CN115560497A - A low-temperature air source heat pump and its control method with an improved control method for supplementing air and increasing enthalpy - Google Patents

Abstract

The invention discloses a low-temperature air source heat pump and a control method for improving the control method of air supplementation and enthalpy increase, and relates to the technical field of air conditioning and control methods, including a compressor for air supplementation and enthalpy increase, one end of which is connected to an exhaust pipe The end of the exhaust pipe away from the compressor is fixedly installed with a four-way valve assembly, and one end of the four-way valve assembly is fixedly connected with an outdoor heat exchanger. One end of the one-way valve assembly is fixedly connected with a liquid reservoir, and one end of the water-side heat exchanger is fixedly connected with one end of the gas fraction and one end of the compressor. On the one hand, it effectively solves the situation that the control of the main electronic expansion valve and the auxiliary electronic expansion valve is not coordinated, the goals are inconsistent, and the control effect offsets, and on the other hand, it also effectively solves the overshoot or overshoot of the main electronic expansion valve and the auxiliary electronic expansion valve. If the system state is unstable and the control time is too long, the system state converges quickly, the stability is good, and the operation is more reliable and stable.

Description

A low-temperature air source heat pump and its control method with an improved control method for supplementing air and increasing enthalpy

technical field

The invention relates to the technical field of air conditioning and control method processing, in particular to a low-temperature air source heat pump and a control method for improving the control method of air supplementation and enthalpy increase.

Background technique

At present, low-temperature air-source heat pumps have been widely used in heating in northern regions. The technology of supplementing air to increase enthalpy can provide normal heat pump heating in a low temperature environment of -25°C. Wide range of applications.

The control method for increasing the enthalpy of the supplementary gas in the current period is mainly to control the superheat degree of the supplementary gas circuit and the exhaust temperature of the compressor through the auxiliary electronic expansion valve of the supplementary gas circuit, or when the exhaust temperature is too high and the main electronic expansion valve is opened to the maximum , open the auxiliary electronic expansion valve for protection control. The disadvantages of the current control method are:

1. The main electronic expansion valve controls the action of the main electronic expansion valve according to the exhaust temperature and exhaust superheat, and the auxiliary electronic expansion valve controls the action of the auxiliary electronic expansion valve through the exhaust temperature, exhaust superheat and superheat of the supplementary air circuit. 1. If the auxiliary electronic expansion valve is not controlled in coordination, there will be problems of inconsistent control targets and offsetting control effects.

2. The main and auxiliary electronic expansion valves are only controlled according to the deviation between the exhaust temperature, exhaust superheat and the target value, and the trend of the exhaust temperature over time is not judged, and there is an overshoot or overshoot phenomenon, resulting in an unstable system state , The control time is too long.

Therefore, it needs to be improved in order to better meet the market demand. For this reason, we propose a low-temperature air source heat pump and a control method that improve the control method of supplementing air to increase enthalpy to solve the above problems.

Contents of the invention

The purpose of the present invention is to provide a low-temperature air source heat pump and control method for improving the control method of air supplementation and enthalpy increase, so as to solve the problem in the above-mentioned background technology that the main electronic expansion valve controls the action of the main electronic expansion valve according to the exhaust temperature and the degree of superheat of the exhaust gas. , the auxiliary electronic expansion valve controls the action of the auxiliary electronic expansion valve through the exhaust temperature, the superheat of the exhaust gas and the superheat of the supplementary air circuit. If the main and auxiliary electronic expansion valves are not controlled cooperatively, there will be problems of inconsistent control targets and offsetting control effects .

In order to achieve the above object, the present invention provides the following technical solution: a low-temperature air source heat pump with an improved control method for air supplementation and enthalpy increase, comprising a compressor for air supplementation and enthalpy increase, one end of the compressor is connected to an exhaust pipe, and the exhaust pipe A four-way valve assembly is fixedly installed at one end of the air pipe away from the compressor, and one end of the four-way valve assembly is fixedly connected with an outdoor heat exchanger, and the outdoor heat exchanger is fixedly connected. One end of the one-way valve assembly is fixedly connected to a liquid reservoir, and the water-side heat exchanger includes a shell tube, casing or plate exchanger, and one end of the water-side heat exchanger is fixedly connected to one end of the gas component and the compressor One end of the machine is fixedly connected. The one-way valve assembly, the liquid reservoir, and the auxiliary electronic expansion valve, between the one-way valve assembly, the economizer and the auxiliary electronic expansion valve, there is a connection between the end of the main electronic expansion valve connected to the silencer and the compressor. Fixed connection between.

By adopting the above technical solution, on the one hand, it effectively solves the situation that the control of the main electronic expansion valve and the auxiliary electronic expansion valve is not coordinated, the goals are inconsistent, and the control effect offsets. On the other hand, it also effectively solves the problem of the main electronic expansion valve and the auxiliary electronic expansion valve There are cases where overshoot or overshoot leads to unstable system state and long control time. The system state converges quickly and has good stability, making the operation more reliable and stable. Moreover, the invention can cover all low-temperature air-source heat pump units with supplementary air to increase enthalpy, and has wide application value.

Preferably, the discharge side of the compressor is provided with a discharge temperature probe for detecting the discharge temperature Td, the discharge side of the compressor is provided with a discharge pressure sensor for detecting the discharge pressure Pd, and the gas supply circuit of the economizer The inlet is provided with a temperature probe for detecting the inlet temperature Tv_in of the supplementary air, and the outlet of the economizer air supply circuit is provided with a temperature probe for detecting the outlet temperature Tv_out of the supplementary air.

A control method of a low-temperature air source heat pump that improves the control method of supplementing air to increase enthalpy, comprising the following steps:

S1. The unit is turned on and running;

S2. Detect the starting and running time of the compressor, if the starting and running time is ≥ 5 minutes, go to step S3, otherwise go to step S4;

S3. If Td1>100°C, open the main electronic expansion valve to the maximum and the auxiliary electronic expansion valve to the maximum, otherwise go to step S5;

S4. The main electronic expansion valve and the auxiliary electronic expansion valve maintain the initial opening, and return to step S2;

S5. If TdSH>30°C, go to step S6, otherwise go to step S8;

S6. If k>0°C, open the main electronic expansion valve for 2*(TdSH-25)+3*k, otherwise, open the main electronic expansion valve for 2*(TdSH-25); go to step S7

S7. If TvSH>5°C, open the auxiliary electronic expansion valve for 2*(TdSH-25), otherwise, keep the opening of the auxiliary electronic expansion valve; return to step S3;

S8. If 20°C<TdSH≤30°C, go to step S9, otherwise, go to step S14;

S9. If k>2°C, open the main electronic expansion valve by 3*k, and go to step S10; otherwise, go to step S11.

S10. If TvSH>5°C, open the auxiliary electronic expansion valve for 2*k, otherwise, keep the opening of the auxiliary electronic expansion valve; return to step S3;

S11. If k<-2°C, close the main electronic expansion valve by -3*k, otherwise, keep the opening of the main electronic expansion valve; go to step S12.

S12. If TvSH>10°C, open the auxiliary electronic expansion valve TvSH-10, and return to step S3; otherwise, go to step S13;

S13. If TvSH<3°C, close the auxiliary electronic expansion valve for 4 steps, otherwise, keep the opening of the auxiliary electronic expansion valve; return to step S3;

S14. If 10°C<TdSH≤20°C, go to step S15, otherwise, go to step S17;

S15. If k>3°C, keep the opening of the main electronic expansion valve, otherwise, close the main electronic expansion valve -2*(TdSH-25); go to step S16.

S16. If TvSH>5°C, maintain the opening of the auxiliary electronic expansion valve, otherwise, close the auxiliary electronic expansion valve by -2*(TdSH-25); return to step S3.

S17. Closing of the main electronic expansion valve-3*(TdSH-25); closing of the auxiliary electronic expansion valve-3*(TdSH-25); return to step S3.

Further, the minimum opening of the main electronic expansion valve is 70 steps, and the maximum opening is 450 steps; the minimum opening of the auxiliary electronic expansion valve is 0 steps, and the maximum opening is 450 steps.

The beneficial effects of the present invention are:

The present invention integrates components such as the main electronic expansion valve and the auxiliary electronic expansion valve with reasonable design, clear logic, and convenient control. The situation where the control effect is offset, on the other hand, it also effectively solves the situation that the main electronic expansion valve and the auxiliary electronic expansion valve have overshoot or overshoot, resulting in unstable system state and long control time. The system state converges quickly and has good stability. The operation is more reliable and stable. Moreover, the invention can cover all low-temperature air-source heat pump units with supplementary air to increase enthalpy, and has wide application value.

Description of drawings

Fig. 1 is the structure and system schematic diagram of the present invention.

Fig. 2 is a control flow chart of the present invention.

In the figure: 1. Compressor; 2. Four-way valve assembly; 3. Outdoor heat exchanger; 4. Heat exchange fan; 5. Check valve assembly; 6. Main electronic expansion valve; 7. Economizer; 8. Auxiliary Electronic expansion valve; 9. Muffler; 10. Liquid reservoir; 11. Water side heat exchanger; 12. Gas distribution.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment: As shown in Figure 1-2, the present invention provides a low-temperature air source heat pump with an improved control method for air supplementation and enthalpy increase, including a compressor 1 for air supplementation and enthalpy increase, and one end of the compressor 1 is connected to an exhaust gas A four-way valve assembly 2 is fixedly installed on the end of the exhaust pipe away from the compressor 1 , and an outdoor heat exchanger 3 is fixedly connected to one end of the four-way valve assembly 1 . The compressor 1 compresses the low-pressure and low-temperature refrigerant into a high-temperature, high-pressure superheated gas, which reaches the four-way valve assembly 2 through the exhaust pipe, and then reaches the outdoor heat exchanger 3 for condensation.

The outdoor heat exchanger 3 is provided with a heat exchange fan 4 , and one end of the outdoor heat exchanger 3 is fixedly connected with a check valve assembly 5 . An economizer 7 and an auxiliary electronic expansion valve 8 are arranged between the one-way valve assembly 5 and the liquid reservoir 10 , and a main electronic expansion valve is arranged between the one-way valve assembly 5 , the economizer 7 and the auxiliary electronic expansion valve 8 . valve 6. After the refrigerant is condensed by the outdoor heat exchanger, it passes through the check valve assembly 5 and reaches the economizer 7, where it exchanges heat with the refrigerant in the supplementary air circuit after the throttling of the auxiliary electronic expansion valve 8, thereby obtaining a supercooled high-pressure medium-temperature refrigerant, of which One end of the one-way valve assembly 5 is fixedly connected to the liquid accumulator 10, and the supercooled high-pressure medium-temperature refrigerant is throttled by the main electronic expansion valve 6 and then reaches the liquid accumulator 10 through the one-way valve assembly 5. In addition, the accumulator One end of the liquid container 10 is fixedly connected to a water-side heat exchanger 11 , and the refrigerant reaches the water-side heat exchanger 11 after passing through the liquid accumulator 10 .

The water-side heat exchanger 11 includes a shell tube, casing or plate exchanger. One end of the water-side heat exchanger 11 is fixedly connected with an air component 12 , and the end of the gas component 12 away from the water-side heat exchanger 11 is connected to the One end of the compressor 1 is fixedly connected. A muffler 9 is connected to the outside of the economizer 7 , and the end of the muffler 9 away from the economizer 7 is fixedly connected to the compressor 1 . The water-side heat exchanger 11 can be a shell-and-tube, casing or plate exchanger. After heat exchange between the refrigerant and water, the low-pressure and low-temperature superheated steam is returned to the air separator 12 through the four-way valve, and then returned to the compressor 1 through the air separator. . After the auxiliary electronic expansion valve 8 throttles, the refrigerant in the supplementary air circuit is exchanged by the economizer 7 to obtain medium-pressure and medium-temperature superheated steam, and returns to the medium-pressure cavity of the compressor 1 after the muffler 9 eliminates pulsation and noise.

The discharge side of the compressor 1 is provided with a discharge temperature probe for detecting the discharge temperature Td, the discharge side of the compressor 1 is provided with a discharge pressure sensor for detecting the discharge pressure Pd, and the economizer 7 gas supply circuit The inlet of the compressor 1 is provided with a temperature probe for detecting the inlet temperature Tv_in of the supplementary air, and the outlet of the economizer 7 supplementary air circuit is provided with a temperature probe for detecting the outlet temperature of the supplementary air Tv_out. The pressure calculation corresponds to the condensation temperature Tc.

If the current exhaust temperature, exhaust pressure, and condensation temperature are Td1, Pd1, and Tc1, the exhaust temperature before one valve adjustment cycle is Td0. The controller calculates exhaust superheat TdSH=Td1-Tc1 based on the current exhaust temperature and condensing temperature, and calculates the supplement air superheat TvSH=Tv_out-Tv_in according to the inlet and outlet temperature of the economizer supplement air circuit. The change trend of exhaust temperature k=Td1-Td0, k>0 indicates that the exhaust temperature rises, and k<0 indicates that the exhaust temperature decreases, and the larger the absolute value, the stronger the trend.

A control method of a low-temperature air source heat pump that improves the control method of supplementing air to increase enthalpy, comprising the following steps:

S1. The unit is turned on and running;

S2. Detect the starting and running time of the compressor, if the starting and running time is ≥ 5 minutes, go to step S3, otherwise go to step S4;

S3. If Td1>100°C, open the main electronic expansion valve to the maximum and the auxiliary electronic expansion valve to the maximum, otherwise go to step S5;

S4. The main electronic expansion valve and the auxiliary electronic expansion valve maintain the initial opening, and return to step S2;

S5. If TdSH>30°C, go to step S6, otherwise go to step S8;

S6. If k>0°C, open the main electronic expansion valve for 2*(TdSH-25)+3*k, otherwise, open the main electronic expansion valve for 2*(TdSH-25); go to step S7

S7. If TvSH>5°C, open the auxiliary electronic expansion valve for 2*(TdSH-25), otherwise, keep the opening of the auxiliary electronic expansion valve; return to step S3;

S8. If 20°C<TdSH≤30°C, go to step S9, otherwise, go to step S14;

S9. If k>2°C, open the main electronic expansion valve by 3*k, and go to step S10; otherwise, go to step S11.

S10. If TvSH>5°C, open the auxiliary electronic expansion valve for 2*k, otherwise, keep the opening of the auxiliary electronic expansion valve; return to step S3;

S11. If k<-2°C, close the main electronic expansion valve by -3*k, otherwise, keep the opening of the main electronic expansion valve; go to step S12.

S12. If TvSH>10°C, open the auxiliary electronic expansion valve TvSH-10, and return to step S3; otherwise, go to step S13;

S13. If TvSH<3°C, close the auxiliary electronic expansion valve for 4 steps, otherwise, keep the opening of the auxiliary electronic expansion valve; return to step S3;

S14. If 10°C<TdSH≤20°C, go to step S15, otherwise, go to step S17;

S15. If k>3°C, keep the opening of the main electronic expansion valve, otherwise, close the main electronic expansion valve -2*(TdSH-25); go to step S16.

S16. If TvSH>5°C, maintain the opening of the auxiliary electronic expansion valve, otherwise, close the auxiliary electronic expansion valve by -2*(TdSH-25); return to step S3.

S17. Closing of the main electronic expansion valve-3*(TdSH-25); closing of the auxiliary electronic expansion valve-3*(TdSH-25); return to step S3.

Further, the minimum opening of the main electronic expansion valve is 70 steps, and the maximum opening is 450 steps; the minimum opening of the auxiliary electronic expansion valve is 0 steps, and the maximum opening is 450 steps.

When in use, the compressor 1 compresses the low-pressure and low-temperature refrigerant into a high-temperature, high-pressure superheated gas, which reaches the four-way valve assembly 2 through the exhaust pipe, and then reaches the outdoor heat exchanger 3 for condensation. After the refrigerant is condensed by the outdoor heat exchanger 3 , reaches the economizer 7 through the check valve assembly 5, and performs heat exchange with the refrigerant in the supplementary air circuit throttled by the auxiliary electronic expansion valve 8, thereby obtaining a supercooled high-pressure medium-temperature refrigerant, which is throttled by the main electronic expansion valve 6 and then passed through The one-way valve assembly 5 reaches the liquid receiver 10, and the refrigerant passes through the liquid receiver 10 and then reaches the water-side heat exchanger 11. After heat exchange between the refrigerant and water, the low-pressure and low-temperature superheated steam is returned to the gas fraction 12 through the four-way valve. , and then return to the compressor 1 through the gas fraction 12. After the auxiliary electronic expansion valve 8 throttles, the refrigerant in the supplementary air circuit is exchanged by the economizer 7 to obtain medium-pressure and medium-temperature superheated steam, and returns to the medium-pressure cavity of the compressor 1 after the muffler 9 eliminates pulsation and noise. Use the exhaust temperature probe on the exhaust side of compressor 1 to detect the exhaust temperature Td, use the exhaust pressure sensor to detect the exhaust pressure Pd, and use the temperature probe at the inlet of the air supply circuit of the air supply economizer 7 to detect the air supply inlet For the temperature Tv_in, the temperature probe at the outlet of the air supply circuit of the air supply economizer 7 is used to detect the temperature Tv_out of the air supply outlet. The controller calculates the corresponding condensation temperature Tc according to the exhaust pressure. The current exhaust temperature, exhaust pressure, and condensation temperature are Td1, Pd1, and Tc1, and the exhaust temperature before one valve adjustment cycle is Td0. The controller calculates exhaust superheat TdSH=Td1-Tc1 according to the current exhaust temperature and condensing temperature, and calculates the supplement air superheat TvSH=Tv_out-Tv_in according to the inlet and outlet temperature of the economizer supplement air circuit. The change trend of exhaust temperature k=Td1-Td0, k>0 indicates that the exhaust temperature rises, and k<0 indicates that the exhaust temperature decreases, and the larger the absolute value, the stronger the trend.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (6)

1. The low-temperature air source heat pump comprises an air-supplying enthalpy-increasing compressor (1) and is characterized in that: the one end of compressor (1) is connected with the blast pipe, the one end fixed mounting that compressor (1) was kept away from to the blast pipe has cross valve subassembly (2), the one end fixedly connected with outdoor heat exchanger (3) of cross valve subassembly (1), outdoor heat exchanger (3) are equipped with heat transfer fan (4), the one end fixedly connected with check valve subassembly (5) of outdoor heat exchanger (3).

2. The low-temperature air source heat pump for the improved air-supply enthalpy-increasing control method according to claim 1, characterized in that: the compressor is characterized in that one end of the check valve assembly (5) is fixedly connected with a liquid storage device (10), one end of the liquid storage device (10) is fixedly connected with a water side heat exchanger (11), the water side heat exchanger (11) comprises a shell tube, a sleeve or a plate exchanger, one end of the water side heat exchanger (11) is fixedly connected with an air distributor (12), and one end, far away from the water side heat exchanger (11), of the air distributor (12) is fixedly connected with one end of the compressor (1).

3. The low-temperature air source heat pump for the improved air-supply enthalpy-increasing control method according to claim 2, characterized in that: an economizer (7) and an auxiliary electronic expansion valve (8) are arranged between the check valve component (5) and the liquid storage device (10), and a main electronic expansion valve (6) is arranged between the check valve component (5) and the economizer (7) and between the check valve component and the auxiliary electronic expansion valve (8).

4. The low-temperature air source heat pump for the improved air-supply enthalpy-increasing control method according to claim 3, characterized in that: the outside of the economizer (7) is connected with a silencer (9), and one end of the silencer (9) far away from the economizer (7) is fixedly connected with the compressor (1).

5. The low-temperature air source heat pump for the improved air-supply enthalpy-increasing control method according to claim 4, characterized in that: the air discharge side of the compressor (1) is provided with an air discharge temperature probe for detecting an air discharge temperature Td, the air discharge side of the compressor (1) is provided with an air discharge pressure sensor for detecting an air discharge pressure Pd, the inlet of the air supply loop of the economizer (7) is provided with a temperature probe for detecting an air supply inlet temperature Tv _ in, and the outlet of the air supply loop of the economizer (7) is provided with a temperature probe for detecting an air supply outlet temperature Tv _ out.

6. A control method of a low-temperature air source heat pump for improving a gas-supplementing enthalpy-increasing control method is characterized by comprising the following steps:

s1, starting up a unit to operate;

s2, detecting the starting running time of the compressor, wherein the starting running time is more than or equal to 5min, turning to the step S3, and otherwise, turning to the step S4;

s3, if Td1 is more than 100 ℃, the main electronic expansion valve is opened to the maximum, the auxiliary electronic expansion valve is opened to the maximum, and otherwise, the step S5 is executed;

s4, maintaining the initial opening degree of the main electronic expansion valve and the auxiliary electronic expansion valve, and returning to the step S2;

s5, if TdSH is more than 30 ℃, turning to the step S6, otherwise, turning to the step S8;

s6, if k is more than 0 ℃, opening 2 x (TdSH-25) +3*k by the main electronic expansion valve, otherwise, opening 2 x (TdSH-25) by the main electronic expansion valve; go to step S7

S7, if the TvSH is more than 5 ℃, opening a valve 2 (TdSH-25) by the auxiliary electronic expansion valve, otherwise, keeping the opening degree of the auxiliary electronic expansion valve; returning to the step S3;

s8, if the temperature is more than 20 ℃ and the TdSH is less than or equal to 30 ℃, turning to the step S9, otherwise, turning to the step S14;

s9, if k is more than 2 ℃, opening a valve 3*k of the main electronic expansion valve, and going to the step S10, otherwise, going to the step S11.

S10, if the TvSH is higher than 5 ℃, opening a valve 2*k by the auxiliary electronic expansion valve, and otherwise, keeping the opening degree of the auxiliary electronic expansion valve; returning to the step S3;

s11, if k is less than-2 ℃, closing a valve-3*k by the main electronic expansion valve, and otherwise, keeping the opening degree of the main electronic expansion valve; go to step S12.

S12, if the TvSH is more than 10 ℃, opening the TvSH-10 by the auxiliary electronic expansion valve, and returning to the step S3; otherwise, go to step S13;

s13, if the TvSH is less than 3 ℃, closing the valve by the auxiliary electronic expansion valve for 4 steps, otherwise, keeping the opening degree of the auxiliary electronic expansion valve; returning to the step S3;

s14, if the temperature is more than 10 ℃ and the TdSH is less than or equal to 20 ℃, turning to the step S15, otherwise, turning to the step S17;

s15, if k is larger than 3 ℃, the opening degree of the main electronic expansion valve is kept, otherwise, the main electronic expansion valve is closed by-2X (TdSH-25); go to step S16.

S16, if the TvSH is more than 5 ℃, keeping the opening degree of the auxiliary electronic expansion valve, otherwise, closing the valve-2 (TdSH-25) by the auxiliary electronic expansion valve; the process returns to step S3.

S17, closing a valve-3 (TdSH-25) by a main electronic expansion valve; auxiliary electronic expansion valve closing-3 (TdSH-25); the process returns to step S3.

Further, the minimum opening degree of the main electronic expansion valve is 70 steps, and the maximum opening degree is 450 steps; the minimum opening degree of the auxiliary electronic expansion valve is 0 step, and the maximum opening degree is 450 steps.

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