A low-temperature air source heat pump with improved air supply and enthalpy increase control method and control method thereof

Abstract

The present invention discloses a low-temperature air source heat pump and control method with an improved air-supply and enthalpy-increasing control method, which relates to the technical field of air conditioning and control method processing, including an air-supply and enthalpy-increasing compressor, one end of the compressor is connected to an exhaust pipe, and 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 to an outdoor heat exchanger. One end of the one-way valve assembly is fixedly connected to a liquid reservoir, and one end of the water-side heat exchanger is fixedly connected to one end of the gas distributor and one end of the compressor. On the one hand, it effectively solves the problems of the main electronic expansion valve and the auxiliary electronic expansion valve being out of coordination, inconsistent targets, and control effect offset. On the other hand, it also effectively solves the problems of the main electronic expansion valve and the auxiliary electronic expansion valve being over-adjusted or over-adjusted, resulting in unstable system state and long control time. The system state converges quickly, has good stability, and operates more reliably and stably.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning and control method processing, in particular to a low-temperature air source heat pump with an improved air supply and enthalpy increase control method and a control method. Background Art

[0002] At present, low-temperature air source heat pumps have been widely used for heating in northern regions. The air-injection enthalpy increase technology can provide normal heat pump heating in a low-temperature environment of -25°C. Therefore, the air-injection enthalpy increase technology has been widely used in low-temperature air source heat pump units.

[0003] The current control method for increasing enthalpy by air injection mainly controls the superheat of the air injection circuit and the exhaust temperature of the compressor through the auxiliary electronic expansion valve of the air injection circuit, or opens the auxiliary electronic expansion valve for protection control when the exhaust temperature is too high and the main electronic expansion valve is opened to the maximum. The current control method has the following disadvantages:

[0004] 1. The main electronic expansion valve controls its action according to the exhaust temperature and exhaust superheat, while the auxiliary electronic expansion valve controls its action according to the exhaust temperature, exhaust superheat and superheat of the air supply circuit. If the main and auxiliary electronic expansion valves are not controlled in a coordinated manner, there will be problems such as inconsistent control targets and offset of control effects.

[0005] 2. The main and auxiliary electronic expansion valves are controlled only based on the deviation between the exhaust temperature and exhaust superheat and the target value, without judging the trend of exhaust temperature changes over time. There is overshoot or overshoot, resulting in unstable system status and long control time.

[0006] Therefore, it is necessary to improve it in order to better meet market demand. To this end, we propose a low-temperature air source heat pump and control method with an improved air replenishment and enthalpy increase control method to solve the above problems. Summary of the Invention

[0007] The purpose of the present invention is to provide a low-temperature air source heat pump and control method with an improved air supply enthalpy increase control method, so as to solve the problem proposed in the above background technology that the main electronic expansion valve controls the action of the main electronic expansion valve according to the exhaust temperature and the exhaust superheat, and the auxiliary electronic expansion valve controls the action of the auxiliary electronic expansion valve according to the exhaust temperature, the exhaust superheat and the air supply circuit superheat. If the main and auxiliary electronic expansion valves are not controlled in a coordinated manner, there will be problems such as inconsistent control targets and offset of control effects.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: A low-temperature air source heat pump with an improved air supply and enthalpy increase control method, comprising an air supply and enthalpy increase compressor, one end of the compressor is connected to an exhaust pipe, and a four-way valve assembly is fixedly installed at the end of the exhaust pipe away from the compressor, and one end of the four-way valve assembly is fixedly connected to an outdoor heat exchanger. One end of the one-way valve assembly is fixedly connected to a liquid reservoir, and the water-side heat exchanger includes a shell and tube, a sleeve or a plate exchanger, and one end of the water-side heat exchanger is fixedly connected to an end of the gas separator and an end of the compressor. The one-way valve assembly, the liquid reservoir and the auxiliary electronic expansion valve, the one-way valve assembly, the economizer and the auxiliary electronic expansion valve are provided between which one end of the main electronic expansion valve connected to the outside of the muffler is fixedly connected to the compressor.

[0009] By adopting the above technical solution, on the one hand, it effectively solves the problems of uncoordinated control, inconsistent targets, and offset control effects between the main and auxiliary electronic expansion valves. On the other hand, it also effectively solves the problems of overshoot or overshoot of the main and auxiliary electronic expansion valves, which lead to unstable system state and long control time. The system state converges quickly, has good stability, and operates more reliably and stably. Moreover, the present invention can cover all low-temperature air-source heat pump units with air injection and enthalpy increase, and has wide application value.

[0010] Preferably, the exhaust side of the compressor is provided with an exhaust temperature probe for detecting the exhaust temperature Td, the exhaust side of the compressor is provided with an exhaust pressure sensor for detecting the exhaust pressure Pd, the inlet of the economizer air supply circuit is provided with a temperature probe for detecting the air supply inlet temperature Tv_in, and the outlet of the economizer air supply circuit is provided with a temperature probe for detecting the air supply outlet temperature Tv_out.

[0011] A control method for a low-temperature air source heat pump with an improved air supply and enthalpy increase control method comprises the following steps:

[0012] S1, the unit starts running;

[0013] S2. Detect the startup and running time of the compressor. If the startup and running time is ≥ 5 minutes, go to step S3; otherwise, go to step S4.

[0014] S3. If Td1>100°C, the main electronic expansion valve and the auxiliary electronic expansion valve are opened to the maximum, otherwise go to step S5;

[0015] S4, the main electronic expansion valve and the auxiliary electronic expansion valve maintain their initial openings, and return to step S2;

[0016] S5. If TdSH>30°C, go to step S6, otherwise go to step S8;

[0017] S6. If k>0°C, the main electronic expansion valve opens 2*(TdSH-25)+3*k; otherwise, the main electronic expansion valve opens 2*(TdSH-25); go to step S7

[0018] S7. If TvSH>5°C, the auxiliary electronic expansion valve opens by 2*(TdSH-25); otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3.

[0019] S8. If 20°C < TdSH ≤ 30°C, go to step S9; otherwise, go to step S14;

[0020] S9. If k>2°C, the main electronic expansion valve opens 3*k, and the process goes to step S10; otherwise, the process goes to step S11.

[0021] S10. If TvSH>5°C, the auxiliary electronic expansion valve opens by 2*k; otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3.

[0022] S11. If k is less than -2°C, the main electronic expansion valve is closed by -3*k; otherwise, the main electronic expansion valve remains open; go to step S12.

[0023] S12. If TvSH>10°C, the auxiliary electronic expansion valve opens TvSH-10, and the process returns to step S3; otherwise, the process goes to step S13;

[0024] S13. If TvSH is less than 3°C, the auxiliary electronic expansion valve closes for 4 steps; otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3.

[0025] S14. If 10°C < TdSH ≤ 20°C, go to step S15; otherwise, go to step S17;

[0026] S15. If k>3°C, the main electronic expansion valve maintains its opening; otherwise, the main electronic expansion valve closes by -2*(TdSH-25); and the process goes to step S16.

[0027] S16. If TvSH>5°C, the auxiliary electronic expansion valve maintains its opening; otherwise, the auxiliary electronic expansion valve closes by -2*(TdSH-25); and the process returns to step S3.

[0028] S17, the main electronic expansion valve closes valve-3* (TdSH-25); the auxiliary electronic expansion valve closes valve-3* (TdSH-25); and the process returns to step S3.

[0029] Furthermore, 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.

[0030] The beneficial effects of the present invention are:

[0031] The present invention combines components such as a main electronic expansion valve and an auxiliary electronic expansion valve, resulting in a rational design, clear logic, and convenient control. This effectively addresses the issues of uncoordinated control, inconsistent targets, and offset control effects between the main and auxiliary electronic expansion valves. It also effectively addresses the issues of overshoot or overshoot of the main and auxiliary electronic expansion valves, leading to unstable system states and prolonged control times. The system achieves rapid state convergence, excellent stability, and more reliable and stable operation. Furthermore, the present invention can cover all low-temperature air-source heat pump units with air injection and enthalpy increase, and has broad application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure and system principle of the present invention.

[0033] Figure 2 This is a control flow chart of the present invention.

[0034] In the figure: 1. Compressor; 2. Four-way valve assembly; 3. Outdoor heat exchanger; 4. Heat exchange fan; 5. One-way valve assembly; 6. Main electronic expansion valve; 7. Economizer; 8. Auxiliary electronic expansion valve; 9. Muffler; 10. Liquid receiver; 11. Water-side heat exchanger; 12. Gas separator. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Example: Figure 1-2 As shown, the present invention provides a low-temperature air-source heat pump with an improved air-compensation and heat-increasing control method, comprising an air-compensation and heat-increasing compressor 1, one end of which is connected to an exhaust pipe. A four-way valve assembly 2 is fixedly mounted on the end of the exhaust pipe remote from the compressor 1, and one end of the four-way valve assembly 2 is fixedly connected to an outdoor heat exchanger 3. Compressor 1 compresses low-pressure, low-temperature refrigerant into high-temperature, high-pressure, superheated gas, which then flows through the exhaust pipe to the four-way valve assembly 2 and then to the outdoor heat exchanger 3 for condensation.

[0037] The outdoor heat exchanger 3 is equipped with a heat exchange fan 4, and one end of the outdoor heat exchanger 3 is fixedly connected to a one-way valve assembly 5. An economizer 7 and an auxiliary electronic expansion valve 8 are located between the one-way valve assembly 5 and the liquid reservoir 10. A main electronic expansion valve 6 is located between the one-way valve assembly 5, the economizer 7, and the auxiliary electronic expansion valve 8. After condensing in the outdoor heat exchanger, the refrigerant passes through the one-way valve assembly 5 and reaches the economizer 7. There, it undergoes heat exchange with the refrigerant in the air supply circuit that has been throttled by the auxiliary electronic expansion valve 8, thereby producing subcooled, high-pressure, and medium-temperature refrigerant. One end of the one-way valve assembly 5 is fixedly connected to the liquid reservoir 10. The subcooled, high-pressure, and medium-temperature refrigerant is throttled by the main electronic expansion valve 6 and then passes through the one-way valve assembly 5 to reach the liquid reservoir 10. Furthermore, one end of the liquid reservoir 10 is fixedly connected to a water-side heat exchanger 11. After passing through the liquid reservoir 10, the refrigerant reaches the water-side heat exchanger 11.

[0038] The water-side heat exchanger 11 includes a shell and tube, a sleeve or a plate exchanger. One end of the water-side heat exchanger 11 is fixedly connected to a gas separator 12, and the end of the gas separator 12 away from the water-side heat exchanger 11 is fixedly connected to one end of the compressor 1. The outside of the economizer 7 is connected to a muffler 9, 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, a sleeve or a plate exchanger. After the refrigerant exchanges heat with water, low-pressure and low-temperature superheated steam is obtained, which returns to the gas separator 12 through a four-way valve and then returns to the compressor 1 through the gas separator. The refrigerant in the air supply circuit after throttling by the auxiliary electronic expansion valve 8 obtains medium-pressure and medium-temperature superheated steam after heat exchange with the economizer 7. After the muffler 9 eliminates pulsation and noise, it returns to the medium-pressure chamber of the compressor 1.

[0039] An exhaust temperature probe for detecting the exhaust temperature Td is provided on the exhaust side of the compressor 1, an exhaust pressure sensor for detecting the exhaust pressure Pd is provided on the exhaust side of the compressor 1, a temperature probe for detecting the air inlet temperature Tv_in is provided at the inlet of the air supply circuit of the economizer 7, and a temperature probe for detecting the air outlet temperature Tv_out is provided at the outlet of the air supply circuit of the economizer 7. A controller is provided inside the compressor 1, and the controller calculates the corresponding condensation temperature Tc according to the exhaust pressure.

[0040] If the current exhaust temperature, exhaust pressure, and condensing temperature are Td1, Pd1, and Tc1, and the exhaust temperature one valve adjustment cycle ago is Td0, the controller calculates the exhaust superheat (TdSH) based on the current exhaust temperature and condensing temperature (Td1 - Tc1). The controller also calculates the supply air superheat (TvSH) based on the economizer supply air circuit inlet and outlet temperatures (Tv_out - Tv_in). The exhaust temperature trend (k) is calculated as Td1 - Td0, where k > 0 indicates an increase in exhaust temperature and k < 0 indicates a decrease. A larger absolute value indicates a stronger trend.

[0041] A control method for a low-temperature air source heat pump with an improved air supply and enthalpy increase control method comprises the following steps:

[0042] S1, the unit starts running;

[0043] S2. Detect the startup and running time of the compressor. If the startup and running time is ≥ 5 minutes, go to step S3; otherwise, go to step S4.

[0044] S3. If Td1>100°C, the main electronic expansion valve and the auxiliary electronic expansion valve are opened to the maximum, otherwise go to step S5;

[0045] S4, the main electronic expansion valve and the auxiliary electronic expansion valve maintain their initial openings, and return to step S2;

[0046] S5. If TdSH>30°C, go to step S6, otherwise go to step S8;

[0047] S6. If k>0°C, the main electronic expansion valve opens 2*(TdSH-25)+3*k; otherwise, the main electronic expansion valve opens 2*(TdSH-25); go to step S7

[0048] S7. If TvSH>5°C, the auxiliary electronic expansion valve opens by 2*(TdSH-25); otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3.

[0049] S8. If 20°C < TdSH ≤ 30°C, go to step S9; otherwise, go to step S14;

[0050] S9. If k>2°C, the main electronic expansion valve opens 3*k, and the process goes to step S10; otherwise, the process goes to step S11.

[0051] S10. If TvSH>5°C, the auxiliary electronic expansion valve opens by 2*k; otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3.

[0052] S11. If k is less than -2°C, the main electronic expansion valve is closed by -3*k; otherwise, the main electronic expansion valve remains open; go to step S12.

[0053] S12. If TvSH>10°C, the auxiliary electronic expansion valve opens TvSH-10, and the process returns to step S3; otherwise, the process goes to step S13;

[0054] S13. If TvSH is less than 3°C, the auxiliary electronic expansion valve closes for 4 steps; otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3.

[0055] S14. If 10°C < TdSH ≤ 20°C, go to step S15; otherwise, go to step S17;

[0056] S15. If k>3°C, the main electronic expansion valve maintains its opening; otherwise, the main electronic expansion valve closes by -2*(TdSH-25); and the process goes to step S16.

[0057] S16. If TvSH>5°C, the auxiliary electronic expansion valve maintains its opening; otherwise, the auxiliary electronic expansion valve closes by -2*(TdSH-25); and the process returns to step S3.

[0058] S17, the main electronic expansion valve closes valve-3* (TdSH-25); the auxiliary electronic expansion valve closes valve-3* (TdSH-25); and the process returns to step S3.

[0059] Furthermore, 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.

[0060] During operation, compressor 1 compresses low-pressure, low-temperature refrigerant into high-temperature, high-pressure, superheated gas. The gas then flows through the exhaust pipe to the four-way valve assembly 2 and then to the outdoor heat exchanger 3 for condensation. After condensation by the outdoor heat exchanger 3, the refrigerant passes through the one-way valve assembly 5 and reaches the economizer 7. It then undergoes heat exchange with the refrigerant in the air supply circuit, which has been throttled by the auxiliary electronic expansion valve 8, thereby producing subcooled, high-pressure, medium-temperature refrigerant. This refrigerant is throttled by the main electronic expansion valve 6 and then passes through the one-way valve assembly 5 to the liquid reservoir 10. After passing through the liquid reservoir 10, the refrigerant reaches the water-side heat exchanger 11. After exchanging heat with water, the refrigerant produces low-pressure, low-temperature, superheated vapor, which then flows through the four-way valve back to the gas separator 12 and then back to compressor 1. The refrigerant in the air supply circuit, which has been throttled by the auxiliary electronic expansion valve 8, undergoes heat exchange in the economizer 7 to produce medium-pressure, medium-temperature superheated vapor. This vapor is then returned to the medium-pressure chamber of compressor 1 after passing through the muffler 9 to eliminate pulsation and noise. The exhaust temperature probe on the exhaust side of compressor 1 detects the exhaust temperature Td, the exhaust pressure sensor detects the exhaust pressure Pd, the temperature probe at the inlet of the supply air circuit of supply air economizer 7 detects the supply air inlet temperature Tv_in, and the temperature probe at the outlet of the supply air circuit of supply air economizer 7 detects the supply air outlet temperature Tv_out. The controller calculates the corresponding condensing temperature Tc based on the exhaust pressure. The current exhaust temperature, exhaust pressure, and condensing temperature are Td1, Pd1, and Tc1, and the exhaust temperature one valve adjustment cycle ago is Td0. The controller calculates the exhaust superheat TdSH = Td1 - Tc1 based on the current exhaust temperature and condensing temperature. The controller calculates the supply air superheat TvSH = Tv_out - Tv_in based on the inlet and outlet temperatures of the economizer supply air circuit. The exhaust temperature change trend k = Td1 - Td0, where k > 0 indicates an increase in exhaust temperature and k < 0 indicates a decrease in exhaust temperature. A larger absolute value indicates a stronger trend.

[0061] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A control method for a low-temperature air source heat pump with an improved air supply and enthalpy increase control method, comprising an air supply and enthalpy increase compressor (1), characterized in that: One end of the compressor (1) is connected to an exhaust pipe, and a four-way valve assembly (2) is fixedly installed on the end of the exhaust pipe away from the compressor (1). One end of the four-way valve assembly (2) is fixedly connected to an outdoor heat exchanger (3), and the outdoor heat exchanger (3) is provided with a heat exchange fan (4). One end of the outdoor heat exchanger (3) is fixedly connected to a one-way valve assembly (5); One end of the one-way valve assembly (5) is fixedly connected to a liquid reservoir (10), one end of the liquid reservoir (10) is fixedly connected to a water-side heat exchanger (11), the water-side heat exchanger (11) comprises a shell and tube, a sleeve or a plate exchanger, one end of the water-side heat exchanger (11) is fixedly connected to a gas separator (12), and one end of the gas separator (12) away from the water-side heat exchanger (11) is fixedly connected to one end of the compressor (1); An economizer (7) and an auxiliary electronic expansion valve (8) are provided between the one-way valve assembly (5) and the liquid reservoir (10), and a main electronic expansion valve (6) is provided between the one-way valve assembly (5), the economizer (7) and the auxiliary electronic expansion valve (8); 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); an exhaust temperature probe for detecting the exhaust temperature Td is provided on the exhaust side of the compressor (1), an exhaust pressure sensor for detecting the exhaust pressure Pd is provided on the exhaust side of the compressor (1), a temperature probe for detecting the exhaust inlet temperature Tv_in is provided on the inlet of the air supply circuit of the economizer (7), and a temperature probe for detecting the exhaust outlet temperature Tv_out is provided on the outlet of the air supply circuit of the economizer (7); The steps include: S1, the unit starts running; S2. Detect the startup and running time of the compressor. If the startup and running time is ≥ 5 minutes, go to step S3; otherwise, go to step S4. S3. If Td1>100°C, the main electronic expansion valve and the auxiliary electronic expansion valve are opened to the maximum, otherwise go to step S5; S4, the main electronic expansion valve and the auxiliary electronic expansion valve maintain their initial openings, and return to step S2; S5. If TdSH>30°C, go to step S6, otherwise go to step S8; S6. If k>0°C, the main electronic expansion valve opens 2*(TdSH-25)+3*k; otherwise, the main electronic expansion valve opens 2*(TdSH-25); go to step S7 S7. If TvSH>5°C, the auxiliary electronic expansion valve opens by 2*(TdSH-25); otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3. S8. If 20°C < TdSH ≤ 30°C, go to step S9; otherwise, go to step S14; S9, if k>2°C, then open the main electronic expansion valve 3*k, and go to step S10; otherwise, go to step S11; S10. If TvSH>5°C, the auxiliary electronic expansion valve opens by 2*k; otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3. S11. If k is less than -2°C, the main electronic expansion valve is closed by -3*k; otherwise, the main electronic expansion valve remains open; go to step S12; S12. If TvSH>10°C, the auxiliary electronic expansion valve opens TvSH-10, and the process returns to step S3; otherwise, the process goes to step S13; S13. If TvSH is less than 3°C, the auxiliary electronic expansion valve closes for 4 steps; otherwise, the auxiliary electronic expansion valve remains open; and the process returns to step S3. S14. If 10°C < TdSH ≤ 20°C, go to step S15; otherwise, go to step S17; S15. If k>3°C, the main electronic expansion valve remains open; otherwise, the main electronic expansion valve is closed by -2*(TdSH-25); then go to step S16; S16. If TvSH>5°C, the auxiliary electronic expansion valve maintains its opening; otherwise, the auxiliary electronic expansion valve closes by -2*(TdSH-25); and returns to step S3. S17, the main electronic expansion valve closes valve-3*(TdSH-25); the auxiliary electronic expansion valve closes valve-3*(TdSH-25); return to step S3; Furthermore, 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.

Images