U.S. patent application number 15/111025 was filed with the patent office on 2016-11-24 for method for controlling number of pumps, device for controlling number of pumps, pump system, heat source system, and program.
This patent application is currently assigned to MITSUBISHI HEAVY INDUSTRIES, LTD.. The applicant listed for this patent is MITSUBISHI HEAVY INDUSTRIES, LTD.. Invention is credited to Minoru MATSUO, Satoshi NIKAIDO, Toshiaki OUCHI, Koki TATEISHI.
Application Number | 20160341440 15/111025 |
Document ID | / |
Family ID | 53756451 |
Filed Date | 2016-11-24 |
United States Patent
Application |
20160341440 |
Kind Code |
A1 |
OUCHI; Toshiaki ; et
al. |
November 24, 2016 |
METHOD FOR CONTROLLING NUMBER OF PUMPS, DEVICE FOR CONTROLLING
NUMBER OF PUMPS, PUMP SYSTEM, HEAT SOURCE SYSTEM, AND PROGRAM
Abstract
A method for controlling number of pumps includes a process of
increasing or decreasing the number of operating pumps based on a
flow rate of a heat medium that is forcibly fed to a load (40) by a
plurality of pumps connected in parallel or a heat load required by
the load and a frequency command value commanded to each pump in
operation among the plurality of pumps.
Inventors: |
OUCHI; Toshiaki; (Tokyo,
JP) ; NIKAIDO; Satoshi; (Tokyo, JP) ; MATSUO;
Minoru; (Tokyo, JP) ; TATEISHI; Koki; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI HEAVY INDUSTRIES, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
MITSUBISHI HEAVY INDUSTRIES,
LTD.
Tokyo
JP
|
Family ID: |
53756451 |
Appl. No.: |
15/111025 |
Filed: |
June 18, 2014 |
PCT Filed: |
June 18, 2014 |
PCT NO: |
PCT/JP2014/066141 |
371 Date: |
July 12, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24F 11/83 20180101;
F04B 49/06 20130101; Y02B 30/745 20130101; F04B 41/06 20130101;
F25B 49/02 20130101; F25B 25/005 20130101; F04B 49/065 20130101;
F25B 2600/13 20130101; Y02B 30/70 20130101; F04B 49/02 20130101;
F04B 2207/041 20130101 |
International
Class: |
F24F 11/06 20060101
F24F011/06; F04B 49/06 20060101 F04B049/06; F04B 41/06 20060101
F04B041/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2014 |
JP |
2014-017187 |
Claims
1-11. (canceled)
12. A method for controlling number of pumps, comprising: a process
of acquiring a number-of-pumps determination flow rate value
indicating a flow rate of a heat medium forcibly fed to a load from
a measurement value of a discharge flow rate by the pumps in
operation among a plurality of pumps, and a process of increasing
or decreasing a number of operating pumps based on the flow rate of
the heat medium that is forcibly fed to the load by the plurality
of pumps connected in parallel or a heat load required by the load
and a frequency command value commanded to each pump in operation
among the plurality of pumps, wherein, in the process of increasing
or decreasing the number of operating pumps, the number of
operating pumps is increased when the number-of-pumps determination
flow rate value is equal to or larger than a predetermined
threshold value G.alpha., and the frequency command value commanded
to each pump is equal to or larger than a predetermined threshold
value F.alpha., and the number of operating pumps is decreased when
the number-of-pumps determination flow rate value is equal to or
smaller than a predetermined threshold value G.beta., and the
frequency command value commanded to each pump is equal to or
smaller than a predetermined threshold value F.beta..
13. A method for controlling number of pumps, comprising: a process
of calculating a heat load required by a load, and a process of
increasing or decreasing a number of operating pumps based on a
flow rate of a heat medium that is forcibly fed to the load by the
plurality of pumps connected in parallel or the heat load required
by the load and a frequency command value commanded to each pump in
operation among the plurality of pumps, wherein, in the process of
increasing or decreasing the number of operating pumps, the number
of operating pumps is increased when the heat load is equal to or
larger than a predetermined threshold value L.alpha., and the
frequency command value commanded to each pump is equal to or
larger than a predetermined threshold value F.alpha., and the
number of operating pumps is decreased when the heat load is equal
to or smaller than a predetermined threshold value L.beta., and the
frequency command value commanded to each pump is equal to or
smaller than a predetermined threshold value F.beta..
14. The method for controlling number of pumps according to claim
12, wherein, in the process of increasing or decreasing the number
of operating pumps, a pump head of the pump is further compared
with an increase permission pump head serving as a threshold value
for increasing the number of pumps or a decrease permission pump
head serving as a threshold value for decreasing the number of
pumps, the number of operating pumps is increased only when the
increase permission pump head is smaller than the pump head, and
the number of operating pumps is decreased only when the decrease
permission pump head is larger than the pump head.
15. The method for controlling number of pumps according to claim
14, further comprising: a process of obtaining the increase
permission pump head by calculating the pump head when a frequency
of the pump is operated at the predetermined threshold value
F.beta. from the pump head calculated based on the discharge flow
rate of the pump after the number of operating pumps is increased
and a predetermined correlation of the pump head for the discharge
flow rate of the pump and obtaining the decrease permission pump
head by calculating the pump head when the frequency of the pump is
operated at the predetermined threshold value F.alpha. from the
pump head calculated based on the discharge flow rate of the pump
after the number of operating pumps is decreased and the
predetermined correlation.
16. The method for controlling number of pumps according to claim
12, further comprising: a process of acquiring a frequency command
value after the number of operating pumps is increased and a
frequency command value after the number of operating pumps is
decreased based on a predetermined correlation between the pump
head and the discharge flow rate of the pump at a predetermined
frequency of the pump in operation under a condition that the pump
head after the number of operating pumps is increased or decreased
to be equal to a current pump head, wherein, in the process of
increasing or decreasing the number of operating pumps, the number
of operating pumps is further increased only when the frequency
command value after the number of operating pumps is increased is
larger than the threshold value F.beta., and the number of
operating pumps is decreased only when the frequency command value
after the number of operating pumps is decreased is smaller than
the threshold value F.alpha..
17. The method for controlling number of pumps according to claim
12, further comprising: a process of acquiring a pump efficiency
after the number of operating pumps is increased, a pump efficiency
after the number of operating pumps is decreased, and a current
pump efficiency based on a predetermined correlation between the
discharge flow rate and the pump efficiency at the predetermined
frequency of the pump in operation, wherein, in the process of
increasing or decreasing the number of operating pumps, the number
of operating pumps is further increased only when the pump
efficiency after the number of operating pumps is increased is
equal to or larger than the current pump efficiency, and the number
of operating pumps is decreased only when the pump efficiency after
the number of operating pumps is decreased is equal to or larger
than the current pump efficiency.
18. A device for controlling number of pumps, comprising: a
number-of-pumps determination flow rate value acquiring unit
configured to acquire a number-of-pumps determination flow rate
value indicating a flow rate of a heat medium forcibly fed to a
load from a measurement value of a discharge flow rate by the pumps
in operation among a plurality of pumps, and a number-of-pumps
control unit configured to increase or decrease the number of
operating pumps that are connected in parallel to forcibly feed the
heat medium to the load based on the flow rate of the heat medium
forcibly fed to the load or a heat load required by the load and a
frequency command value commanded to each pump in operation among
the plurality of pumps, wherein, the number-of-pumps control unit
is configured so that the number of operating pumps is increased
when the number-of-pumps determination flow rate value is equal to
or larger than a predetermined threshold value G.alpha., and the
frequency command value commanded to each pump is equal to or
larger than a predetermined threshold value F.alpha., and the
number of operating pumps is decreased when the number-of-pumps
determination flow rate value is equal to or smaller than a
predetermined threshold value G.beta., and the frequency command
value commanded to each pump is equal to or smaller than a
predetermined threshold value F.beta..
19. A pump system, comprising: a plurality of pumps connected in
parallel; and the device for controlling number of pumps according
to claim 18, wherein the number of operating pumps is changed so
that the pump head per pump and the flow rate measurement value are
not changed.
20. A heat source system, comprising: a load; a plurality of heat
source machines configured to forcibly feed a heat medium and
connected in parallel; a secondary pump configured to further
forcibly feed the heat medium forcibly fed from the plurality of
heat source machines connected in parallel to the load; and the
device for controlling number of pumps according to claim 18.
21. A non-transitory computer-readable storage medium storing a
program causing a computer of a device for controlling number of
pumps to function as: a number-of-pumps determination flow rate
value acquiring unit configured to acquire a number-of-pumps
determination flow rate value indicating a flow rate of a heat
medium forcibly fed to a load from a measurement value of a
discharge flow rate by the pumps in operation among a plurality of
pumps, and a unit configured to increase or decrease the number of
operating pumps based on the flow rate of the heat medium that is
forcibly fed to the load by the plurality of pumps connected in
parallel or a heat load required by the load and a frequency
command value commanded to each pump in operation among the
plurality of pumps wherein, the unit configured to increase or
decrease the number of operating pumps is configured so that the
number of operating pumps is increased when the number-of-pumps
determination flow rate value is equal to or larger than a
predetermined threshold value G.alpha., and the frequency command
value commanded to each pump is equal to or larger than a
predetermined threshold value F.alpha., and the number of operating
pumps is decreased when the number-of-pumps determination flow rate
value is equal to or smaller than a predetermined threshold value
G.beta., and the frequency command value commanded to each pump is
equal to or smaller than a predetermined threshold value
F.beta..
22. The method for controlling number of pumps according to claim
13, wherein, in the process of increasing or decreasing the number
of operating pumps, a pump head of the pump is further compared
with an increase permission pump head serving as a threshold value
for increasing the number of pumps or a decrease permission pump
head serving as a threshold value for decreasing the number of
pumps, the number of operating pumps is increased only when the
increase permission pump head is smaller than the pump head, and
the number of operating pumps is decreased only when the decrease
permission pump head is larger than the pump head.
23. The method for controlling number of pumps according to claim
22, further comprising: a process of obtaining the increase
permission pump head by calculating the pump head when a frequency
of the pump is operated at the predetermined threshold value
F.beta. from the pump head calculated based on the discharge flow
rate of the pump after the number of operating pumps is increased
and a predetermined correlation of the pump head for the discharge
flow rate of the pump and obtaining the decrease permission pump
head by calculating the pump head when the frequency of the pump is
operated at the predetermined threshold value F.alpha. from the
pump head calculated based on the discharge flow rate of the pump
after the number of operating pumps is decreased and the
predetermined correlation.
24. The method for controlling number of pumps according to claim
13, further comprising: a process of acquiring a frequency command
value after the number of operating pumps is increased and a
frequency command value after the number of operating pumps is
decreased based on a predetermined correlation between the pump
head and the discharge flow rate of the pump at a predetermined
frequency of the pump in operation under a condition that the pump
head after the number of operating pumps is increased or decreased
to be equal to a current pump head, wherein, in the process of
increasing or decreasing the number of operating pumps, the number
of operating pumps is further increased only when the frequency
command value after the number of operating pumps is increased is
larger than the threshold value F.beta., and the number of
operating pumps is decreased only when the frequency command value
after the number of operating pumps is decreased is smaller than
the threshold value F.alpha..
25. The method for controlling number of pumps according to claim
13, further comprising: a process of acquiring a pump efficiency
after the number of operating pumps is increased, a pump efficiency
after the number of operating pumps is decreased, and a current
pump efficiency based on a predetermined correlation between the
discharge flow rate and the pump efficiency at the predetermined
frequency of the pump in operation, wherein, in the process of
increasing or decreasing the number of operating pumps, the number
of operating pumps is further increased only when the pump
efficiency after the number of operating pumps is increased is
equal to or larger than the current pump efficiency, and the number
of operating pumps is decreased only when the pump efficiency after
the number of operating pumps is decreased is equal to or larger
than the current pump efficiency.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for controlling
number of pumps, a device for controlling number of pumps, a pump
system, a heat source system, and a program.
[0002] Priority is claimed on Japanese Patent Application No.
2014-017187, filed on Jan. 31, 2014, the content of which is
incorporated herein by reference.
BACKGROUND ART
[0003] In a heat source system that supplies a heat medium such as
cold water or hot water (hereinafter, "cold/hot water") from a heat
source machine to a load device such as an air conditioner, a
plurality of secondary pumps that are connected in parallel between
the heat source machine and the air conditioner are often installed
to forcibly feed the heat medium to the air conditioner apart from
the heat source machine again in addition to a primary pump that
forcibly feeds the cold/hot water to the heat source machine. In
the heat source system including the secondary pumps, a technique
of deciding the number of secondary pumps that are operated so that
a discharge flow rate to the load device is satisfied is used.
Generally, in this technique, a threshold value serving as a
reference for increasing or decreasing the number of pumps is set,
and control is often performed such that an additional pump is
started when the flow rate of the heat medium measured by measuring
equipment installed in the middle of a supply path exceeds the
threshold value thereof, whereas when the measured flow rate of the
heat medium is the threshold value or less, a pump is stopped.
However, if it is determined whether or not the number of operating
pumps is increased or decreased based on only the measured flow
rate, it is likely for an additional pump to be started even when
there is still room in the capability of the pumps, that is, the
frequency of the pumps is enough compared to the rated
frequency.
[0004] For example, in a technique disclosed in Patent Literature
1, by changing the number of operating pumps using a flow rate as a
threshold value which is decided at a crossing point between a
curved line indicating a relation of a pump discharge pressure and
a pump discharge flow rate which are decided for each of the number
of operating secondary pumps and a control line indicating a
correlation of a flow rate of a heat medium to be supplied to a
load device and a pump discharge pressure necessary for it, the
threshold value of the flow rate at which discharge pressure can be
maintained even after the number of pumps is changed is set.
CITATION LIST
[Patent Literature]
[Patent Literature 1]
[0005] Japanese Patent No. 5261153
SUMMARY OF INVENTION
[Technical Problem]
[0006] In the case of the technique disclosed in Patent Literature
1, it is difficult to obtain a significant threshold value unless a
pressure drop characteristic of a pipe is accurately detected, and
a control line in which the pressure drop characteristic is
reflected is obtained. The pressure drop of the pipe refers to loss
of pump discharge pressure caused by friction occurring when a heat
medium flows in a pipe, a curved pipe, resistance by a valve, or
the like, and the pressure drop characteristic is a change
characteristic of the pressure drop to the flow rate of the heat
medium. Particularly, when the load device is an air conditioner, a
pressure drop of a system is changed by a control valve with which
the air conditioner is equipped, and thus a threshold value used
for control of the number of operating pumps undergoes deviation
unless a change in the control line is additionally considered. If
the number of operating pumps is not changed at an appropriate
timing, for example, the flow rate or the pressure of the heat
medium changes due to the unnecessary change in the number of
pumps, and it is hard to operate the heat source system stably.
[0007] The present invention provides a method for controlling
number of pumps, a device for controlling number of pumps, a pump
system, a heat source system, and a program.
[Solution to Problem]
[0008] According to a first aspect of the present invention, a
method for controlling number of pumps includes a process of
increasing or decreasing a number of operating pumps based on a
flow rate of a heat medium that is forcibly fed to a load by a
plurality of pumps connected in parallel or a heat load required by
the load and a frequency command value commanded to each pump in
operation among the plurality of pumps.
[0009] According to a second aspect of the present invention, the
method for controlling number of pumps according to the first
aspect further includes a process of acquiring a number-of-pumps
determination flow rate value indicating the flow rate of the heat
medium forcibly fed to the load from a measurement value of a
discharge flow rate by the pumps in operation among the plurality
of pumps, wherein, in the process of increasing or decreasing the
number of operating pumps, the number of operating pumps is
increased when the number-of-pumps determination flow rate value is
equal to or larger than a predetermined threshold value G.alpha.,
and the frequency command value commanded to each pump is equal to
or larger than a predetermined threshold value F.alpha., and the
number of operating pumps is decreased when the number-of-pumps
determination flow rate value is equal to or smaller than a
predetermined threshold value G.beta., and the frequency command
value commanded to each pump is equal to or smaller than a
predetermined threshold value F.beta..
[0010] According to a third aspect of the present invention, the
method for controlling number of pumps according to the first
aspect further includes a process of calculating the heat load
required by the load, wherein, in the process of increasing or
decreasing the number of operating pumps, the number of operating
pumps is increased when the heat load is equal to or larger than a
predetermined threshold value L.alpha., and the frequency command
value commanded to each pump is equal to or larger than a
predetermined threshold value F.alpha., and the number of operating
pumps is decreased when the heat load is equal to or smaller than a
predetermined threshold value L.beta., and the frequency command
value commanded to each pump is equal to or smaller than a
predetermined threshold value F.beta..
[0011] According to a fourth aspect of the present invention, in
the method for controlling number of pumps according to the second
or third aspect, in the process of increasing or decreasing the
number of operating pumps, a pump head of the pump is further
compared with an increase permission pump head serving as a
threshold value for increasing the number of pumps or a decrease
permission pump head serving as a threshold value for decreasing
the number of pumps, the number of operating pumps is increased
only when the increase permission pump head is smaller than the
pump head, and the number of operating pumps is decreased only when
the decrease permission pump head is larger than the pump head.
[0012] According to a fifth aspect of the present invention, the
method for controlling number of pumps according to the fourth
aspect further includes a process of obtaining the increase
permission pump head by calculating the pump head when a frequency
of the pump is operated at the predetermined threshold value
F.beta. from the pump head calculated based on the discharge flow
rate of the pump after the number of operating pumps is increased
and a predetermined correlation of the pump head for the discharge
flow rate of the pump and obtaining the decrease permission pump
head by calculating the pump head when the frequency of the pump is
operated at the predetermined threshold value F.alpha. from the
pump head calculated based on the discharge flow rate of the pump
after the number of operating pumps is decreased and the
predetermined correlation.
[0013] According to a sixth aspect of the present invention, the
method for controlling number of pumps according to the second or
third aspect further includes a process of acquiring a frequency
command value after the number of operating pumps is increased and
a frequency command value after the number of operating pumps is
decreased based on a predetermined correlation between the pump
head and the discharge flow rate of the pump at a predetermined
frequency of the pump in operation under a condition that the pump
head after the number of operating pumps is increased or decreased
to be equal to a current pump head, wherein, in the process of
increasing or decreasing the number of operating pumps, the number
of operating pumps is further increased only when the frequency
command value after the number of operating pumps is increased is
larger than the threshold value F.beta., and the number of
operating pumps is decreased only when the frequency command value
after the number of operating pumps is decreased is smaller than
the threshold value F.alpha..
[0014] According to a seventh aspect of the present invention, the
method for controlling number of pumps according to any one of the
second to sixth aspect further includes a process of acquiring a
pump efficiency after the number of operating pumps is increased, a
pump efficiency after the number of operating pumps is decreased,
and a current pump efficiency based on a predetermined correlation
between the discharge flow rate and the pump efficiency at the
predetermined frequency of the pump in operation, wherein, in the
process of increasing or decreasing the number of operating pumps,
the number of operating pumps is further increased only when the
pump efficiency after the number of operating pumps is increased is
equal to or larger than the current pump efficiency, and the number
of operating pumps is decreased only when the pump efficiency after
the number of operating pumps is decreased is equal to or larger
than the current pump efficiency.
[0015] According to an eighth aspect of the present invention, a
device for controlling number of pumps includes a number-of-pumps
control unit configured to increase or decrease the number of
operating pumps that are connected in parallel to forcibly feed a
heat medium to a load based on a flow rate of the heat medium
forcibly fed to the load or a heat load required by the load and a
frequency command value commanded to each pump in operation among
the plurality of pumps.
[0016] According to a ninth aspect of the present invention, a pump
system includes a plurality of pumps connected in parallel and the
device for controlling number of pumps according to the eighth
aspect, wherein the number of operating pumps is changed so that
the pump head per pump and the flow rate measurement value are not
changed.
[0017] According to a tenth aspect of the present invention, a heat
source system includes a load, a plurality of heat source machines
configured to forcibly feed a heat medium and connected in
parallel, a secondary pump configured to further forcibly feed the
heat medium forcibly fed from the plurality of heat source machines
connected in parallel to the load, and the device for controlling
number of pumps according to the eighth aspect.
[0018] According to an eleventh aspect of the present invention, a
program causes a computer of a device for controlling number of
pumps to function as a unit configured to increase or decrease the
number of operating pumps based on a flow rate of a heat medium
that is forcibly fed to a load by a plurality of pumps connected in
parallel or a heat load required by the load and a frequency
command value commanded to each pump in operation among the
plurality of pumps.
[Advantageous Effects of Invention]
[0019] According to the method for controlling number of pumps, the
device for controlling number of pumps, the pump system, the heat
source system, and the program described above, it is possible to
appropriately control the number of operating pumps at an
appropriate timing without knowing characteristics of facilities
such as the pressure drop characteristics.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a schematic diagram showing a heat source system
according to a first embodiment of the present invention.
[0021] FIG. 2 is a functional block diagram showing a device for
controlling number of pumps according to the first embodiment of
the present invention.
[0022] FIG. 3 is a diagram showing a process flow of the device for
controlling number of pumps according to the first embodiment of
the present invention.
[0023] FIG. 4 is a schematic diagram showing a heat source system
according to a modified example of the first embodiment of the
present invention.
[0024] FIG. 5 is a functional block diagram showing a device for
controlling number of pumps according to the modified example of
the first embodiment of the present invention.
[0025] FIG. 6 is a functional block diagram showing a device for
controlling number of pumps according to a second embodiment of the
present invention.
[0026] FIG. 7 is a diagram showing an example of Q-H
characteristics indicating characteristics of a pump.
[0027] FIG. 8A is a diagram showing a change when the number of
operating secondary pumps is increased from 1 to 2.
[0028] FIG. 8B is a diagram showing a change when the number of
operating secondary pumps is increased from 1 to 2.
[0029] FIG. 9 is a diagram showing a process flow of the device for
controlling number of pumps according to the second embodiment of
the present invention.
[0030] FIG. 10 is a functional block diagram showing a device for
controlling number of pumps according to a third embodiment of the
present invention.
[0031] FIG. 11 is a diagram showing a process flow of the device
for controlling number of pumps according to the third embodiment
of the present invention.
[0032] FIG. 12 is a functional block diagram showing a device for
controlling number of pumps according to the fourth embodiment of
the present invention.
[0033] FIG. 13 is a diagram showing an example of a correlation
between a pump discharge flow rate and pump efficiency.
[0034] FIG. 14 is a diagram showing a process flow of the device
for controlling number of pumps according to the fourth embodiment
of the present invention.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0035] Hereinafter, a heat source system according to a first
embodiment of the present invention will be described with
reference to FIGS. 1 to 3.
[0036] FIG. 1 is a schematic diagram showing the heat source system
according to the first embodiment of the present invention.
[0037] As shown in FIG. 1, the heat source system of the present
embodiment includes heat source machines 30, primary pumps 10,
secondary pumps 20, a load 40, a flowmeter 21, and a device for
controlling number of pumps 50.
[0038] The heat source machines 30 are devices that supply a heat
medium for cooling or heating such as water to the load. The
primary pumps 10 forcibly feed the heat medium to the heat source
machines 30. The heat source machines 30 are devices that supply a
heat medium for cooling or heating such as water to a load. In the
heat source system according to the present embodiment, a plurality
of combinations of the heat source machines 30 and the primary
pumps 10 may be installed in parallel. FIG. 1 shows a state in
which the plurality of primary pumps 10 are installed in
parallel.
[0039] The secondary pumps 20 forcibly feed the heat medium fed
from the heat source machines 30 to the load 40. The secondary
pumps 20 are installed to be connected to each other in parallel,
and control the flow rate of the heat medium to be supplied to the
load 40 according to a request from the load 40.
[0040] The flowmeter 21 is a flowmeter that measures a flow rate
per unit time of the heat medium forcibly fed from the pumps.
[0041] The load 40 is, for example, an air conditioner. The load 40
performs heat dissipation or heat absorption on the heat medium,
and causes the resulting heat medium to flow back to the heat
source machine 30.
[0042] The device for controlling number of pumps 50 is a device
having a function of increasing or decreasing the number of
operating secondary pumps 20 according to a requested load required
by the load 40.
[0043] In FIG. 1, the two heat source machines 30, the two primary
pumps 10, and the two secondary pumps 20 are installed, but the
number of heat source machines 30, the number of primary pumps 10,
and the number of secondary pumps 20 are not limited thereto. For
example, six heat source machines 30, six primary pumps 10, and
nine secondary pumps 20 may be installed.
[0044] In the heat source system, a device (not shown) that
controls the number of operating heat source machines 30 such that
a supply amount of the heat medium is adjusted according to the
requested load of the load 40 may be installed.
[0045] FIG. 2 is a functional block diagram showing the device for
controlling number of pumps according to the first embodiment of
the present invention. The device for controlling number of pumps
50 according to the present embodiment will be described with
reference to FIG. 2.
[0046] The device for controlling number of pumps 50 includes a
number-of-pumps determination flow rate value acquiring unit 101, a
number-of-pumps determination frequency value acquiring unit 102, a
pump frequency setting unit 103, a flow rate acquiring unit 104, a
number-of-pumps control unit 105, and a storage unit 200 as shown
in FIG. 2.
[0047] The number-of-pumps determination flow rate value acquiring
unit 101 reads and acquires a flow rate increase threshold value
G.alpha. or a flow rate decrease threshold value G.beta. serving as
a threshold value used when increasing or decreasing the number of
operating secondary pumps 20 according to the flow rate from the
storage unit 200. The number-of-pumps determination flow rate value
acquiring unit 101 calculates the number-of-pumps determination
flow rate value, for example, according to the following Formula
(1).
[ Math . 1 ] G load i n G 0 i ( 1 ) ##EQU00001##
[0048] Here, Gload is a measurement value of the flow rate of the
heat medium such as water forcibly fed from all the secondary pumps
20 which are in operation. G0i is a rated flow rate of the
secondary pumps which are currently in operation. The
number-of-pumps determination flow rate value is a ratio of the
measurement values of the discharge flow rates by all the pumps in
operation with respect to a sum of the rated flow rates of the
secondary pumps in operation.
[0049] The number-of-pumps determination frequency value acquiring
unit 102 reads and acquires a frequency increase threshold value
F.alpha. or a frequency decrease threshold value F.beta. used when
increasing or decreasing the number of operating secondary pumps 20
according to a frequency from the storage unit 200. The
number-of-pumps determination frequency value acquiring unit 102
acquires a frequency command value that is output from the pump
frequency setting unit 103 to the secondary pumps 20 from the pump
frequency setting unit 103, and uses the acquired frequency command
value as a number-of-pumps determination frequency value.
[0050] The pump frequency setting unit 103 gives a command
indicating the frequency for operating the pumps to the secondary
pump 20. The frequency is a frequency of electric power for
rotating a motor for driving the secondary pump 20, and the pump
frequency setting unit 103 controls an output of the pumps by
designating the frequency and changing the number of revolutions of
the pumps. The pump frequency setting unit 103 is assumed to output
the same frequency command value to the plurality of secondary
pumps 20 in the operation state.
[0051] The flow rate acquiring unit 104 acquires the flow rate of
the heat medium measured by the flowmeter 21.
[0052] The number-of-pumps control unit 105 increases the number of
operating pumps when the flow rate of the heat medium forcibly fed
by the pump or the frequency of the pump satisfies a predetermined
condition. In the present embodiment, the number of operating pumps
is increased when the following two conditions are satisfied.
<Increase condition 1: determined based on flow
rate>number-of-pumps determination flow rate
value.gtoreq.G.alpha. (2)
<Increase condition 2: determined based on
frequency>number-of-pumps determination frequency value F.alpha.
(3)
[0053] Here, the number-of-pumps determination frequency value is
the same value as a frequency command value Fset that is output
from the pump frequency setting unit 103 to the secondary pump 20.
F.alpha. is a threshold value acquired by the number-of-pumps
determination frequency value acquiring unit 102.
[0054] In other words, when the ratio of the flow rates forcibly
fed by all the secondary pumps 20 that are currently in operation
with respect to the total sum of water feeding capabilities of the
secondary pumps 20 in operation is equal to or larger than the
threshold value G.alpha. (Formula (2)), and the frequency command
value output to each secondary pump 20 is equal to or larger than
the threshold value F.alpha. (Formula (3)), the number-of-pumps
control unit 105 increases the number of operating secondary pumps
20.
[0055] Further, the number-of-pumps control unit 105 decreases the
number of operating pumps when the flow rate of the heat medium
forcibly fed by the pump or the frequency of the pump satisfies a
predetermined condition. In the present embodiment, when the
following two conditions are satisfied, the number of operating
pumps is decreased.
<Decrease condition 1: determination based on flow
rate>number-of-pumps determination flow rate value G.beta.
(4)
[0056] Here, G.beta. is a threshold value acquired by the
number-of-pumps determination flow rate value acquiring unit
101.
<Decrease condition 2: determination based on
frequency>number-of-pumps determination frequency value F.beta.
(5)
[0057] Here, FP is a threshold value acquired by the
number-of-pumps determination frequency value acquiring unit 102.
The number-of-pumps determination frequency value is, for example,
a frequency command value which is designated to the secondary
pumps 20 by the pump frequency setting unit 103. In other words,
when the ratio of the flow rates forcibly fed by all the secondary
pumps 20 that are currently in operation with respect to the total
sum of water feeding capabilities of the secondary pumps 20 that
are currently in operation is equal to or smaller than the
threshold value G.beta. (Formula (4)), and the frequency command
value output to each secondary pump 20 is equal to or smaller than
the threshold value F.beta. (Formula (5)), the number-of-pumps
control unit 105 decreases the number of operating secondary pumps
20.
[0058] The storage unit 200 holds the threshold values G.alpha. and
F.alpha. used for determining whether or not the number of pumps is
increased or decreased, information indicating characteristics of
the secondary pumps 20, or the like. The characteristic information
is, for example, Q-H characteristics, a graph indicating a
correlation between the discharge flow rate of the pumps and the
pump efficiency, or the like.
[0059] FIG. 3 is a diagram showing a process flow of the device for
controlling number of pumps according to the present
embodiment.
[0060] A process of increasing or decreasing the number of
operating secondary pumps 20 through the device for controlling
number of pumps 50 will be described with reference to the process
flow of FIG. 3.
[0061] It is assumed that the heat source system shown in FIG. 1 is
operating, for example, the load 40 is the air conditioner, and
when the user increases or decreases a temperature setting, the
requested load is increased or decreased, and the device for
controlling number of pumps 50 controls the number of operating
secondary pumps 20 accordingly. Further, it is assumed that the sum
of the flow rates of the secondary pumps 20 directly after the
number of pumps is increased or decreased does not change from that
before the number of pumps is increased or decreased, and the pump
head (head of the pumps) per secondary pump 20 does not change.
[0062] First, the flow rate acquiring unit 104 acquires a flow rate
per unit time measured by the flowmeter 21 (step S1). The flow rate
measured by the flowmeter 21 is a total flow rate of the heat
medium forcibly fed by the one or more secondary pumps 20. The
measurement value is a value obtained by actually measuring the
flow rate flowing through the pipe and thus can be considered to be
a value in which the pressure drop characteristics of the pipe are
reflected.
[0063] Then, the number-of-pumps determination flow rate value
acquiring unit 101 reads and acquires the threshold values G.alpha.
and G.beta. stored in the storage unit 200. The number-of-pumps
determination flow rate value acquiring unit 101 calculates the
number-of-pumps determination flow rate value using Formula (1)
(step S2). The number-of-pumps determination flow rate value
acquiring unit 101 outputs the values to the number-of-pumps
control unit 105.
[0064] Then, the number-of-pumps determination frequency value
acquiring unit 102 reads and acquires the threshold values F.alpha.
and F.beta. stored in the storage unit 200. The number-of-pumps
determination frequency value acquiring unit 102 acquires the pump
frequency command value that is commanded from the pump frequency
setting unit 103 to the secondary pump 20 as the number-of-pumps
determination frequency value (step S3). The number-of-pumps
determination frequency value acquiring unit 102 outputs the values
to the number-of-pumps control unit 105.
[0065] Then, the number-of-pumps control unit 105 evaluates Formula
(2) and Formula (3), and performs determination of the "increase
condition 1" and the "increase condition 2" (step S4). Then, when
both of the conditions are satisfied (Yes in step S4), the
number-of-pumps control unit 105 increases the number of secondary
pumps 20 by starting up one of the secondary pumps 20 that are
currently in the stop state (step S5).
[0066] When it is determined through comparison that none of the
"increase condition 1" and the "increase condition 2" is satisfied
(No in step S4), the process proceeds to step S6.
[0067] Then, the number-of-pumps control unit 105 evaluates Formula
(4) and Formula (5), and performs determination of the "decrease
condition 1" and the "decrease condition 2" (step S6). Then, when
both of the conditions are satisfied (Yes in step S6), the
number-of-pumps control unit 105 decreases the number of secondary
pumps 20 by stopping one of the secondary pumps 20 which are
currently in operation (step S7).
[0068] When it is determined through comparison that none of the
"decrease condition 1" and the "decrease condition 2" is satisfied
(No in step S6), the process proceeds to step S8.
[0069] Finally, the device for controlling number of pumps 50
determines whether or not the heat source system has been stopped,
for example, by an operation of the user according to a
predetermined method. When the operation of the heat source system
has been stopped (Yes in step S8), the present process flow ends.
When the operation is continued (No in step S8), the process
starting from step S1 is repeated.
[0070] Effects of the present embodiment will be described. For
example, in a "first heat source system state" in which a value of
the air conditioner is narrowed by a decrease in a load, and the
pressure drop of the system is large, one secondary pump 20 is in
operation, and the measurement value of the discharge flow rate at
that time is 100 m.sup.3/h. On the other hand, in a "second heat
source system state" in which the pressure drop is decreased by an
increase in a load, one secondary pump 20 is in operation, and the
measurement value of the discharge flow rate is 100 m.sup.3/h as
well. Then, a threshold value for increasing the number of
operating secondary pumps 20 from 1 to 2 is 100 m.sup.3/h.
[0071] At this time, in the "first heat source system state," the
pressure drop is large, and thus if the measurement value of the
discharge flow rate is 100 m.sup.3/h although the secondary pump 20
is operating at a frequency of a value close to a maximum, control
of increasing the number of operating secondary pumps 20 to 2
according to the threshold value that is set in advance is
considered to be appropriate. On the other hand, in the "second
heat source system state," the pressure drop is small, and thus,
for example, the secondary pump 20 is operated at a frequency that
is about half a maximum frequency, and the flow rate of 100
m.sup.3/h is obtained. In this case, it is not necessarily
appropriate to increase the number of operating secondary pumps 20,
and there is also a possibility that the flow rate required by the
load device can be supplied by increasing the frequency of the
secondary pump 20 that is currently in operation. In this case, in
the technique of the related art in which only the flow rate is
used for determination as to whether or not the number of pumps is
increased or decreased, the number of secondary pumps is increased.
The increase in the number of pumps significantly changes the
pressure and the flow rate of the heat medium flowing in the
system.
[0072] According to the present embodiment, the determination is
performed based on the frequency command value in addition to the
actual measurement value of the flow rate including the pressure
drop information of the system, and thus it is possible to increase
or decrease the number of secondary pumps 20 without knowing the
details of facilities such as the pressure drop. Further, it is
determined whether or not the number of pumps is increased or
decreased using the pump frequency command value, and thus it is
possible to increase or decrease the number of secondary pumps 20
in view of an available capacity of the pump, and, for example,
control of increasing the number of pumps although there is a room
in capability of the pump can be prevented. Thus, an increase or
decrease in the number of pumps does not occur often, and the heat
source system can be operated more stably than in the technique of
the related art. Similarly, even when the number of pumps is
decreased, the number of pumps can be prevented from being
decreased although the capability of the pump can be decreased by
decreasing the frequency.
Modified Example
[0073] In a modified example of the present embodiment, a heat load
required by the load 40 can be used instead of the flow rate of the
heat medium. The modified example will be described below with
reference to FIGS. 4 and 5.
[0074] FIG. 4 is a schematic diagram showing a heat source system
according to the modified example of the present embodiment.
[0075] The heat source system of the modified example includes a
thermometer 22 and a thermometer 23. The remaining configuration is
the same as in the first embodiment.
[0076] The thermometer 22 is installed nearby an inlet of the load
40. The thermometer 22 measures the temperature of the heat medium
to be supplied to the load 40.
[0077] The thermometer 23 is installed nearby an outlet of the load
40. The thermometer 23 measures the temperature of the heat medium
to flow from the load 40 back to the heat source machine 30.
[0078] FIG. 5 is a functional block diagram showing the device for
controlling number of pumps according to the modified example of
the present embodiment.
[0079] The device for controlling number of pumps 50 of the
modified example differs from that of the first embodiment in that
the device for controlling number of pumps includes a temperature
acquiring unit 110, and includes a number-of-pumps determination
heat load acquiring unit 111 instead of the number-of-pumps
determination flow rate value acquiring unit 101. The remaining
configuration of the present embodiment is the same as in the first
embodiment.
[0080] The temperature acquiring unit 110 acquires the temperatures
of the heat medium measured by the thermometer 22 and the
thermometer 23.
[0081] The number-of-pumps determination heat load acquiring unit
111 reads a heat load increase threshold value La and a heat load
decrease threshold value L.beta. serving as a predetermined
threshold value from the storage unit 200. The number-of-pumps
determination heat load acquiring unit 111 acquires the flow rate
of the heat medium from the flow rate acquiring unit 104, acquires
the temperatures of the heat medium measured by the thermometer 22
and the thermometer 23 from the temperature acquiring unit 110, and
calculates a load (a heat load) required by the load 40. The heat
load may be calculated using, for example, the following
formula:
heat load=flow rate of heat medium.times.(|temperature of heat
medium to flow back-temperature of the heat medium to be
supplied|).times.specific heat of heat medium.times.specific
gravity of heat medium (6)
[0082] Here, the "flow rate of the heat medium" is a value that is
measured by the flowmeter 21 and acquired from the flow rate
acquiring unit 104 by the number-of-pumps determination heat load
acquiring unit 111. The "temperature of the heat medium to flow
back" is a temperature measured by the thermometer 23 and a value
acquired from the temperature acquiring unit 110 by the
number-of-pumps determination heat load acquiring unit 111. The
"temperature of the heat medium to be supplied" is a temperature
measured by the thermometer 22 and a value acquired from the
temperature acquiring unit 110 by the number-of-pumps determination
heat load acquiring unit 111. The specific heat of the heat medium
and the specific gravity of the heat medium are recorded in the
storage unit 200 in advance, and the number-of-pumps determination
heat load acquiring unit 111 reads the values from the storage unit
200.
[0083] In the present embodiment, the number-of-pumps control unit
105 increases the number of operating pumps when the heat load
calculated by the number-of-pumps determination heat load acquiring
unit 111 or the frequency of the pump acquired by the
number-of-pumps determination frequency value acquiring unit 102
satisfies a predetermined condition. Specifically, the number of
operating pumps is increased when the following two conditions are
satisfied.
<Increase condition 1-1: determination based on heat
load>heat load.gtoreq.L.alpha. (7)
<Increase condition 2: determination based on
frequency>number-of-pumps determination frequency
value.gtoreq.F.alpha. (8)
[0084] The number-of-pumps control unit 105 decreases the number of
operating pumps when the heat load or the frequency of the pump
satisfies a predetermined condition. Specifically, the number of
operating pumps is decreased when the following two conditions are
satisfied.
<Decrease condition 1-1: determination based on heat
load>heat load.ltoreq.L.beta. (9)
<Decrease condition 2: determination based on
frequency>number-of-pumps determination frequency
value.ltoreq.F.beta. (10)
[0085] In the modified example, the increase condition 1-1 and the
decrease condition 1-1 differ from those in the first embodiment.
The increase condition 2 and the decrease condition 2 are the same
as those in the first embodiment.
[0086] A process flow will be described. In the modified example,
in step S1 of FIG. 3, the flow rate acquiring unit 104 acquires the
flow rate measured by the flowmeter 21, and the temperature
acquiring unit 110 further acquires the temperatures of the heat
medium measured by the thermometer 22 and the thermometer 23. In
step S2, the number-of-pumps determination heat load acquiring unit
111 reads the threshold values
[0087] L.alpha. and L.beta. stored in the storage unit 200. The
number-of-pumps determination heat load acquiring unit 111 acquires
the flow rate of the heat medium from the flow rate acquiring unit
104, and acquires the temperature of the heat medium to be supplied
from the temperature acquiring unit 110 to the load 40 and the
temperature of the heat medium to flow from the load 40 back to the
heat source machine 30. Then, the number-of-pumps determination
heat load acquiring unit 111 calculates the heat load using Formula
(6). In step S4, the number-of-pumps control unit 105 performs
determination of the "increase condition 1-1" and the "increase
condition 2." In step S6, the number-of-pumps control unit 105
performs determination of the "decrease condition 1-1" and the
"decrease condition 2." The remaining process steps in the present
modified example are the same as those in the first embodiment.
[0088] The threshold values G.alpha., G.beta., F.alpha., F.beta.,
L.alpha., and L.beta. used in the present embodiment and the
modified example are values that are decided in advance through
experimentation, simulation, or the like.
Second Embodiment
[0089] A heat source system according to a second embodiment of the
present invention will be described below with reference to FIGS. 6
to 9.
[0090] The second embodiment relates to an example in which
repetition of an increase or a decrease in the number of pumps is
prevented so that the operation of the pumps is more stably
performed in addition to the first embodiment.
[0091] FIG. 6 is a functional block diagram showing the device for
controlling number of pumps according to the present
embodiment.
[0092] The device for controlling number of pumps 50 of the present
embodiment differs from that of the first embodiment in that the
device for controlling number of pumps includes a pump head
acquiring unit 107. The remaining configuration of the present
embodiment is the same as in the first embodiment.
[0093] The pump head acquiring unit 107 acquires the pump head of
the secondary pumps 20 that are currently in operation among the
secondary pumps 20 or the pump head after the number of secondary
pumps is increased or decreased based on the Q-H characteristics
stored in the storage unit 200. Here, the pump head refers to a
head of the pumps. The Q-H characteristics refer to a performance
curve of the pumps indicating a relation between the discharge flow
rate and the pump head when the pumps are operated at a maximum
frequency. FIG. 7 shows an example of the Q-H characteristics.
Generally, the discharge flow rate (Q) and the pump head (H) of the
pumps have a relation in which the pump head decreases as the
discharge flow rate increases, and the Q-H characteristics draw a
different trajectory according to a type of pump. The Q-H
characteristics indicating the Q-H correlation of the secondary
pumps 20 used in the heat source system are stored in the storage
unit 200, and the pump head acquiring unit 107 acquires the pump
head corresponding to the discharge flow rate of secondary pumps
per secondary pump 20 before and after the number of pumps is
increased or decreased using the Q-H characteristics.
[0094] Next, a method of obtaining the pump head will be described
more specifically. First, for example, symbols used for obtaining
the pump head will be described in connection with an example in
which the number of pumps is increased.
[0095] FIGS. 8A and 8B are diagrams showing a change when the
number of operating secondary pumps 20 is increased from 1 to 2.
Hereinafter, a secondary pump 20 in the operation state from the
beginning is referred to as a "pump 20-1," and a second secondary
pump 20 to be added is referred to as a "pump 20-2."
[0096] FIG. 8A is a diagram showing that one pump is in the
operation state. The flow rate per unit time which is forcibly fed
by one pump 20-1 is indicated by GA, and the total flow rate per
unit time which is forcibly fed by all pumps 20-1 is indicated by
GinA. In FIG. 8A, since the number of operating pumps is 1,
GinA=GA. The frequency of the pump 20-1 is indicated by fA, and a
head of the pump 20-1 is indicated by HA.
[0097] FIG. 8B is a diagram showing that two pumps are in the
operation state. A flow rate per unit time which is forcibly fed by
each of the pump 20-1 and the pump 20-2 is indicated by GB, and a
total flow rate per unit time which is forcibly fed by the two
pumps, that is, the pump 20-1 and the pump 20-2, is indicated by
GinB. In FIG. 8B, since the number of operating pumps is 2,
GinB=GB.times.2. A frequency of the pump 20-1 and the pump 20-2 is
indicated by fB, and a head of the pump 20-1 and the pump 20-2 is
indicated by HB. In other words, in FIG. 8B, the device for
controlling number of pumps 50 performs control such that each of
the secondary pumps 20 in the operation state has the same
frequency regardless of the number of operating pumps. Further, the
device for controlling number of pumps 50 performs control such
that the total flow rate (GinA) and the pump head (HA) do not
change before and after the number of secondary pumps 20 is
increased or decreased when the number of secondary pumps 20 is
increased or decreased. These conditions are prerequisites common
to the first to fourth embodiments.
[0098] In summary, after the number of pumps is increased from n to
n+m, respective values can be indicated as follows: [0099] total
flow rate: GinB=GinA; [0100] discharge flow rate per pump:
GB=(n/(n+m))GA; [0101] pump head per pump: HB=HA; and [0102] pump
frequency: fB (the same in all pumps in operation).
[0103] Next, a method of obtaining the pump head will be described.
The secondary pumps 20 are assumed to operate at a frequency 1, and
a discharge flow rate 1 is assumed to be obtained. First, the
discharge flow rate when the pumps operate at the maximum frequency
can be obtained by multiplying the discharge flow rate 1 by a value
obtained by dividing the maximum frequency by the frequency 1.
Then, the Q-H characteristics are read using the obtained discharge
flow rate of the maximum frequency, and the pump head corresponding
to the discharge flow rate when the pumps operate at the maximum
frequency is obtained. Then, the obtained pump head is multiplied
by the square of the ratio of the current frequency 1 to the pump
maximum frequency. A value obtained as a result is the pump
head.
[0104] First, an increase permission pump head (HB') is obtained
using the following Formula (11).
[ Math . 2 ] H B ' = F ( n n + m G A f max F .beta. ) .times. ( F
.beta. f max ) 2 ( 11 ) ##EQU00002##
[0105] Here, the first term F(x) on the right side indicates a
function for obtaining the pump head based on the discharge flow
rate indicated by the Q-H characteristics. F.beta. is the frequency
decrease threshold value described in the first embodiment.
Further, fmax is the maximum frequency (the pump maximum frequency)
of each secondary pump 20. The pump head obtained using the
frequency decrease threshold value F.beta. indicates the pump head
(the increase permission pump head) when the number of secondary
pumps 20 is decreased by 1 from a state in which the number of
secondary pumps 20 is increased by 1.
[0106] The pump head acquiring unit 107 similarly obtains the pump
head (HB) in the state after the number of pumps is increased using
the following Formula (12). Here, the frequency or the flow rate
before the increase is used because the number of secondary pumps
20 is increased so that the pump head does not change, and thus the
pump head after the increase is equal to the current pump head
(before the increase).
[ Math . 3 ] H B = F ( G A f max f A ) .times. ( f A f max ) 2 ( 12
) ##EQU00003##
[0107] Then, the number-of-pumps control unit 105 performs
determination of the following condition using the values in
addition to the two increase conditions in the first
embodiment.
<Increase condition 3: determination based on pump
head>increase permission pump head<pump head after increase
(13)
[0108] In other words, the number-of-pumps control unit 105
increases the number of operating secondary pumps 20 when it is
equal to or larger than the increase permission pump head in
addition to the "increase condition 1" and the "increase condition
2." The increase permission pump head is a value that is obtained
using the frequency decrease threshold value and used as a
reference for decreasing the number of operating pumps after the
number of operating pumps is increased. Since there is a
possibility that the number of pumps will be decreased again if the
pump head after the increase falls below the value even after the
number of operating pumps is increased, the above condition is
added in the present embodiment to eliminate such waste.
[0109] Next, a method of obtaining the decrease permission pump
head through the pump head acquiring unit 107 will be described.
The decrease permission pump head is a value used as a reference
for increasing the pump after the number of operating pumps is
decreased.
[0110] Similarly to the case of increase, respective values after
the number of secondary pumps 20 is decreased from n to n-m can be
indicated as follows. [0111] water feeding flow rate: GinB=GinA
[0112] water feeding flow rate per pump: GB=(n/(n-m))GA [0113] pump
head per pump: HB=HA [0114] pump frequency: fB (the same in all
pumps in operation)
[0115] The decrease permission pump head may be obtained using the
following Formula (14).
[ Math . 4 ] H B ' = F ( n n - m G A f max F .alpha. ) .times. ( F
.alpha. f max ) 2 ( 14 ) ##EQU00004##
[0116] F.alpha. is the frequency increase threshold value described
in the first embodiment. The pump head acquiring unit 107 obtains
the pump head (HB) in the state after the number of pumps is
decreased using the following Formula (12). The pump head after the
decrease does not differ from the pump head before the number of
pumps is decreased and thus can be obtained using Formula (12).
[0117] Then, the number-of-pumps control unit 105 performs
determination of the following condition using the values in
addition to the two decrease conditions in the first
embodiment.
<Decrease condition 3: determination based on pump
head>decrease permission pump head>pump head after decrease
(15)
[0118] In other words, the number-of-pumps control unit 105
decreases the number of operating secondary pumps 20 when it is
equal to or less than the decrease permission pump head in addition
to the "decrease condition 1" and the "decrease condition 2." This
condition is a condition in consideration of the fact that there is
a possibility that the number of pumps will be increased again
after the number of operating pumps is decreased, similarly to the
case of the increase.
[0119] FIG. 9 is a diagram showing a process flow of the device for
controlling number of pumps according to the present
embodiment.
[0120] A process of increasing or decreasing the number of
operating secondary pumps 20 through the device for controlling
number of pumps 50 will be described with reference to a process
flow of FIG. 9. The same processes as those in FIG. 3 are denoted
by the same reference numerals.
[0121] First, steps S1 to S3 are the same as those in the first
embodiment. In other words, the flow rate acquiring unit 104
acquires the flow rate measured by the flowmeter 21, the
number-of-pumps determination flow rate value acquiring unit 101
acquires the threshold values G.alpha. and G.beta. and the
number-of-pumps determination flow rate value, and the
number-of-pumps determination frequency value acquiring unit 102
acquires the threshold values F.alpha. and F.beta. and the
number-of-pumps determination frequency value.
[0122] Then, the pump head acquiring unit 107 obtains the pump head
after the number of pumps is increased or decreased using Formula
(12), obtains the increase permission pump head using Formula (11),
and obtains the decrease permission pump head using Formula (14)
(step S10).
[0123] Then, the number-of-pumps control unit 105 performs
determination of the "increase condition 1," the "increase
condition 2," and the "increase condition 3" (step S11). Then, when
all the three conditions are satisfied (Yes in step S11), the
number-of-pumps control unit 105 increases the number of operating
secondary pumps 20 by 1 (step S5).
[0124] When it is determined through comparison that any of the
"increase condition 1," the "increase condition 2," and the
"increase condition 3" is not satisfied (No in step S11), the
process proceeds to step S12.
[0125] Then, the number-of-pumps control unit 105 performs
determination of the "decrease condition 1," the "decrease
condition 2," and the "decrease condition 3" (step S12). Then, when
all the three conditions are satisfied (Yes in step S12), the
number-of-pumps control unit 105 decreases the number of operating
secondary pumps 20 by 1 (step S7).
[0126] When it is determined through comparison that any of the
"decrease condition 1," the "decrease condition 2," and the
"decrease condition 3" is not satisfied (No in step S12), the
process proceeds to step S8. The process of step S8 is the same as
that in FIG. 3. In other words, the process starting from step S1
is repeated until the heat source system is stopped.
[0127] In the first embodiment, the determination criterion as to
whether or not the number of secondary pumps 20 is increased or
decreased using the measured flow rate and the pump frequency has
been described. However, since the state after the number of pumps
is increased or decreased is not considered in only the method of
the first embodiment, the determination as to whether or not the
number of pumps is increased or decreased is performed again, and
there is a possibility that the increase and the decrease will be
repeated.
[0128] According to the present embodiment, when the determination
as to whether or not the number of pumps is increased or decreased
is performed, the number of pumps is increased or decreased by
performing a comparison of the pump operation state after the
increase (decrease) with the pump head of the decrease (increase)
threshold value estimated from the Q-H characteristics in addition
to the flow rate measurement value and the pump frequency after the
increase or the decrease, and thus the repetition of the increase
and the decrease can be prevented.
[0129] The present embodiment may be combined with the modified
example of the first embodiment.
Third Embodiment
[0130] Next, a heat source system according to a third embodiment
of the present invention will be described with reference to FIGS.
10 and 11.
[0131] The third embodiment relates to an example in which
repetition of an increase or a decrease in the number of pumps is
prevented so that the operation of the pump is more stably
performed in addition to the first embodiment, similarly to the
second embodiment.
[0132] FIG. 10 is a functional block diagram showing a device for
controlling number of pumps 50 according to the present
embodiment.
[0133] The device for controlling number of pumps 50 of the present
embodiment differs from that of the first embodiment in that the
device for controlling number of pumps 50 includes a pump frequency
estimation value acquiring unit 108. The remaining configuration of
the present embodiment is the same as in the first embodiment.
[0134] The pump frequency estimation value acquiring unit 108
acquires a pump frequency estimation value after the increase and a
pump frequency estimation value after the decrease serving as an
estimation value of a frequency after the number of secondary pumps
20 is increased or decreased.
[0135] Specifically, the pump head after the increase may be
obtained using Formula (16).
[ Math . 5 ] H B = F ( n n + m G A f max f B ) .times. ( f B f max
) 2 ( 16 ) ##EQU00005##
[0136] In other words, the necessary discharge flow rate
((n/n+m).times.GA) per pump after the increase at the pump
frequency (fB) after the increase is obtained, and the pump head
(HB) after the increase is obtained by multiplying the pump head
acquired from the Q-H characteristics by the square of the ratio of
the pump frequency (fB) after the increase to the pump maximum
frequency (fmax) based on the discharge flow rate at the pump
maximum frequency in this case.
[0137] Meanwhile, HB obtained using Formula (16) is the same as HA
(the number of pumps is increased or decreased so that HB=HA), and
HA may be calculated using the current pump frequency, the flow
rate measurement value, and the Q-H characteristics (Formula (12)).
The pump frequency estimation value acquiring unit 108 derives the
frequency fB at which HB is HA using this relation from a map or an
inverse function indicating a correlation between a frequency and a
pump head which is prepared in advance, and uses fB as the pump
frequency estimation value after the increase.
[0138] Then, the number-of-pumps control unit 105 performs increase
permission determination (an "increase condition 4") based on the
frequency that prevents the decrease condition from being triggered
again after the increase in addition to the "increase condition 1"
and the "increase condition 2."
<Increase condition 4: determination based on
frequency>fB>F.beta. (17)
[0139] Here, fB is the pump frequency estimation value after the
increase acquired by the pump frequency estimation value acquiring
unit 108, and F.beta. is the frequency decrease threshold value
described in the first embodiment. In the present embodiment, since
there is a possibility that the number of pumps will be decreased
again unless the frequency after the increase exceeds the frequency
decrease threshold value in addition to the "increase condition 1"
and the "increase condition 2", in order to prevent this, this
condition is added for determination as to whether or not the
number of pumps is increased.
[0140] The determination after the decrease is similarly performed.
The pump frequency estimation value acquiring unit 108 substitutes
the flow rate or the pump maximum frequency per pump after the
decrease into Formula (18), and acquires the pump frequency
estimation value fB after the decrease from a map or an inverse
function using the fact that the value of Formula (18) is equal to
HA.
[ Math . 6 ] H B = F ( n n - m G A f max f B ) .times. ( f B f max
) 2 ( 18 ) ##EQU00006##
[0141] Then, the number-of-pumps control unit 105 performs decrease
permission determination (the "decrease condition 4") based on the
frequency that prevents the increase condition from being triggered
again after the decrease in addition to the "decrease condition 1"
and the "decrease condition 2."
<Decrease condition 4: determination based on
frequency>fB<F.alpha. (19)
[0142] Here, fB is the pump frequency estimation value after the
decrease acquired by the pump frequency estimation value acquiring
unit 108, and F.alpha. is the frequency increase threshold value
described in the first embodiment. In other words, in the present
embodiment, since there is a possibility that the number of pumps
will be increased again unless the frequency after the decrease
falls below the frequency increase threshold value in addition to
the "decrease condition 1" and the "decrease condition 2" , in
order to prevent this, this condition is added for determination as
to whether or not the number of pumps is decreased.
[0143] FIG. 11 is a diagram showing a process flow of the device
for controlling number of pumps according to the present
embodiment.
[0144] A process of increasing or decreasing the number of
operating secondary pumps 20 through the device for controlling
number of pumps 50 will be described with reference to a process
flow of FIG. 11. The same processes as those in FIG. 3 are denoted
by the same reference numerals.
[0145] First, steps S1 to S3 are the same as those in the first
embodiment. Then, the pump frequency estimation value acquiring
unit 108 acquires an estimation value fB of the pump frequency
after the number of pumps is increased or decreased according to
the map or the inverse function (step S13).
[0146] Then, the number-of-pumps control unit 105 performs
determination of the "increase condition 1," the "increase
condition 2," and the "increase condition 4" (step S14). Then, when
all the three conditions are satisfied (Yes in step S14), the
number-of-pumps control unit 105 increases the number of operating
secondary pumps 20 by 1 (step S5).
[0147] When it is determined through comparison that any of the
"increase condition 1," the "increase condition 2," and the
"increase condition 4" is not satisfied (No in step S14), the
process proceeds to step S15.
[0148] Then, the number-of-pumps control unit 105 performs
determination of the "decrease condition 1," the "decrease
condition 2," and the "decrease condition 4" (step S15). Then, when
all the three conditions are satisfied (Yes in step S15), the
number-of-pumps control unit 105 decreases the number of operating
secondary pumps 20 by 1 (step S7).
[0149] When it is determined through comparison that any of the
"decrease condition 1," the "decrease condition 2," and the
"decrease condition 3" is not satisfied (No in step S12), the
process proceeds to step S8. The process of step S8 is the same as
that in FIG. 3. In other words, the process starting from step S1
is repeated until the heat source system is stopped.
[0150] According to the present embodiment, the pump frequency
after the increase (decrease) is estimated, and the value is
compared with the frequency decrease (increase) threshold value.
Then, in addition to the two conditions described in the first
embodiment, when the pump frequency estimation value after the
increase exceeds the frequency decrease threshold value, the number
of secondary pumps 20 is increased. Similarly, in addition to the
two conditions described in the first embodiment, when the pump
frequency estimation value after the decrease falls below the
frequency increase threshold value, the number of secondary pumps
20 is decreased. Since the frequency after the number of secondary
pumps 20 is increased or decreased is considered, the repetition of
the increase and the decrease can be prevented.
[0151] The present embodiment may be combined with the modified
example of the first embodiment.
Fourth Embodiment
[0152] A heat source system according to a fourth embodiment of the
present invention will be described below with reference to FIGS.
12 to 14.
[0153] The fourth embodiment relates to an example in which the
number of operating pumps is changed in view of the pump efficiency
in addition to the first to third embodiments.
[0154] FIG. 12 is a functional block diagram showing a device for
controlling number of pumps according to the present
embodiment.
[0155] The device for controlling number of pumps 50 of the present
embodiment differs from that of the first embodiment in that the
device for controlling number of pumps 50 includes a pump frequency
estimation value acquiring unit 108 and a pump efficiency acquiring
unit 109. The remaining configuration of the present embodiment is
the same as in the first embodiment.
[0156] The pump frequency estimation value acquiring unit 108
acquires the pump frequency estimation value after the increase and
the pump frequency estimation value after the decrease using the
map or the inverse function as described above in the third
embodiment.
[0157] The pump efficiency acquiring unit 109 acquires the
estimation value of the pump efficiency after the number of
secondary pumps 20 is increased or decreased, for example, using a
graph indicating a correlation between the discharge flow rate and
the pump efficiency of the pump stored in the storage unit 200.
FIG. 13 shows an example of the correlation between the discharge
flow rate and the pump efficiency when the pump is operated at the
maximum frequency. FIG. 13 shows that the pump efficiency changes
according to the discharge flow rate of the pump. When the number
of operating secondary pumps 20 is increased or decreased, the
discharge flow rate per pump changes, and thus the pump efficiency
can be understood to change accordingly.
[0158] A current pump efficiency .eta..sub.A per pump in the state
before the increase is obtained using the following Formula
(20).
[ Math . 7 ] .eta. A = .eta. ( G A f max f A ) ( 20 )
##EQU00007##
[0159] Here, .eta.(x) is a function indicating a relation between
the discharge flow rate and the pump efficiency of the pump.
[0160] Similarly, the pump efficiency .eta..sub.B per pump after
the increase is obtained using the following Formula (21).
[ Math . 8 ] .eta. B = .eta. ( n n + m G A f max f B ) ( 21 )
##EQU00008##
[0161] Here, f.sub.B is the pump frequency estimation value after
the increase calculated by the pump frequency estimation value
acquiring unit 108.
[0162] Then, the number-of-pumps control unit 105 performs increase
permission determination (the "increase condition 5") based on the
pump efficiency in addition to the "increase condition 1" and the
"increase condition 2."
<Increase condition 5: determination based on pump
efficiency>.eta..sub.B.gtoreq..eta..sub.A (22)
[0163] In other words, the number-of-pumps control unit 105 does
not increase the number of pumps unless the pump efficiency after
the increase is equal to or larger than the pump efficiency before
the increase in addition to the "increase condition 1" and the
"increase condition 2."
[0164] Similarly, the pump efficiency acquiring unit 109 obtains
the pump efficiency per pump after the decrease using the following
Formula (23).
[ Math . 9 ] .eta. B = .eta. ( n n - m G A f max f B ) ( 23 )
##EQU00009##
[0165] Then, the number-of-pumps control unit 105 performs decrease
permission determination (the "decrease condition 5") based on the
pump efficiency in addition to the "decrease condition 1" and the
"decrease condition 2."
<Decrease condition 5: determination based on pump
efficiency>.eta..sub.B.gtoreq..eta..sub.A (24)
[0166] In other words, the number-of-pumps control unit 105 does
not decrease the number of pumps unless the pump efficiency after
the decrease is equal to or larger than the pump efficiency before
the decrease in addition to the "decrease condition 1" and the
"decrease condition 2."
[0167] In the first to third embodiments, since the pump efficiency
is not considered, there is a possibility that an increase or
decrease in the number of pumps will cause the pumps to be operated
at an operation point at which the efficiency is bad.
[0168] According to the present embodiment, because the pump
efficiency is considered, it is possible to increase or decrease
the number of pumps while suppressing power consumption.
[0169] FIG. 14 is a diagram showing a process flow of the device
for controlling number of pumps according to the present
embodiment.
[0170] A process of increasing or decreasing the number of
operating secondary pumps 20 through the device for controlling
number of pumps 50 will be described with reference to a process
flow of FIG. 14. The same processes as those in FIG. 11 are denoted
by the same reference numerals.
[0171] Steps S1 to S3 are the same as those in the first to third
embodiments. Step S13 is the same as in the third embodiment (FIG.
11).
[0172] Then, the pump efficiency acquiring unit 109 acquires the
pump efficiencies before and after the number of pumps is increased
or decreased (step S17).
[0173] Then, the number-of-pumps control unit 105 performs
determination of the "increase condition 1," the "increase
condition 2," and the "increase condition 5" (step S18). Then, when
all the three conditions are satisfied (Yes in step S18), the
number-of-pumps control unit 105 increases the number of operating
secondary pumps 20 by 1 (step S5).
[0174] When it is determined through comparison that any of the
"increase condition 1," the "increase condition 2," and the
"increase condition 5" is not satisfied (No in step S18), the
process proceeds to step S18.
[0175] Then, the number-of-pumps control unit 105 performs
determination of the "decrease condition 1," the "decrease
condition 2," and the "decrease condition 5" (step S18). Then, when
all the three conditions are satisfied (Yes in step S18), the
number-of-pumps control unit 105 decreases the number of operating
secondary pumps 20 by 1 (step S7).
[0176] When it is determined through comparison that any of the
"decrease condition 1," the "decrease condition 2," and the
"decrease condition 5" is not satisfied (No in step S18), the
process proceeds to step S8. The process of step S8 is the same as
in FIG. 3. In other words, the process starting from step S1 is
repeated until the heat source system is stopped.
[0177] The present embodiment may be combined with the second or
third embodiment as well as the first embodiment and the modified
example of the first embodiment. When the present embodiment is
combined with the second or third embodiment, it is possible to
prevent the repetition of the increase and the decrease in the
number of secondary pumps 20 and decide the number of operating
pumps so that the flow rate measurement value to the load is
satisfied while searching for a good operation point at which the
pump efficiency is good, and thus an energy saving effect can be
expected.
[0178] The device for controlling number of pumps includes an
internal computer. The steps of each process of the device for
controlling number of pumps is stored in a computer readable
recording medium in the form of a program, and the above process is
performed by reading the program through the computer. Here, the
computer readable recording medium refers to a magnetic disk, a
magneto-optical disc, a CD-ROM, a DVD-ROM, a semiconductor memory,
or the like. The computer program may be delivered to the computer
via a communication line, and the computer that has received the
computer program may execute the program.
[0179] The program may be configured to implement some of the
above-described functions.
[0180] Further, the program may be configured to implement the
above-described functions in combination with a program previously
recorded in a computer system, that is, may be a differential file
(a differential program).
[0181] In addition, the components in the above embodiments can be
appropriately replaced with known components within the scope not
departing from the gist of the present invention. Further, claims
of the invention are not limited to the above embodiments, and
various changes can be made within the scope not departing from the
gist of the present invention.
INDUSTRIAL APPLICABILITY
[0182] According to the method for controlling number of pumps, the
device for controlling number of pumps, the pump system, the heat
source system, and the program, it is possible to appropriately
control the number of operating pumps at an appropriate timing
without knowing characteristics of facilities such as the pressure
drop characteristics.
REFERENCE SIGNS LIST
[0183] 10 Primary pump [0184] 20 Secondary pump [0185] 21 Flowmeter
[0186] 22 Thermometer [0187] 23 Thermometer [0188] 30 Heat source
machine [0189] 40 Load [0190] 50 Device for controlling number of
pumps [0191] 101 Number-of-pumps determination flow rate value
acquiring unit [0192] 102 Number-of-pumps determination frequency
value acquiring unit [0193] 103 Pump frequency setting unit [0194]
104 Flow rate acquiring unit [0195] 105 Number-of-pumps control
unit [0196] 107 Pump head acquiring unit [0197] 108 Pump frequency
estimation value acquiring unit [0198] 109 Pump efficiency
acquiring unit [0199] 110 Temperature acquiring unit [0200] 111
Number-of-pumps determination heat load acquiring unit [0201] 200
Storage unit
* * * * *