CN111288676A - Water chilling unit - Google Patents
Water chilling unit Download PDFInfo
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- CN111288676A CN111288676A CN202010092671.0A CN202010092671A CN111288676A CN 111288676 A CN111288676 A CN 111288676A CN 202010092671 A CN202010092671 A CN 202010092671A CN 111288676 A CN111288676 A CN 111288676A
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- heat recovery
- expansion valve
- electronic expansion
- 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
- F25B6/00—Compression machines, plants or systems, with several condenser circuits
- F25B6/02—Compression machines, plants or systems, with several condenser circuits arranged in parallel
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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
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
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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
- F25B41/00—Fluid-circulation arrangements
- F25B41/30—Expansion means; Dispositions thereof
- F25B41/31—Expansion valves
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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
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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)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Air Conditioning Control Device (AREA)
Abstract
The embodiment of the invention provides a water chilling unit. The water chilling unit comprises a compressor, a refrigeration condenser, an evaporator and a heat recovery condenser connected in parallel with the refrigeration condenser, wherein the compressor, the refrigeration condenser and the evaporator are sequentially connected. The water chilling unit also comprises a first electronic expansion valve arranged at the outlet of the refrigeration condenser and a second electronic expansion valve arranged at the outlet of the heat recovery condenser. The water chilling unit disclosed by the embodiment of the invention can realize stepless regulation according to the actual heat load requirement, and has the advantages of small water temperature fluctuation and high comfort level.
Description
Technical Field
The embodiment of the invention relates to the technical field of air conditioners, in particular to a water chilling unit.
Background
With the further development of refrigeration technology, the requirement for additional functions of the water chilling unit is higher and higher. For the heat recovery unit, the current units are mainly divided into a total heat recovery unit and a partial heat recovery unit. However, the two units can switch the heating and cooling modes according to the heat recovery demand of customers, but cannot perform stepless regulation according to the heat load, so that the temperature of the heat recovery water greatly fluctuates. Fig. 1 discloses a schematic block diagram of a prior art water chiller. As shown in fig. 1, a conventional water chiller 10 generally includes a compressor 11, a refrigeration condenser 12, a heat recovery condenser 13 connected in parallel to the refrigeration condenser 12, a first solenoid valve 161 provided after the refrigeration condenser 12, a second solenoid valve 162 provided after the heat recovery condenser 13, an accumulator 17, an electronic expansion valve 15, and an evaporator 14.
During the use process of the water chilling unit 10, the switching between the refrigeration mode and the heat recovery mode of the water chilling unit 10 is realized by controlling the on-off of the first electromagnetic valve 161 and the second electromagnetic valve 162. However, the amount of heat recovered by the chiller 10 cannot be flexibly adjusted in a stepless manner according to the actual needs of the customers.
Disclosure of Invention
The embodiment of the invention aims to provide a water chilling unit capable of adjusting heat recovery in a stepless mode.
The embodiment of the invention provides a water chilling unit, which comprises a compressor, a refrigeration condenser, an evaporator and a heat recovery condenser connected with the refrigeration condenser in parallel, wherein the compressor, the refrigeration condenser and the evaporator are sequentially connected. The water chilling unit further comprises a first electronic expansion valve arranged at an outlet of the refrigeration condenser and a second electronic expansion valve arranged at an outlet of the heat recovery condenser.
Further, the water chilling unit comprises a pure refrigeration mode, a total heat recovery mode and a partial heat recovery mode, and the water chilling unit is controlled to be switched among the pure refrigeration mode, the total heat recovery mode and the partial heat recovery mode based on the opening degrees of the first electronic expansion valve and the second electronic expansion valve.
Further, when the water chilling unit is in a partial heat recovery mode, the opening degree of the second electronic expansion valve is controlled according to a heat recovery outlet water temperature set value, the total opening degree/flow area of the first electronic expansion valve and the second electronic expansion valve of the water chilling unit is controlled by the liquid level/outlet superheat degree of the evaporator, and the opening degree/flow area of the first electronic expansion valve is the difference value between the total opening degree/flow area and the opening degree/flow area of the second electronic expansion valve.
Further, when the water chilling unit is in a pure refrigeration mode, the opening degree of the first electronic expansion valve is controlled according to the liquid level/outlet superheat degree of the evaporator, and the second electronic expansion valve is closed.
Further, when the first supercooling degree at the outlet of the refrigerant condenser is lower than a first target supercooling degree, the second electronic expansion valve is opened, and the opening degree of the second electronic expansion valve is controlled according to the first supercooling degree.
Further, the water chilling unit further comprises a first temperature sensor and a first pressure sensor which are located at an outlet of the refrigeration condenser, the first temperature sensor and the first pressure sensor are respectively used for sensing a first refrigerant temperature and a first refrigerant pressure at the outlet of the refrigeration condenser, and the first supercooling degree at the outlet of the refrigeration condenser is calculated based on the first refrigerant temperature measured by the first temperature sensor and the first refrigerant pressure measured by the first pressure sensor.
Further, when the first supercooling degree is smaller than the difference value between the first target supercooling degree and the first preset temperature, the second electronic expansion valve is opened to increase the first supercooling degree, and when the first supercooling degree is larger than or equal to the sum of the first target supercooling degree and the second preset temperature, the second electronic expansion valve is closed until the second electronic expansion valve is closed.
Further, the first predetermined temperature is between 1 and 3 degrees Fahrenheit according to experimental practice, and the second predetermined temperature is between 0 and 2 degrees Fahrenheit according to requirements.
Further, when the water chilling unit is in a total heat recovery mode, the opening degree of the second electronic expansion valve is controlled according to the liquid level/outlet superheat degree of the evaporator, and the first electronic expansion valve is closed.
Further, when a second supercooling degree at the outlet of the heat recovery condenser is lower than a second target supercooling degree, the first electronic expansion valve is opened, and the opening degree of the first electronic expansion valve is controlled according to the second supercooling degree.
Further, the water chilling unit further comprises a second temperature sensor and a second pressure sensor which are located at an outlet of the heat recovery condenser, the second temperature sensor and the second pressure sensor are respectively used for sensing a second refrigerant temperature and a second refrigerant pressure at the outlet of the heat recovery condenser, and the second supercooling degree at the outlet of the heat recovery condenser is calculated based on the second refrigerant temperature measured by the second temperature sensor and the second refrigerant pressure measured by the second pressure sensor.
Further, when the second supercooling degree is smaller than the difference value between the second target supercooling degree and the first preset temperature, the first electronic expansion valve is opened to increase the second supercooling degree, and when the second supercooling degree is larger than or equal to the sum of the second target supercooling degree and the second preset temperature, the first electronic expansion valve is closed until the second electronic expansion valve is closed.
Further, the first predetermined temperature is between 1 and 3 degrees Fahrenheit according to experimental practice, and the second predetermined temperature is between 0 and 2 degrees Fahrenheit according to requirements.
Further, when the difference value between the heat recovery outlet water temperature and the set heat recovery outlet water temperature value is larger than a first temperature threshold value, the water chilling unit is switched to a pure refrigeration mode; when the difference value between the heat recovery outlet water temperature and the heat recovery outlet water temperature set value is smaller than a second temperature threshold value, the water chilling unit is switched to a full heat recovery mode; and when the difference value between the heat recovery outlet water temperature and the heat recovery outlet water temperature set value is between the second temperature threshold and the first temperature threshold, switching the water chilling unit to a partial heat recovery mode, wherein the first temperature threshold is larger than the second temperature threshold.
Further, the first temperature threshold is any value between 2 and 8 degrees Fahrenheit, and the second temperature threshold is any value between-8 and-2 degrees Fahrenheit.
Further, the refrigeration condenser comprises a finned condenser or a shell-and-tube condenser.
According to the water chilling unit provided by the embodiment of the invention, the first electronic expansion valve and the second electronic expansion valve are respectively arranged at the outlets of the refrigeration condenser and the heat recovery condenser which are connected in parallel, and the opening degree of the first electronic expansion valve and the opening degree of the second electronic expansion valve are controlled, so that the requirement of a customer on the heat recovery amount can be met, the stepless regulation of the heat recovery amount of the water chilling unit can be realized, the water temperature fluctuation is small, and the comfort level is high.
Moreover, the water chilling unit provided by the embodiment of the invention can ensure the reliability on the basis of meeting the stepless regulation of the heat recovery quantity.
Drawings
FIG. 1 is a schematic block diagram of a prior art chiller;
FIG. 2 is a schematic block diagram of a chiller according to one embodiment of the present invention;
FIG. 3 is a fluid flow diagram of the chiller shown in FIG. 2 in a pure cooling mode;
FIG. 4 is a fluid flow diagram of the chiller shown in FIG. 2 in a full heat recovery mode;
fig. 5 is a fluid routing diagram of the chiller shown in fig. 2 in a partial heat recovery mode.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus consistent with certain aspects of the invention, as detailed in the appended claims.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the description and in the claims does not indicate any order, quantity, or importance, but rather is used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. "plurality" or "a number" means two or more. Unless otherwise indicated, "front", "rear", "lower" and/or "upper" and the like are for convenience of description and are not limited to one position or one spatial orientation. The word "comprising" or "comprises", and the like, means that the element or item listed as preceding "comprising" or "includes" covers the element or item listed as following "comprising" or "includes" and its equivalents, and does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
Fig. 2 discloses a schematic block diagram of a chiller 20 according to one embodiment of the present invention. As shown in fig. 2, a water chiller 20 according to an embodiment of the present invention includes a compressor 21, a refrigeration condenser 22, an evaporator 24, and a heat recovery condenser 23 connected in parallel to the refrigeration condenser 22. In one embodiment, the refrigeration condenser 22 may be, for example, a finned condenser. The cold source of the refrigeration condenser 22 comes from the wind blown by the variable frequency fan 220. However, the refrigeration condenser 22 of the embodiment of the present invention is not limited to the fin condenser. In other embodiments, the refrigerated condenser 22 may also be a shell and tube condenser with water on the cold source side and no fan. These minor changes do not affect the essence of the invention, and are all within the scope of the invention.
The water chilling unit 20 further includes a first electronic expansion valve 251 provided at the outlet a of the refrigeration condenser 22 and a second electronic expansion valve 252 provided at the outlet b of the heat recovery condenser 23.
According to the water chilling unit 20 provided by the embodiment of the invention, the first electronic expansion valve 251 and the second electronic expansion valve 252 are respectively arranged at the outlets a and b of the refrigeration condenser 22 and the heat recovery condenser 23 which are connected in parallel, and the opening degree of the first electronic expansion valve 251 and the opening degree of the second electronic expansion valve 252 are controlled, so that the requirement of a customer on the heat recovery amount can be met, the stepless regulation of the heat recovery amount of the water chilling unit 20 can be realized, the water temperature fluctuation is small, and the comfort level is high.
With continued reference to fig. 2, the chiller 20 of the present embodiment further includes a first temperature sensor T1 and a first pressure sensor P1 located at the outlet a of the refrigerant condenser 22. The first temperature sensor T1 and the first pressure sensor P1 are used to sense a first refrigerant temperature and a first refrigerant pressure at the outlet a of the refrigerant condenser 22, respectively, and a first supercooling degree at the outlet a of the refrigerant condenser 22 can be calculated based on the first refrigerant temperature measured by the first temperature sensor T1 and the first refrigerant pressure measured by the first pressure sensor P1.
The water chilling unit 20 of the embodiment of the present invention further includes a second temperature sensor T2 and a second pressure sensor P2 at the outlet b of the heat recovery condenser 23. The second temperature sensor T2 and the second pressure sensor P2 are used to sense a second refrigerant temperature and a second refrigerant pressure at the outlet b of the heat recovery condenser 23, respectively. The second supercooling degree at the outlet b of the heat recovery condenser 23 may be calculated based on the second refrigerant temperature measured by the second temperature sensor T2 and the second refrigerant pressure measured by the second pressure sensor P2.
The water chilling unit 20 according to the embodiment of the present invention includes a pure refrigeration mode, a total heat recovery mode, and a partial heat recovery mode. The switching of the chiller 20 between the pure cooling mode, the total heat recovery mode, and the partial heat recovery mode may be controlled based on the opening degrees of the first electronic expansion valve 251 and the second electronic expansion valve 252.
In the operation process of the water chilling unit 20 according to the embodiment of the present invention, when the difference between the heat recovery outlet water temperature and the heat recovery outlet water temperature set value is greater than the first temperature threshold, the water chilling unit 20 switches to the pure refrigeration mode. When the difference between the heat recovery leaving water temperature and the heat recovery leaving water temperature set value is smaller than the second temperature threshold, the chiller 20 switches to the full heat recovery mode. Wherein the first temperature threshold is greater than the second temperature threshold. When the difference between the heat recovery leaving water temperature and the heat recovery leaving water temperature set value is between the second temperature threshold and the first temperature threshold, the water chiller 20 switches to the partial heat recovery mode.
In one embodiment, the first temperature threshold may be, for example, any value between 2 and 8 degrees Fahrenheit, and the second temperature threshold may be, for example, any value between-8 and-2 degrees Fahrenheit, depending on experimental considerations.
Fig. 3 discloses a fluid flow diagram of the chiller 20 of fig. 2 in a pure cooling mode. As shown in fig. 3, when the water chiller 20 according to the embodiment of the present invention is in the pure cooling mode, the first electronic expansion valve 251 is opened, and the second electronic expansion valve 252 is closed. The opening degree of the first electronic expansion valve 251 is controlled in accordance with the liquid level/outlet superheat degree of the evaporator 24, and the rotational speed of the inverter fan 220 in the refrigeration condenser 22 is controlled in accordance with the outdoor ambient temperature. The refrigerant is compressed in the compressor 21, and the low-temperature and low-pressure refrigerant gas is compressed into a high-temperature and high-pressure refrigerant gas, which is then discharged from a discharge port of the compressor 21. The high-temperature and high-pressure refrigerant gas flows into the refrigeration condenser 22, and is condensed into a high-temperature and high-pressure refrigerant liquid in the refrigeration condenser 22. The refrigerant liquid of high temperature and high pressure is throttled and depressurized by the first electronic expansion valve 251 to become a two-phase refrigerant fluid of low temperature and low pressure in which the refrigerant liquid occupies a large part. The low-temperature, low-pressure two-phase refrigerant fluid then enters the evaporator 24. The low-temperature low-pressure refrigerant liquid absorbs heat in the evaporator 24 and is vaporized, thereby evaporating into a low-temperature low-pressure refrigerant gas. The low-temperature and low-pressure refrigerant gas is sucked into the compressor 21 from the suction port of the compressor 21 and enters the next refrigeration cycle.
The second electronic expansion valve 252 is normally closed when the chiller 20 is in a pure cooling mode. However, when the chiller 20 is in the pure cooling mode, the refrigerant liquid may gradually increase while being stored in the heat recovery condenser 23, and if the refrigerant liquid is stored excessively, the refrigerant may be short in the circulation circuit of the chiller 20, which may affect the normal operation of the chiller 20. And the heat recovery condenser 23 accumulates excessive refrigerant in the form that the first supercooling degree at the outlet a of the refrigerant condenser 22 becomes small. Therefore, in order to ensure the reliability of the chiller 20, the first supercooling degree at the outlet a of the refrigerant condenser 22 may be timely monitored. The first supercooling degree may be calculated from the first refrigerant temperature and the first refrigerant pressure measured by the first temperature sensor T1 and the first pressure sensor P1 at the outlet a of the refrigerant condenser 22, respectively.
When the first supercooling degree at the outlet a of the refrigerant condenser 22 is lower than the first target supercooling degree at the outlet a of the refrigerant condenser 22, the second electronic expansion valve 252 is opened, as shown by a dotted line in fig. 3, and the opening degree of the second electronic expansion valve 252 is controlled according to the first supercooling degree.
Table 1 shows a first target subcooling (F, fahrenheit) for the refrigerant condenser 22 at outlet a for different operating conditions in one embodiment. The first target subcooling degree at the outlet a of the refrigerant condenser 22 is shown in table 1 for different loads, such as full load, half load and minimum load, different ambient temperatures and different evaporator leaving water temperatures, as indicated by the italic character in table 1. For example, at full load, when the ambient temperature is 125F and the evaporator leaving water temperature is 40F, the first target subcooling degree at the outlet a of the corresponding refrigeration condenser 22 is 12.0F. The first target subcooling for the operating points not specified in table 1 may be calculated by interpolation.
TABLE 1
When the second electronic expansion valve 252 is opened, the refrigerant in the heat recovery condenser 23 is discharged, and an appropriate amount of refrigerant can flow into the refrigeration cycle circuit of the chiller 20, thereby ensuring the refrigerant circulation amount of the chiller 20 and ensuring the reliability of the operation of the chiller 20. In addition, since the second electronic expansion valve 252 is opened according to the supercooling degree control at this time, the amount of refrigerant discharged is appropriate to ensure that a normal refrigeration cycle is suitable, and therefore, the chiller 20 shown in fig. 2 of the present invention may omit an accumulator compared to the existing chiller 10 shown in fig. 1. The first supercooling degree at the outlet a of the refrigerant condenser 22 immediately rises after the refrigerant is discharged; when the first subcooling degree at the outlet a of the refrigerant condenser 22 is returned to the first target subcooling degree, the second electronic expansion valve 252 is again kept normally closed.
In one embodiment, when the first supercooling degree at the outlet a of the refrigerant condenser 22 is less than the difference between the first target supercooling degree and the first predetermined temperature, the second electronic expansion valve 252 is opened to increase the first supercooling degree, as shown in the following equation (1).
T1＜Tsc1-2F (1)
Wherein, T1Represents the measured first degree of subcooling, T, at the outlet a of the condenser 22sc1Representing a first target supercooling degree at the outlet a of the condenser 22.
The first predetermined temperature may be between 1 and 3 degrees fahrenheit based on experimental practice.
When the first subcooling degree is greater than or equal to the sum of the first target subcooling degree and the second predetermined temperature, the second electronic expansion valve 252 is closed until closed as shown in equation (2) below.
T1≥Tsc1+1F (2)
The second predetermined temperature may be between 0 and 2 degrees fahrenheit, depending on the requirements.
Fig. 4 discloses a fluid routing diagram of the chiller 20 of fig. 2 in a full heat recovery mode. As shown in fig. 4, when the water chiller 20 according to the embodiment of the present invention is in the full heat recovery mode, the second electronic expansion valve 252 is opened, and the first electronic expansion valve 251 is closed. The opening degree of the second electronic expansion valve 252 is controlled in accordance with the liquid level/outlet superheat of the evaporator 24. The compressor 21 compresses the original low-temperature and low-pressure refrigerant gas into high-temperature and high-pressure refrigerant gas, and then the refrigerant gas enters the heat recovery condenser 23, cold water in a customer water tank (not shown) is pumped by a water pump and enters the heat recovery condenser 23, in the heat recovery condenser 23, the cold water and the high-temperature and high-pressure refrigerant gas exchange heat, the high-temperature and high-pressure refrigerant gas is condensed to release heat, the heat is changed into high-temperature and high-pressure refrigerant liquid, and the cold water is heated to the temperature required by a customer. Subsequently, the refrigerant liquid with high temperature and high pressure is throttled and depressurized by the second electronic expansion valve 252, and becomes a two-phase refrigerant fluid with low temperature and low pressure to enter the evaporator 24, and is evaporated by the evaporator 24 to become a refrigerant gas with low temperature and low pressure to return to the compressor 21. And heated hot water is returned from the heat recovery condenser 23 to the customer tank. And the process is repeated in a reciprocating way.
When the chiller 20 is in the full heat recovery mode, the first electronic expansion valve 251 is normally closed. However, when the chiller 20 is in the total heat recovery mode, the refrigerant liquid may be accumulated in the refrigeration condenser 22 and gradually increase, and if the refrigerant liquid is excessively accumulated, the refrigerant may be short in the circulation circuit of the chiller 20, which may affect the normal operation of the chiller 20. And the refrigerant condenser 22 accumulates excessive refrigerant in the form that the second supercooling degree at the outlet b of the heat recovery condenser 23 becomes small. Therefore, in order to ensure the reliability of the chiller 20, the second supercooling degree at the outlet b of the heat recovery condenser 23 may be timely monitored. The second supercooling degree may be calculated from the second refrigerant temperature and the second refrigerant pressure measured by the second temperature sensor T2 and the second pressure sensor P2 at the outlet b of the heat recovery condenser 23, respectively.
When the second supercooling degree at the outlet b of the heat recovery condenser 23 is lower than the second target supercooling degree at the outlet b of the heat recovery condenser 23, the first electronic expansion valve 251 is opened, as shown by a dotted line in fig. 4, and the opening degree of the first electronic expansion valve 251 is controlled according to the second supercooling degree.
Table 2 shows a second target subcooling (F, fahrenheit) for the outlet of the heat recovery condenser 23 for different operating conditions in one embodiment. The second target subcooling degree at the outlet b of the heat recovery condenser 23 is shown in table 2 for different loads such as full load, half load and minimum load, different heat recovery feed water temperatures and different evaporator exit water temperatures, as indicated by the italic letters in table 2. For example, at full load, when the heat recovery inlet water temperature is 140F and the evaporator outlet water temperature is 40F, the second target supercooling degree at the outlet b of the corresponding heat recovery condenser 23 is 6.7F. The second target subcooling for the operating points not specified in table 2 may be calculated by interpolation.
TABLE 2
When the first electronic expansion valve 251 is opened, the refrigerant in the refrigeration condenser 22 is discharged, and an appropriate amount of refrigerant can flow into the heat recovery circulation circuit of the chiller 20, thereby ensuring the refrigerant circulation amount of the chiller 20 and ensuring the reliability of the operation of the chiller 20. The second supercooling degree at the outlet b of the heat recovery condenser 23 immediately rises after the refrigerant is discharged; when the second supercooling degree at the outlet b of the heat recovery condenser 23 is restored to the second target supercooling degree, the first electronic expansion valve 251 is again maintained in a normally closed state.
In one embodiment, when the second supercooling degree at the outlet b of the heat recovery condenser 23 is less than the difference between the second target supercooling degree and the first predetermined temperature, the first electronic expansion valve 251 is opened to increase the second supercooling degree, as shown in the following equation (3).
T2＜Tsc2-1.5F (3)
Wherein, T2Represents the second measured supercooling degree, T, at the outlet b of the heat recovery condenser 23sc2Representing a second target subcooling degree at the outlet b of the heat recovery condenser 23.
When the second supercooling degree is greater than or equal to the sum of the second target supercooling degree and the second predetermined temperature, the first electronic expansion valve 251 is closed down until being closed, as shown in the following equation (4).
T2≥Tsc2+1F (4)
Fig. 5 discloses a fluid routing diagram of the chiller 20 of fig. 2 in a partial heat recovery mode. As shown in fig. 5, when the water chiller 20 according to the embodiment of the present invention is in the partial heat recovery mode, the second electronic expansion valve 252 and the first electronic expansion valve 251 are partially opened, wherein the second electronic expansion valve 252 is a main valve and the first electronic expansion valve 251 is an auxiliary valve, and the refrigerant gas of high temperature and high pressure coming out of the compressor 21 is distributed to the heat recovery condenser 23 and the refrigeration condenser 22. In the partial heat recovery mode, the total opening degree/flow area of the first electronic expansion valve and the second electronic expansion valve of the chiller 20 is controlled by the liquid level/outlet superheat degree of the evaporator 24, the opening degree/flow area of the second electronic expansion valve 252 is controlled according to a heat recovery outlet water temperature set value set by a customer, and the opening degree/flow area of the first electronic expansion valve 251 is the difference between the total opening degree/flow area and the opening degree/flow area of the second electronic expansion valve 252.
Under low ambient conditions, the refrigerant is more easily condensed into the refrigeration condenser 22, and particularly, when the heat recovery requirement is large, that is, the opening degree of the second electronic expansion valve 252 is large, and the opening degree of the first electronic expansion valve 251 is small, the refrigerant liquid is more easily stored in the refrigeration condenser 22. Therefore, when the ambient temperature is lower than the heat recovery water temperature, the second subcooling degree at the outlet b of the heat recovery condenser 23 is detected, and when the second subcooling degree at the outlet b of the heat recovery condenser 23 is detected to be smaller than the difference between the second target subcooling degree and the first predetermined temperature (as shown in formula (3)), the control is switched to the control main valve of the first electronic expansion valve 251, and the opening degree of the first electronic expansion valve 251 is increased to increase the second subcooling degree at the outlet b of the heat recovery condenser 23, and at this time, the second electronic expansion valve 252 is an auxiliary valve, and the opening degree/flow area corresponds to the difference between the total opening degree/flow area and the opening degree/flow area of the first electronic expansion valve 251. When the second supercooling degree at the outlet b of the heat recovery condenser 23 is greater than or equal to the sum of the second target supercooling degree and the second predetermined temperature (as shown in equation (4)), the control is switched to the normal partial heat recovery control.
Therefore, the heat recovery amount of the water chilling unit 20 according to the embodiment of the present invention can be realized by adjusting the opening degree of the second electronic expansion valve 252 according to the set value of the heat recovery outlet water temperature set by the customer, so as to realize stepless adjustment of the heat recovery amount according to the actual heat load, and at the same time, through the cooperation between the first electronic expansion valve 251 and the second electronic expansion valve 252, on the premise of ensuring the liquid level/outlet superheat degree of the evaporator 24, the amounts of the refrigerants respectively entering the refrigeration condenser 22 and the heat recovery condenser 23 are adjusted, so as to achieve the purposes of adjusting the heat recovery amount and ensuring the reliability of the water chilling unit 20.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention shall be included in the scope of the present invention.
Claims (16)
1. The utility model provides a water chilling unit, its including the compressor, refrigeration condenser and the evaporimeter that connect gradually and with the parallelly connected heat recovery condenser of refrigeration condenser, its characterized in that: the water chilling unit further comprises a first electronic expansion valve arranged at an outlet of the refrigeration condenser and a second electronic expansion valve arranged at an outlet of the heat recovery condenser.
2. The chiller according to claim 1 wherein: the water chilling unit comprises a pure refrigeration mode, a total heat recovery mode and a partial heat recovery mode, and is controlled to be switched among the pure refrigeration mode, the total heat recovery mode and the partial heat recovery mode based on the opening degrees of the first electronic expansion valve and the second electronic expansion valve.
3. The chiller according to claim 2 wherein: when the water chilling unit is in a partial heat recovery mode, the opening degree of the second electronic expansion valve is controlled according to a set value of the temperature of the heat recovery outlet water, the total opening degree/flow area of a first electronic expansion valve and a second electronic expansion valve of the water chilling unit is controlled by the liquid level/outlet superheat degree of the evaporator, and the opening degree/flow area of the first electronic expansion valve is the difference value between the total opening degree/flow area and the opening degree/flow area of the second electronic expansion valve.
4. The chiller according to claim 2 wherein: when the water chilling unit is in a pure refrigeration mode, the opening degree of the first electronic expansion valve is controlled according to the liquid level/outlet superheat degree of the evaporator, and the second electronic expansion valve is closed.
5. The chiller according to claim 4 wherein: when the first supercooling degree at the outlet of the refrigeration condenser is lower than a first target supercooling degree, the second electronic expansion valve is opened, and the opening degree of the second electronic expansion valve is controlled according to the first supercooling degree.
6. The chiller according to claim 5 wherein: the refrigerant condenser is characterized by further comprising a first temperature sensor and a first pressure sensor which are located at an outlet of the refrigeration condenser, wherein the first temperature sensor and the first pressure sensor are respectively used for sensing a first refrigerant temperature and a first refrigerant pressure at the outlet of the refrigeration condenser, and the first supercooling degree at the outlet of the refrigeration condenser is calculated on the basis of the first refrigerant temperature measured by the first temperature sensor and the first refrigerant pressure measured by the first pressure sensor.
7. The chiller according to claim 5 wherein: when the first supercooling degree is smaller than the difference value between the first target supercooling degree and the first preset temperature, the second electronic expansion valve is opened to increase the first supercooling degree; and when the first supercooling degree is greater than or equal to the sum of the first target supercooling degree and a second preset temperature, closing the second electronic expansion valve until the second electronic expansion valve is closed.
8. The chiller according to claim 7 wherein: the first preset temperature is between 1 and 3 degrees Fahrenheit and is taken according to the actual experimental condition, and the second preset temperature is between 0 and 2 degrees Fahrenheit and is taken according to the requirement.
9. The chiller according to claim 2 wherein: when the water chilling unit is in a full heat recovery mode, the opening degree of the second electronic expansion valve is controlled according to the liquid level/outlet superheat degree of the evaporator, and the first electronic expansion valve is closed.
10. The chiller according to claim 9 wherein: when a second supercooling degree at the outlet of the heat recovery condenser is lower than a second target supercooling degree, the first electronic expansion valve is opened, and the opening degree of the first electronic expansion valve is controlled according to the second supercooling degree.
11. The chiller according to claim 10 wherein: the refrigerant condenser further comprises a second temperature sensor and a second pressure sensor which are located at the outlet of the heat recovery condenser, the second temperature sensor and the second pressure sensor are respectively used for sensing a second refrigerant temperature and a second refrigerant pressure at the outlet of the heat recovery condenser, and the second supercooling degree at the outlet of the heat recovery condenser is calculated based on the second refrigerant temperature measured by the second temperature sensor and the second refrigerant pressure measured by the second pressure sensor.
12. The chiller according to claim 10 wherein: and when the second supercooling degree is smaller than the difference value between the second target supercooling degree and the first preset temperature, the first electronic expansion valve is opened to increase the second supercooling degree, and when the second supercooling degree is larger than or equal to the sum of the second target supercooling degree and the second preset temperature, the first electronic expansion valve is closed until the second electronic expansion valve is closed.
13. The chiller according to claim 12 wherein: the first preset temperature is between 1 and 3 degrees Fahrenheit and is taken according to the actual experimental condition, and the second preset temperature is between 0 and 2 degrees Fahrenheit and is taken according to the requirement.
14. The chiller according to claim 2 wherein: when the difference value between the heat recovery outlet water temperature and the set heat recovery outlet water temperature is greater than a first temperature threshold value, the water chilling unit is switched to a pure refrigeration mode; when the difference value between the heat recovery outlet water temperature and the heat recovery outlet water temperature set value is smaller than a second temperature threshold value, the water chilling unit is switched to a full heat recovery mode; and when the difference value between the heat recovery outlet water temperature and the heat recovery outlet water temperature set value is between the second temperature threshold and the first temperature threshold, switching the water chilling unit to a partial heat recovery mode, wherein the first temperature threshold is larger than the second temperature threshold.
15. The chiller according to claim 14 wherein: the first temperature threshold is any value between 2 degrees and 8 degrees Fahrenheit, and the second temperature threshold is any value between-8 degrees and-2 degrees Fahrenheit.
16. The chiller according to claim 1 wherein: the refrigeration condenser comprises a finned condenser or a shell-and-tube condenser.
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| CN114152028A (en) * | 2021-11-30 | 2022-03-08 | 广东乐畅制冷科技有限公司 | Water chiller with intelligent cooling water circulation system |
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| CN111288676B (en) | 2021-11-02 |
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