CN115451599A - Air source heat pump continuous steam supply system and control method - Google Patents
Air source heat pump continuous steam supply system and control method Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 15
- 238000010257 thawing Methods 0.000 claims abstract description 70
- 230000005494 condensation Effects 0.000 claims abstract description 38
- 238000009833 condensation Methods 0.000 claims abstract description 38
- 239000003507 refrigerant Substances 0.000 claims description 73
- 239000007788 liquid Substances 0.000 claims description 16
- 230000001502 supplementing effect Effects 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000004781 supercooling Methods 0.000 claims description 10
- 230000009977 dual effect Effects 0.000 claims description 9
- 238000001704 evaporation Methods 0.000 claims description 7
- 230000008020 evaporation Effects 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 230000000295 complement effect Effects 0.000 abstract description 5
- 230000006835 compression Effects 0.000 abstract description 4
- 238000007906 compression Methods 0.000 abstract description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 239000008400 supply water Substances 0.000 description 1
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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
- F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B1/00—Methods of steam generation characterised by form of heating method
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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
- F25B41/34—Expansion valves with the valve member being actuated by electric means, e.g. by piezoelectric actuators
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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
- F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
- F25B47/02—Defrosting cycles
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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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- Air Conditioning Control Device (AREA)
Abstract
The invention provides an air source heat pump continuous steam supply system and a control method, wherein the air source heat pump continuous steam supply system comprises a low-temperature-level double system, a high-temperature-level system, an intermediate heat exchanger and a condensation evaporator, the energy in air is gradually increased through a cascade compression heat pump technology, steam is directly generated for a terminal user to use, the supply of the steam with the temperature of over 100 ℃ is realized through the control of an electronic expansion valve, and defrosting is carried out through an alternating complementary defrosting technology, so that the system can still provide stable steam.
Description
Technical Field
The invention belongs to the technical field of renewable energy application, particularly relates to the field of steam supply of an air source heat pump, and particularly relates to a system and a control method for continuously supplying steam to the air source heat pump.
Background
The air source heat pump technology is to convert the energy in the air into heat for use by utilizing the inverse Carnot cycle principle and through the processes of evaporation heat absorption, compression temperature rise and condensation heat release of a refrigerant, and is well applied in the fields of hot water (55 ℃), heating (41-50 ℃) and the like. The air source heat pump can realize high-temperature hot water (above 80 ℃) supply by adopting a cascade type circulating compression mode, and can supply steam through flash evaporation when the supply water temperature exceeds 100 ℃.
At present, the air source heat pump industry does not have a unit for directly supplying steam, when the unit supplies steam, the steam demand of continuity stability of a user terminal needs to be met, however, the existing air source heat pump system cannot run stably to ensure continuous steam supply. And the air source heat pump unit is easy to frost, when frosting, the prior art adopts a mode that the unit stops supplying heat and takes heat from the condenser for defrosting the fin evaporator, and the mode influences the supply of steam and wastes the heat of the condenser (a heat reservoir).
Disclosure of Invention
The invention provides a system and a control method for continuously supplying steam by an air source heat pump, which improve the energy in the air step by a cascade compression heat pump technology, directly generate steam for end users, realize the supply of the steam with the temperature of over 100 ℃ by the control of an electronic expansion valve, defrost by an alternate complementary defrosting technology and ensure that the system can still provide stable steam.
The invention is realized by the following technical scheme:
an air source heat pump continuous steam supply system comprises a low-temperature-level double system, a high-temperature-level system, an intermediate heat exchanger and a condensing evaporator;
the low-temperature-stage double system comprises a 1# circulation loop and a 2# circulation loop, wherein the 1# circulation loop and the 2# circulation loop respectively comprise a variable frequency compressor, a four-way valve, a first heat exchanger and a first economizer, a first interface of the four-way valve is sequentially communicated with the variable frequency compressor and a second interface of the four-way valve, a third interface of the four-way valve is communicated with the first heat exchanger, and a fourth interface of the four-way valve is sequentially communicated with the intermediate heat exchanger and the condensing evaporator;
the interface of the condensation evaporator is communicated with a main loop of the first economizer, the other end of the main loop of the first economizer is respectively communicated with a first main-loop electronic expansion valve and a first auxiliary-loop electronic expansion valve, the first main-loop electronic expansion valve is communicated with the first heat exchanger, the first auxiliary-loop electronic expansion valve is communicated with the gas supplementing loop of the first economizer, and the other end of the gas supplementing loop of the first economizer is communicated with a gas supplementing port of the variable frequency compressor;
the high-temperature stage system comprises a fixed-frequency compressor, a second condenser and a second economizer, wherein an outlet on the heat exchange side of the condensation evaporator is communicated with an air inlet of the fixed-frequency compressor, an air outlet of the fixed-frequency compressor is communicated with the second condenser, an outlet of the second condenser is communicated with a main loop of the second economizer, the other end of the main loop of the second economizer is respectively communicated with a second main electronic expansion valve and a second auxiliary electronic expansion valve, the second main electronic expansion valve is communicated with an inlet on the heat exchange side of the condensation evaporator, the second auxiliary electronic expansion valve is communicated with an air supplementing loop of the second economizer, and the other end of the air supplementing loop of the second economizer is communicated with an air supplementing port of the fixed-frequency compressor.
The invention discloses a control method of an air source heat pump continuous steam supply system, which adopts the air source heat pump continuous steam supply system to control the supply of steam and comprises the following steps:
(1) In a low-temperature-level dual system, a variable frequency compressor in a 1# circulation loop and a variable frequency compressor in a 2# circulation loop operate simultaneously, a refrigerant enters a first heat exchanger, is evaporated to absorb heat and then is changed into low-temperature low-pressure gas, then enters the variable frequency compressor to be compressed into medium-temperature medium-pressure gas, passes through a four-way valve and an intermediate heat exchanger, enters a condensation evaporator to be condensed to release heat, is changed into gas-liquid refrigerant, flows out of the condensation evaporator, finally enters a first main-path electronic expansion valve through a liquid storage device and a first economizer, is throttled by the first main-path electronic expansion valve, enters the first heat exchanger to be evaporated again to absorb heat, and therefore a low-temperature-level cycle is completed;
adjusting a first main circuit electronic expansion valve through a PID controller to enable a main circuit refrigerant to have superheat degree, wherein the superheat degree is adjustable and ranges from-2 ℃ to 5 ℃;
opening a first auxiliary circuit electronic expansion valve, and adjusting a second auxiliary circuit electronic expansion valve through a PID controller to enable an auxiliary circuit refrigerant to have a supercooling degree, wherein the supercooling degree is adjustable and ranges from 3 ℃ to 10 ℃; (ii) a
(2) In the high-temperature stage system, the refrigerant enters a condensation evaporator after being throttled by a second main-path electronic expansion valve, the heat of the intermediate-temperature gaseous refrigerant compressed by a variable-frequency compressor in the low-temperature stage dual system is evaporated and absorbed in the condensation evaporator to be changed into a gaseous refrigerant, the gaseous refrigerant enters a fixed-frequency compressor, the gaseous refrigerant is compressed into a high-temperature refrigerant by the fixed-frequency compressor, the high-temperature refrigerant enters a second condenser to be condensed and release heat, finally the refrigerant enters a second main-path electronic expansion valve through a liquid storage device and a second economizer, and the refrigerant enters a condensation evaporation heater to be evaporated and absorb heat after being throttled by a second main-path electronic expansion valve, so that a high-temperature stage cycle is completed;
adjusting a second main circuit electronic expansion valve through a PID controller to enable a main circuit refrigerant to have superheat degree, wherein the superheat degree is adjustable and ranges from 5 ℃ to 12 ℃; adjusting a second auxiliary circuit electronic expansion valve through a PID controller to enable an auxiliary circuit refrigerant to have a supercooling degree, wherein the supercooling degree is adjustable and ranges from 3 ℃ to 10 ℃;
(3) The second condenser can be matched with a high-temperature water side heat exchanger to heat water to 120 ℃, and can also be matched with a steam generator to directly heat and evaporate water into steam;
(4) In a cryogenic stage dual system, when one of the circulation loops reaches the following defrost conditions, i.e.:
K: the coefficient of the calculation of the ring temperature,
when the temperature is higher than the set temperatureTWhen the temperature of a is less than 0 ℃,K=0.8；
when in useTWhen a is more than or equal to 0 ℃,K=0.6；
and entering a defrosting cycle, switching the cycle loop into a defrosting working condition through the four-way valve, keeping the other cycle loop in a heating working condition, and stopping the high-temperature system.
Further, in step (4), when one of the circulation loops reaches the defrosting condition, the frequency conversion compressors of the two circulation loops simultaneously reduce the frequency to the target frequency of 40Hz,
in the circulation loop, through the switching of the four-way valve, gaseous refrigerant flowing out of the variable frequency compressor enters the first heat exchanger through the four-way valve to release heat, frost on the outer wall of the first heat exchanger is melted, the refrigerant is condensed to become gas-liquid refrigerant, the gas-liquid refrigerant sequentially passes through the first main-path electronic expansion valve, the first economizer and the condensation evaporator, the refrigerant is not evaporated and does not absorb heat in the condensation evaporator, the refrigerant flows out of the condensation evaporator, enters the intermediate heat exchanger to be evaporated and absorbs heat of the refrigerant in the other circulation loop, and the refrigerant enters the variable frequency compressor through the four-way valve to be compressed again after being evaporated, so that a defrosting cycle is formed;
when the temperature of the first heat exchanger outer coil in the circulation loop does not reach the defrosting condition, the circulation loop is switched by the four-way valve to exit the defrosting condition and enter the heating condition again.
Further, in the step (4), whether the 1# circulation loop reaches the defrosting condition is judged firstly, if the 1# circulation loop reaches the defrosting condition, the 1# circulation loop is made to enter the defrosting working condition firstly, and after the defrosting condition is removed, whether the 1# circulation loop reaches the defrosting condition is judged;
if the 1# circulation loop does not reach the defrosting condition, judging whether the 1# circulation loop reaches the defrosting condition;
the defrosting quitting conditions are as follows: when the temperature of the outer coil pipe of the first heat exchanger reaches a set exit temperature value, the set exit temperature value is 5-20 ℃; or meeting the requirement of the maximum defrosting time, wherein the set value of the maximum defrosting time is 2-10 min).
Compared with the prior art, the invention has the following beneficial effects:
1. the low-temperature-stage double system and the high-temperature-stage system form a cascade heat pump system through an intermediate heat exchanger and a condensing evaporator to increase the energy in the air step by step and directly generate steam for a terminal user to use;
in the control process, the superheat degree is adjusted and controlled through electronic expansion valves, the supply of 120 ℃ steam is realized, in a low-temperature-level dual system, when one circulation loop reaches a defrosting condition, a defrosting cycle is started, the circulation loop is switched into a defrosting working condition through a four-way valve, the other circulation loop keeps a heating working condition, the high-temperature-level system stops working, defrosting is carried out through an alternating complementary defrosting technology, and the system is ensured to still provide stable steam;
2. when the defrosting working condition is entered, the 1# circulation loop is judged to not reach the defrosting condition, and then whether the 1# circulation loop reaches the defrosting condition is judged, so that the alternating complementary defrosting process is realized.
Drawings
FIG. 1 is a schematic diagram of an air source heat pump continuous steam supply system according to the present invention;
FIG. 2 is a schematic diagram of the defrosting status of the air source heat pump continuous steam supply system according to the present invention;
in the figure: 1. the system comprises a variable frequency compressor, a four-way valve 2, a four-way valve 3, a first heat exchanger 4, a first economizer 5, a first main circuit electronic expansion valve 6, an intermediate heat exchanger 7, a condensation evaporator 8, a first auxiliary circuit electronic expansion valve 9, a fixed frequency compressor 10, a second condenser 11, a second economizer 12, a second main circuit electronic expansion valve 13 and a second auxiliary circuit electronic expansion valve.
Detailed Description
The invention will be further explained with reference to the following drawings and examples
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
As shown in fig. 1, the present embodiment discloses an air source heat pump continuous steam supply system, which includes a low-temperature-stage dual system, a high-temperature-stage system, an intermediate heat exchanger 6 and a condensing evaporator 7, wherein the condensing evaporator 7 is a plate heat exchanger. The low-temperature-stage double system is formed by connecting a 1# circulation loop and a 2# circulation loop in parallel, the 1# circulation loop and the 2# circulation loop are identical in structure composition, taking the 1# circulation loop as an example, the low-temperature-stage double system comprises a variable frequency compressor 1, a four-way valve 2, a first heat exchanger 3 and a first economizer 4, a first interface of the four-way valve 2 is sequentially communicated with a second interface of the variable frequency compressor 1 and a second interface of the four-way valve 2, a third interface of the four-way valve 2 is communicated with the first heat exchanger 3, and a fourth interface of the four-way valve 2 is sequentially communicated with an intermediate heat exchanger 6 and a condensing evaporator 7. The interface of the condensation evaporator 7 is communicated with the main loop of the first economizer 4, the other end of the main loop of the first economizer 4 is correspondingly communicated with a first main-path electronic expansion valve 5 and a first auxiliary-path electronic expansion valve 8 in two paths, the first main-path electronic expansion valve 5 is communicated with the first heat exchanger 3, and the first heat exchanger 3 can be a fin coil type heat exchanger commonly used in a heat pump system. The first auxiliary electronic expansion valve 8 is communicated with the air supplementing loop of the first economizer 4, and the other end of the air supplementing loop of the first economizer 4 is communicated with an air supplementing port of the variable frequency compressor 1. The 1# circulation circuit is the same as the 2# circulation circuit, and the 2# circulation circuit will not be described in detail. The 1# circulation loop and the 2# circulation loop are connected in parallel at the heat supply side of the condensing evaporator 7,
the high-temperature stage system comprises a fixed-frequency compressor 9, a second condenser 10 and a second economizer 11, wherein an outlet on the heat exchange side of a condensation evaporator 7 is communicated with an air inlet of the fixed-frequency compressor 9, an air outlet of the fixed-frequency compressor 9 is communicated with the second condenser 10, an outlet of the second condenser 10 is communicated with a main loop of the second economizer 11, the other end of the main loop of the second economizer 11 is divided into two paths to be correspondingly communicated with a second main path electronic expansion valve 12 and a second auxiliary path electronic expansion valve 13 respectively, the second main path electronic expansion valve 12 is communicated with an inlet on the heat exchange side of the condensation evaporator 7, the second auxiliary path electronic expansion valve 13 is communicated with an air supply loop of the second economizer 11, and the other end of the air supply loop of the second economizer 11 is communicated with an air supply port of the fixed-frequency compressor 9.
Based on the above air source heat pump continuous steam supply system, the present embodiment discloses a control method for an air source heat pump continuous steam supply system, which can continuously supply steam of more than 100 ℃, and includes the following steps:
(1) In a low-temperature stage double system, a variable frequency compressor 1 in a 1# circulation loop and a 2# circulation loop operates simultaneously, taking the 1# circulation loop as an example, a refrigerant enters a first heat exchanger 3, enters a low-temperature low-pressure gas after evaporation and heat absorption, then enters the variable frequency compressor 1 to be compressed into a medium-temperature medium-pressure gas, enters a condensation evaporator 7 after passing through a four-way valve 2 and an intermediate heat exchanger 6, is condensed and releases heat, becomes a gas-liquid refrigerant and flows out of the condensation evaporator 7, and finally enters a first main-path electronic expansion valve 5 after passing through a liquid storage device and a first economizer 4, enters the first heat exchanger 3 after throttling by the first main-path electronic expansion valve 5 to be evaporated and heat absorbed again, so that a low-temperature stage cycle is completed;
in the system, there are two kinds of electronic expansion valves, which are a first main-path electronic expansion valve 5 and a second main-path electronic expansion valve 12, and the main function of the electronic expansion valves is to adjust the throttling degree of the refrigerant of the frequency conversion system. The degree of throttling of the first main electronic expansion valve 5 can be directly reflected by the superheat degree of the refrigerant of the main loop. The control of the first main electronic expansion valve 5 is adjusted by PID control, so that the superheat degree of the main refrigerant is set to 3 ℃ (the value is adjustable). The main superheat degree can not be too small or too large, the superheat degree is too small, and the risk of liquid accumulation of a compressor is caused; the superheat degree of the main path cannot be too large, so that the energy efficiency of the compressor is reduced and the COP of the whole compressor is reduced. The opening of the first auxiliary electronic expansion valve 8 is determined by the ring temperature, when the ring temperature is lower than 7 ℃, the first auxiliary electronic expansion valve 8 is opened, the air-supplying and enthalpy-increasing functions of the variable frequency compressor 1 are added, and the system energy efficiency is improved. The regulation of the first auxiliary circuit electronic expansion valve 8 is controlled and regulated by PID control, so that the supercooling degree of the auxiliary circuit is set to be 5 ℃ (the value is adjustable).
(2) In the high-temperature stage system, the refrigerant enters the condensation evaporator 7 after being throttled by the second main-path electronic expansion valve 12, the heat of the medium-temperature gaseous refrigerant compressed by the variable-frequency compressor 1 in the low-temperature stage double system is evaporated and absorbed in the condensation evaporator 7 to be changed into gaseous refrigerant, the gaseous refrigerant enters the fixed-frequency compressor 9, the gaseous refrigerant is compressed into high-temperature refrigerant by the fixed-frequency compressor 9, the high-temperature refrigerant enters the second condenser 10 for condensation and heat release, finally the refrigerant enters the second main-path electronic expansion valve 12 through the liquid storage device and the second economizer 11, and the refrigerant enters the condensation evaporation heater for re-evaporation and heat absorption after being throttled by the second main-path electronic expansion valve 12, so that a high-temperature stage cycle is completed;
in the system, a PID controller is used for adjusting a second main circuit electronic expansion valve 12 to enable the superheat degree of a main circuit refrigerant to be 8 ℃ (the numerical value is adjustable), and a PID controller is used for adjusting a second auxiliary circuit electronic expansion valve 13 to enable the supercooling degree of an auxiliary circuit refrigerant to be 5 ℃ (the numerical value is adjustable);
(3) The second condenser 10 may cooperate with a high-temperature water-side heat exchanger to heat water to 120 ℃ to form steam, or cooperate with a steam generator to directly heat and evaporate water to form steam, in this embodiment, the second condenser is placed in the steam generator to directly heat and evaporate water to form steam;
(4) In a low-temperature-level dual system, the fins of the outer coil of the first heat exchanger 3 are easy to frost, and if the defrosting is not carried out timely, the steam supply efficiency of the whole system is affected, so that the defrosting circulation function is added. Before judging whether the defrosting condition is met, the inverter compressor 1 heats and continuously runs for 10 minutes, the accumulated running time is greater than a defrosting set period, the defrosting set period is in a range of 20-200min, and in the embodiment, 50min is defaulted. Firstly, judging whether the 1# circulation loop reaches a defrosting condition, if the 1# circulation loop reaches the defrosting condition, enabling the 1# circulation loop to enter the defrosting working condition, and judging whether the 1# circulation loop reaches the defrosting condition after the defrosting condition is removed; if the 1# circulation loop does not reach the defrosting condition, whether the 1# circulation loop reaches the defrosting condition is judged again. In this embodiment, taking the first heat exchanger 3 of the 1# circulation loop and the 2# circulation loop as an example, as shown in fig. 2, the specific steps are as follows:
when the 1# circulation loop reaches the following defrost conditions, namely:
K: the coefficient of the calculation of the ring temperature,
when the temperature is higher than the set temperatureTWhen the temperature of a is less than 0 ℃,K=0.8；
when in useTWhen a is more than or equal to 0 ℃,K=0.6；
the frequency conversion compressors 1 of the two circulation loops simultaneously reduce the frequency to a target frequency of 40Hz, the 2# circulation loop keeps a heating working condition, and the high-temperature-level system stops operating;
in the 1# circulation loop, through the switching of the four-way valve 2, a gaseous refrigerant flowing out of the variable frequency compressor 1 enters the first heat exchanger 3 through the four-way valve 2 to release heat, frosting and melting are carried out on the outer wall of the first heat exchanger 3, the refrigerant is changed into a gas-liquid refrigerant after being condensed, the gas-liquid refrigerant sequentially passes through the first main circuit electronic expansion valve 5, the first economizer 4 and the condensation evaporator 7, the refrigerant is not evaporated in the condensation evaporator 7 and does not absorb heat, and the refrigerant flows out of the condensation evaporator 7 and enters the intermediate heat exchanger 6; meanwhile, the 2# circulation loop keeps the heating working condition, and the refrigerant carries heat into the intermediate heat exchanger 6. The refrigerant in the 1# circulation loop evaporates and absorbs the heat of the refrigerant in the 2# circulation loop in the intermediate heat exchanger 6, and the refrigerant enters the variable frequency compressor 1 through the four-way valve 2 to be compressed again after being evaporated, so that defrosting circulation is formed;
when the temperature of the outer coil of the first heat exchanger 3 in the 1# circulation loop does not reach the defrosting condition, the circulation loop exits the defrosting condition through the switching of the four-way valve 2 and reenters the heating condition, then the 2# circulation loop enters the defrosting condition, and the defrosting operation of the 1# circulation loop is repeated.
And (4) defrosting quit: when the temperature of the coil reaches the set exit temperature (the temperature is adjustable, the default temperature is 15 ℃) or meets the requirement of the maximum defrosting time (the time is adjustable, the default time is 8min in the embodiment).
In the invention, a low-temperature-stage double system and a high-temperature-stage system form a cascade heat pump system through an intermediate heat exchanger 6 and a condensing evaporator 7 to improve the energy in the air step by step and directly generate steam for a terminal user to use; in the control process, the superheat degree is adjusted and controlled through electronic expansion valves, the supply of 120 ℃ steam is realized, in a low-temperature-level dual system, when one circulation loop reaches a defrosting condition, a defrosting circulation is started, the circulation loop is switched into a defrosting working condition through the four-way valve 2, the other circulation loop keeps a heating working condition, the high-temperature-level system stops working, defrosting is carried out through an alternating complementary defrosting technology, and the system is guaranteed to still provide stable steam.
Claims (4)
1. An air source heat pump continuous supply steam system is characterized by comprising a low-temperature-level double system, a high-temperature-level system, an intermediate heat exchanger and a condensing evaporator;
the low-temperature-stage double system comprises a 1# circulation loop and a 2# circulation loop, wherein the 1# circulation loop and the 2# circulation loop respectively comprise a variable frequency compressor, a four-way valve, a first heat exchanger and a first economizer, a first interface of the four-way valve is sequentially communicated with the variable frequency compressor and a second interface of the four-way valve, a third interface of the four-way valve is communicated with the first heat exchanger, and a fourth interface of the four-way valve is sequentially communicated with the intermediate heat exchanger and the condensing evaporator;
the interface of the condensation evaporator is communicated with a main loop of the first economizer, the other end of the main loop of the first economizer is respectively communicated with a first main-loop electronic expansion valve and a first auxiliary-loop electronic expansion valve, the first main-loop electronic expansion valve is communicated with the first heat exchanger, the first auxiliary-loop electronic expansion valve is communicated with the gas supplementing loop of the first economizer, and the other end of the gas supplementing loop of the first economizer is communicated with a gas supplementing port of the variable frequency compressor;
the high-temperature stage system comprises a fixed-frequency compressor, a second condenser and a second economizer, wherein an outlet on the heat exchange side of the condensation evaporator is communicated with an air inlet of the fixed-frequency compressor, an air outlet of the fixed-frequency compressor is communicated with the second condenser, an outlet of the second condenser is communicated with a main loop of the second economizer, the other end of the main loop of the second economizer is respectively communicated with a second main electronic expansion valve and a second auxiliary electronic expansion valve, the second main electronic expansion valve is communicated with an inlet on the heat exchange side of the condensation evaporator, the second auxiliary electronic expansion valve is communicated with an air supplementing loop of the second economizer, and the other end of the air supplementing loop of the second economizer is communicated with an air supplementing port of the fixed-frequency compressor.
2. A method for controlling an air-source heat pump continuous supply steam system, wherein the air-source heat pump continuous supply steam system of claim 1 is used for controlling the supply steam, and the method comprises the following steps:
(1) In a low-temperature-level dual system, a variable frequency compressor in a 1# circulation loop and a variable frequency compressor in a 2# circulation loop operate simultaneously, a refrigerant enters a first heat exchanger, is evaporated to absorb heat and then is changed into low-temperature low-pressure gas, then enters the variable frequency compressor to be compressed into medium-temperature medium-pressure gas, passes through a four-way valve and an intermediate heat exchanger, enters a condensation evaporator to be condensed to release heat, is changed into gas-liquid refrigerant, flows out of the condensation evaporator, finally enters a first main-path electronic expansion valve through a liquid storage device and a first economizer, is throttled by the first main-path electronic expansion valve, enters the first heat exchanger to be evaporated again to absorb heat, and therefore a low-temperature-level cycle is completed;
adjusting a first main circuit electronic expansion valve through a PID controller to enable a main circuit refrigerant to have superheat degree, wherein the superheat degree is adjustable and ranges from-2 ℃ to 5 ℃;
opening a first auxiliary circuit electronic expansion valve, and adjusting a second auxiliary circuit electronic expansion valve through a PID controller to enable an auxiliary circuit refrigerant to have a supercooling degree, wherein the supercooling degree is adjustable and ranges from 3 ℃ to 10 ℃; (ii) a
(2) In the high-temperature stage system, the refrigerant enters a condensation evaporator after being throttled by a second main-path electronic expansion valve, the heat of the medium-temperature gaseous refrigerant compressed by a variable-frequency compressor in the low-temperature stage double system is evaporated and absorbed in the condensation evaporator to be changed into gaseous refrigerant, the gaseous refrigerant enters a fixed-frequency compressor, the fixed-frequency compressor compresses the gaseous refrigerant into high-temperature refrigerant, the gaseous refrigerant enters a second condenser for condensation and heat release, finally the refrigerant enters a second main-path electronic expansion valve through a liquid storage device and a second economizer, the gaseous refrigerant enters a condensation evaporation heater after being throttled by the second main-path electronic expansion valve to be evaporated and heat absorbed again, and therefore a high-temperature stage cycle is completed;
adjusting a second main circuit electronic expansion valve through a PID controller to enable a main circuit refrigerant to have superheat degree which is adjustable and ranges from 5 ℃ to 12 ℃; adjusting a second auxiliary circuit electronic expansion valve through a PID controller to enable an auxiliary circuit refrigerant to have a supercooling degree, wherein the supercooling degree is adjustable and ranges from 3 ℃ to 10 ℃;
(3) The second condenser can be matched with a high-temperature water side heat exchanger to heat water to 120 ℃, and can also be matched with a steam generator to directly heat and evaporate water into steam;
(4) In a cryogenic stage dual system, when one of the circulation loops reaches the following defrost conditions:
K: the coefficient of the calculation of the ring temperature,
when in useTWhen the temperature a is less than 0 ℃,K=0.8；
when in useTWhen a is more than or equal to 0 ℃,K=0.6；
and entering a defrosting cycle, switching the cycle loop into a defrosting working condition through the four-way valve, keeping the other cycle loop in a heating working condition, and stopping the high-temperature system.
3. The control method of the air source heat pump continuous supply steam system as claimed in claim 2, wherein in step (4), when one of the circulation loops reaches the defrosting condition, the frequency conversion compressors of the two circulation loops are simultaneously down-converted to the target frequency of 40Hz,
in the circulation loop, through the switching of the four-way valve, gaseous refrigerant flowing out of the variable frequency compressor enters the first heat exchanger through the four-way valve to release heat, frost on the outer wall of the first heat exchanger is melted, the refrigerant is condensed to become gas-liquid refrigerant, the gas-liquid refrigerant sequentially passes through the first main-path electronic expansion valve, the first economizer and the condensation evaporator, the refrigerant is not evaporated and does not absorb heat in the condensation evaporator, the refrigerant flows out of the condensation evaporator, enters the intermediate heat exchanger to be evaporated and absorbs heat of the refrigerant in the other circulation loop, and the refrigerant enters the variable frequency compressor through the four-way valve to be compressed again after being evaporated, so that a defrosting cycle is formed;
when the temperature of the first heat exchanger outer coil in the circulation loop does not reach the defrosting condition, the circulation loop is switched by the four-way valve to exit the defrosting condition and enter the heating condition again.
4. The control method of the air source heat pump continuous steam supply system according to claim 3, wherein in the step (4), whether the 1# circulation loop reaches the defrosting condition is judged, if the 1# circulation loop reaches the defrosting condition, the 1# circulation loop is firstly put into the defrosting condition, and after the defrosting condition is removed, whether the 1# circulation loop reaches the defrosting condition is judged;
if the 1# circulation loop does not reach the defrosting condition, judging whether the 1# circulation loop reaches the defrosting condition;
the defrosting quitting conditions are as follows: when the temperature of the outer coil pipe of the first heat exchanger reaches a set exit temperature value, the set exit temperature value is 5-20 ℃; or the requirement of the maximum defrosting time is met, and the set value of the maximum defrosting time is 2-10 min.
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| CN116123744A (en) * | 2023-03-24 | 2023-05-16 | 哈尔滨工业大学 | Ultralow-temperature single-stage and double-stage hybrid air source heat pump unit |
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