CN110966784B - Double-stage throttling multi-temperature carbon dioxide heat pump unit and control method thereof - Google Patents
Double-stage throttling multi-temperature carbon dioxide heat pump unit and control method thereof Download PDFInfo
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- CN110966784B CN110966784B CN201911335642.6A CN201911335642A CN110966784B CN 110966784 B CN110966784 B CN 110966784B CN 201911335642 A CN201911335642 A CN 201911335642A CN 110966784 B CN110966784 B CN 110966784B
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- carbon dioxide
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- inlet
- evaporator
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 168
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 84
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 11
- 239000007789 gas Substances 0.000 claims description 68
- 239000003507 refrigerant Substances 0.000 claims description 18
- 239000007788 liquid Substances 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 3
- 239000002826 coolant Substances 0.000 description 21
- 230000001105 regulatory effect Effects 0.000 description 9
- 230000001276 controlling effect Effects 0.000 description 4
- 230000007613 environmental effect Effects 0.000 description 3
- 238000004134 energy conservation Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000003570 air Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
Classifications
-
- 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
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
- F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
-
- 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
Abstract
According to the double-stage throttling multi-temperature carbon dioxide heat pump unit and the control method thereof, the plurality of gas coolers are arranged and connected in parallel and then are connected in series as a whole on the second pipeline connecting the second inlet of the intermediate heat exchanger and the outlet of the oil separator, so that the double-stage throttling multi-temperature carbon dioxide heat pump unit provided by the invention can realize multi-temperature heat supply, can realize multi-stage throttling, takes superheat degree and target pressure as control targets, takes pressure control as a main part in a high-pressure section and temperature control as a main part in a low-pressure section, has a good energy-saving effect, and has the advantages of high heat supply temperature, various heat supply modes and wide application range, wherein the highest heat supply air temperature can reach 120 ℃, fills the gap of a common heat pump heating range of more than 60 ℃, meets the requirements of energy-saving and environment-friendly heat supply equipment in the market, and has great social benefit and economic benefit.
Description
Technical Field
The invention relates to heating equipment, in particular to a two-stage throttling multi-temperature carbon dioxide heat pump unit and a control method thereof.
Background
In the large environment with sustainable development of the environment, the energy conservation and environmental protection of the heating equipment are improved to unprecedented important heights. Under the dual drive of national policy and market demand, heat pump products are continuously applied and popularized in the market due to the advantages of the heat pump products in environmental protection and energy conservation, and replace part of heat supply equipment with high energy consumption and poor environmental protection, such as coal-fired boilers, oil-fired boilers and the like. The functional demands are moving toward higher temperatures, higher efficiency, and greenness. The searching of the heat pump working medium which is environment-friendly, renewable and excellent in cycle performance is one of key points and difficulties for widening the application range of the heat pump technology.
What is needed is a carbon dioxide heat pump unit capable of providing multi-temperature heat supply (water/air/other) to improve the problems of high energy consumption, low heat supply temperature, large heat attenuation in low-temperature environment, insufficient heat supply capacity, electric heating compensation and the like of a conventional heat pump unit using freon working media, and improve the comprehensive energy utilization rate of the heat pump unit.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a carbon dioxide heat pump unit with double-stage throttling and multi-temperature heat supply and a control method thereof.
In order to achieve the above purpose, the product in the technical scheme adopted by the invention is a two-stage throttling multi-temperature carbon dioxide heat pump unit, which comprises:
a carbon dioxide compressor;
the inlet of the oil separator is connected with the exhaust outlet of the carbon dioxide compressor through a pipeline;
the first outlet of the intermediate heat exchanger is connected with the inlet of the carbon dioxide compressor through a first pipeline, and the second inlet of the intermediate heat exchanger is connected with the outlet of the oil separator through a second pipeline;
the gas cooler is connected in series with the second pipeline, and a bypass throttle valve is connected to the right outlet of the gas cooler;
the inlet of the evaporator is connected with the second outlet of the intermediate heat exchanger through a third pipeline, and the outlet of the evaporator is connected with the first inlet of the intermediate heat exchanger through a fourth pipeline;
the liquid storage device is connected in series on the third pipeline, and a main path throttle valve is connected to the outlet of the liquid storage device;
the gas-liquid separator is connected in series with the fourth pipeline;
the plurality of gas coolers are connected in parallel and then connected in series on the second pipeline as a whole, and the gas coolers are used for exchanging heat between the carbon dioxide output by the carbon dioxide compressor and air, water or other mediums;
the gas cooler is provided with a secondary refrigerant inlet and a secondary refrigerant outlet, a first temperature sensor for detecting the temperature Tn_in of the secondary refrigerant entering the gas cooler is arranged at the secondary refrigerant inlet, and a second temperature sensor for detecting the temperature Tn_out of the secondary refrigerant exiting the gas cooler is arranged at the secondary refrigerant outlet.
Preferably, an oil return port of the oil separator is connected with an oil return port of the carbon dioxide compressor, a third temperature sensor for detecting the air inlet temperature Ts of the carbon dioxide compressor is arranged at an inlet of the carbon dioxide compressor, a fourth temperature sensor for detecting the exhaust temperature Td of the carbon dioxide compressor is arranged at an exhaust outlet of the carbon dioxide compressor, and a first pressure sensor for detecting the exhaust pressure Pd of the carbon dioxide compressor is arranged at an outlet of the oil separator.
Preferably, the plurality of branch throttle valves are arranged, and the branch throttle valves are arranged in one-to-one correspondence with the gas coolers.
Preferably, a fifth temperature sensor for detecting the carbon dioxide side outlet temperature Tgc of the gas cooler is provided between the gas cooler and the bypass throttle valve.
Preferably, the evaporator is a heat exchanger for exchanging heat between carbon dioxide and air or other gases, a second pipeline between the oil separator and the gas cooler is connected with a third pipeline between the main path throttle valve and the evaporator through a bypass pipe, and an electromagnetic valve or an electric valve is arranged on the bypass pipe.
Further preferably, a sixth temperature sensor for detecting the carbon dioxide side outlet temperature Teo of the evaporator and a second pressure sensor for detecting the carbon dioxide side outlet pressure Ps of the evaporator are provided on a fourth pipe between the evaporator outlet and the gas-liquid separator inlet, and a seventh temperature sensor for detecting the inlet side temperature Tei of the evaporator is provided on a third pipe between the evaporator inlet and the main path throttle valve.
In order to achieve the above purpose, the method in the technical scheme adopted by the invention is a control method for controlling any one of the two-stage throttling multi-temperature carbon dioxide heat pump units, comprising the following steps:
the opening degree of the main path throttle valve is adjusted according to the actual superheat degree SP of the evaporator and the target superheat degree SP_ evp of the evaporator, and the opening degree of the branch path throttle valve is adjusted according to the carbon dioxide outlet side pressure Popt of the gas cooler and the exhaust pressure Pd of the carbon dioxide compressor.
Preferably, the actual superheat degree sp=teo-Tei of the evaporator, the target superheat degree sp_ evp =a (Teo-Tei) +b×pd/Ps (Ts-Tei), the value range of a is-0.2 to 1.5, the value range of b is 0 to 2, when SP > sp_ evp +0.5 ℃, the main throttle valve is gradually opened, when SP < sp_ evp-0.5 ℃, the main throttle valve is gradually closed, and when sp_ evp-0.5 ℃ SP < sp_ evp +0.5 ℃, the opening degree of the main throttle valve is kept unchanged.
Preferably, the gas cooler carbon dioxide outlet side pressure
Wherein, K, C are compressor performance parameters, wherein k=0.121, c=1.003, a, b are experimental data, when the discharge pressure Pd is taken>When popt+2bar, the branch throttle valve is gradually opened, and when the exhaust pressure Pd is<When Popt-2bar is adopted, the branch throttle valve is gradually closed, and when Popt-2 Pd is more than or equal to Popt+2, the branch throttle valve is gradually closedKeeping the current opening unchanged.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:
according to the double-stage throttling multi-temperature carbon dioxide heat pump unit and the control method thereof, the plurality of gas coolers are arranged and connected in parallel and then are connected in series as a whole on the second pipeline connecting the second inlet of the intermediate heat exchanger and the outlet of the oil separator, so that the double-stage throttling multi-temperature carbon dioxide heat pump unit provided by the invention can realize multi-temperature heat supply, can realize multi-stage throttling, takes superheat degree and target pressure as control targets, takes pressure control as a main part in a high-pressure section and temperature control as a main part in a low-pressure section, has a good energy-saving effect, and has the advantages of high heat supply temperature, various heat supply modes and wide application range, wherein the highest heat supply air temperature can reach 120 ℃, fills the gap of a common heat pump heating range of more than 60 ℃, meets the requirements of energy-saving and environment-friendly heat supply equipment in the market, and has great social benefit and economic benefit.
Drawings
Fig. 1 is a schematic structural view of the present invention.
Wherein: 1. a carbon dioxide compressor; 11. an inlet; 111. a temperature sensor; 12. an exhaust outlet; 121. a temperature sensor; 13. an oil return port; 2. an oil separator; 21. an inlet; 22. an outlet; 221. a pressure sensor; 23. an oil return port; 3. an intermediate heat exchanger; 31. a first inlet; 32. a first outlet; 33. a second inlet; 34. a second outlet; 4. a gas cooler group; 41. a first gas cooler; 411. a coolant inlet; 4111. a temperature sensor; 412. a coolant outlet; 4121. a temperature sensor; 42. a first branch throttle valve; 421. a temperature sensor; 43. a second gas cooler; 431. a coolant inlet; 4311. a temperature sensor; 432. a coolant outlet; 4321. a temperature sensor; 44. a second bypass throttle valve; 422. a temperature sensor; 45. a third gas cooler; 451. a coolant inlet; 4511. a temperature sensor; 452. a coolant outlet; 4521. a temperature sensor; 46. a third branch throttle valve; 461. a temperature sensor; 5. an evaporator; 51. an inlet; 511. a temperature sensor; 52. an outlet; 521. a temperature sensor; 522. a pressure sensor; 6. a reservoir; 61. an inlet; 62. an outlet; 7. a main path throttle valve; 8. a gas-liquid separator; 90. a pipe; 91. a first pipe; 92. a second pipe; 93. a third conduit; 94. a fourth conduit; 95. a bypass pipe; 96. a solenoid valve.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the attached drawings so that the advantages and features of the present invention will be more readily understood by those skilled in the art, thereby making clear and defining the scope of the present invention.
The left and right directions described in the present invention refer to the left and right directions in fig. 1.
As shown in fig. 1, the two-stage throttling multi-temperature carbon dioxide heat pump unit provided by the invention comprises: the carbon dioxide compressor 1, the oil separator 2, the intermediate heat exchanger 3, the gas cooler group 4, the evaporator 5, the liquid reservoir 6, the main path throttle valve 7 and the gas-liquid separator 8, wherein an inlet 21 of the oil separator 2 is connected with an outlet 12 of the carbon dioxide compressor 1 through a pipeline 90; the intermediate heat exchanger 3 has a first inlet 31, a first outlet 32, a second inlet 33, a second outlet 34, wherein the first inlet 31 and the first outlet 32 are located on the low pressure side of the intermediate heat exchanger 3, the second inlet 33 and the second outlet 34 are located on the high pressure side of the intermediate heat exchanger 3, the first outlet 32 of the intermediate heat exchanger 3 is connected to the inlet 11 of the carbon dioxide compressor 1 by a first conduit 91, and the second inlet 33 of the intermediate heat exchanger 3 is connected to the outlet 22 of the oil separator 2 by a second conduit 92; a temperature sensor 111 for detecting the air inlet temperature Ts of the carbon dioxide compressor is arranged at the inlet 11 of the carbon dioxide compressor 1, a temperature sensor 121 for detecting the exhaust temperature Td of the carbon dioxide compressor 1 is arranged at the exhaust outlet 12 of the carbon dioxide compressor 1, and a pressure sensor 221 for detecting the exhaust pressure Pd of the carbon dioxide compressor 1 is arranged at the outlet 22 of the oil separator 2; the gas cooler group 4 is connected in series with the second pipeline 92, the gas cooler group 4 is formed by connecting a first gas cooler 41, a second gas cooler 43 and a third gas cooler 45 in parallel, the gas coolers are used for exchanging heat between carbon dioxide output by the exhaust outlet 12 of the carbon dioxide compressor 1 and air, water or other mediums so as to realize the technical effects of multi-temperature heat supply and various heat supply forms, the first gas cooler 41 is provided with a secondary refrigerant inlet 411 and a secondary refrigerant outlet 412, a temperature sensor 4111 for detecting the secondary refrigerant temperature Tn_in entering the first gas cooler 41 is arranged at the secondary refrigerant inlet 411, and a temperature sensor 4121 for detecting the secondary refrigerant temperature Tn_out flowing out of the first gas cooler 41 is arranged at the secondary refrigerant outlet 412; the second gas cooler 43 has a coolant inlet 431 and a coolant outlet 432, the coolant inlet 431 being provided with a temperature sensor 4311 for detecting the coolant temperature Tn_in entering the second gas cooler 43, the coolant outlet 432 being provided with a temperature sensor 4321 for detecting the coolant temperature Tn_out exiting the second gas cooler 43; the third gas cooler 45 has a coolant inlet 451 and a coolant outlet 452, the coolant inlet 451 being provided with a temperature sensor 4511 for detecting a coolant temperature Tn_in entering the third gas cooler 45, the coolant outlet 452 being provided with a temperature sensor 4521 for detecting a coolant temperature Tn_out exiting the third gas cooler 45; each gas cooler is correspondingly provided with a branch regulating valve, the branch regulating valve is connected to the right side outlet of the gas cooler, namely, a first branch regulating valve 42 is connected to the right side outlet of a first gas cooler 41, a second branch regulating valve 44 is connected to the right side outlet of a second gas cooler 43, a third branch regulating valve 46 is connected to the right side outlet of a third gas cooler 45, and the branch regulating valves are used for controlling the flow of carbon dioxide passing through the gas cooler on the current branch; a temperature sensor 421 for detecting the carbon dioxide side outlet temperature Tgc of the first gas cooler 41 is provided between the first gas cooler 41 and the first bypass throttle valve 42, a temperature sensor 441 for detecting the carbon dioxide side outlet temperature Tgc of the second gas cooler 43 is provided between the second gas cooler 43 and the second bypass throttle valve 44, and a temperature sensor 461 for detecting the carbon dioxide side outlet temperature Tgc of the third gas cooler 45 is provided between the third gas cooler 45 and the third bypass throttle valve 46; the inlet 51 of the evaporator 5 is connected to the second outlet 34 of the intermediate heat exchanger 3 via a third conduit 93, and the outlet 52 of the evaporator 5 is connected to the first inlet 31 of the intermediate heat exchanger 3 via a fourth conduit 94; the liquid storage device 6 is connected in series with the third pipeline 93, and the outlet 62 of the liquid storage device 6 is connected with the main path throttle valve 7; the gas-liquid separator 8 is connected in series with the fourth pipeline 94; a temperature sensor 521 for detecting the carbon dioxide side outlet temperature Teo of the evaporator 5 and a pressure sensor 522 for detecting the carbon dioxide side outlet pressure Ps of the evaporator 5 are provided on the fourth pipe 94 between the outlet 52 of the evaporator 5 and the inlet of the gas-liquid separator 8, and a temperature sensor 511 for detecting the inlet side temperature Tei of the evaporator 5 is provided on the third pipe 93 between the inlet 51 of the evaporator 5 and the main throttle valve 7; the oil return port 23 of the oil separator 2 is connected with the oil return port 13 of the carbon dioxide compressor 1; the evaporator 5 is a heat exchanger for exchanging heat between carbon dioxide and air, water or other medium, in this embodiment, the evaporator 5 is a heat exchanger for exchanging heat between carbon dioxide and air or other gas, the second pipe 92 between the oil separator 2 and the gas cooler group 4 is connected to the third pipe 93 between the main path throttle valve 7 and the evaporator 5 through the bypass pipe 95, the bypass pipe 95 is provided with a solenoid valve 96 for controlling the flow rate of carbon dioxide passing through the bypass pipe 95, and when the evaporator 5 is started, the solenoid valve 96 is opened to switch the bypass pipe 95 on, so that the high-temperature carbon dioxide discharged through the exhaust outlet 12 of the carbon dioxide compressor 1 is introduced to defrost the evaporator 5.
The control method for controlling the two-stage throttling multi-temperature carbon dioxide heat pump unit in the embodiment comprises the following steps:
the opening degree of the main throttle valve 7 is adjusted according to the actual superheat degree SP of the evaporator 5 and the target superheat degree sp_ evp of the evaporator 5, specifically, the actual superheat degree sp=teo-Tei of the evaporator 5, the target superheat degree sp_ evp =a (Teo-Tei) +b×pd/Ps (Ts-Tei), the value range of a is-0.2 to 1.5, the value range of b is 0 to 2, the main throttle valve 7 is gradually opened when SP > sp_ evp +0.5 ℃, the main throttle valve 7 is gradually closed when SP < sp_ evp-0.5 ℃, and the opening degree of the main throttle valve 7 is kept unchanged when sp_ evp-0.5 ℃ is less than or equal to sp_ evp +0.5 ℃.
The opening degree of the branch regulating valve is adjusted according to the carbon dioxide outlet side pressure Popt of the corresponding branch gas cooler and the exhaust pressure Pd of the carbon dioxide compressor 1, and the adjustment manners of the upper branch regulating valves on all the branches are the same, and the opening degree adjustment method of the first branch regulating valve 42 will be described as an example.
The pressure on the carbon dioxide outlet side of the first gas cooler 41 is
Where K, C is the compressor performance parameter, k=0.121, c=1.003, a, b are experimental data, teo is the temperature value detected by the carbon dioxide outlet side temperature sensor 521 of the evaporator 5, tgc is the temperature value detected by the carbon dioxide outlet side temperature sensor 421 of the first gas cooler 41, td is the temperature value detected by the temperature sensor 121 at the exhaust outlet 12 of the carbon dioxide compressor 1, pd is the pressure value detected by the pressure sensor 221 at the outlet 22 of the oil separator 2, ps is the pressure value detected by the pressure sensor 521 at the outlet 52 of the evaporator 5, tn_in is the temperature value detected by the coolant sensor 4111 at the coolant inlet 411 of the first gas cooler 41, tn_out is the temperature value detected by the coolant outlet 412 of the first gas cooler 41, and when the exhaust pressure Pd is>When popt+2bar, the branch throttle valve is gradually opened, and when the exhaust pressure Pd is<When Popt-2bar is adopted, the branch throttle valve is gradually closed, and when Popt-2 Pd is more than or equal to Popt+2, the current opening of the branch throttle valve is kept unchanged.
According to the double-stage throttling multi-temperature carbon dioxide heat pump unit, the plurality of gas coolers are arranged and connected in parallel and then are connected in series as a whole on the second pipeline connecting the second inlet of the intermediate heat exchanger and the outlet of the oil separator, so that the double-stage throttling multi-temperature carbon dioxide heat pump unit can realize multi-temperature heat supply, and the heat supply temperature is high, the heat supply mode is various and the application range is wide by adopting carbon dioxide as a heat pump working medium, the highest hot air supply temperature can reach 120 ℃, the gap between the heat supply temperature of a common heat pump and the heat supply temperature of more than 60 ℃ is filled, the requirements of the market on energy-saving and environment-friendly heat supply equipment are met, and great social benefits and economic benefits are achieved.
Claims (3)
1. Two-stage throttling multi-temperature carbon dioxide heat pump unit includes:
a carbon dioxide compressor;
the inlet of the oil separator is connected with the exhaust outlet of the carbon dioxide compressor through a pipeline;
the intermediate heat exchanger is provided with a first inlet and a first outlet which are positioned on the low pressure side, and a second inlet and a second outlet which are positioned on the high pressure side, the first outlet is connected with the carbon dioxide compressor inlet through a first pipeline, and the second inlet is connected with the oil separator outlet through a second pipeline;
the plurality of gas coolers are connected in parallel and then are connected in series on the second pipeline as a whole, the gas coolers are used for exchanging heat between the carbon dioxide output by the carbon dioxide compressor and air, water or other mediums, a branch throttle valve is connected to the right side outlet of the gas cooler, and the plurality of branch throttle valves are arranged in a one-to-one correspondence manner with the gas coolers;
the inlet of the evaporator is connected with the second outlet through a third pipeline, and the outlet of the evaporator is connected with the first inlet through a fourth pipeline;
the liquid storage device is connected in series on the third pipeline, and a main path throttle valve is connected to the outlet of the liquid storage device;
the gas-liquid separator is connected in series with the fourth pipeline;
the method is characterized in that:
a third temperature sensor for detecting the air inlet temperature Ts of the carbon dioxide compressor is arranged at the inlet of the carbon dioxide compressor, and a fourth temperature sensor for detecting the exhaust temperature Td of the carbon dioxide compressor is arranged at the exhaust outlet of the carbon dioxide compressor;
a first pressure sensor for detecting the exhaust pressure Pd of the carbon dioxide compressor is arranged at the outlet of the oil separator;
the gas cooler is provided with a secondary refrigerant inlet and a secondary refrigerant outlet, a first temperature sensor for detecting the temperature Tn_in of the secondary refrigerant entering the gas cooler is arranged at the secondary refrigerant inlet, and a second temperature sensor for detecting the temperature Tn_out of the secondary refrigerant flowing out of the gas cooler is arranged at the secondary refrigerant outlet;
a fifth temperature sensor for detecting the carbon dioxide side outlet temperature Tgc of the gas cooler is arranged between the gas cooler and the bypass throttle valve;
a sixth temperature sensor for detecting the carbon dioxide side outlet temperature Teo of the evaporator and a second pressure sensor for detecting the carbon dioxide side outlet pressure Ps of the evaporator are arranged on a fourth pipeline between the evaporator outlet and the inlet of the gas-liquid separator, and a seventh temperature sensor for detecting the inlet side temperature Tei of the evaporator is arranged on a third pipeline between the inlet of the evaporator and the main path throttle valve;
the opening of the main path throttle valve is adjusted according to the actual superheat degree SP of the evaporator and the target superheat degree SP_ evp of the evaporator, and the opening of the branch path throttle valve is adjusted according to the carbon dioxide outlet side pressure Popt of the gas cooler and the exhaust pressure Pd of the carbon dioxide compressor;
the actual superheat degree SP=teo-Tei of the evaporator, the target superheat degree SP_ evp =a (Teo-Tei) +b (Ts-Tei), the value range of a is-0.2 to 1.5, the value range of b is 0 to 2, when SP > SP_ evp +0.5 ℃, the main throttle valve is gradually opened, when SP < SP_ evp-0.5 ℃, the main throttle valve is gradually closed, and when SP_ evp-0.5 ℃ SP < SP_ evp +0.5 ℃, the opening degree of the main throttle valve is kept unchanged;
the carbon dioxide outlet side pressure of the gas coolerWherein K, C is the compressor performance parameter, wherein K=0.121, C=1.003, a, b are taken as experimental data, when the discharge pressure Pd>When popt+2bar, the branch throttle valve is gradually opened, and when the exhaust pressure Pd is<When Popt-2bar is used, the branch joint is gradually closedAnd when Popt-2 is less than or equal to Pd and less than or equal to Popt+2, the current opening degree of the bypass throttle valve is kept unchanged.
2. The two-stage throttling multi-temperature carbon dioxide heat pump unit according to claim 1, wherein: and an oil return port of the oil separator is connected with an oil return port of the carbon dioxide compressor.
3. The two-stage throttling multi-temperature carbon dioxide heat pump unit according to claim 1, wherein: the evaporator is a heat exchanger for exchanging heat between carbon dioxide and air or other gases, a second pipeline between the oil separator and the gas cooler is connected with a third pipeline between the main path throttle valve and the evaporator through a bypass pipe, and an electromagnetic valve or an electric valve is arranged on the bypass pipe.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911335642.6A CN110966784B (en) | 2019-12-23 | 2019-12-23 | Double-stage throttling multi-temperature carbon dioxide heat pump unit and control method thereof |
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| CN201911335642.6A CN110966784B (en) | 2019-12-23 | 2019-12-23 | Double-stage throttling multi-temperature carbon dioxide heat pump unit and control method thereof |
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