JP3957309B2 - Operation control method for two-pump heat source equipment - Google Patents

Description

  The present invention relates to an operation control method for a two-pump heat source facility 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.

  2. Description of the Related Art Conventionally, a two-pump heat source facility is known as a heat source supply system that is 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.

  For example, as shown in FIG. 4, the two-pump heat source facility is configured such that a heat medium from the return header 50 is sent by primary water pumps 52 </ b> A to 52 </ b> C, and a heat source device 51 </ b> A such as a heat exchanger including a refrigerator, a boiler, and the like. After passing through ~ 51C and being heated or cooled, it reaches the first feed header 54 and is then sent to the second feed header 57 by the secondary water feed pumps 55, 55. .. Are fed to the heat exchangers (air conditioners) 58, 58... Arranged in each part (room) via the second feed header 57 and then circulated to the return header 50. Secondary water pumps 55, 55... Disposed between the first feed header 54 and the second feed header 57 are each provided with an inverter 56, and between the first feed header 54 and the second feed header 57. A first bypass 64 and a first bypass valve 65 are disposed, and a second bypass 62 that connects the first feed header 54 and the return header 50 is disposed (see Patent Documents 1 and 2 below).

  The discharge pressure control of the secondary water supply pump 55 by the control device 60 detects the differential pressure DS between the second feed header 57 and the return header 50, and the secondary water supply so that the required differential pressure is set in advance. By controlling the number of revolutions of the inverters 56, 56 of the pumps 55, 55, etc., variable flow rate control is performed under a constant water supply pressure condition.

  The increase / decrease stage control of the heat source devices 51A to 51C is, for example, unit number control based on the heat source inlet temperature TI, the going water temperature TS, the flow rate F, and the load heat amount L ((TI−TS) × F). .

  However, if the cold water return temperature difference (TI-TS) decreases at the time of a small load, the circulation flow rate Q increases even if there is no change in the amount of heat. When the circulation flow rate Q increases from the heat source device water flow rate Qr, a part of the return cold water passes through the bypass 62 and joins to the cold water piping side, so the cold water return temperature TS rises and exceeds the heat source device additional temperature setting value. However, there is a problem that the operation of the unnecessary heat source device is induced, such as an unnecessary increase in the number of operating units, even though the heat source device performs the throttle operation.

  The cause of the phenomenon that the temperature difference of water going back and forth that occurs at the time of a small load is reduced is the presence of a terminal bypass for the purpose of keeping the circulating water quantity Q above a certain value, and the air conditioning load control valve (MV) deadline capacity is insufficient For example, the chilled water may be returned to the chilled water piping without exchanging heat due to leakage due to the system and the existence of a system that has abolished the control valve to simplify the equipment. As a method for preventing these problems, it is effective to lower the discharge pressure when the load is small. At the same time, lowering the pump discharge pressure leads to a reduction in pump power.

  Therefore, Patent Document 3 below discloses an operation control method in which the pump discharge pressure set value P is increased or decreased according to the following equation (4) by the circulating water amount Q corresponding to the air conditioning load processed by the air conditioner.

JP 2002-213802 A JP 2004-101104 A JP 2003-106731 A

  However, in the case of the pump control method disclosed in Patent Document 3, the operating state of the air conditioning equipment varies depending on various factors such as building use and season, so the constants K0, K1, K2, and n in the above equation (4) are It always changes and it is difficult to identify each constant as a constant value. As a result, depending on the operating conditions, the discharge pressure may be insufficient and the chilled water supply may be insufficient, and at low loads (especially with a load flow rate of 40% or less), the pump discharge pressure cannot be reduced and more power than necessary. In some cases, it is considered that the operation is stabilized when the discharge pressure is low, and it is not possible to flexibly cope with the changing heat load state. Furthermore, there is a problem that it is necessary to use a large amount of operation data for setting the constants.

  Accordingly, the main problem of the present invention is to stabilize the operation state by controlling the discharge pressure of the secondary pump so that the operation state is always economical in response to the changing heat load, and the pump power An object of the present invention is to provide an operation control method for a two-pump heat source facility that can realize energy saving by reducing the amount of heat.

In order to solve the above-mentioned problem, the present invention according to claim 1 includes a plurality of heat source devices for cooling or heating the heat medium and a heat source device that is provided corresponding to each heat source device and that pumps the cooled or heated heat medium. A secondary pump, a first feed header that collects the heat medium from the heat source device, a plurality of secondary pumps that send the heat medium from the first feed header, and a second feed header that collects the heat medium from the secondary pump And an external load device to which a heat medium is supplied from the second feed header, a terminal bypass that bypasses the external load device, and a heat medium that is heat-exchanged by the external load device are returned to each heat source device. A return header to be distributed, a first bypass and a first bypass valve that connect the first feed header and the second feed header, and a second that connects the first feed header portion or the vicinity thereof and the return header portion or the vicinity thereof. Bypass and before In 2 pump type heat source equipment and a control device that performs operation number control and operation control of the secondary pump of the heat source equipment,
A flow meter for measuring the circulating flow rate Q of the heat medium, a forward water thermometer for measuring the forward water temperature TS, a return water thermometer for measuring the return water temperature TR, the first feed header, and the second A pump head pressure gauge is installed to measure the differential pressure dP between the feed header and
The control device calculates a reference pump discharge pressure curve based on the following equation (1) from the circulation flow rate Q, the pump discharge pressure design value Pls, the actual lift Ps, the circulation flow rate design value Qs, and the coefficient n. When the secondary pump is controlled according to the pressure curve and the water supply temperature difference (TR-TS) between the outgoing water temperature TS and the return water temperature TR falls below a preset minimum temperature difference dTI, There is provided an operation control method for a two-pump heat source facility, wherein correction is performed on the discharge pressure P based on the reference pump discharge pressure curve based on the equation (2) .

  In the present invention as set forth in claim 1, except for arbitrarily set n, since it is controlled by all measurements or values known at the time of design, it is always economical to respond to changing thermal loads. It becomes possible to control the discharge pressure of the secondary pump so as to be in the state.

  Further, the reference pump discharge pressure curve is a curve in which the pump discharge pressure is reduced in a quadratic curve when the heat load is approximately 40% or less, so that a part of the return cold water is bypassed 62 at a small load. The chilled water going temperature TS rises as it passes through the chilled water piping side, and it is possible to prevent unnecessary increase in the number of operating units even though the heat source equipment is in the throttle operation. The pump power can be reduced.

Further, when the water supply temperature difference (TR-TS) between the outgoing water temperature TS and the return water temperature TR is less than a preset minimum set temperature difference dTI , particularly at a small load, the reference pump discharge pressure curve The minimum set temperature difference dTI can always be ensured by correcting the pump discharge pressure P value. The above-mentioned “terminal bypass, etc.” refers to leakage due to insufficient air conditioning load control valve (MV) deadlines in addition to terminal bypass, systems that have eliminated control valves to simplify equipment, etc. It refers to the piping route that enters the return cold water piping.

  When the load is small, the pump discharge pressure is greatly reduced, ensuring a minimum amount of circulating water and preventing a part of the incoming cold water from returning and entering the chilled water piping side. As a result, the pump power can be further reduced.

As a second aspect of the present invention, a pump discharge pressure lower limit value curve shown in the following equation (3) is set, and the discharge pressure of the secondary pump is controlled by using the pump discharge pressure lower limit value curve as a minimum discharge pressure. 1 Symbol placement of 2 pump type heat source equipment operation control method is provided.

  As described above in detail, according to the present invention, it becomes possible to control the discharge pressure of the secondary pump so as to always be in an economical operating state corresponding to the changing heat load, so that the operating state is stabilized. Energy saving can be realized by reducing pump power.

Further, the effects are listed as follows.
(1) Unlike the control method disclosed in Patent Document 3, operation control is possible without using a large amount of operation data for setting constants.
(2) Even if the pipe resistance curve changes depending on the load condition, it is possible to operate to some extent by correcting the water supply temperature difference.
(3) Since the discharge pressure at the start of operation starts from a discharge pressure (reference pump discharge pressure curve) higher than the required pressure, it is possible to prevent a shortage of circulating water due to insufficient discharge pressure.

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 heat source device 2A to 2C, and 1 that pumps the heat medium. Secondary pumps 3A to 3C, a first feed header 4 that collects the heat medium from the heat source devices 2A to 2C, secondary pumps 6A to 6C that supply the heat medium from the first feed header 4, and these secondary pumps Inverters 7A to 7C that respectively control the rotational speeds of 6A to 6C, a second feed header 5 that is supplied with a heat medium from secondary pumps 6A to 6C, an air conditioner that is supplied with a heat medium from the second feed header 5, and the like Of the external load devices 9, 9 ..., the end bypass 18 bypassing the external load devices 9, 9 ..., and the heat medium exchanged by the external load devices 9, 9 ... are returned, and each heat source device 2A Return header 10 distributed to ~ 2C; The first bypass 11 and the first bypass valve 12 that connect the first feed header 4 and the second feed header 5, the first feed header portion 4 or the vicinity thereof, and the return header portion 10 or the vicinity thereof are connected. 2 bypass 13 and the control apparatus 8 which performs operation number control of the said heat-source equipment 2A-2C and operation control of the said secondary pumps 6A-6C (inverters 7A-7C).

As measuring instruments, a flow meter 14 for measuring the circulating flow rate of the heating medium, a return water thermometer 15 for measuring the return water temperature TR, and a forward water thermometer for measuring the outgoing water temperature TS. 20, a thermometer 16 for measuring the inlet temperature TI of the heat source device, a thermometer 18 for measuring the outlet temperature TO of the heat source device, and the first feed header 4 and the second feed header 5 And a pump head pressure gauge 17 for measuring the differential pressure dP.
[Operation control by the control device 8]
In the present two-pump heat source facility 1, the discharge pressures of the secondary pumps 6A to 6C are controlled according to the secondary pump discharge pressure calculation logic flow shown in FIG. First, a reference pump discharge pressure curve that is an operation control condition of the secondary pumps 6A to 6C is set by the following equation (1).

  In the above equation (1), numerical values other than the coefficient n are measured values or values known at the time of design. FIG. 3 shows reference pump discharge pressure curves when n = 2, 3, and 5, and as a comparative example, a primary curve when n = 1, a pipe resistance curve described later, and a pump discharge pressure. A lower limit curve is shown. As is apparent from FIG. 3, by setting the coefficient n to a predetermined appropriate value, the pump discharge pressure can be expressed in a quadratic curve corresponding to the thermal load state at the time of a small load (especially 40% or less). It can be seen that it can be reduced. When n = 1, the pump discharge pressure becomes a linear curve and the pump discharge pressure cannot be reduced at a small load.

  According to the control method of the present invention, when n> 1, the discharge pressure curve can lower the discharge pressure like a quadratic curve when the load is small, and the pump power can be reduced. Further, since a curve with n = 3 or n = 5 can be arbitrarily set corresponding to the piping resistance curve, an appropriate discharge pressure control curve can be obtained according to the piping resistance curve.

  Although the secondary pumps 6A to 6C are operated and controlled according to the reference pump discharge pressure curve, the minimum value (minimum set temperature difference dTI) of the water supply temperature difference (TR-TS) between the outgoing water temperature TS and the return water temperature TR in advance. ), And when the water supply temperature difference (TR-TS) falls below the minimum set temperature difference dTI, the reference pump is set so that the water supply temperature difference (TR-TS) becomes the minimum set temperature difference dTI. The value P of the discharge pressure curve is corrected by the following calculation formula.

  From the heat balance, the following formula (5) is obtained.

  When the above equation (5) is solved for Qb, the following equation (6) is obtained.

Assuming that the water supply temperature difference dTI (for example, dTI = 3 ° C is set when the design water supply temperature difference is 5 ° C), the flow rate Qbl for the terminal bypass is calculated from the following equation (7). I want.

Further, the differential pressures Pb and Pbl for the terminal bypass and the like at the flow rates Qb and Qbl for the terminal bypass are represented by the following equations (8) and (9), respectively, where the resistance coefficient for the terminal bypass and the like is CVb.

Here, the resistance coefficient CVb of the terminal bypass or the like can be obtained from the following equation (10) using the circulation flow rate Q ₀ when the air-conditioning load automatic valves of all systems have an opening degree of 0% and the pump discharge pressure P ₀ .

  From the above, if the pressure is lowered by Pb−Pbl, the flow rate of the terminal bypass or the like becomes Qbl. Therefore, the corrected pressure P ′ can be obtained from the following equation (11) (= (2) equation).

  On the other hand, it is desirable to set a lower limit for the pump discharge pressure in order to ensure a minimum cold water flow rate.

  The lower limit value of the pump discharge pressure can be expressed by the following formula (12), and the graph is a curve shown in FIG.

  The object controlled according to the piping resistance curve is preferably the differential pressure between the suction side and the discharge side of the secondary pumps 6A to 6C, that is, the pump head dP.

  As described above, in the present invention, first, the secondary pumps 6A to 6C are operated and controlled according to the reference pump discharge pressure curve, and the minimum water temperature difference (TR-TS) is set in advance when the load is small. If a phenomenon that falls below the temperature difference dTI occurs, the value P of the reference pump discharge pressure curve is corrected so that the water supply temperature difference (TR-TS) becomes the minimum set temperature difference dTI. Further, in order to secure the minimum flow rate, even when the pump discharge pressure is lowered, the secondary pumps 6A to 6C are controlled with the pump discharge pressure lower limit curve as the minimum discharge pressure.

1 is a block diagram showing a two-pump heat source facility 1 according to the present invention. It is a flowchart which shows the calculation logic of a secondary pump discharge pressure. It is a graph which shows a reference | standard pump discharge pressure curve, a piping resistance curve, and a pump discharge pressure lower limit curve. It is a block diagram which shows the conventional 2 pump system heat source installation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 2 pump system heat source equipment, 2A-2C ... Heat source equipment, 3A-3C ... Primary pump, 4 ... 1st feed header, 5 ... 2nd 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 ... flow meter, 15, 16, 18, 20 ... temperature Meter, 17 ... Differential pressure gauge

Claims (2)

A plurality of heat source devices for cooling or heating the heat medium, a primary pump for pumping the cooled or heated heat medium and a first heat pump for collecting the heat medium from the heat source device. Feed header, a plurality of secondary pumps that send the heat medium from the first feed header, a second feed header that collects the heat medium from the secondary pump, and an external load to which the heat medium is supplied from the second feed header A device, a terminal bypass that bypasses the external load device, a heat medium that is heat-exchanged by the external load device, and a return header that is distributed to each heat source device; a first feed header and a second feed header; A first bypass and a first bypass valve that connect the first bypass header, a second bypass that connects the first feed header portion or the vicinity thereof and the return header portion or the vicinity thereof, control of the number of operating heat source devices and the secondary pump Operation control In 2 pump type heat source equipment and a control unit that performs,
A flow meter for measuring the circulating flow rate Q of the heat medium, a forward water thermometer for measuring the forward water temperature TS, a return water thermometer for measuring the return water temperature TR, the first feed header, and the second A pump head pressure gauge is installed to measure the differential pressure dP between the feed header and
The control device calculates a reference pump discharge pressure curve based on the following equation (1) from the circulation flow rate Q, the pump discharge pressure design value Pls, the actual lift Ps, the circulation flow rate design value Qs, and the coefficient n. When the secondary pump is controlled according to the pressure curve and the water supply temperature difference (TR-TS) between the outgoing water temperature TS and the return water temperature TR falls below a preset minimum temperature difference dTI, An operation control method for a two-pump heat source facility, wherein a correction is made to the discharge pressure P based on the reference pump discharge pressure curve based on the equation (2) .

Set the pump discharge pressure limit value curve shown in the following equation (3), the secondary pump discharge pressure 2 pump type heat source equipment according to claim 1 Symbol placement controls the pump discharge pressure limit value curve as the minimum discharge pressure Operation control method.

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