control means for controlling the number of operating heat source units based on the load flow rate,
A primary pump system heat source comprising primary pump rotational speed control means for controlling the rotational speed of the primary pump so that the differential pressure of the heat source water between the forward header and the return header is a set differential pressure. In variable flow control system,
Forced control means for fully opening the bypass valve for a predetermined time and simultaneously maximizing the number of rotations of the primary pump currently controlled when a deviation of the differential pressure from the set differential pressure exceeds an allowable range; A primary pump type heat source variable flow rate control system comprising: A heat source machine for generating heat source water;
A primary pump for conveying heat source water generated by the heat source unit;
A forward header for receiving heat source water from the heat source machine;
An external load that receives the supply of heat source water via this forward header,
A return header to which the heat source water exchanged in the external load is returned;
A bypass conduit for communicating the forward header and the return header;
A bypass valve provided in the bypass line;
A primary pump system heat source comprising primary pump rotational speed control means for controlling the rotational speed of the primary pump so that the differential pressure of the heat source water between the forward header and the return header is a set differential pressure. In variable flow control system,
When the deviation of the differential pressure from the set differential pressure exceeds an allowable range, the bypass valve is fully opened for a predetermined time, and at the same time, the rotation speed of the primary pump is maximized. How to secure the minimum flow rate of the primary pump. First to Nth (N ≧ 2) heat source units for generating heat source water;
First to Nth primary pumps for conveying heat source water generated by the first to Nth heat source units;
A forward header for mixing heat source water from the first to Nth heat source units;
An external load that receives the supply of heat source water via this forward header,
A return header to which the heat source water exchanged in the external load is returned;
A bypass conduit for communicating the forward header and the return header;
A bypass valve provided in the bypass line;
A water temperature sensor that measures the temperature of the heat source water from the forward header to the external load as a forward water temperature;
A return water temperature sensor for measuring the temperature of the heat source water returned to the return header as a return water temperature;
A flow meter for measuring the flow rate of the heat source water returned to the return header as a load flow rate,
The current load calorie obtained from the water flow temperature measured by the water flow temperature sensor, the water return temperature measured by the water return temperature sensor and the load flow rate measured by the flow meter, or measured by the flow meter Number of operation control means for controlling the number of operating heat source units based on the load flow rate,
A primary pump system heat source comprising primary pump rotational speed control means for controlling the rotational speed of the primary pump so that the differential pressure of the heat source water between the forward header and the return header is a set differential pressure. In variable flow control system,
When the deviation of the differential pressure from the set differential pressure exceeds the allowable range, the bypass valve is fully opened for a predetermined time, and at the same time, the rotation speed of the primary pump currently being controlled is maximized. A method for ensuring the minimum flow rate of the primary pump.

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