CN111623555B - Refrigerant active jet heat pump based on low-grade heat source and control method thereof - Google Patents
Refrigerant active jet heat pump based on low-grade heat source and control method thereof Download PDFInfo
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- CN111623555B CN111623555B CN202010341180.5A CN202010341180A CN111623555B CN 111623555 B CN111623555 B CN 111623555B CN 202010341180 A CN202010341180 A CN 202010341180A CN 111623555 B CN111623555 B CN 111623555B
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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
- F25B30/00—Heat pumps
- F25B30/02—Heat pumps of the compression type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B40/00—Subcoolers, desuperheaters or superheaters
- F25B40/02—Subcoolers
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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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- 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
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
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- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
Abstract
The heat pump heating capacity and energy efficiency can be improved through the refrigerant injection, but the injection heat comes from the heat pump, the injection is passive injection, the injection characteristic is that the heat pump performance improvement range is limited, and the heat pump cannot operate in an extremely low-temperature environment. Aiming at the problem, the invention provides a low-grade heat source-based refrigerant active injection heat pump, which fully utilizes low-grade heat sources such as solar energy, high-temperature waste water, waste gas and the like, ensures that heat of an external heat source and injected refrigerant exchange heat fully in a subcooler, and the obtained heat refrigerant is injected into a middle pressure cavity of a compressor, so that the external heat is converted into a heat pump unit, and thermal power gain is obtained, thereby greatly improving the heating capacity and energy efficiency of the heat pump, effectively improving the use comfort of users, widening the application range of the heat pump, and being applied to areas below-15 ℃. Meanwhile, the invention also provides a control method of the refrigerant active injection heat pump based on the low-grade heat source.
Description
Technical Field
The invention relates to a heat pump, in particular to a low-grade heat source-based refrigerant active injection heat pump and a control method thereof.
Background
With the development of economy and the continuous improvement of living standard of people and the development of urban construction, the air-conditioning heating system is increasingly widely applied, and thus, the energy consumption of the building is huge.
When the heat pump is used for heating and warming, the problems of serious heating capacity and energy efficiency attenuation at low ambient temperature exist, and the problems become main factors which prevent the popularization and the use of the technology. In order to solve the above problems, the present heat pump mostly adopts the vapor injection enthalpy increasing technology, and the principle is that a part of refrigerant with intermediate pressure is sucked through an intermediate pressure suction hole and is compressed after being mixed with the refrigerant with partial compression, so that two stages of compression are realized by a single compressor, the flow of the refrigerant in the condenser is increased, the enthalpy difference of a main circulation loop is enlarged, and the efficiency of the compressor is further improved.
The vapor injection enthalpy-increasing technology improves the heating capacity and the energy efficiency of the heat pump to a certain extent, but the refrigerant injection with the subcooler adopts internal heat exchange and does not absorb heat from the outside as the refrigerant in the injection refrigerant and the main loop is the refrigerant passive injection, so that the heating capacity and the energy efficiency of the heat pump are limited in practice, the heating capacity of the heat pump is generally improved by about 10 percent in the practical application process, the maximum heating capacity is not more than 20 percent after the optimal control measures are adopted, the energy efficiency improvement capacity of the heat pump is more limited, and the use of the heat pump is limited, so that the low-temperature heat pump cannot play a role in heating when the environmental temperature is lower than-15 ℃.
Disclosure of Invention
One of the technical problems to be solved by the invention is to provide the refrigerant active injection heat pump based on the low-grade heat source, which has good heating capacity and energy efficiency and wide application range.
The invention provides a low-grade heat source-based refrigerant active injection heat pump which comprises a heat pump system, an injection system, an external heat source and an external heat source pump, wherein the heat pump system comprises a compressor, a condenser, an evaporator, a main throttle valve and a four-way valve which are in circulating communication, the injection system comprises a subcooler and a subcooling throttle valve, the subcooler is provided with a refrigerant heat exchange tube and an external heat source heat exchange tube, one end of the subcooling throttle valve is communicated with the outlet end of the condenser, the other end of the subcooling throttle valve is communicated with the inlet end of the refrigerant heat exchange tube, the outlet end of the refrigerant heat exchange tube is communicated with a middle pressure cavity of the compressor, and the external heat source pump is communicated between the inlet end of the external heat source heat exchange tube and the outlet end of the external heat source.
By adopting the structure, compared with the prior art, the refrigerant active injection heat pump based on the low-grade heat source has the advantages that the refrigerant active injection heat pump based on the low-grade heat source can fully utilize an external heat source, particularly the low-grade heat source, and converts the low-grade heat source into a high-grade heat source, so that the heat exchange performance of a subcooler can be effectively improved, the heating capacity and the energy efficiency of the heat pump are greatly improved, the problem that the heating capacity and the energy efficiency of the heat pump are seriously attenuated at a low ambient temperature is solved, and the heat pump can be applied to an area with the ambient temperature lower than-15 ℃, so that the application range of the heat pump is greatly widened.
The invention discloses a low-grade heat source-based refrigerant active injection heat pump, wherein an external heat source temperature sensor is arranged at the outlet end of an external heat source, a subcooler inlet temperature sensor is arranged at the inlet end of a refrigerant heat exchange tube, and a subcooler outlet temperature sensor is arranged at the outlet end of the refrigerant heat exchange tube.
The structure can accurately control the start and stop of the external heat source pump, so that the operation of the heat pump is more stable, and the heating capacity and energy efficiency of the heat pump are ensured.
The invention aims to provide a control method of the refrigerant active injection heat pump based on the low-grade heat source.
In order to solve the technical problems, the invention provides a control method of a refrigerant active injection heat pump based on a low-grade heat source, which comprises the following steps:
In the operation process of the heat pump, the external heat source temperature T h,in is detected in real time through an external heat source temperature sensor, the subcooler injection inlet temperature T inj,in at the inlet end of the refrigerant heat exchange tube is detected in real time through a subcooler inlet temperature sensor, and the subcooler injection inlet temperature T inj,out at the outlet end of the refrigerant heat exchange tube is detected in real time through a subcooler outlet temperature sensor;
When the temperature T h,in of the external heat source is less than or equal to the temperature T inj,out of the jet outlet of the subcooler, controlling the external heat source pump to stop running, so that the external heat source cannot enter the subcooler;
when the external heat source temperature T h,in is higher than the subcooler jet outlet temperature T inj,out, the external heat source pump is controlled to start to operate, so that the external heat source can enter the subcooler.
Compared with the prior art, the control method of the refrigerant active injection heat pump based on the low-grade heat source has the following advantages:
The control method of the refrigerant active injection heat pump based on the low-grade heat source can make full use of the external heat source, particularly the low-grade heat source, and convert the low-grade heat source into the high-grade heat source, thereby not only effectively improving the heat exchange performance of the subcooler in the heat pump, greatly improving the heating capacity and energy efficiency of the heat pump, but also enabling the heat pump to be applied to the area with the environmental temperature lower than-15 ℃, and greatly widening the application range of the heat pump.
The invention relates to a control method of a refrigerant active injection heat pump based on a low-grade heat source, wherein in the refrigerant active injection heat pump based on the low-grade heat source, a pipeline connected with an air suction port of a compressor is provided with an air suction temperature sensor, and a pipeline connected with an inlet end of an evaporator is provided with an evaporator inlet temperature sensor;
the main throttle valve is controlled and regulated according to the superheat degree of the heat pump, the superheat of the heat pump is defined as:
compressor suction temperature T s -defrost temperature T def;
when the actual superheat degree is greater than the target superheat degree, the main throttle valve is opened;
When the actual superheat degree is less than the target superheat degree, the main throttle valve is closed;
when the actual superheat degree=the target superheat degree, the main throttle valve maintains the current opening degree;
The target superheat degree is a system preset temperature value of the heat pump, the air suction temperature T s of the compressor is obtained by an air suction temperature sensor, and the defrosting temperature T def is obtained by an evaporator inlet temperature sensor.
The control and adjustment of the main throttle valve can effectively ensure the operation reliability of the heat pump.
The invention relates to a control method of a refrigerant active injection heat pump based on a low-grade heat source, wherein a condenser outlet temperature sensor is arranged on a pipeline connected with an outlet end of a condenser in the refrigerant active injection heat pump based on the low-grade heat source, and a high-pressure sensor is arranged on a pipeline connected with an exhaust port of a compressor;
The supercooling throttle valve is controlled and regulated according to the supercooling degree of the heat pump, and the supercooling degree of the heat pump is defined as:
the saturation temperature P d_t corresponding to the high pressure of the heat pump is the liquid pipe temperature T liq;
when the actual supercooling degree is greater than the target supercooling degree, the supercooling throttle valve is opened;
when the actual supercooling degree is less than the target supercooling degree, the supercooling throttle valve is closed;
when the actual supercooling degree=the target supercooling degree, the supercooling throttle valve maintains the current opening degree;
The target supercooling degree is a system preset temperature value of the heat pump, the saturation temperature P d_t corresponding to the high pressure of the heat pump is obtained by converting the high pressure of the heat pump obtained by the high pressure sensor, and the liquid pipe temperature T liq is obtained by a condenser outlet temperature sensor.
The control and adjustment of the supercooling throttle valve can effectively ensure the operation reliability of the heat pump.
The invention relates to a control method of a refrigerant active injection heat pump based on a low-grade heat source, wherein an exhaust temperature sensor is arranged on a pipeline connected with an exhaust port of a compressor in the refrigerant active injection heat pump based on the low-grade heat source;
The supercooling throttle valve is corrected and adjusted according to the exhaust superheat degree of the compressor of the heat pump, and the exhaust superheat degree of the compressor of the heat pump is defined as:
compressor discharge temperature T d —saturation temperature P d_t corresponding to heat pump high pressure;
when the actual compressor exhaust superheat degree is less than the set value B, the supercooling throttle valve is closed;
when the actual compressor exhaust superheat degree is greater than the set value C, the supercooling throttle valve is opened;
When the set value B is less than or equal to the actual compressor exhaust superheat degree is less than or equal to the set value C, the supercooling throttle valve is controlled and regulated according to the target supercooling degree of the heat pump;
the set value B and the set value C are system preset temperature values of the heat pump, the set value C is greater than the set value B, and the exhaust temperature T d of the compressor is obtained by an exhaust temperature sensor.
The correction adjustment of the supercooling throttle valve can further ensure the operation reliability of the heat pump.
The invention discloses a control method of a refrigerant active injection heat pump based on a low-grade heat source, which comprises the following steps:
After the external heat source pump is started to operate,
When the subcooler injection inlet temperature T inj,in plus the set value A is less than or equal to the external heat source temperature T h,in and is less than the subcooler injection outlet temperature T inj,out, the external heat source pump is kept in a continuous running state;
When the external heat source temperature T h,in is less than the subcooler injection inlet temperature T inj,in + set value A, controlling the external heat source pump to stop running;
The set value A is a system preset temperature value of the heat pump, and the subcooler injection inlet temperature T inj,in plus the set value A is less than the subcooler injection outlet temperature T inj,out.
The control method can effectively prevent the frequent start and stop of the external heat source pump in the heat pump, so that the heat pump can run more stably, and the heating capacity and energy efficiency of the heat pump are ensured.
Drawings
FIG. 1 is a simplified schematic diagram of a prior art heat pump system during heating;
fig. 2 is a cyclic pressure enthalpy diagram of a prior art heat pump heating;
FIG. 3 is a detailed schematic diagram of the system of the invention when the refrigerant active injection heat pump based on low-grade heat source heats;
FIG. 4 is a simplified schematic diagram of a system for heating a refrigerant-based active injection heat pump of the present invention;
Fig. 5 is a cyclic pressure enthalpy chart of the invention when the refrigerant based on the low-grade heat source is heated by the active injection heat pump.
Reference numerals illustrate:
for the prior art heat pump 101, compressor, 102, condenser, 103, evaporator, 104, main throttle valve, 105, subcooler, 106, cold throttle valve.
The low-grade heat source-based refrigerant active injection heat pump comprises 1, a compressor, 2, a condenser, 3, an evaporator, 4, a main throttle valve, 5, a four-way valve, 6, a liquid storage tank, 7, a gas-liquid separator, 8, an outdoor fan, 9, a heat preservation water tank, 10, a host water pump, 11, a refrigerant conduit, 12, a heat preservation water conduit, 13, a high-pressure switch, 14, a high-pressure sensor, 15, a low-pressure switch, 16, a subcooler, 17, a supercooling throttle valve, 18, a refrigerant heat exchange tube, 19, an external heat source heat exchange tube, 20, an external heat source, 21, an external heat source pump, 22, an external heat source temperature sensor, 23, a subcooler inlet temperature sensor, 24, a subcooler outlet temperature sensor, 25, an exhaust temperature sensor, 26, an air suction temperature sensor, 27, a condenser outlet temperature sensor, 28 and an evaporator inlet temperature sensor.
Detailed Description
The refrigerant active injection heat pump based on the low-grade heat source and the control method thereof are further described in detail below with reference to the accompanying drawings and the detailed description.
A simplified schematic diagram of a system during heat pump heating in the prior art is shown in fig. 1:
When the refrigerant is not injected, the heat pump cycle is as follows, the supercooling throttle valve 106 is closed, the compressor 101 is operated, the refrigerant enters the compressor 101 through the air suction port of the compressor 101 and is compressed, then becomes high-temperature gaseous refrigerant and is discharged from the air discharge port of the compressor 101, then flows into the condenser 102 and exchanges heat with air or water, then the refrigerant which releases heat flows into the evaporator 103 through the supercooler 105 and the main throttle valve 104, exchanges heat with air in the evaporator 103, finally returns to the air suction port of the compressor 101 and enters the compressor 101 again;
When the refrigerant is injected, the heat pump cycle is performed by opening the supercooling throttle valve 106 to adjust according to a certain target (for example, according to the supercooling degree or the superheating degree of the heat pump), the refrigerant enters the compressor 101 through the air suction port of the compressor 101 and is compressed, then becomes high-temperature gaseous refrigerant and is discharged from the air discharge port of the compressor 101, then flows into the condenser 102 and exchanges heat with air or water, then the refrigerant flows through two paths, the main circulation path flows into the evaporator 103 through the cooler 105 and the main throttle valve 104, exchanges heat with air in the evaporator 103 and finally returns to the air suction port of the compressor 101 and enters the compressor 101 again, and the other path is throttled through the cold throttle valve 106, enters the supercooling device 105 and exchanges heat with the refrigerant of the main circulation path and finally is injected into the middle pressure cavity of the compressor 101 under the pressure difference.
The corresponding pressure enthalpy diagram of the heat pump in the prior art is shown in fig. 2, where h is specific enthalpy and P is pressure.
V A、VB、VC and V D in fig. 1 and 2 are refrigerant state points when no injection is performed on the refrigerant, and correspond to refrigerant state points after throttling the compressor 101 suction port, the compressor 101 discharge port, the condenser 102 outlet and the main throttle valve 104, V 1-V9 is a refrigerant state point when the refrigerant is injected, V 1、V2、V3、V4 and V 8 correspond to state points after the main circulation flow path refrigerant is compressed in the compressor 101 suction port, the compressor 101 discharge port, the main throttle valve 104 inlet, the main throttle valve 104 outlet and the first stage of the compressor 101, V 5、V6 and V 7 correspond to state points after the injection flow path refrigerant is compressed in the supercooling throttle valve 106 inlet, the supercooling throttle valve 106 outlet and enters the intermediate pressure chamber of the compressor 101, and V 9 corresponds to a state point after the main circulation flow path refrigerant and the injection flow path refrigerant are mixed in the intermediate chamber of the compressor 101.
As can be seen from fig. 2, the refrigerant undergoes two stages of compression in the compressor 101, where V 1 to V 8 are the first stage of compression and V 9 to V 2 are the second stage of compression.
According to the heat pump cycle principle, the heating quantity Q h,V of the heat pump of the prior art is equal to the sum of the air energy Q e,V absorbed by the evaporator 103 and the compression work EP V, and the expression is:
Qh,V＝Qe,V+EPV
wherein, the expression of the air energy Q e,V absorbed by the evaporator 103 is:
One part of the refrigerant returns to the compressor 101 after heat exchange in the evaporator 103, the other part of the refrigerant is injected into the middle cavity of the compressor 101, and the two parts of the refrigerant are mixed and then subjected to second-stage compression, so that the compression work expression of the heat pump in the prior art is as follows:
the expression of the energy efficiency COP V of the heat pump of the prior art is:
In the above expression, m V and m i,V are the compressor discharge amount and the refrigerant injection mass flow rate, respectively.
The above shows that the performance gain of the heat pump of the prior art is derived from the increased air energy (enthalpy difference between the point V 5 and the point V 3) with increased supercooling degree and the increase of compression work, while the heat quantity of the refrigerant injection (heat quantity calculated by enthalpy difference between the point V 7 and the point V 6) is not calculated into the heat quantity Q h,V.
Therefore, the invention aims to develop a refrigerant active injection heat pump based on the action of an external low-grade heat source so as to fully utilize the low-grade heat source, such as solar energy, waste heat and the like, and achieve the aim of greatly improving the heating capacity and energy efficiency of the heat pump.
Example 1:
as shown in fig. 3, the refrigerant active injection heat pump based on low-grade heat source of the invention comprises a heat pump system, an injection system, an external heat source 20 and an external heat source pump 21, wherein the heat pump system comprises a compressor 1, a condenser 2, an evaporator 3, a main throttle valve 4, a four-way valve 5, a liquid storage tank 6, a gas-liquid separator 7, an outdoor fan 8, a heat preservation water tank 9 and a host water pump 10, wherein the condenser 2 is provided with a refrigerant conduit 11 and a heat preservation water conduit 12, an exhaust port of the compressor 1 is communicated with a D port of the four-way valve 5, an E port of the four-way valve 5 is communicated with an inlet end of the refrigerant conduit 11 on the condenser 2, an outlet end of the refrigerant conduit 11 is communicated with one end of the liquid storage tank 6, the other end of the liquid storage tank 6 is communicated with one end of the main throttle valve 4, the other end of the main throttle valve 4 is communicated with one end of the evaporator 3, the other end of the evaporator 3 is communicated with a C port of the four-way valve 5, an S port of the four-way valve 5 is communicated with an inlet end of the gas-liquid separator 7, an outlet end of the gas-liquid separator 7 is communicated with an air intake port of the compressor 1, the host water pump 10 is communicated with an inlet end of the heat preservation water conduit 12 and an outlet end of the heat preservation water tank 9 is communicated with an inlet end of the heat preservation water tank 9 through the heat preservation water tank 9, and an inlet end of the heat preservation water is arranged near the heat preservation water tank 8 is communicated with the heat preservation water inlet end of the heat preservation water tank 9; the injection system comprises a subcooler 16 and a subcooling throttle valve 17, a refrigerant heat exchange tube 18 and an external heat source heat exchange tube 19 are arranged on the subcooler 16, one end of the subcooling throttle valve 17 is communicated with the outlet end of the condenser 2, the supercooling throttle valve 17 in this embodiment is connected at one end to a pipeline between the outlet end of the refrigerant conduit 11 and one end of the liquid storage tank 6, the other end of the supercooling throttle valve 17 is connected with the inlet end of the refrigerant heat exchange tube 18, the outlet end of the refrigerant heat exchange tube 18 is connected with the middle pressure cavity of the compressor 1, the external heat source pump 21 is connected between the inlet end of the external heat source heat exchange tube 19 and the outlet end of the external heat source 20, the outlet end of the external heat source heat exchange tube 19 is connected through a pipeline, the external heat source 20 in this embodiment can be hot water, steam or hot air heated by low-grade heat sources such as solar energy and waste heat, an external heat source temperature sensor 22 is arranged at the outlet end of the external heat source 20, a supercooler inlet temperature sensor 23 is arranged at the inlet end of the refrigerant heat exchange tube 18, an outlet temperature sensor 24 is arranged at the outlet end of the refrigerant heat exchange tube 18, an exhaust temperature sensor 25 is arranged on a pipeline connected with the exhaust port of the compressor 1, an air suction temperature sensor 26 is arranged on a pipeline connected with the outlet end of the condenser 2, and an evaporator temperature sensor 27 is arranged on the pipeline connected with the outlet end of the evaporator 3.
The simplified schematic diagram of the system when the refrigerant based on the low-grade heat source is heated by the active injection heat pump in this embodiment is shown in fig. 4:
The supercooling throttle valve 17 is closed, the compressor 1 is operated, the refrigerant enters the compressor 1 through the air suction port of the compressor 1 and is compressed, then becomes high-temperature gaseous refrigerant and is discharged from the air discharge port of the compressor 1, then flows into the condenser 2 and exchanges heat with air or water, then the refrigerant which discharges heat flows into the evaporator 3 through the main throttle valve 4, exchanges heat with air in the evaporator 3, finally returns to the air suction port of the compressor 1 and enters the compressor 1 again;
When the refrigerant is injected, the heat pump cycle is performed by opening the supercooling throttle valve 17 to perform adjustment according to a certain target (for example, adjustment according to the supercooling degree or the superheating degree of the heat pump), inputting an external heat source 20 into the supercooler 16, operating the compressor 1, enabling the refrigerant to be changed into high-temperature gaseous refrigerant after entering the compressor 1 through the air suction port of the compressor 1 and being compressed, discharging the high-temperature gaseous refrigerant from the air discharge port of the compressor 1, flowing into the condenser 2 and exchanging heat with air or water, enabling the refrigerant to flow through two paths, enabling the refrigerant to flow into the evaporator 3 through the main throttle valve 4, exchanging heat with the air in the evaporator 3, returning to the air suction port of the compressor 1 and entering the compressor 1 again, enabling the other path to flow into the supercooler 16 through the cold throttle valve 17 and exchanging heat with the external heat source 20, and finally injecting the refrigerant into an intermediate pressure cavity of the compressor 1 under the pressure difference effect.
The corresponding pressure enthalpy diagram of the refrigerant active injection heat pump based on the low-grade heat source in the embodiment during heating is shown in fig. 5:
The expression of the heating amount of the refrigerant active injection heat pump based on the low-grade heat source in this embodiment is:
Qh,V＝Qe,V+Qsc,inj+EPV
wherein, Q sc,inj is the heat absorbed by the refrigerant in the subcooler, and the expression is:
The compression work expression of the refrigerant active injection heat pump based on the low-grade heat source in the embodiment is as follows:
As can be seen from the above, the heating capacity of the refrigerant active injection heat pump based on the low-grade heat source in the present embodiment is greater than the heating capacity of the heat pump in the prior art by the heat Q sc,inj absorbed by the refrigerant in the subcooler, so that the energy efficiency COP V of the refrigerant active injection heat pump based on the low-grade heat source in the present embodiment is also improved.
Example 2:
The embodiment discloses a control method of a refrigerant active injection heat pump based on a low-grade heat source in embodiment 1, comprising the following steps:
In the operation process of the heat pump, the main throttle valve 4 and the supercooling throttle valve 17 are adjusted according to a certain target, such as the supercooling degree or the superheat degree of the heat pump, and simultaneously, the external heat source temperature T h,in is detected in real time by the external heat source temperature sensor 22, the supercooler injection inlet temperature T inj,in at the inlet end of the refrigerant heat exchange tube 18 is detected in real time by the supercooler inlet temperature sensor 23, and the supercooler injection inlet temperature T inj,out at the outlet end of the refrigerant heat exchange tube 18 is detected in real time by the supercooler outlet temperature sensor 24;
When the external heat source temperature T h,in is less than or equal to the subcooler injection outlet temperature T inj,out, controlling the external heat source pump 21 to stop running so that the external heat source 20 cannot enter the subcooler 16;
When the external heat source temperature T h,in > the subcooler injection outlet temperature T inj,out, the external heat source pump 21 is controlled to start operation so that the external heat source 20 can enter the subcooler 16.
In the present embodiment, the main throttle valve 4 is controlled and adjusted according to the superheat degree of the heat pump, which is defined as:
compressor suction temperature T s -defrost temperature T def;
when the actual superheat degree is greater than the target superheat degree, the main throttle valve 4 is opened;
when the actual superheat degree is less than the target superheat degree, the main throttle valve 4 is closed;
when the actual degree of superheat=target degree of superheat, the main throttle valve 4 maintains the current opening degree;
The target superheat degree is a system preset temperature value of the heat pump, the air suction temperature T s of the compressor is acquired by the air suction temperature sensor 26, and the defrosting temperature T def is acquired by the evaporator inlet temperature sensor 28.
The supercooling throttle 17 is controlled and regulated according to the supercooling degree of the heat pump, which is defined as:
the saturation temperature P d_t corresponding to the high pressure of the heat pump is the liquid pipe temperature T liq;
When the actual supercooling degree > the target supercooling degree, the supercooling throttle valve 17 is opened;
when the actual supercooling degree < target supercooling degree, the supercooling throttle valve 17 is closed;
when the actual supercooling degree=the target supercooling degree, the supercooling throttle valve 17 maintains the current opening degree;
The target supercooling degree is a preset temperature value of a system of the heat pump, the saturation temperature P d_t corresponding to the high pressure of the heat pump is obtained by converting the high pressure of the heat pump obtained by the high pressure sensor 14, and the liquid pipe temperature T liq is obtained by the condenser outlet temperature sensor 27.
In order to ensure the operation reliability of the heat pump, the supercooling throttle valve 17 performs correction adjustment according to the compressor discharge superheat degree of the heat pump, which is defined as:
compressor discharge temperature T d —saturation temperature P d_t corresponding to heat pump high pressure;
when the actual compressor discharge superheat degree is less than the set value B, the supercooling throttle valve 17 is closed;
when the actual compressor discharge superheat degree is greater than the set value C, the supercooling throttle valve 17 is opened;
when the set value B is less than or equal to the actual compressor exhaust superheat degree is less than or equal to the set value C, the supercooling throttle valve 17 is controlled and regulated according to the target supercooling degree of the heat pump;
The set value B and the set value C are system preset temperature values of the heat pump, the set value C is greater than the set value B, and the compressor exhaust temperature T d is acquired by an exhaust temperature sensor 25.
The setting value B and the setting value C can enable the supercooling throttle valve 17 to participate in controlling and adjusting the compressor exhaust temperature T d when the compressor exhaust temperature T d is too low and too high, so that the compressor exhaust temperature T d is always in a reliability range, for example, the existing heat pump generally requires the compressor exhaust superheat degree to be above 10 ℃, the setting value B can be set to 15-20 ℃ under the condition of ensuring a certain allowance, the protection value of the compressor exhaust temperature T d of the existing heat pump is generally about 120 ℃, the saturation temperature P d_t corresponding to the general heat pump high pressure (the frequency-limiting high pressure is 37-38 bar) is about 60 ℃, and the setting value C can be set to 45-55 ℃ under the condition of ensuring a certain allowance.
Of course, since the supercooling throttle valve 17 is normally adjusted according to the supercooling degree control of the heat pump, and the supercooling throttle valve 17 is corrected and adjusted according to the compressor discharge superheat degree of the heat pump to ensure the operation reliability of the heat pump, when the opening of the supercooling throttle valve 17 is adjusted, the operation reliability of the heat pump needs to be preferentially ensured, that is, the supercooling throttle valve 17 is adjusted according to the supercooling degree control of the heat pump on the premise that the operation reliability of the heat pump can be ensured.
Example 3:
The difference between this embodiment and embodiment 2 is that this embodiment adds a control method for preventing frequent start and stop of the external heat source pump 21, and specifically includes the following steps:
During the operation of the heat pump, the main throttle valve 4 and the supercooling throttle valve 17 regulate the opening according to a certain target, and simultaneously, the external heat source temperature T h,in is detected in real time through the external heat source temperature sensor 22, the supercooling injection inlet temperature T inj,in at the inlet end of the refrigerant heat exchange tube 18 is detected in real time through the supercooling inlet temperature sensor 23, and the supercooling injection inlet temperature T inj,out at the outlet end of the refrigerant heat exchange tube 18 is detected in real time through the supercooling outlet temperature sensor 24;
When the external heat source temperature T h,in is higher than the subcooler jet outlet temperature T inj,out, controlling the external heat source pump 21 to start running so that the external heat source 20 can enter the subcooler 16;
after the external heat source pump 21 is started to operate,
When the subcooler injection inlet temperature T inj,in plus the set value A is less than or equal to the external heat source temperature T h,in and is less than the subcooler injection outlet temperature T inj,out, the external heat source pump 21 is kept in a continuous running state;
When the external heat source temperature T h,in is less than the subcooler injection inlet temperature T inj,in + set value A, controlling the external heat source pump 21 to stop running;
The set value A is a system preset temperature value of the heat pump, and the subcooler injection inlet temperature T inj,in plus the set value A is less than the subcooler injection outlet temperature T inj,out.
The setting value A is mainly used for preventing the heat source from being frequently switched, and can be determined according to actual Th and in changes.
The setting value a is mainly set to prevent frequent start-up and shut-down of the external heat source pump 21, so that a specific value thereof can be determined according to the actual external heat source temperature T h,in.
The opening degree adjustment manners of the main throttle valve 4 and the supercooling throttle valve 17 in this embodiment are the same as those in embodiment 2, and are not described in detail here.
The above examples are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solution of the present invention should fall within the scope of protection defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (5)
1. A control method of a refrigerant active injection heat pump based on a low-grade heat source is characterized in that the refrigerant active injection heat pump based on the low-grade heat source comprises a heat pump system, an injection system, an external heat source (20) and an external heat source pump (21), the heat pump system comprises a compressor (1), a condenser (2), an evaporator (3), a main throttle valve (4) and a four-way valve (5) which are in circulation communication, the injection system comprises a subcooler (16) and a supercooling throttle valve (17), a refrigerant heat exchange tube (18) and an external heat source heat exchange tube (19) are arranged on the subcooler (16), one end of the supercooling throttle valve (17) is communicated with the outlet end of the condenser (2), the other end of the supercooling throttle valve (17) is communicated with the inlet end of the refrigerant heat exchange tube (18), the outlet end of the refrigerant heat exchange tube (18) is communicated with an intermediate pressure cavity of the compressor (1), the external heat source pump (21) is communicated between the inlet end of the external heat source heat exchange tube (19) and the outlet end of the external heat source (20), the temperature sensor (22) is arranged at the outlet end of the external heat source (20) is provided with a temperature sensor (23), a subcooler outlet temperature sensor (24) is arranged at the outlet end of the refrigerant heat exchange tube (18);
The control method comprises the following steps:
In the operation process of the heat pump, the main throttle valve (4) and the supercooling throttle valve (17) regulate the opening according to a certain target, and simultaneously, the external heat source temperature T h,in is detected in real time through the external heat source temperature sensor (22), the supercooling jet inlet temperature T inj,in at the inlet end of the refrigerant heat exchange tube (18) is detected in real time through the supercooling jet inlet temperature sensor (23), and the supercooling jet inlet temperature T inj,out at the outlet end of the refrigerant heat exchange tube (18) is detected in real time through the supercooling jet outlet temperature sensor (24);
When the external heat source temperature T h,in is less than or equal to the subcooler jet outlet temperature T inj,out, controlling the external heat source pump (21) to stop running, so that the external heat source (20) does not enter the subcooler (16);
When the external heat source temperature T h,in is higher than the subcooler injection outlet temperature T inj,out, the external heat source pump (21) is controlled to start to operate, so that the external heat source (20) can enter the subcooler (16).
2. The method for controlling a low-grade heat source-based refrigerant active injection heat pump according to claim 1, wherein a suction temperature sensor (26) is provided on a line connected to a suction port of the compressor (1), and an evaporator inlet temperature sensor (28) is provided on a line connected to an inlet end of the evaporator (3);
The main throttle valve (4) is controlled and regulated according to the superheat degree of the heat pump, and the superheat degree of the heat pump is defined as:
compressor suction temperature T s -defrost temperature T def;
when the actual superheat degree is greater than the target superheat degree, the main throttle valve (4) is opened;
When the actual superheat degree is less than the target superheat degree, the main throttle valve (4) is closed;
When the actual superheat degree=the target superheat degree, the main throttle valve (4) maintains the current opening degree;
The target superheat degree is a system preset temperature value of the heat pump, the air suction temperature T s of the compressor is acquired by the air suction temperature sensor (26), and the defrosting temperature T def is acquired by the evaporator inlet temperature sensor (28).
3. The method for controlling a low-grade heat source-based refrigerant active injection heat pump according to claim 1, wherein a condenser outlet temperature sensor (27) is provided on a pipe connected to an outlet end of the condenser (2), and a high-pressure sensor (14) is provided on a pipe connected to an exhaust port of the compressor (1);
the supercooling throttle valve (17) is controlled and regulated according to the supercooling degree of the heat pump, and the supercooling degree of the heat pump is defined as:
the saturation temperature P d_t corresponding to the high pressure of the heat pump is the liquid pipe temperature T liq;
When the actual supercooling degree is greater than the target supercooling degree, the supercooling throttle valve (17) is opened;
when the actual supercooling degree is less than the target supercooling degree, the supercooling throttle valve (17) is closed;
when the actual supercooling degree=target supercooling degree, the supercooling throttle valve (17) maintains the current opening degree;
The target supercooling degree is a system preset temperature value of the heat pump, the saturation temperature P d_t corresponding to the high pressure of the heat pump is obtained by converting the high pressure of the heat pump obtained by the high pressure sensor (14), and the liquid pipe temperature T liq is obtained by the condenser outlet temperature sensor (27).
4. The method for controlling a low-grade heat source-based refrigerant active injection heat pump according to claim 3, wherein an exhaust gas temperature sensor (25) is provided on a pipe connected to an exhaust port of the compressor (1) in the low-grade heat source-based refrigerant active injection heat pump;
The supercooling throttle valve (17) is corrected and adjusted according to the exhaust superheat degree of the compressor of the heat pump, and the exhaust superheat degree of the compressor of the heat pump is defined as:
compressor discharge temperature T d —saturation temperature P d_t corresponding to heat pump high pressure;
when the actual compressor exhaust superheat degree is less than a set value B, the supercooling throttle valve (17) is closed;
when the actual compressor exhaust superheat degree is greater than a set value C, the supercooling throttle valve (17) is opened;
when the set value B is less than or equal to the actual compressor exhaust superheat degree is less than or equal to the set value C, the supercooling throttle valve (17) is controlled and regulated according to the target supercooling degree of the heat pump;
The set value B and the set value C are system preset temperature values of the heat pump, the set value C is larger than the set value B, and the exhaust temperature T d of the compressor is acquired by the exhaust temperature sensor (25).
5. The control method of a low-grade heat source-based refrigerant active injection heat pump according to claim 1 or 2 or 3 or 4, further comprising the steps of:
after the external heat source pump (21) is started to operate,
When the subcooler injection inlet temperature T inj,in plus the set value A is less than or equal to the external heat source temperature T h,in and is less than the subcooler injection outlet temperature T inj,out, the external heat source pump (21) is kept in a continuous running state;
When the external heat source temperature T h,in is less than the subcooler injection inlet temperature T inj,in + set value A, controlling the external heat source pump (21) to stop running;
The set value A is a system preset temperature value of the heat pump, and the subcooler injection inlet temperature T inj,in plus the set value A is less than the subcooler injection outlet temperature T inj,out.
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| CN212029926U (en) * | 2020-04-27 | 2020-11-27 | 宁波工程学院 | Refrigerant active injection heat pump based on low-grade heat source |
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| CN109556321A (en) * | 2018-11-09 | 2019-04-02 | 广东申菱环境系统股份有限公司 | A kind of injection boosting type air source heat pump circulatory system and working method |
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| CN212029926U (en) * | 2020-04-27 | 2020-11-27 | 宁波工程学院 | Refrigerant active injection heat pump based on low-grade heat source |
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