JP6198398B2 - Control method for determining the number of operating pumps in a two-pump heat source facility - Google Patents

Description

  The present invention relates to a method for determining the number of secondary pumps to be operated in a heat source supply system such as a district heating and cooling facility or a two-pump heat source facility used as a heat source supply system in a factory or a building.

  2. Description of the Related Art Conventionally, a two-pump heat source facility is known as a heat source supply system used as a heat source supply system such as a district cooling and heating facility or a heat source supply system such as a factory or a building.

  In the two-pump heat source equipment, for example, as shown in FIG. 12, the heat medium from the return header 50 is sent by the primary water pumps 52A to 52C, and the heat source equipment 51A such as a heat exchanger composed of a refrigerator, a boiler or the like. After passing through 51C and being heated or cooled, the first feed header 54 reaches the second feed header 63, and then is sent to the third feed header 57 by the secondary water feed pumps 55, 55. .. Are fed to the heat exchangers (air conditioners) 58, 58... Arranged in the respective parts (rooms) via the third feed header 57 and then circulated to the return header 50. Secondary water pumps 55, 55... Disposed between the second feed header 63 and the third feed header 57 are each provided with an inverter 56, and between the second feed header 63 and the third feed header 57. A first bypass 64 and a first bypass valve 65 are provided, and a second bypass 62 that connects the first feed header 54 and the return header 50 is provided (see Patent Documents 1 and 2 below). ).

  The discharge pressure control of the secondary water supply pump 55 by the variable pressure control device 60A of the control device 60 detects the differential pressure DS between the third feed header 57 and the second feed header 63 and sets a necessary differential pressure that is set in advance. Thus, the variable flow rate control is performed under a constant water supply pressure condition by applying rotation speed control to the inverters 56, 56... Of the secondary water supply pumps 55, 55.

  In addition, as shown in FIG. 13, the increase / decrease stage control of the secondary pumps 55, 55... Is performed when the number of pumps operated is N and the load flow rate Ql to the air conditioner side is set to the heat source device increase stage flow rate setting value Qup_N. When the time exceeds T10 for a certain period of time, control for issuing an operation command from the pump operation number determination control device 60B of the control device 60 is performed so as to increase the number of pump operation to N + 1. Similarly, when the number of pumps operated is N, and the load flow rate Ql to the air conditioner side falls below the heat source equipment step-down flow setting value Qdown_N for a certain period of time T10, the number of pumps operated is reduced to N-1 units. A stop command is issued from the pump operation number determination control device 60B.

  In addition, as a method for determining the pump operating frequency, the differential pressure diagram between headers (see FIG. 3) using the characteristic that the pipe resistance (inter-header differential pressure hP) is a quadratic function of the load flow rate Ql to the air conditioner side. The header differential pressure setting value Ps is calculated in advance from the following equation (3), and the actual header differential pressure measurement value hPm is calculated by proportional control or the method described in Patent Document 3 below. The variable pressure control by the variable pressure control device 60A is employed to reduce the pump power by operating the pump operating frequency fs so that

ここで、Ps：両ヘッダ間の差圧の設定値
Ql：外部負荷機器側の循環流量
Ahp，Bhp，Chp：実験的に求まる配管抵抗曲線の係数

Where Ps: set value of differential pressure between both headers
Ql: Circulation flow on the external load equipment side
Ahp, Bhp, Chp: Coefficient of pipe resistance curve obtained experimentally

JP 2002-213802 A JP 2004-101104 A JP 2008-224182 A

  However, the following problems have occurred in determining the number of pumps to be operated.

  As a first problem, in the variable pressure control, the inter-header differential pressure setting value Ps (the coefficients Ahp, Bhp, Chp in the inter-header differential pressure diagram shown in the above equation (3)) is changed for operational reasons. In addition, since the optimum values of the heat source device step-up flow set value Qup_N and the heat source device step-down flow set value Qdown_N change, there is a problem that the number of operating units cannot be determined accurately.

Specific examples of the first problem include the following two.
First, as shown in FIG. 14, the header differential pressure curve in operation is higher than the header differential pressure curve assumed when the increase / decrease setting value of the number of pumps operated is determined. When differential pressure is indicated, the operation increase point shifts to the lower flow rate side than the set increase point, so the number of operating units does not increase, and as a result, the load flow rate to the air conditioner side can be satisfied. There wasn't.

  On the contrary, as shown in FIG. 15, the differential pressure curve between the headers in operation is greater than the differential pressure curve between headers assumed when the increase / decrease setting value of the number of pumps operated is determined. When the pressure difference between the headers is low, the operation step reduction point shifts to the larger flow rate side than the set step reduction point. Therefore, the number of operating units increases even in the operating range where the number of operating units can be reduced. Therefore, there is a problem that the pump power cannot be reduced or the operation time of the pump becomes long.

  Note that the header differential pressure setting value Ps for the variable pressure control is a coefficient Ahp, Bhp, a header differential pressure diagram depending on conditions such as a specific air conditioner being operated for each season during cooling and heating. You may need to change Chp. For the variable pressure control, in addition to the one using the differential pressure diagram between the headers, a differential pressure transmitter is installed in the inlet / outlet pipe of the air conditioner farthest in pressure, and the measured value of the differential pressure transmitter is always There is also a method of determining to be constant.

  Next, as a second problem, the conventional operation number control method assumes that the pump efficiency e does not change even if the pump flow rate Q and the operation frequency f change (see FIG. 6). Therefore, changes in pump efficiency e are not taken into account when determining whether to increase or decrease the number of operating heat source devices. However, in the actual pump, the pump efficiency e also changes depending on the pump flow rate Q and the operation frequency f. Therefore, the conventional control method has an inefficient operation, and the pump power consumption Wp is wasted.

  Therefore, the main problem of the present invention is that when determining the increase / decrease of the number of pumps to be operated, the increase / decrease point is appropriately obtained so that the number of operation can be determined accurately and the actual number of pumps It is an object of the present invention to provide a control method for determining the number of pumps to be operated in a two-pump heat source facility that can determine the step-up point and the step-down point in consideration of the operation state.

ここで、Ps：両ヘッダ間の差圧の設定値
Qs：２次ポンプの流量設定値
ｅ：ポンプ効率
Ｎ：２次ポンプの運転台数 In order to solve the above-mentioned problems, as the present invention according to claim 1, a plurality of heat source devices for cooling or heating the heat medium and a heat medium that is provided corresponding to each heat source device and pumps the cooled or heated heat medium. A primary pump, a first feed header that collects the heat medium from the heat source device, a second feed header into which the heat medium from the first feed header flows, and a plurality that sends the heat medium from the second feed header Secondary pump, a third feed header that collects the heat medium from the secondary pump, an external load device that is supplied with the heat medium from the third feed header, and a heat medium that is heat-exchanged by the external load device Is returned, a return header that is distributed to each heat source device, a first bypass and first bypass valve that connects the second feed header and the third feed header, the first feed header section or its vicinity, and the return The header or its vicinity Ingredients and a second bypass, the 2-pump heat source equipment and a control device for controlling the operation of the heat source device operating units control and the secondary pump,
A flow meter for measuring the circulation flow rate Q on the external load device side, a differential pressure meter for measuring a differential pressure between the second feed header and the third feed header, and a means for detecting the number of operating secondary pumps And
The control device obtains the power consumption Wp of the secondary pump by the following equation (11), determines the number of operating units including the condition that the pump power consumption Wp is minimum as the optimum operating unit number Nop , A two-pump heat source that executes a command to change the number of operating secondary pumps to the optimum operating number Nop when the operating number N and the optimum operating number Nop are continuously different for a predetermined time or more. A method for determining the number of operating pumps in a facility is provided.

Where Ps: set value of differential pressure between both headers
Qs: Secondary pump flow rate setting value e: Pump efficiency N: Number of secondary pumps

According to the first aspect of the present invention, when determining the optimum operating number Nop of the secondary pump, the power consumption Wp of the secondary pump is obtained, and the optimum number of operating times including the condition that the pump power consumption Wp is minimized is determined. When the current operation number N and the optimum operation number Nop are continuously different from each other for a predetermined time or longer, a command to change the operation number of the secondary pump to the optimum operation number Nop is executed. Yes. In other words, unlike the conventional method for determining the number of operating units, it is not a method for determining the setting value for step increase or decrease from the header differential pressure curve and the PQ characteristic diagram of the pump. As a result, the increase and decrease points are appropriately calculated from the condition that the pump power consumption Wp is minimized because the shortage or surplus of flow rate does not occur due to the difference between the point of operation and the points of increase or decrease of operation. The number of operating units can be determined accurately.

  Further, in the calculation of the pump power consumption Wp, the pump efficiency e corresponding to the actual pump operation state is taken into consideration as shown in the above equation (11). That is, as shown in FIG. 6, a pump efficiency e corresponding to the current operating state (pump operating frequency f and flow rate Q) is calculated from an approximate expression of a predetermined pump efficiency curve, and pump power consumption at that time is calculated. By obtaining Wp, the number of operating units at which the pump power consumption Wp is minimum is determined as the optimum operating number Nop. For this reason, it is possible to determine the step increase point and the step decrease point in consideration of the actual operation state of the pump.

Furthermore , in order to stabilize the system, when the current operation number N and the optimum operation number Nop are continuously different for a predetermined time or longer, control is performed to change the operation number of the secondary pump to the optimum operation number Nop. I have to.

ここで、Ps：両ヘッダ間の差圧の設定値
Qs：２次ポンプの流量設定値
ｅ：ポンプ効率（下式(10)により算出したもの）
Ｎ：２次ポンプの運転台数

ここで、Qs：２次ポンプの流量設定値
fs：２次ポンプの運転周波数
Ｆ：ポンプの定格周波数
Ae，Be，Ce：係数 The present invention according to claim 2 includes a plurality of heat source devices that cool or heat the heat medium, a primary pump that is provided corresponding to each heat source device and that pumps the cooled or heated heat medium, and the heat source. A first feed header that collects the heat medium from the device, a second feed header into which the heat medium from the first feed header flows, a plurality of secondary pumps that feed the heat medium from the second feed header, A third feed header that collects the heat medium from the secondary pump, an external load device to which the heat medium is supplied from the third feed header, and a heat medium that has been heat-exchanged by the external load device are returned, and each heat source A return header distributed to the device, a first bypass and a first bypass valve connecting the second feed header and the third feed header, the first feed header portion or the vicinity thereof, and the return header portion or the vicinity thereof. A second bypass to connect, In 2 pump type heat source equipment and a control device that performs operation number control and operation control of the secondary pump sources equipment,
A flow meter for measuring the circulation flow rate Q on the external load device side, a differential pressure meter for measuring a differential pressure between the second feed header and the third feed header, and a means for detecting the number of operating secondary pumps And
The control device obtains the power consumption Wp of the secondary pump by the following equation (11), and determines the number of operating units including the condition that the pump power consumption Wp is minimized as the optimum operating number Nop. A method for determining the number of pumps to be operated in a two-pump heat source facility is provided.

Where Ps: set value of differential pressure between both headers
Qs: Secondary pump flow rate setting
e: Pump efficiency (calculated by the following formula (10))
N: Number of operating secondary pumps

Where, Qs: Secondary pump flow rate setting value
fs: secondary pump operating frequency F: rated pump frequency
Ae, Be, Ce: Coefficient

In the invention described in claim 2, the pump efficiency e based on the pump flow rate set value Qs and the pump operating frequency fs at this time is obtained from the approximate expression of the performance curve of the pump efficiency e as shown in FIG. Means are shown.

ここで、A'＝Cp／Ｆ^２
B"＝Bp×Qs／Ｆ
C"＝Ap×Qs^２−Ps
Qs：２次ポンプの流量設定値
Ps：両ヘッダ間の差圧の設定値
Ｆ：ポンプの定格周波数
Ap，Bp，Cp：係数
条件１：ポンプ運転周波数fsがポンプ最大周波数fmax以下。
条件２：ポンプ消費電力Wpが最小。 As a third aspect of the present invention, the control device is configured such that when the number of the secondary pumps currently operating is increased, when one unit is increased from the current number of operating units, and when the number of the current operating units is one. The pump power consumption Wp is obtained for each time when one unit is reduced, and the pump operation frequency fs is obtained by the following equation (7), and the optimum operation is performed when the number of operation satisfies the following conditions 1 and 2. A pump operation number determination control method for a two-pump heat source facility according to claim 1 or 2 is determined as the number Nop.

Here, A ′ = Cp / F ²
B "= Bp × Qs / F
C "= Ap × Qs ² −Ps
Qs: Secondary pump flow rate setting
Ps: Set value of differential pressure between both headers F: Rated frequency of pump
Ap, Bp, Cp: Coefficient condition 1: Pump operating frequency fs is less than pump maximum frequency fmax.
Condition 2: Pump power consumption Wp is minimum.

The invention according to the third aspect further defines the control method for determining the number of pumps operated by the control device, wherein the number of secondary pumps currently operating, when one is increased, and when one is decreased. Respectively, the pump power consumption Wp and the pump operating frequency fs are obtained, and the number of operating units satisfying the conditions 1 and 2 is determined as the optimum operating number Nop. For this reason, the secondary pump can be operated in an appropriate frequency range, and the system can be stabilized.

  As described above in detail, according to the present invention, when determining the increase / decrease of the number of pumps to be operated, the increase point and the decrease point are appropriately obtained, and the determination of the number of operations can be performed accurately. The increase / decrease point can be determined in consideration of the actual operating state of the pump.

1 is a piping diagram showing a two-pump heat source facility 1 according to the present invention. It is a flowchart which shows the operation control method. It is a graph which shows the relationship between the circulating flow volume Q by the side of an external load apparatus, and the header differential pressure hP. It is a piping diagram which shows the 2 pump system heat source equipment 1 in the actual machine characteristic test of a secondary pump. It is a graph which shows the relationship between the flow volume Q, the header differential pressure hP, and the pump efficiency e. It is a graph which shows the relationship between the flow volume Q and the pump efficiency e which concerns on this invention and a prior art. It is the graph which compared the calculated value and experimental value of pump power consumption Wp based on this invention and a prior art. It is a graph which shows the circulation flow rate appearance time by the side of the external load apparatus of the system used for the Example. It is a result which shows the relationship between the flow volume and the number of operation according to the present invention and the prior art. It is a result which shows the relationship between the flow volume and power consumption based on this invention and a prior art. It is a result which shows the comparison of annual power consumption based on this invention and a prior art. It is a piping diagram which shows the conventional 2 pump system heat source equipment. It is a flowchart which shows the conventional pump operation number control method. It is the relationship figure (the 1) of the flow volume which shows the trouble of the conventional operating number control method, and the differential pressure between headers. It is the relationship figure (the 2) of the flow volume which shows the trouble of the conventional operating number control method, and the differential pressure between headers.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Configuration of two-pump heat source equipment]
A two-pump heat source facility 1 shown in FIG. 1 is provided corresponding to a plurality of heat source devices 2A to 2C for cooling or heating a heat medium and each of the heat source devices 2A to 2C, and a primary for pressure-feeding the heat medium. Pumps 3A to 3C, a first feed header 4 that collects the heat medium from the heat source devices 2A to 2C, a second feed header 18 into which the heat medium from the first feed header 4 flows, and the second feed The secondary pumps 6A to 6C for supplying the heat medium from the header 18, the inverters 7A to 7C for controlling the rotational speeds of the secondary pumps 6A to 6C, and the secondary pumps 6A to 6C are supplied with the heat medium. Are provided corresponding to each external load device 9 and the external load devices 9, 9... Such as an air conditioner to which a heat medium is supplied from the third feed header 5. Adjust the flow rate of the heat medium flowing through the device 9 The heat medium exchanged by the flow rate adjusting valve 16 and the external load devices 9, 9... Is returned, the return header 10 distributed to each of the heat source devices 2A to 2C, the second feed header 18 and the third feed. A first bypass 11 and a first bypass valve 12 that connect the header 5; a second bypass 13 that connects the first feed header section 4 or its vicinity and the return header section 10 or its vicinity; and the secondary pump 6A. The control device 8 includes a variable pressure control device 8A that performs variable pressure control of ˜6C and a pump operation number determination control device 8B that performs control of the number of operating secondary pumps 6A to 6C.

  Further, as measuring instruments, a flow meter 14 for measuring a circulating flow rate on the external load device 9 side, and a differential pressure gauge 17 for measuring a differential pressure between the second feed header 18 and the third feed header 5; A flow meter 15 for measuring the flow rate of the heat medium in the first bypass 11 and an operating number detecting means (not shown) for detecting the operating number of the secondary pumps are provided.

  The secondary pumps 6 </ b> A to 6 </ b> C do not have to have the same specifications such as a flow rate range and a model, and a plurality of pumps having different specifications may be provided. In that case, the control device 8 holds in advance a relational expression between the discharge pressure and the flow rate of each secondary pump measured by an operation test with an actual machine. Thereby, even if the secondary pumps 6A to 6C having different specifications such as the flow rate range and the model are installed, the secondary pumps 6A to 6C can be individually controlled so as to be in an optimum operation state. .

The details will be described below.
[Characteristic test of secondary pump]
First, as shown in FIG. 4, in the circulation system around the secondary pumps 6 </ b> A to 6 </ b> C, the third feed header 5, the first bypass 11, and the second feed header 18, for each secondary pump 6 </ b> A to 6 </ b> C. The relational expression between the header differential pressure hP and the pump flow rate Q is obtained.

  Specifically, in the actual machine, the supply of the heat medium to the external load devices 9, 9... Is cut off to form a flow path that circulates through the first bypass 11, and the secondary pumps 6A to 6C are rated. While operating at the frequency F (50 Hz or 60 Hz), the opening degree of the bypass valve 12 is changed (for example, 100% → 0% in the opening degree 10% step), and the differential pressure hP between the two headers by the differential pressure gauge 17 And the flow rate Q of the heat medium flowing through the first bypass 11 are measured, and a relational expression between them is experimentally obtained. Thereby, a PQ characteristic diagram as a pump group including a resistance portion such as a pipe can be obtained (see FIG. 5). This PQ characteristic is measured for all the corresponding secondary pumps 6A to 6C.

  Here, in order to cut off the supply of the heat medium to the external load device side, for example, a manual valve 19 is provided between the feed header 5 and the external load devices 9, 9... As shown in FIG. Provided, the valve 19 is fully closed. The flow meter 15 may be anything that can be measured in an actual machine characteristic test of the pump, and may be arranged so that it can be removed during steady operation.

  The relational expression between the differential pressure hP between the headers and the pump flow rate Q can be approximated by the following expression (1).

  Since the above relational expression is based on the condition of operating at the rated frequency F (50 Hz or 60 Hz), the relational expression when the pump operating frequency is an arbitrary frequency f should be approximated as the following expression (2). Can do.

ここで、hP：両ヘッダ間の差圧
Ｑ：ポンプ流量
ｆ：ポンプの運転周波数
Ｆ：ポンプの定格周波数
Ap，Bp，Cp：係数

Where hP: differential pressure between both headers Q: pump flow rate f: pump operating frequency F: pump rated frequency
Ap, Bp, Cp: Coefficient

  By the way, the above method is an experimentally obtained method. However, when the PQ characteristic diagram of the pump and the PQ characteristic diagram of the piping system are known in advance, (the pressure according to the PQ characteristic diagram of the pump). By approximating the PQ characteristic diagram by-) (pressure drop by the PQ characteristic diagram of the piping system) with the above formula (1), the above formula (2) can be derived.

[Determination control method for number of pumps]
Next, a control method for determining the number of operating secondary pumps 6A to 6C will be described. In the pump operation number determination control method according to the present invention, the pump operation number determination control device 8B obtains the pump power consumption Wp of the secondary pumps 6A to 6C by the equation (11) described in detail later, and this pump power consumption Wp. Is determined as the optimum operating number Nop.

More specifically, the control device 8B is configured to increase the number of secondary pumps 6A to 6C that are currently operated, one that is increased by one from the current number of operating pumps, and one that is from the current number of operating pumps. The pump power consumption Wp is determined for each of the decreased units, and the pump operating frequency fs is determined by the equation (7) described in detail later. When the number of operating units satisfies the following conditions 1 and 2, It is determined as the optimal operation number Nop.
Condition 1: The pump operating frequency fs is below the pump maximum frequency fmax.
Condition 2: Pump power consumption Wp is minimum.

  As described above, in the present invention, when determining the optimum operation number Nop of the secondary pumps 6A to 6C, the pump consumption power Wp of the secondary pump is obtained, and the operation number including the condition that the pump consumption power Wp is minimum is optimum. Unlike the conventional control method for determining the number of steps to increase or decrease from the PQ characteristic diagram of the pump and the PQ characteristic diagram of the pump, the determined increase number is determined as the number of operations Nop. The increase and decrease points are appropriate from the condition that the pump power consumption Wp is minimized because there is no flow shortage or surplus due to the difference between the stage and step reduction points and the operation increase or decrease points. As a result, the number of operating units can be determined accurately.

  Further, in the calculation of the pump power consumption Wp, the pump efficiency e corresponding to the actual pump operation state is taken into consideration as shown in the following equation (11). That is, as shown in FIG. 6, the pump efficiency e corresponding to the current operating state (pump operating frequency f and flow rate Q) is calculated from an approximate expression of a predetermined pump efficiency curve (see formula (10) in the subsequent stage). By calculating and obtaining the pump power consumption Wp at that time, the number of operating units at which the pump power consumption Wp is minimum is determined as the optimum operating number Nop. For this reason, it is possible to determine the step increase point and the step decrease point in consideration of the actual operation state of the pump.

  In order to obtain the pump power consumption Wp, it is necessary to calculate the header differential pressure setting value Ps, the pump flow rate setting value Qs, the pump operating frequency fs, and the pump efficiency e. Each calculation method will be described in detail below.

(Header differential pressure setting value Ps)
The calculation method of the differential pressure setting value Ps between headers includes end pressure prediction control based on the circulation flow rate Ql on the external load side, and calculation method based on the opening of the flow adjustment valve on the external load device side. The method is selectively used depending on the installation status and purpose of the heat source facility 1. Here, a method of calculating the inter-header differential pressure setting value Ps by the terminal pressure prediction control will be described. In this calculation method, a relational expression (pipe resistance curve) between the flow rate on the external load device side measured by the flow meter 14 and the differential pressure between both headers at each flow rate measured by the differential pressure gauge 17 is obtained in advance. . This piping resistance curve is generally represented by a quadratic function such as the following equation (3), as shown in FIG. By substituting the circulation flow rate Ql on the external load device side measured by the flow meter 14 into the following equation (3), the set value Ps of the differential pressure between the headers according to the current operation state can be obtained. It becomes like this.

ここで、Ps：両ヘッダ間の差圧の設定値
Ql：外部負荷機器側の循環流量
Ahp，Bhp，Chp：実験的に求まる配管抵抗曲線の係数

Where Ps: set value of differential pressure between both headers
Ql: Circulation flow on the external load equipment side
Ahp, Bhp, Chp: Coefficient of pipe resistance curve obtained experimentally

(Pump flow setting value Qs)
Next, the set value Qs of the operation flow rate of the secondary pumps 6A to 6C is calculated. The flow rate set value Qs is determined based on the idea of distributing the flow rate of the heat medium circulating on the external load device side among the operating secondary pumps.

  Specifically, when the capacity ranges of the secondary pumps are the same, the circulation flow rate Ql on the external load device side is measured by the flow meter 14, and this circulation flow rate Ql is calculated by the number N of operating secondary pumps in operation. Further, the surplus flow rate q is added so that the circulation flow rate is not insufficient, and the operation flow rate set value Qs per secondary pump is calculated from the following equation (4).

ここで、Qs：２次ポンプの流量設定値
Ql：外部負荷機器側の循環流量
Ｎ：２次ポンプの運転台数
ｑ：余裕流量

Where, Qs: Secondary pump flow rate setting value
Ql: Circulation flow rate on the external load equipment side N: Number of secondary pumps operated q: Excess flow rate

Then, the flow rate set value Qs of the secondary pump 6A-6C, a set value Qs operation flow of the secondary pump in accordance with the operable flow rate range of the secondary pump 6A~6C _{(Q rmin ~Q rmax),} Calculate from the following equation (5)

ここで、Qs：２次ポンプの運転流量の設定値
Ｑ_ｒｍａｘ：２次ポンプの運転可能流量の最大値
Ｑ_ｒｍｉｎ：２次ポンプの運転可能流量の最小値

Here, Qs: set value of the operational flow rate of the secondary pump _Qrmax : maximum value of the operational flow rate of the secondary pump _Qrmin : minimum value of the operational flow rate of the secondary pump

  Here, the above equation (4) shows the case where the capacity ranges of the secondary pumps 6A to 6C are the same, and each secondary pump is used when a secondary pump with a different flow rate range is used. By proportionally allocating in accordance with the pump capacity, the set value Qs of the operation flow rate of each secondary pump is calculated.

(Secondary pump operating frequency setting fs)
Next, the set value fs of the operating frequency corresponding to the operating flow rate Qs of the secondary pump calculated from the above equation (5) is calculated based on the above equation (2). Specifically, the above equation (2), which is a PQ relational expression at an arbitrary operating frequency f, is solved for an arbitrary operating frequency f of the secondary pump, and transformed into the following equation (6).

ここで、A'＝Cp／Ｆ^２
B'＝Bp×Ｑ／Ｆ
C'＝Ap×Ｑ^２−hp

Here, A ′ = Cp / F ²
B '= Bp × Q / F
C ′ = Ap × Q ² −hp

  As a result, the operating frequency fs of the secondary pump was calculated by the set value Ps of the differential pressure between the headers calculated by the above equation (3) to hP and Q of the above equation (6) and the above equation (5). Given the set value Qs of the operation flow rate of the secondary pump, it can be calculated from the following equation (7).

ここで、A'＝Cp／Ｆ^２
B"＝Bp×Qs／Ｆ
C"＝Ap×Qs^２−Ps

Here, A ′ = Cp / F ²
B "= Bp × Qs / F
C "= Ap × Qs ² −Ps

Here, a specific example will be described. PQ characteristic diagram (coefficient Ap = -0.0027, Bp = -0.0319, Cp = 127.1 in the above equation (1)) and one secondary pump with rated frequency F = 60Hz (N = 1) is operating. Assuming that the header differential pressure setting value Ps = 100 kPa and the pump flow rate setting value Qs = 100 m ³ / h, the setting value fs of the secondary pump is fs = 59.0 Hz. Assuming that two secondary pumps with the same characteristics (N = 2) are operating, if the differential pressure setting between headers Ps = 100 kPa and the pump flow rate setting Qs = 50 m ³ / h, the secondary pump The operating frequency setting value fs = 54.3Hz.

  When the set value fs of the pump operating frequency calculated by the above equation (7) is less than or equal to the minimum pump frequency fmin, fs = fmin is set and the pump flow rate set value Qs at this time is calculated again. Specifically, the above equation (2) is solved for the pump flow rate setting value Qs, and is obtained from the following equation (8) in which the pump operating frequency fs (= fmin) and the inter-header differential pressure setting value Ps are substituted.

ここで、Af＝Ap
Bf＝Bp×fs／Ｆ
Cf＝Cp×（fs／Ｆ）^２−Ps

Where Af = Ap
Bf = Bp × fs / F
Cf = Cp × (fs / F) ² −Ps

(Pump efficiency e)
In the control method according to the present invention, the pump efficiency e according to the actual operation flow rate and operation frequency of the pump is taken into account when setting the increase or decrease of the secondary pumps 6A to 6C. For this reason, in the conventional control method in which the pump efficiency is constant with respect to the flow rate, there is a point that the operation becomes inefficient, and the pump power consumption is wasted. By considering e, the power consumption of the pump can be minimized and efficient operation becomes possible.

  Explaining a specific calculation method, it is clear from experiments that the pump efficiency e at an arbitrary pump operating frequency f and pump flow rate Q can be approximated by the following equation (9).

ここで、ｆ：ポンプの運転周波数
Ｆ：ポンプの定格周波数（例えば、60Hz）
Ae，Be，Ce：係数

Where f: pump operating frequency F: pump rated frequency (for example, 60 Hz)
Ae, Be, Ce: Coefficient

As shown in FIG. 5, the coefficients Ae, Be, and Ce of the above equation (9) are obtained by using a quadratic function e = Ae × Q ² + Be × It is a coefficient when approximated by Q + Ce. In the case of FIG. 5, Ae = −0.007, Be = 1.5115, and Ce = 0.0717.

  By substituting the pump flow rate setting value Qs and the pump operation frequency setting value fs obtained in the previous stage into the above equation (9), the pump efficiency e can be calculated from the following equation (10).

Here, a specific example will be described. A characteristic diagram of the flow rate Q and pump efficiency e shown in FIG. 5 (with the coefficients Ae = −0.007, Be = 1.5115, Ce = 0.0717 in the above equation (9)), one secondary pump (N = 1) Assuming that the pump is operating, when the differential pressure setting between headers Ps = 100kPa, the pump flow rate setting Qs = 100m ³ / h, and the secondary pump operating frequency setting fs = 59.0Hz, the pump efficiency e = 78.7%. Assuming that two secondary pumps with the same characteristics are operating (N = 2), the differential pressure setting between headers Ps = 100 kPa, the pump flow rate setting Qs = 50 m ³ / h, the operation of the secondary pump When the frequency setting value fs = 54.3 Hz, the pump efficiency e = 51.3%.

(Pump power consumption Wp)
The pump power consumption Wp of the entire secondary pump when the inter-header differential pressure setting value Ps, the pump flow rate setting value Qs, the number of pumps operated N, and the pump efficiency e can be calculated from the following equation (11).

Here, a specific example will be described. Assuming that one secondary pump (N = 1) is operating, the differential pressure setting between headers Ps = 100 kPa, the pump flow rate setting Qs = 100 m ³ / h When the set value fs = 59.0 Hz for the operating frequency of the secondary pump and the pump efficiency e = 78.7%, the pump power consumption Wp = 3.5 kW. Assuming that two secondary pumps with the same characteristics are operating (N = 2), the differential pressure setting between headers Ps = 100 kPa, the pump flow rate setting Qs = 50 m ³ / h, the operation of the secondary pump When the frequency setting value fs = 54.3 Hz and pump efficiency e = 51.3%, the pump power consumption Wp = 5.4 kW.

(Operation control)
The control device 8B has the current number of operating units of the secondary pumps (N = N), the number of operating units increased by one (N = N + 1) increased by one from the current number of operating units. The number of pumps that satisfy the following conditions 1 and 2 is determined as the optimum operating number Nop, respectively, when one unit is decreased from N (N = N-1).
Condition 1: The pump operating frequency fs is below the pump maximum frequency fmax.
Condition 2: Pump power consumption Wp is minimum.

  As a specific example, when the number of operating secondary pumps is one (N = 1) and the pump operating frequency fs = 59.0 Hz <the maximum pump frequency fmax = F = 60 Hz, the pump power consumption Wp = 3.5kW. In addition, when operating two pumps, the number of secondary pumps increased by one from the current number of operating pumps, if pump operating frequency fs = 54.3 Hz <pump maximum frequency fmax = F = 60 Hz, pump power consumption Wp = 5.4kW. The above condition 1 is satisfied when the number of operating pumps is N = 1 (when the current number of operating units) and when N = 2 (when one unit is increased), but the pump power consumption is when N = 1. Since Wp is the minimum, the optimal operation number Nop = 1.

  In order to stabilize the system, the pump increase or decrease command is changed to the optimal operation number Nop when the current operation number N and the optimal operation number Nop continue to differ for a predetermined time or longer. To do. The time for which N ≠ Nop continues can be, for example, about 5 minutes to 30 minutes.

  FIG. 7 shows calculated values and actual measured values of the pump power consumption Wp when the pump efficiency e is constant at a maximum efficiency of 65% as the prior art and when the pump efficiency e is calculated by the equation (10) as the present invention. It is the graph which compared with. As a result, in the case of the conventional technology in which the pump efficiency is constant at the maximum efficiency, the calculated value tends to be lower than the actually measured value. However, in this control method, the actually measured value and the calculated value agree well. Yes. Therefore, it can be seen that this control method has a high calculation accuracy of the pump power consumption and is more suitable for an actual machine.

Further, in the condition that the maximum external load equipment side flow rate is 320 m ³ / h, the maximum pump discharge pressure is 110 kPa, and the external load equipment side flow rate appearance time is as shown in FIG. Comparison with the optimal number control using the control method was performed. As the pump equipment, the number of installed units was 4, the maximum flow rate per pump was 80 m ³ / h, and the maximum pump discharge pressure was 110 kPa. The coefficients (pipe resistance characteristics) in the header differential pressure diagram were Ahp = 0.0009766, Bhp = 0, and Chp = 10. This pipe resistance characteristic is the same as in the conventional control method.

  As the pump characteristics, the coefficients of the PQ characteristic diagram are Ap = -0.0027, Bp = -0.0319, Cp = 127.1, and the coefficients of the characteristic diagram of the pump flow rate Q and the pump efficiency e are Ae = -0.007, Be = 1.5115 Ce = 0.0717. The rated frequency F was set to 60 Hz.

In the conventional control method, according to the flow of FIG. 13, when the number of operating units N is 4, the load flow rate Ql is less than Qdown_4 = 240 m ³ / h, and the number of operating units is reduced to 3 units. When the number of operating units is N = 3, the load flow rate Ql is less than Qdown_3 = 160 m ³ / h, the number of operating units is reduced to 2 units, and when Qup_3 = 240 m ³ / h is exceeded, the number of operating units is increased to 4 units. When the number of operating units is N = 2, the load flow rate Ql is less than Qdown_2 = 80m ³ / h, and the number of operating units is reduced to one unit. When Qup_2 = 160m ³ / h is exceeded, the number of operating units is increased to three units. In addition, when the number of operating units is N = 1, the load flow rate Ql exceeds Qup_1 = 80 m ³ / h, and the number of operating units increases to two.

In this control method, the pump power consumption Wp and pump operating frequency fs are calculated based on the above formulas (3) to (11) using the given pump characteristics. Determine Nop. However, the marginal flow q = 0m ³ / h, the maximum operable flow rate Qrmax = 140m ³ / h, the minimum operable flow rate Qrmin = 10m ³ / h, the minimum pump frequency fmin = 10Hz, the maximum pump frequency fmax = 60Hz .

  The simulation was performed for the present control method and the conventional control method under the above conditions. As a result, FIG. 9 shows the relationship between the number of pumps operated and the flow rate, FIG. 10 shows the relationship between the power consumption and the flow rate, and FIG. 11 shows a comparison of the annual power consumption. As a result, even with a system that requires 9251 kWh of annual power consumption with the conventional control method, 8054 kWh is required according to this control method, and 1467 kWh, or approximately 15% of the amount of power can be reduced.

  DESCRIPTION OF SYMBOLS 1 ... 2 pump system heat source equipment, 2A-2C ... Heat source equipment, 3A-3C ... Primary pump, 4 ... 1st feed header, 5 ... 3rd feed header, 6A-6C ... Secondary pump, 7A-7C ... Inverter , 8 ... Control device, 9 ... External load device, 10 ... Return header, 11 ... First bypass, 12 ... First bypass valve, 13 ... Second bypass, 14.15 ... Flow meter, 16 ... Flow control valve, 17 ... Differential pressure gauge, 18 ... Second feed header, 19 ... Valve

Claims (3)

A plurality of heat source devices that cool or heat the heat medium, a primary pump that is provided corresponding to each heat source device and that pumps the cooled or heated heat medium, and a heat pump that collects the heat medium from the heat source device. One feed header, a second feed header into which the heat medium from the first feed header flows, a plurality of secondary pumps that feed the heat medium from the second feed header, and a heat medium from the secondary pump are collected A third feed header, an external load device to which a heat medium is supplied from the third feed header, a heat medium that is heat-exchanged by the external load device is returned, and a return header that is distributed to each heat source device, A first bypass and a first bypass valve that connect the second feed header and the third feed header; a second bypass that connects the first feed header portion or its vicinity and the return header portion or its vicinity; and the heat source device Operation unit control and front In 2 pump type heat source equipment and a control device that performs operation control of the secondary pump,
A flow meter for measuring the circulation flow rate Q on the external load device side, a differential pressure meter for measuring a differential pressure between the second feed header and the third feed header, and a means for detecting the number of operating secondary pumps And
The control device obtains the power consumption Wp of the secondary pump by the following equation (11), determines the number of operating units including the condition that the pump power consumption Wp is minimum as the optimum operating unit number Nop, A two-pump heat source that executes a command to change the number of operating secondary pumps to the optimum operating number Nop when the operating number N and the optimum operating number Nop are continuously different for a predetermined time or more. Control method for determining the number of pumps in the facility.

Where Ps: set value of differential pressure between both headers
Qs: Secondary pump flow rate setting value e: Pump efficiency N: Number of secondary pumps A plurality of heat source devices that cool or heat the heat medium, a primary pump that is provided corresponding to each heat source device and that pumps the cooled or heated heat medium, and a heat pump that collects the heat medium from the heat source device. One feed header, a second feed header into which the heat medium from the first feed header flows, a plurality of secondary pumps that feed the heat medium from the second feed header, and a heat medium from the secondary pump are collected A third feed header, an external load device to which a heat medium is supplied from the third feed header, a heat medium that is heat-exchanged by the external load device is returned, and a return header that is distributed to each heat source device, A first bypass and a first bypass valve that connect the second feed header and the third feed header; a second bypass that connects the first feed header portion or its vicinity and the return header portion or its vicinity; and the heat source device Operation unit control and front In 2 pump type heat source equipment and a control device that performs operation control of the secondary pump,
A flow meter for measuring the circulation flow rate Q on the external load device side, a differential pressure meter for measuring a differential pressure between the second feed header and the third feed header, and a means for detecting the number of operating secondary pumps And
The control device obtains the power consumption Wp of the secondary pump by the following equation (11), and determines the number of operating units including the condition that the pump power consumption Wp is minimized as the optimum operating number Nop. A control method for determining the number of operating pumps in a two-pump heat source facility

Where Ps: set value of differential pressure between both headers
Qs: Secondary pump flow rate set value e: Pump efficiency (calculated by the following formula (10))
N: Number of operating secondary pumps

Where, Qs: Secondary pump flow rate setting value
fs: secondary pump operating frequency F: rated pump frequency
Ae, Be, Ce: Coefficient The control device includes a current operation number of the secondary pumps, an increase of one unit that is increased from the current operation number, and a decrease of one unit that is decreased by one from the current operation number. The pump power consumption Wp is obtained for each of the above, and the pump operating frequency fs is obtained by the following equation (7), and the number of operating vehicles satisfying the following conditions 1 and 2 is determined as the optimum operating number Nop: 2. A method for determining the number of pumps to be operated in the two-pump heat source facility according to any one of the above.

Here, A ′ = Cp / F ²
B "= Bp × Qs / F
C "= Ap × Qs ² −Ps
Qs: Secondary pump flow rate setting
Ps: Set value of differential pressure between both headers F: Rated frequency of pump
Ap, Bp, Cp: Coefficient condition 1: Pump operating frequency fs is less than pump maximum frequency fmax.
Condition 2: Pump power consumption Wp is minimum.

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