CN115540375A - Rotating speed control method and device for variable-frequency centrifugal water chilling unit and air conditioner - Google Patents
Rotating speed control method and device for variable-frequency centrifugal water chilling unit and air conditioner Download PDFInfo
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- CN115540375A CN115540375A CN202211024489.7A CN202211024489A CN115540375A CN 115540375 A CN115540375 A CN 115540375A CN 202211024489 A CN202211024489 A CN 202211024489A CN 115540375 A CN115540375 A CN 115540375A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
- F25B1/053—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type of turbine type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
- F24F11/63—Electronic processing
- F24F11/64—Electronic processing using pre-stored data
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/70—Control systems characterised by their outputs; Constructional details thereof
- F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
- F24F11/86—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling compressors within refrigeration or heat pump circuits
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
- F24F5/0007—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning
- F24F5/001—Compression cycle type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
- F25B49/022—Compressor control arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/19—Pressures
- F25B2700/195—Pressures of the condenser
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/19—Pressures
- F25B2700/197—Pressures of the evaporator
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
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- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
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- Combustion & Propulsion (AREA)
- Signal Processing (AREA)
- Fuzzy Systems (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
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- Air Conditioning Control Device (AREA)
Abstract
The invention discloses a method and a device for controlling the rotating speed of a variable-frequency centrifugal water chilling unit and an air conditioner.
Description
Technical Field
The invention relates to the technical field of air conditioner refrigeration, in particular to a method and a device for controlling the rotating speed of a variable-frequency centrifugal water chilling unit and an air conditioner.
Background
In the operation process of the centrifugal water chilling unit, the freezing water outlet temperature TLo is taken as a control target, when the water temperature does not reach the set target, the compressor can be continuously loaded until the refrigeration requirement is met, but in the operation process of the water chilling unit, the problems of blockage due to damage of a throttle valve, leakage of a refrigerant and the like can occur, so that the liquid supply of an evaporator is insufficient, and the heat exchange temperature difference of the evaporator is increased. At this time, if the freezing water temperature is still used as the target for continuous loading, the rotating speed of the compressor is increased, the operating pressure ratio of the compressor is increased, the power is increased, the energy efficiency of the whole machine is reduced, the refrigerating capacity is reduced on the contrary, and when the situation that the liquid supply of the evaporator is insufficient is serious, the evaporation pressure is too low, faults such as freezing pipes of the evaporator can be caused, and the unit cannot operate normally.
Disclosure of Invention
The technical purpose is as follows: the invention discloses a method and a device for controlling the rotating speed of a variable-frequency centrifugal water chilling unit, and an air conditioner, which can limit the upper limit of the rotating speed of the unit, reduce the heat exchange temperature difference and ensure the refrigerating capacity and the energy efficiency of the unit when liquid supply of an evaporator is insufficient and the heat exchange temperature difference of the evaporator is increased.
The technical scheme is as follows: in order to achieve the technical purpose, the invention adopts the following technical scheme:
a method for controlling the rotating speed of a variable-frequency centrifugal water chilling unit comprises the following steps:
s01, fitting a correlation curve L of the rotating speed and the pressure ratio of a centrifugal compressor when the water chilling unit maintains the outlet water temperature of chilled water of the evaporator;
s02, according to the actual heat exchange temperature difference of the current evaporator, the maximum rotating speed n of the centrifugal compressor is adjusted lim Limitation, n lim ＝n min +a(n max -n min ) Wherein n is min = fl (epsilon), minimum rotational speed equation for centrifugal compressor, n max The = fh (epsilon) is a maximum rotating speed limiting equation of the centrifugal compressor, epsilon is the current pressure ratio of the centrifugal compressor, a is a temperature difference limiting coefficient, a is inversely related to the actual heat exchange temperature difference of the evaporator, and a belongs to the [0,1 ]]And is increased along with the increase of heat exchange temperature differenceThe modulation is reduced.
S03, correlation curves L and n lim And the rotating speed value corresponding to the intersection point in the same coordinate system is the highest rotating speed of the centrifugal compressor in operation under the current heat exchange temperature difference.
Preferably, in step S02, the actual heat exchange temperature difference Δ T and the set heat exchange temperature difference Δ T are set 0 Reference difference value c between, and Δ T 0 C > 0, temperature difference limiting coefficient is delta T = delta T 0 First threshold a is reached at c 1 At Δ T = Δ T 0 A second threshold a is reached at + c 2 Wherein the first threshold value a 1 Approaches 1 at the first threshold a 1 N of lim Approaches to n max (ii) a Second threshold a 2 Approaches 0 at a second threshold a 2 N is lim Approaches to n min At Δ T, at Δ T 0 -c to Δ T 0 Within the range of + c, the temperature difference limiting coefficient is from a first threshold value a 1 To a second threshold value a 2 The trend is straight and gradually decreased.
Preferably, the first threshold value a 1 Between 0.9 and 1, a second threshold value a 2 Between 0 and 0.1.
Preferably, the temperature difference limiting coefficient:
wherein, delta T is the actual heat exchange temperature difference of the evaporator, delta T = TLo-Te, TLo is the temperature of the frozen water, te is the saturation temperature corresponding to the evaporation pressure Pe, delta T is the temperature of the evaporator 0 The heat exchange temperature difference of the evaporator is set.
A rotation speed control device of a variable-frequency centrifugal water chilling unit comprises a centrifugal compressor, a frequency converter, an evaporator, a condenser, an evaporation pressure sensor, a freezing water outlet temperature sensor and a condensation pressure sensor, wherein the evaporation pressure sensor and the freezing water outlet temperature sensor are arranged on the evaporator, the condensation pressure sensor is arranged on the condenser, a controller is arranged in the frequency converter, the evaporation pressure sensor, the freezing water outlet temperature sensor and the condensation pressure sensor are all electrically connected with the controller, and the controller controls the rotation speed of the centrifugal compressor through the frequency converter according to feedback data of the sensors and according to a rotation speed control method of the variable-frequency centrifugal water chilling unit.
An air conditioner comprises the rotating speed control device of the variable-frequency centrifugal water chilling unit.
Has the advantages that: the method for controlling the rotating speed of the variable-frequency centrifugal water chilling unit has the following beneficial effects:
1. when the refrigerant of the evaporator is insufficient, the highest loading rotating speed of the centrifugal compressor is limited by the temperature difference limiting coefficient, so that the problems that the evaporation pressure is too low and the unit cannot normally operate due to too large temperature difference of the evaporator can be prevented, and the service life of the unit is prolonged.
2. The invention enables the unit to operate in a high-efficiency interval by limiting the rotating speed of the centrifugal compressor, and can reduce the energy consumption of the unit and improve the energy efficiency of the whole machine under the condition of meeting the requirement of the same refrigerating capacity.
3. The invention carries out three-level control on the rotating speed of the centrifugal compressor by setting the reference difference value between the actual heat exchange temperature difference and the set heat exchange temperature difference, and when delta T is less than delta T 0 C, the values of the temperature difference limiting coefficients are all larger than the first threshold value a 1 At this time, the rotational speed n is limited lim Approaches to n max The water chilling unit can normally run without the influence of the rotating speed, and when the delta T is more than the delta T 0 At + c, the temperature difference limiting coefficients are all smaller than a second threshold value a 2 ，n lim Approaches to n min At Δ T 0 -c to Δ T 0 Within the interval + c, the temperature difference limiting coefficient tends to decrease linearly, and the highest limiting rotating speed can be correspondingly adjusted according to different working conditions, so that the situation that the evaporation pressure is too low can be avoided, and the normal operation of the unit can be maintained.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.
FIG. 1 is a schematic structural diagram of a variable frequency centrifugal chiller according to the present invention;
FIG. 2 shows that Δ T < Δ T in the present invention 0 -c, the centrifugal compressor limit speed profile;
FIG. 3 shows that Δ T > Δ T according to the present invention 0 At + c, the centrifugal compressor limits the speed curve;
FIG. 4 is a diagram illustrating the variation of the temperature difference limiting coefficient a according to the embodiment of the present invention;
FIG. 5 is a graph illustrating a limiting speed of a centrifugal compressor according to an embodiment of the present invention;
wherein, the system comprises a centrifugal compressor 1, a frequency converter 2, an evaporator 3, a condenser 4, an evaporation pressure sensor 5, a frozen effluent temperature sensor 6, a condensation pressure sensor 7 and a throttle valve 8.
Detailed Description
The present invention will be more clearly and completely described below by way of a preferred embodiment in conjunction with the accompanying drawings, without thereby limiting the scope of the invention to the described embodiment.
As shown in fig. 1, the present invention discloses a control device of a variable frequency centrifugal chiller, which comprises a centrifugal compressor 1, a frequency converter 2, an evaporator 3, a condenser 4, an evaporation pressure sensor 5 and a chilled effluent temperature sensor 6 which are arranged on the evaporator 3, and a condensing pressure sensor 7 which is arranged on the condenser 4, wherein a controller is arranged in the frequency converter 2, the evaporation pressure sensor 5, the chilled effluent temperature sensor 6 and the condensing pressure sensor 7 are all electrically connected with the controller, the evaporator 3 is communicated with the condenser 4 through a throttle valve 8, the heat of chilled water is transferred to a refrigerant in the evaporator 3, the liquid refrigerant is changed into a gas state, the centrifugal compressor 1 compresses a low-temperature low-pressure gas refrigerant into a high-temperature high-pressure gas refrigerant, the high-pressure gas refrigerant is liquefied after the heat of the high-pressure gas refrigerant is dissipated in the condenser 4, and the high-pressure liquid refrigerant enters the evaporator 3 through the throttle valve 8 to be evaporated again to absorb heat.
When the refrigerant leaks or the throttle valve fails, the refrigerant entering the evaporator is insufficient, the heat exchange temperature difference of the evaporator is increased, the heat exchange quantity with the chilled water is reduced, if the load is continuously carried out by taking the chilled water temperature as a target, the load is not limited, the rotating speed of the compressor is increased, the operating pressure ratio of the compressor is increased, the operating power is increased, the energy efficiency of the whole machine is reduced, and the refrigerating capacity is reduced on the contrary due to the reduction of the quantity of the refrigerant in the evaporator.
The invention discloses a method for controlling the rotating speed of a variable-frequency centrifugal water chilling unit, which comprises the following steps:
s01, fitting a correlation curve L of the rotating speed and the pressure ratio of a centrifugal compressor when the water chilling unit maintains the outlet water temperature of chilled water of the evaporator;
s02, according to the actual heat exchange temperature difference of the current evaporator, the maximum rotating speed n of the centrifugal compressor is adjusted lim Limitation, n lim ＝n min +a(n max -n min ) Wherein n is min = fl (epsilon), minimum rotational speed equation for centrifugal compressor, n max The = fh (epsilon) is a maximum rotating speed limiting equation of the centrifugal compressor, epsilon is the current pressure ratio of the centrifugal compressor, a is a temperature difference limiting coefficient, a is inversely related to the actual heat exchange temperature difference of the evaporator, and a belongs to the [0,1 ]]And monotonically decreases as the heat exchange temperature difference increases.
S03, correlation curves L and n lim And the rotating speed value corresponding to the intersection point in the same coordinate system is the highest rotating speed of the centrifugal compressor under the current heat exchange temperature difference.
When the quantity of the refrigerant entering the evaporator changes to cause heat exchange change, the control method is used for controlling the rotating speed of the centrifugal compressor, the problem that the centrifugal compressor continuously carries out ballast, the refrigerating capacity is reduced on the contrary although the rotating speed is increased, and the energy efficiency of the whole machine is reduced is solved.
In order to avoid the influence of the limited rotating speed on the operation of the water chilling unit when the water chilling unit normally operates, the actual heat exchange temperature difference delta T and the set heat exchange temperature difference delta T are set 0 Reference difference value c between, and Δ T 0 C > 0, temperature difference limiting coefficient is delta T = delta T 0 A first threshold a is reached at c 1 At Δ T = Δ T 0 A second threshold a is reached at c 2 Wherein the first threshold value a 1 Is close to 1,n lim Approaches to n max (ii) a Second threshold a 2 A is approximately 0,n lim Approaches to n min At Δ T, at Δ T 0 -c to Δ T 0 Within the range of + c, the temperature difference limiting coefficient is from a first threshold value a 1 To a second threshold a 2 The trend is decreasing linearly.
The change of the temperature difference limiting coefficient a through the actual heat exchange temperature difference comprises three stages, such as the limiting rotating speed n shown in figure 3 and figure 4 when the heat exchange temperature difference is in the normal range lim Approaches to n max After the actual heat exchange temperature difference reaches or exceeds the set heat exchange temperature difference, the limit rotating speed synchronously changes along with the heat exchange temperature difference situation, so that the operation working condition of the centrifugal compressor synchronously changes along with the heat exchange temperature difference, and after the actual heat exchange temperature difference exceeds the upper limit, n is lim Approaches to n min The unit is enabled to operate in the lowest state, and unnecessary loss is avoided.
For the three-section type rotating speed control mode, three sections of function setting programs meeting the requirement of the change trend can be used for controlling, and the first threshold value a is detected 1 And a second threshold value a 2 And the corresponding actual heat exchange temperature difference is used for judging the unit operation tool at the moment according to the data measured by the sensor by the frequency converter, and further applying corresponding rotation speed limit.
Preferably, the temperature difference limiting coefficient of the present invention:
wherein, Δ T is the actual heat exchange temperature difference of the evaporator, Δ T = TLo-Te, TLo is the freezing water outlet temperature, which can be measured by the freezing water outlet temperature sensor 6, te is the saturation temperature corresponding to the evaporation pressure Pe, the evaporation pressure is measured by the evaporation pressure sensor 5, so that the corresponding evaporation pressure can be obtained by looking up the table of the evaporation pressure, when the system is applied to a control program, the corresponding relation can be preset in the system, when the frequency converter controls the rotating speed of the centrifugal compressor, the corresponding data can be directly called, Δ T is 0 The temperature difference is exchanged for the set evaporator. The temperature difference limiting coefficient can be obtained by only one formula in the whole temperature difference limiting coefficient control process, and compared with a sectional control mode, the control logic can be simplified.
The invention also provides an air conditioner which comprises the rotating speed control device of the variable-frequency centrifugal water chilling unit.
The following describes the implementation of the control method according to the present invention with a specific embodiment.
(1) Given the centrifugal compressor minimum speed limit equation:
n min ＝fl(ε)＝1777ε 3 -13303ε 2 +36820ε-21399
(2) The maximum rotating speed limiting equation of the centrifugal compressor is given because the compressor has the rotating speed operation upper limit limitation, and the maximum rotating speed limiting equation is a piecewise function:
n max ＝fh(ε)＝-1359.8ε 4 +13224ε 3 -48225ε 2 +81339ε-42829，ε＜2.4；
n max ＝fh(ε)＝14909，ε≥2.4。
(3) Temperature difference limiting coefficient:
ΔT 0 2.5 deg.c, the reference difference c is 0.5 deg.c, and as shown in fig. 4, the temperature difference limiting coefficient corresponding to the position Δ T =2 deg.c is the first threshold value a 1 The temperature difference limiting coefficient corresponding to the position of delta T =3 ℃ is a second threshold value a 2 。
When the pressure ratio epsilon =2.6 and the heat exchange temperature difference of the evaporator is delta T =1, the heat exchange of the evaporator is normal at the moment. Limiting the speed of rotation n lim ＝0.999n max ＝1.150n min I.e., close to the choke region and far from the surge region.
When the pressure ratio epsilon =2.6 and the heat exchange temperature difference of the evaporator reaches delta T =3, the heat exchange of the evaporator is poor at the moment. Limiting the speed of rotation n lim ＝0.889n max ＝1.02n min I.e. far from the choke area and close to the surge area.
When the amount of refrigerant entering the evaporator changes, the actual heat exchange temperature difference of the evaporator increases, the corresponding limited rotation speed curve moves from the maximum rotation speed curve to the minimum rotation speed curve, in order to keep the whole refrigeration amount the same, the operation track rotation speed of the centrifugal compressor increases along with the increase of the pressure ratio, in the process, the operation track of the centrifugal compressor and the rotation speed limited curve are intersected at a point 1, the rotation speed corresponding to the point 1 is the limited rotation speed of the centrifugal compressor under the current refrigeration amount, the heat exchange temperature difference is 2.7 ℃, the operation pressure ratio reaches 2.74, the rotation speed is limited at the moment 14040rpm, and the rotation speed of the compressor stops increasing.
If not, the compressor will continue to increase in speed, and will eventually run to "point 2" to reach the speed of 14909rpm.
The following table is used for comparing the operation energy consumption and the efficiency of the centrifugal compressor under two working conditions:
| operating conditions | With limited rotational speed | Without limiting the rotation speed |
| Rotational speed rpm | 14040 | 14909 |
| Actual heat exchange temperature difference of evaporator | 2.7 | 5 |
| Cold energy kW | 1582 | 1582 |
| Operating pressure ratio | 2.74 | 2.98 |
| Power consumption kW | 260.1 | 284.3 |
Therefore, after the limited rotating speed is increased, the energy consumption of the centrifugal compressor is reduced and the efficiency is improved on the premise of realizing the same refrigerating capacity.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention, and such modifications and adaptations are intended to be within the scope of the invention.
Claims (6)
1. A method for controlling the rotating speed of a variable-frequency centrifugal water chilling unit is characterized by comprising the following steps:
s01, fitting a correlation curve L of the rotating speed and the pressure ratio of the centrifugal compressor when the water chilling unit maintains the outlet water temperature of chilled water of the evaporator;
s02, according to the actual heat exchange temperature difference of the current evaporator, the maximum rotating speed n of the centrifugal compressor is adjusted lim Limitation, n lim ＝n min +a(n max -n min ) Wherein n is min = fl (epsilon), minimum rotational speed equation for centrifugal compressor, n max The equation of the maximum rotating speed limit of the centrifugal compressor is set as = fh (epsilon), v is the current pressure ratio of the centrifugal compressor, a is a temperature difference limiting coefficient, a is inversely related to the actual heat exchange temperature difference of the evaporator, and a belongs to [0,1 ]]And monotonically decreases as the heat exchange temperature difference increases.
S03, correlation curves L and n lim And the rotating speed value corresponding to the intersection point in the same coordinate system is the highest rotating speed of the centrifugal compressor in operation under the current heat exchange temperature difference.
2. The frequency conversion of claim 1The method for controlling the rotating speed of the centrifugal water chilling unit is characterized in that in step S02, an actual heat exchange temperature difference delta T and a set heat exchange temperature difference delta T are set 0 Reference difference value c between, and Δ T 0 C > 0, and a temperature difference limiting coefficient of delta T = delta T 0 A first threshold a is reached at c 1 At Δ T = Δ T 0 A second threshold a is reached at + c 2 Wherein the first threshold value a 1 Approaches 1 at the first threshold a 1 N is lim Approaches to n max (ii) a Second threshold a 2 Approaches 0 and reaches the second threshold value a 2 N of lim Approaches to n min At Δ T, at Δ T 0 -c to Δ T 0 Within the range of + c, the temperature difference limiting coefficient is from a first threshold value a 1 To a second threshold value a 2 The trend is decreasing linearly.
3. The rotating speed control method of the variable-frequency centrifugal water chilling unit according to claim 2, wherein the first threshold a is 1 Between 0.9 and 1, a second threshold value a 2 Between 0 and 0.1.
4. The method for controlling the rotating speed of the variable-frequency centrifugal chiller according to claim 2, wherein the temperature difference limiting coefficient is as follows:
wherein, delta T is the actual heat exchange temperature difference of the evaporator, delta T = TLo-Te, TLo is the temperature of the frozen water, te is the saturation temperature corresponding to the evaporation pressure Pe, delta T is the temperature of the evaporator 0 The heat exchange temperature difference of the evaporator is set.
5. A rotation speed control device of a variable-frequency centrifugal water chilling unit is characterized by comprising a centrifugal compressor (1), a frequency converter (2), an evaporator (3), a condenser (4), an evaporation pressure sensor (5), a freezing water outlet temperature sensor (6) and a condensation pressure sensor (7), wherein the evaporation pressure sensor (5), the freezing water outlet temperature sensor (6) and the condensation pressure sensor (7) are arranged on the evaporator (3), the frequency converter (2) is internally provided with a controller, the evaporation pressure sensor (5), the freezing water outlet temperature sensor (6) and the condensation pressure sensor (7) are electrically connected with the controller, and the controller controls the rotation speed of the centrifugal compressor by using the frequency converter (2) according to feedback data of the sensors and the rotation speed control method of the variable-frequency centrifugal water chilling unit according to any one of claims 1 to 4.
6. An air conditioner characterized in that it comprises the rotational speed control device of the inverter centrifugal chiller as set forth in claim 5.
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| CN202211024489.7A CN115540375A (en) | 2022-08-25 | 2022-08-25 | Rotating speed control method and device for variable-frequency centrifugal water chilling unit and air conditioner |
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| CN202211024489.7A CN115540375A (en) | 2022-08-25 | 2022-08-25 | Rotating speed control method and device for variable-frequency centrifugal water chilling unit and air conditioner |
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