CN1318719A - Variable pressure difference and variable flow rate control method and system for air conditioning water system - Google Patents
Variable pressure difference and variable flow rate control method and system for air conditioning water system Download PDFInfo
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Abstract
A primary circulation pump and a secondary circulation pump set at front and back of cooling water machine of the air conditioning water system. A flow transducer sets in front of the primary circulation pump, and a pressure differential transducer sets between front of primary pump and back of secondary circulation pump. The signals of flow transducer and pressure differential transducer are set to programmable controller. After making logical comparision with calculating result according to mathematics model of delta Pi=A(Qi/Qs)2+B, the analog quantity is exported to control frequency conversion controllor connecting on the secondary circulation pump.
Description
The invention belongs to air-conditioner water system control method and system, particularly a kind of variable pressure difference and variable flow rate control method of air-conditioner water system and system.
In current large-scale senior civil buildings, the energy consumption of air-conditioning system accounts for more than 40 percent of whole building energy consumption greatly at present, so the requirement that air conditioner system energy saving is designed and moves more and more causes owner and insider's care.Design of Air-conditioning Water System for closed cycle, professional designer's unsteady flow amount design philosophy that in actual engineering, generally induced one, but, because the control thought of system's design and concrete control method and the actual pipe characteristic that adopts have greater difference, often handle variable flow system control with the constant flow notion under the design loading condiction, having ignored water system is consideration in the adaptability to changes of operation at part load to annual 85% above time, thereby often the stability of a system appears and adaptability to changes is relatively poor, the operation energy consumption condition with higher in actual moving process; Especially in the bigger system of many refrigeration unit parallel runnings or share summer in winter in the system of a cover water circulating pump, owing to the reason that the systemic circulation water yield changes and the fluid dynamic coefficient of viscosity changes, cause system's reality to take place than great fluctuation process with pressure reduction, make the drift of water circulating pump operating point and transship, be forced to adopt valve throttle in the actual motion management or increase water pump operation platform number with its operating point of the big stability of flow of the little temperature difference, this has increased the operation energy consumption of system undoubtedly.In long-term engineering design and operational management practice process, people are to the stability of air-conditioner water system, the understanding of adaptability to changes and energy-saving run design is further clear and definite, especially the development of computer application and Frequency Conversion and Speed Regulation Technique, automatically control for air-conditioner water system adopts transformation difference unsteady flow amount closed loop, the energy-saving design of tracing system load self-adapting provides great convenience.Air conditioning water system is by connecting the closed circulation system that handpiece Water Chilling Units (heat exchanger), water circulating pump and air conditioner end equipment are formed by pipe-line system.For variable flow system, air conditioner end equipment is regulated quantity of circulating water (being used for AHU, PAHU) by electric two-way valve (being used for FCU) and electronic two logical control valves at random automatically according to terminal indoor load and temperature.Therefore, the pipe characteristic of unsteady flow amount chilled water (air conditioning hot) system can not be used H=SQ simply
2Describe.In fact pipe characteristic is about the system pipeline characteristic coefficient, the function of many variables of the complexity that the coefficient of dynamic viscosity of different temperatures fluid is relevant with how many ratios of the characteristic curve of terminal motor-driven valve and valve switch quantity relation, that is: Δ H=(Q, T, Ni).And valve switch quantitative proportion Ni is a change at random in operation a day or 1 year, and the coefficient of dynamic viscosity of fluid changes because of the winter summer temp is different, the operation conditions of etching system when in fact accurately prediction is a certain.Thereby, in the air conditioning water system design, introduce transformation difference variable flow system control thought, for the optimization system design, energy-saving run is a very important major issue really.
In variable flow system, the systemic circulation flow is proportional variation with load variations.For load side, can control by the electric two-way valve and the electric control valve of end.But; for the low-temperature receiver side; no matter be one-level pumping system or two stage pump system; when low-temperature receiver adopts the compression handpiece Water Chilling Units, should guarantee fully that the flow that flows through evaporimeter is not less than its metered flow, otherwise that low excessively flow will make freezing temperature spend is low; even evaporator section freezes; cause the unit surge, the self-shield control system of import handpiece Water Chilling Units can make the unit disastershutdown, and especially centrifugal refrigerating machines is very remarkable.Therefore, the one-level pumping system of unsteady flow amount is to control by the bypass pipe pressure reduction between the handpiece Water Chilling Units water inlet pipe and water outlet pipe to realize, during sub-load or when transition season underrun, the unnecessary pressure head of water circulating pump is mainly consumed by terminal valve, when especially in fairly large system, adopting many handpiece Water Chilling Units parallel runnings, the variable flow system of pressure reduction control is when operation at part load, because the combined influence of pipe characteristic and terminal electric two-way valve door switch ratio, it is very blunt to cause the pressure reduction control signal that discharge is changed, even imbalance.The parallel running machine is organized a performance several many more, and detuning phenomena more very.Water pump when part is moved usually is in the overlond running state because of the skew of real work point.Therefore, for the design of one-level pumping system, the constant flow water system that system is terminal to be adopted electric T-shaped valve or do not adorn motor-driven valve more can adapt to the hydrodynamic characteristic of pipeline than the variable flow system of pressure reduction control, when sub-load, adopt reliable throttling level pressure difference control classification flow regulative mode, on the contrary can be more effective than primary pump variable flow system the reliability and stability of raising system, it should be noted that operation energy consumption is higher.In some period of transition season day-to-day operation, when the big flow of the little temperature difference of system requirements (as bringing into operation the initial stage), the adaptive capacity of system is relatively poor every morning.But, for the pumping system that lithium-bromide absorption-type refrigerating machine is formed, then can utilize the adjustable adaptation characteristics of unit flow to carry out the design of transformation difference variable flow system fully, when two or the design of many parallel machine operations, systemic circulation discharge can be implemented in 25%-100% or wider between carry out step-less adjustment, on engineering, can satisfy the adjusting needs of water system fully.
At present, the insider recognizes that generally the frequency control unsteady flow amount design of water system has remarkable energy saving effect, but in actual engineering design, people often are used for the constant-pressure variable in the domestic water design air-conditioner water system control of closed cycle simply, because in open feed system, system's static pressure plays a major role, and pipe characteristic is less to the constant voltage influence, and the control of fixed-voltage altering-current amount can be satisfied the energy-saving run requirement well; But the air-conditioner water system in closed cycle is quite different, and one, water circulating pump only provide the circulation power of system, and irrelevant with the system static pressure; Its two, the circulation pressure reduction of variable flow system is function of many variables that are subjected to many-sided factor affecting, the actual service requirement that can not satisfy system of constant voltage or level pressure difference; Its three, systemic circulation changes in flow rate and season and indoor load change and the method for operation relevant, do not have zero delivery.Therefore, when in the air-conditioner water system of closed cycle, adopting the control of fixed-voltage altering-current amount, only under system's design discharge service condition, water circulating pump moves in the peak efficiency operating point, when system during in operation at part load, in fact and do not meet H because pump working characteristic curve and the skew of system in-service pipeline characteristic operating point, the operating point before and after pump rotary speed changes is non-similar operating condition point, and water pump operation shaft power at this moment as shown in Figure 1
A/ H
B=SQ
A 2/ SQ
B 2=(Q
A/ Q
B)
2N
A/ N
B=(Q
A/ Q
B)
3Rule, and should be calculated as follows:
The density of r in the formula---water, KG/M;
Q---circular flow M
3/ H;
G---acceleration of gravity, M/s
2
η---pump efficiency.
H---lift
S---system performance coefficient
When quantity of circulating water changed, the water system circulation needed to reduce to reduce because of the systemic circulation flow with pressure reduction, and the control of fixed-voltage altering-current amount then requires system's pressure reduction constant, just must want system's end portion loop and valve to consume more than pressure reduction, causes energy waste.For the air-conditioner water system of annual most times in operation at part load, this energy waste is a very important problem really.
In sum, air-conditioner water system for closed cycle cannot simply adopt the design of fixed-voltage altering-current amount as can be seen, because its control thought does not meet the pipe characteristic rule of fluid closed circulation system, in actual motion, also can not reach the energy-conservation purpose of expection, often things turn out contrary to one's wishes.And the variable frequency regulating speed control that adopts transformation difference unsteady flow amount is only unique feasible ideal selection.
The variable pressure difference and variable flow rate control method and the system that the purpose of this invention is to provide a kind of air-conditioner water system overcome the shortcoming and defect of prior art.
The object of the present invention is achieved like this:
A kind of variable pressure difference and variable flow rate control method of air-conditioner water system is characterized by: with Mathematical Modeling Δ Pi=A (Qi/Qs)
2+ B is wherein: Qs: design metered flow m
3/ HQi: cross range of flow m
3/ H (variable) Δ Pi: process operating point pressure reduction mH
2O (variable) A: pressure reduction constant mH
2OB: pressure reduction constant mH
2A in the O formula, the B constant, determine according to water pump characteristic and system performance, Δ Pi is as basic pressure reduction, in the series pipe of air-conditioner water system cooling-water machine and end-equipment, circulating pump P1 is set before the cooling-water machine one time, secondary cycle pump P2 is set behind cooling-water machine, before a circulating pump P1 with before the secondary cycle pump P2, be connected bypass pipe PT, before the circulating pump P1 in series pipe, and before series pipe and bypass pipe junction, flow sensor LM is set, before the circulating pump P1 in series pipe, and before series pipe and bypass pipe junction and between behind the secondary cycle pump P2, differential pressure pickup DP is set, the signal of flow sensor LM and differential pressure pickup DP is delivered among the Programmable Logic Controller PLC, and by Mathematical Modeling Δ Pi=A (Qi/Qs)
2After the theoretical pressure reduction that+B calculates carries out the logic judgement, output analog quantity control signal control frequency-variable controller VVF, frequency-variable controller VVF control secondary cycle pump P2 reaches the transformation difference unsteady flow amount control of air-conditioner water system.By the increase and decrease of the positive negative value decision adjustable speed water pump rotating speed of circular flow increment and pressure reduction increment, its logical relation is as follows;
When Qi descends, and Pi is constant or when increasing, the circular flow surplus be described, and then frequency-variable controller control pump rotary speed drops to the stable operating point of correspondence;
Otherwise when Qi rises, Pi is constant or when descending, and the circular flow deficiency be described, then controls the stable operating point that pump rotary speed rises to correspondence.
In the series pipe of air-conditioner water system cooling-water machine and end-equipment, circulating pump P1 is set before the cooling-water machine one time, secondary cycle pump P2 is set behind cooling-water machine; Be connected bypass pipe PT before the circulating pump P1 in series pipe with before the secondary cycle pump P2, before the circulating pump P1 in series pipe, and before series pipe and bypass pipe junction, flow sensor LM is set, before the circulating pump P1 in series pipe, and before series pipe and bypass pipe junction and between behind the secondary cycle pump P2, differential pressure pickup DP is set, the signal output part of flow sensor LM and differential pressure pickup DP is connected Programmable Logic Controller PLC input, the output of Programmable Logic Controller PLC connects control frequency-variable controller VVF, with display XS, frequency-variable controller VVF connects control secondary cycle pump P2, becomes the transformation difference variable flow system of air-conditioner water system at once.
Advantage of the present invention is:
The control of transformation difference unsteady flow amount has significant effect and practical significance for stability and adaptive capacity energy-conservation and the raising system.
Below in conjunction with description of drawings embodiment:
Fig. 1 is a circulation fixed-voltage altering-current amount Δ P-Q curve map
Fig. 2 is a closed circle water system transformation difference unsteady flow amount Δ P-Q curve map
Fig. 3 is the transformation difference unsteady flow amount control system schematic diagram of air-conditioner water system
Fig. 4 is the variable pressure difference and variable flow rate control method Mathematical Modeling working curve diagram of air-conditioner water system
Among the figure: LM flow sensor, Δ P differential pressure pickup, VVF frequency-variable controller, P2 secondary cycle pump, circulating pump of P1, PT bypass pipe, R handpiece Water Chilling Units, MD end-equipment, PLC Programmable Logic Controller, XS display.
Transformation difference unsteady flow amount control thought can be consistent with the pipe characteristic of closed circle water system well, as Fig. 2, satisfies the basic law of pipeline circulation of fluid in running, H=SQ
2For water circulating pump, H
A/ H
B=(Q
A/ Q
B)
2N
A/ N
B=(Q
A/ Q
B)
3, the condition of similar operating point is satisfied in the operating point of velocity fluctuation pump operation.Thereby can under the different flow condition, guarantee system stability, end-equipment branch loop pressure reduction is operated in stable similar operating point condition with flow.The proportional reduction of cube that the actual consumption of system's operation is pressed flow.So the control of transformation difference unsteady flow amount has significant practical significance for stability and adaptive capacity energy-conservation and the raising system.
Transformation difference variable flow system design main points mainly are the runnings of monitoring system effectively, and follow the tracks of control according to the variation of flow system flow and stablize its operating point, must well avoid system's adjustment process to produce the self-excitation open circuit simultaneously.
Figure 3 shows that the transformation difference variable flow system of the air-conditioner water system of forming by a secondary pump.Because the variable flow system characteristic is comparatively complicated function of many variables, be difficult to a strictness accurately mathematical formulae explain.In order to solve actual engineering problem, introduce fuzzy control theory thought according to hydromechanical basic theories, and make full use of water pump parallel running characteristic, but set up the Mathematical Modeling of an engineering demands clear concept in conjunction with the abstract summary of practical engineering experience.One, Mathematical Modeling
ΔPi=A(Qi/Qs)
2+B………………(1)
Qs: design metered flow m
3/ H
Qi: cross range of flow m
3/ H (variable)
Δ Pi: process operating point pressure reduction mH
2O (variable)
A: pressure reduction constant mH
2O
B: pressure reduction constant mH
2O
A, B constant in the formula, according to water pump characteristic and system performance come really+-Ding.Form differently according to system, have two kinds of situations to consider here: first kind of situation be, establishes two secondarys and circulate that (wherein one is stand-by pump to big pump; Or adopt a high-power frequency conversion controller to control many water pump parallel runnings simultaneously; Lithium bromide refrigerator can design the one-level pumping system), its working flow and operting differential pressure are system's design maximum circular flow and design pressure difference, variable frequency regulating speed control can fully satisfy pipeline in the requirement of transformation difference unsteady flow flow characteristic, the control characteristic of water pump overlaps with pipe characteristic, system's operation stability and adaptive capacity are best, are ideal control models.Comparatively generally adopt at western developed country at present.But, for big system,, then often to be subjected to the restriction of Model of pump and characteristic thereof because circular flow is excessive, reality may be difficult to choose suitable water circulating pump in engineering design.Owing to adopt a bigger water circulating pump, the variable-frequency governor operate power of control separate unit water pump is also bigger, and once investment is bigger.The B constant of system's design this moment should be determined by the calculating pressure reduction of the terminal loop of system.Under the not too big condition of every layer of terminal horizontal loop, according to system situation, for different journey loop, generally at 30～50KPa (3～5mH
2O) value can guarantee the stable operation of transformation difference variable flow system between; For same Cheng Huanlu, can get the calculating pressure drop of end-equipment.The calculating pressure reduction that the A value equals the secondary system loop deducts terminal circulation pressure reduction B; Second kind of situation is to control the order soft start of many water circulating pumps and out of service automatically to realize the operation of transformation difference unsteady flow amount respectively by a variable frequency regulating speed control device tracking system flow.But water circulating pump parallel running platform number is not declared at most above five.During normal the operation, have only a water pump to be in the frequency control operation all the time, all the other are power frequency operation, and as long as the power output of its frequency-variable controller is more than or equal to a water circulating pump power.So latter event can define the transformation difference unsteady flow amount pattern that is as the criterion.The constant A of this moment must be determined by the gamut characteristic curve of selected water pump, mainly is to guarantee when systemic circulation pressure reduction reduces the unlikely overload of the water pump of its power frequency operation.Generally speaking, constant A is at 100～140KPa (10～14mH
2O) between.Here be actually the available pressure reduction of the terminal loop of artificial raising, increase the end-equipment flow of part operation, when the system pipeline design condition was identical, the latter was more relatively poor than the former energy-saving effect.Unless the Adjustment System pipe design changes pepeline characteristic, system's main pipe circuit cycle pressure reduction is controlled at A value scope, also can reach desirable energy-saving run purpose, can or pick up in the frequency-variable controller fault simultaneously and adopt water pump platform number to carry out progression control (valve opening is regulated and cooperated) when repairing.The main distinction of the two is once to invest (comprise different frequency-variable controller price differentials once invest with the pipeline under the different pipe characteristics).For a concrete engineering design, adopt that a kind of control mode, must conscientiously carry out the technical economic analysis decision, in the hope of shortening the payback period of energy-saving equipment investment as much as possible.
Two, frequency control transformation difference unsteady flow amount control system is formed
Transformation difference unsteady flow amount control system mainly is made up of following components:
1, Programmable Logic Controller one cover must adopt to have the control of floating-point operation function FPGA
Device (PLC.Programmable?Logic?Controller)
2, frequency converter one cover, (in control system as actuator)
3, flow sensor and transmitter (electromagnetic flowmeter or ultrasonic flowmeter, measure error
Be not more than 0.5%)
4, differential pressure pickup and transmitter one cover (certainty of measurement 0.1%)
Flow sensor here and differential pressure pickup are as the analog quantity input control signal, through compiling
Range controller is accepted and is carried out exporting analog quantity control letter after the computing according to Mathematical Modeling
Number.Frequency converter is actually an actuator.In control system nixie display being set (shows
Show actual flow and pressure difference), to realize the bright operation of full impregnated of system.The PLC controller can be real
Existing many pump equivalent life switchover operations.
Three, transformation difference variable flow system design main points:
1, the type selecting of water circulating pump for the powerful transformation difference of frequency control separate unit unsteady flow amount is
System should be selected the more smooth water circulating pump of characteristic curve for use; For many parallel runnings
Accurate transformation difference variable flow system has only a water pump to be in frequency conversion during owing to system's operation
The speed governing operating mode, remaining water circulating pump is power frequency operation, and desire guarantees the pressure reduction in system
When changing, general pump adapts to it fully to be regulated in the characteristic curve gamut and not
Cause overlond running, characteristic except that should appropriately determining the A value, should select for use to fall type suddenly
Water circulating pump.For secondary pump system reasonable in design, when moving in the winter time, because
The variation of the fluid dynamic coefficient of viscosity can be cut off pump and only with a cover secondary pump
Operation realizes an annual cover water circulating pump method of operation.
2, frequency-variable controller should be selected the Programmable Logic Controller (PLC) with floating-point operation function for use.
Calculate the establishment control program according to system's mathematics of control model and waterpower, and should have and be
System operation debugging can be revised A by actual pipe characteristic, and the possibility of B value should during programming
It (is the fuzzy control interval, to avoid self-excitation open circuit, Δ Q=Q that the action incremental range is set
s
1-1.5%; Δ p=Δ P
S0.1%); For the ascending order incision of many parallel water pumps,
Needn't be from zero H
ZThe Q incision, and should be with 30H
zThe incision operation.
3, according to system design parameters and regulate to require to select for use suitable differential pressure pickup transmitter and
Flow sensor is selected appropriate installation site, wants with the control accuracy that satisfies system
Ask.Owing to introduced fuzzy control thought, differential pressure pickup can directly be contained in nearby
On the turnover jellyfish pipe, pressure is set in the refrigerating plant room thereby solved at the terminal loop of system
The problem that the gap sensor position is difficult to determine.As shown in Figure 3.
Four, certain case history 1, design parameter rated designs maximum stream flow Qs=300m
3/ H unsteady flow amount adjustable range 80m
3/ H≤Qi≤330m
3/ H transformation difference adjustable range 22.6mH
2O≤Pi≤34.10mH
2O pressure reduction constant A=10.0mH
2O
B=22.0mH
2O
Mathematical Modeling Δ Pi=10 (Qi/Qs)
2+ 22m
3/ H
Circular flow increment Delta Qi=5-8m
3/ H
Pressure reduction control accuracy Δ Pi=0.1mH
2O
2, exemplary operation point computational chart
| Sequence number | Flow m 3/H | Flow-rate ratio Qi/Qs | A=10mH 2O 10 (Qi/Qs) | Constant B | Pressure reduction Pi | Remarks |
| 1 | ?330 | ????1.1 | ????12.10 | ?22.00 | ????34.10 | ????110％ |
| 2 | ?300 | ????1.0 | ????10.00 | ?22.00 | ????32.00 | ????100％ |
| 3 | ?285 | ????0.95 | ????9.025 | ?22.00 | ????31.025 | ????95％ |
| 4 | ?270 | ????0.90 | ????8.10 | ?22.00 | ????30.10 | ????90％ |
| 5 | ?255 | ????0.85 | ????7.225 | ?22.00 | ????29.225 | ????85％ |
| 6 | ?240 | ????0.80 | ????6.40 | ?22.00 | ????28.40 | ????80％ |
| 7 | ?225 | ????0.75 | ????5.625 | ?22.00 | ????27.625 | ????75％ |
| 8 | ?210 | ????0.70 | ????4.90 | ?22.00 | ????26.90 | ????70％ |
| 9 | ?195 | ????0.65 | ????4.225 | ?22.00 | ????26.225 | ????65％ |
| 10 | ?180 | ????0.60 | ????3.60 | ?22.00 | ????25.60 | ????60％ |
| 11 | ?165 | ????0.55 | ????3.025 | ?22.00 | ????25.25 | ????55％ |
| 12 | ?150 | ????0.50 | ????2.50 | ?22.00 | ????24.50 | ????50％ |
| 13 | ?135 | ????0.45 | ????2.025 | ?22.00 | ????24.025 | ????45％ |
| 14 | ?120 | ????0.40 | ????1.60 | ?22.00 | ????23.625 | ????40％ |
| 15 | ?105 | ????0.35 | ????1.225 | ?22.00 | ????23.225 | ????35％ |
| 16 | ?90 | ????0.30 | ????0.9 | ?22.00 | ????22.90 | ????30％ |
| 17 | ?75 | ????0.25 | ????0.625 | ?22.00 | ????22.625 | ????25％ |
3, Mathematical Modeling working curve (see figure 4)
It should be noted that, trapezoid figure language is adopted in the programming of Programmable Logic Controller usually, should compare definite pump rotary speed of adding and subtracting according to the analog quantity input of the input of the analog quantity of flow sensor and Mathematical Modeling formula result of calculation and differential pressure pickup during actual program, in the flow increment scope with the interior stable operating point of promptly thinking system.By the increase and decrease of the positive negative value decision adjustable speed water pump rotating speed of circular flow increment and pressure reduction increment, its logical relation is as follows;
When Qi descends, and Pi is constant or when increasing, the circular flow surplus be described, and then frequency-variable controller control pump rotary speed drops to the stable operating point of correspondence;
Otherwise when Qi rises, Pi is constant or when descending, and the circular flow deficiency be described, then controls the stable operating point that pump rotary speed rises to correspondence.
Must reliably avoid control system self-excitation open circuit during programming, realize the closed loop continuous control.Can adjust A according to the pipe characteristic of real system during system debug, the B constant value is determined the optimum operation pattern.
Claims (2)
1, a kind of variable pressure difference and variable flow rate control method of air-conditioner water system is characterized by: with Mathematical Modeling
ΔPi=A(Qi/Qs)
2+B
Wherein:
Qs: design metered flow m
3/ H
Qi: cross range of flow m
3/ H (variable)
Δ Pi: process operating point pressure reduction mH
2O (variable)
A: pressure reduction constant mH
2O
B: pressure reduction constant mH
2O
A in the formula, the B constant, determine according to water pump characteristic and system performance, Δ Pi is as theoretical pressure reduction, in the series pipe of the cooling-water machine of air-conditioner water system and end-equipment, circulating pump P1 is set before the cooling-water machine one time, secondary cycle pump P2 is set behind cooling-water machine, before a circulating pump P1 with before the secondary cycle pump P2, be connected bypass pipe PT, before the circulating pump P1 in series pipe, and before series pipe and bypass pipe junction, flow sensor LM is set, before the circulating pump P1 in series pipe, and before series pipe and bypass pipe junction and between behind the secondary cycle pump P2, differential pressure pickup DP is set, the signal of flow sensor LM and differential pressure pickup DP is delivered among the Programmable Logic Controller PLC, and by Mathematical Modeling Δ Pi=A (Qi/Qs)
2After the theoretical pressure reduction that+B calculates carries out the logic judgement, output analog quantity control signal control frequency-variable controller VVF, frequency-variable controller VVF control secondary cycle pump P2 reaches the transformation difference unsteady flow amount control of air-conditioner water system; By the increase and decrease of the positive negative value decision control adjustable speed water pump rotating speed of circular flow increment and pressure reduction increment, its logical relation is as follows;
When Qi descends, and Pi is constant or when increasing, the circular flow surplus be described, and then frequency-variable controller control pump rotary speed drops to the stable operating point of correspondence;
Otherwise when Qi rises, Pi is constant or when descending, and the circular flow deficiency be described, then controls the stable operating point that pump rotary speed rises to correspondence.
2, the transformation difference unsteady flow amount control system of air-conditioner water system according to claim 1 is characterized by: in the series pipe of air-conditioner water system cooling-water machine and end-equipment, circulating pump P1 is set before the cooling-water machine one time, secondary cycle pump P2 is set behind cooling-water machine; Be connected bypass pipe PT before the circulating pump P1 in series pipe with before the secondary cycle pump P2, before the circulating pump P1 in series pipe, and before series pipe and bypass pipe junction, flow sensor LM is set, before the circulating pump P1 in series pipe, and before series pipe and bypass pipe junction and between behind the secondary cycle pump P2, differential pressure pickup DP is set, the signal output part of flow sensor LM and differential pressure pickup DP is connected Programmable Logic Controller PLC input, the output of Programmable Logic Controller PLC connects control frequency-variable controller VVF, with display XS, frequency-variable controller VVF connects control secondary cycle pump P2, becomes the transformation difference variable flow system of air-conditioner water system at once.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB001058606A CN1186572C (en) | 2000-04-14 | 2000-04-14 | Variable pressure difference and variable flow rate control method and system for air conditioning water system |
Applications Claiming Priority (1)
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| CNB001058606A CN1186572C (en) | 2000-04-14 | 2000-04-14 | Variable pressure difference and variable flow rate control method and system for air conditioning water system |
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| CN100427914C (en) * | 2004-09-24 | 2008-10-22 | 曹琦 | Method of calculating central air conditioning waterway system resistance |
| CN101196311B (en) * | 2008-01-07 | 2012-05-02 | 张伟 | Control device for heating system |
| CN101782260B (en) * | 2010-01-22 | 2012-08-15 | 华中科技大学 | Optimal control method and device for water system of air conditioning |
| CN102889664A (en) * | 2011-07-19 | 2013-01-23 | 香港理工大学 | System and method for controlling water discharge |
| CN103453706A (en) * | 2006-02-23 | 2013-12-18 | 刘民柱 | Industrial process efficiency method and system |
| CN103994554A (en) * | 2014-05-30 | 2014-08-20 | 厦门立思科技股份有限公司 | Variable pressure difference control device, method and system for air-conditioner |
| CN105066343A (en) * | 2015-07-31 | 2015-11-18 | 新智能源系统控制有限责任公司 | Variable water temperature control system applicable to primary pump system of air conditioner |
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