A multi-functional experimental system of a direct expansion solar air source heat pump with variable internal pressure ratio

Abstract

A multi-functional variable internal pressure ratio direct expansion solar air source heat pump experimental system, which relates to the technical fields of solar energy and heat pump. It includes a variable frequency compressor, an oil separator, a check valve, a four-way reversing valve, an air-cooled condenser, a water-cooled condenser, a liquid receiver, an intermediate cooler, a dryer filter, a finned tube evaporator, a solar collector evaporator, a variable frequency water pump, a water tank, a normally closed solenoid valve, a normally open solenoid valve, an electronic expansion valve, and a manual valve; and it can change the internal pressure ratio by selecting the series connection or individual operation of the high and low pressure stage compressors according to different outdoor ambient temperature conditions and required heating capacities, so as to make it closer to the actual external pressure ratio. It can be used to supply warm air and cold air for indoor heating, and can also produce hot water and cold water and use the water tank to store heat and cold; this system includes 33 operating modes, including 27 modes for heating and 6 modes for cooling.

Description

Technical Field

[0001] The invention relates to the technical field of solar energy and heat pumps, and in particular to a multifunctional direct expansion solar air source heat pump experimental system with variable internal pressure ratio. Background Art

[0002] The trend of pursuing environmental protection in countries around the world is becoming more and more clear. Fossil fuels are no longer the energy that people most want to use in the future due to their environmental problems. In recent years, my country has greatly increased the use of wind energy and solar energy. The direct expansion solar air source heat pump is very suitable for use in areas rich in solar energy because of its environmental protection, energy saving and convenient use. In order to adapt to the dark and low temperature environment at night, the air source heat pump with single and double-stage compression cycle or quasi-two-stage compression cycle can maintain a high energy efficiency ratio and ensure stable heating at an outdoor temperature of -25℃.

[0003] The existing direct expansion solar air source heat pump has two forms: single-stage compression and quasi-two-stage compression. In the single-stage compression type, the air-cooled finned tube evaporator is simply replaced with a solar thermal collector evaporator or simply connected in parallel with it. This system has low compressor energy efficiency and unstable heating. The current direct expansion solar air source heat pump is mainly based on the quasi-two-stage compression cycle. When running this cycle, the air supply method is used to achieve two-stage compression. Because the angle between the air supply port and the air intake port and the exhaust port is fixed during the design and manufacturing of the quasi-two-stage compressor, the internal compression ratio cannot be changed. In other words, once the quasi-two-stage compressor is manufactured, the ratio of its air supply pressure to the air intake pressure is determined, and the ratio of its exhaust pressure to the air supply pressure is also determined. That is to say, although the suction pressure is constantly changing, the air supply pressure and the exhaust pressure can only change proportionally with it, and the ratio of the primary compression exhaust volume to the secondary compression exhaust volume cannot be freely changed. When running the direct expansion solar quasi-two-stage compression heat pump cycle, the solar radiation intensity changes over time, so the evaporation pressure of the collector plate also changes continuously, while the condenser pressure generally does not increase, which causes the external pressure ratio to change continuously, and the quasi-two-stage compressor cycle cannot change the internal pressure ratio. At this time, the external pressure ratio and the internal pressure ratio are seriously mismatched, which will cause problems such as reduced gas transmission efficiency and rapid reduction of system energy efficiency ratio, which is very uneconomical. Although the existing solar coupled air source heat pump method can solve the problem of unstable suction pressure, most of them need to set up a hot water storage tank outdoors. For cold areas, the antifreeze problem of water tanks, pumps, and pipelines must be considered, which is extremely inconvenient to use, and this form of heat pump cannot take into account the cooling demand in summer. Summary of the invention

[0004] The object of the present invention is to provide a multi-functional variable internal pressure ratio direct expansion solar air source heat pump system that can adjust the internal pressure ratio, i.e., the ratio of the compressor discharge pressure to the suction pressure, in a timely manner according to the external pressure ratio, i.e., the ratio of the actual condensation pressure to the evaporation pressure; and can select series connection or separate independent operation of the primary and high-pressure stage compressors according to different outdoor ambient temperature conditions and required heating capacities. It can be used for heating and cooling air in the room, and can also produce hot water and cold water and store heat and cold in a water tank. It is a multi-functional direct expansion solar air source heat pump system; this system includes 33 operating modes, including 27 modes for heating and 6 modes for cooling; the present invention uses two variable frequency compressors. When a two-stage compression cycle is adopted, the compressors operate in series, and different gas transmission ratios can be achieved by adjusting the speed ratio, which can improve the energy efficiency ratio.

[0005] The technical solution adopted to achieve the object of the present invention is as follows:

[0006] A multi-functional variable internal pressure ratio direct expansion solar air source heat pump system, comprising a first variable frequency compressor (1), a first oil separator (2), a first check valve (3), a second variable frequency compressor (4), a second oil separator (5), a four-way reversing valve (6), an air-cooled heat exchanger (7), a water-cooled heat exchanger (8), a liquid receiver (9), an intermediate cooler (10), a dryer filter (11), a second check valve (12), a finned tube heat exchanger (13), a solar collector evaporator (14), a variable frequency water pump (15), a water tank (16), a first variable frequency fan (17), a second variable frequency fan (18), a first normally closed solenoid valve (B1), a third normally closed solenoid valve (B3), a fourth normally closed solenoid valve (B4), a sixth normally closed solenoid valve (B6), a seventh normally closed solenoid valve (B7), an eighth normally closed solenoid valve (B8), a second normally open solenoid valve (K2), a fifth normally open solenoid valve (K5), a first expansion valve (P1), a second expansion valve (P2), a third expansion valve (P3), a first manual valve (S1), a second manual valve (S2), a third manual valve (S3);

[0007] The exhaust port of the first variable-frequency compressor (1) is divided into two paths through the first oil separator (2). One path is connected to the suction port of the first variable-frequency compressor (1) through the eighth normally-closed solenoid valve (B8), and the other path is further divided into two branches through the first check valve (3) and is respectively connected to the second normally-open solenoid valve (K2) and the first normally-closed solenoid valve (B1). At the same time, the first normally-closed solenoid valve (B1) is connected to port D of the four-way reversing valve (6), and the second normally-open solenoid valve (K2) is connected to the suction port of the second variable-frequency compressor (4); the exhaust port of the variable-frequency compressor (4) is successively connected to port D of the four-way reversing valve (6) through the second oil separator (5) and the fourth normally-closed solenoid valve (B4); port C of the four-way reversing valve (6) is divided into two paths and is respectively connected to the inlet of the air-cooled heat exchanger (7) and the refrigerant-side inlet of the water-cooled heat exchanger (8); the outlet of the air-cooled heat exchanger (7) is connected to the accumulator (9) through the fifth normally-open solenoid valve (K5); the refrigerant-side outlet of the water-cooled heat exchanger (8) is connected to the accumulator (9) through the sixth normally-closed solenoid valve (B6); at the same time, the accumulator (9) is connected to the tube-side inlet of the shell-and-tube heat exchanger (10). The tube-side outlet of the shell-and-tube heat exchanger (10) is divided into two paths. One path is connected to the inlet of the dryer filter (11), and the other path is successively connected to the first expansion valve (P1), the first manual valve (S1) and the shell-side inlet of the shell-and-tube heat exchanger (10); the shell-side outlet of the shell-and-tube heat exchanger (10) is connected to the suction of the second variable-frequency compressor (4) through the second check valve (12); the outlet of the dryer filter (11) is divided into two paths. One path is successively connected to the inlet of the finned-tube heat exchanger (13) through the second expansion valve (P2) and the second manual valve (S2), and the other path is successively connected to the inlet of the solar collector evaporator (14) through the third expansion valve (P3) and the third manual valve (S3); the outlet of the finned-tube heat exchanger (13) is connected to port E of the four-way reversing valve (6); at the same time, the solar collector evaporator (14) is connected to port E of the four-way reversing valve (6) through the seventh normally-closed solenoid valve (B7); port S of the four-way reversing valve (6) is divided into two paths. One path is connected to the suction port of the second variable-frequency compressor (4) through the third normally-closed solenoid valve (B3), and the other path is connected to the suction port of the first variable-frequency compressor (1); the return water side of the water-cooled heat exchanger (8) is connected to the water tank (16) through the variable-frequency water pump (15), and at the same time, the water tank (16) is connected to the water supply side of the water-cooled heat exchanger (8).

[0008] The first variable-frequency fan (17) is matched with the air-cooled heat exchanger (7), and the second variable-frequency fan (18) is matched with the finned-tube heat exchanger (13).

[0009] The air-cooled heat exchanger (7), the water-cooled heat exchanger (8) and the water tank (16) are located indoors;

[0010] The first variable-frequency compressor (1), the first oil separator (2), the variable-frequency compressor (4), the second oil separator (5), the four-way reversing valve (6), the accumulator (9), the intermediate cooler (10), the dryer filter (11), the finned-tube heat exchanger (13) and the solar collector evaporator (14) are located outdoors.

[0011] In the present invention, the variable-frequency compressor in the heat pump compressor unit is any one of a piston compressor, a scroll compressor, a rotary compressor, a screw compressor, and a sliding vane compressor.

[0012] In the present invention, the first expansion valve (P1), the second expansion valve (P2), and the third expansion valve (P3) in the multi-functional internal pressure ratio variable direct expansion solar air source heat pump experimental system can be any one of an electronic expansion valve, a thermostatic expansion valve, a capillary tube, an orifice throttling device, and a manual throttle valve.

[0013] The above system realizes different function switches by controlling different pairwise connections inside the C, S, D, and E of the four-way reversing valve (6). For example, when CD is connected and SE is connected, the heating mode is realized; when CS is connected and DE is connected, the cooling mode is realized; and so on.

[0014] In this application, the valves, variable-frequency compressors, four-way reversing valves, variable-frequency water pumps, variable-frequency fans, etc. that can be electrically controlled are all electrically connected to the control system, and the control system controls the switch and operation, etc.

[0015] This system realizes the switching between the two-stage compression intermediate incomplete cooling heating cycle, the single-stage compression heat pump cycle for directly collecting solar energy under low ambient temperature conditions, and the single-stage compression refrigeration cycle under high ambient temperature conditions. When the two-stage compression cycle is adopted, the first variable-frequency compressor (1) is used as the low-pressure stage compressor, and the second variable-frequency compressor (4) is used as the high-pressure stage compressor; users can realize the conversion of providing hot air, hot water, cold air, and cold water by switching the connection relationship; it has various functions, convenient mode switching, high equipment utilization rate, and high energy efficiency ratio. Description of the Drawings

[0016] Figure 1 The figure shows a schematic diagram of the operation of the multi-functional internal pressure ratio variable direct expansion solar air source heat pump experimental system of the present invention in the heating mode;

[0017] Figure 2 The figure shows a schematic diagram of the operation of the multi-functional internal pressure ratio variable direct expansion solar air source heat pump experimental system of the present invention in the cooling mode;

[0018] The first variable-frequency compressor (1), the first oil separator (2), the first check valve (3), the variable-frequency compressor (4), the second oil separator (5), the four-way reversing valve (6), the air-cooled heat exchanger (7), the water-cooled heat exchanger (8), the liquid receiver (9), the intercooler (10), the dryer filter (11), the second check valve (12), the finned-tube heat exchanger (13), the solar collector evaporator (14), the variable-frequency water pump (15), the water tank (16), the first variable-frequency fan (17), the second variable-frequency fan (18), the first normally-closed solenoid valve (B1), the third normally-closed solenoid valve (B3), the fourth normally-closed solenoid valve (B4), the sixth normally-closed solenoid valve (B6), the seventh normally-closed solenoid valve (B7), the eighth normally-closed solenoid valve (B8), the second normally-open solenoid valve (K2), the fifth normally-open solenoid valve (K5), the first expansion valve (P1), the second expansion valve (P2), the third expansion valve (P3), the first manual valve (S1), the second manual valve (S2), the third manual valve (S3);

[0019] The fg port of the shell-and-tube heat exchanger (10) is the tube side, and the hk shell side is the tube side. Specific embodiments

[0020] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments.

[0021] Embodiment 1

[0022] The present invention is as Figure 1 Figure 2As shown, it includes a first variable-frequency compressor (1), a first oil separator (2), a first check valve (3), a variable-frequency compressor (4), a second oil separator (5), a four-way reversing valve (6), an air-cooled heat exchanger (7), a water-cooled heat exchanger (8), a liquid receiver (9), an intermediate cooler (10), a dryer filter (11), a second check valve (12), a finned-tube heat exchanger (13), a solar collector evaporator (14), a variable-frequency water pump (15), a water tank (16), a first variable-frequency fan (17), a second variable-frequency fan (18), a first normally-closed solenoid valve (B1), a third normally-closed solenoid valve (B3), a fourth normally-closed solenoid valve (B4), a sixth normally-closed solenoid valve (B6), a seventh normally-closed solenoid valve (B7), an eighth normally-closed solenoid valve (B8), a second normally-open solenoid valve (K2), a fifth normally-open solenoid valve (K5), a first expansion valve (P1), a second expansion valve (P2), a third expansion valve (P3), a first manual valve (S1), a second manual valve (S2), and a third manual valve (S3); the exhaust of the first variable-frequency compressor (1) is divided into two paths by the first oil separator (2). One path is connected to the suction of the first variable-frequency compressor (1) through the eighth normally-closed solenoid valve (B8); the other path is further divided into two branches through the first check valve (3) and is respectively connected to the second normally-open solenoid valve (K2) and the first normally-closed solenoid valve (B1). Among them, the first normally-closed solenoid valve (B1) is connected to port D of the four-way reversing valve (6); the second normally-open solenoid valve (K2) is connected to the suction of the second variable-frequency compressor (4); the exhaust of the variable-frequency compressor (4) is connected to port D of the four-way reversing valve (6) through the second oil separator (5) and the fourth normally-closed solenoid valve (B4); the inlet of port D of the four-way reversing valve (6); port C of the four-way reversing valve (6) is divided into two paths and is respectively connected to the refrigerant sides of the air-cooled heat exchanger (7) and the water-cooled heat exchanger (8); the air-cooled heat exchanger (7) is connected to the liquid receiver (9) through the fifth normally-open solenoid valve (K5); the refrigerant side of the water-cooled heat exchanger (8) is connected to the liquid receiver (9) through the sixth normally-closed solenoid valve (B6); the liquid receiver (9) is connected to the tube side of the shell-and-tube heat exchanger (10); after the tube side of the shell-and-tube heat exchanger (10), it is divided into two paths. One path is connected to the dryer filter (11), and the other path is connected to the shell side of the shell-and-tube heat exchanger (10) through the first expansion valve (P1) and the first manual valve (S1); the shell side of the shell-and-tube heat exchanger (10) is connected to the suction of the second variable-frequency compressor (4) through the second check valve (12); after the dryer filter (11), it is connected to two paths. One path is connected to the finned-tube heat exchanger (13) through the second expansion valve (P2) and the second manual valve (S2); the other path is connected to the solar collector evaporator (14) through the third expansion valve (P3) and the third manual valve (S3); the finned-tube heat exchanger (13) is connected to port E of the four-way reversing valve (6); the solar collector evaporator (14) is connected to port E of the four-way reversing valve (6) through the seventh normally-closed solenoid valve (B7);The S port of the four-way reversing valve (6) is connected to two paths. One path is connected to the suction gas of the second variable-frequency compressor (4) through the third normally-closed solenoid valve (B3), and the other path is connected to the suction gas of the first variable-frequency compressor (1); the return water side of the water-cooled heat exchanger (8) is connected to the water tank (16) through a variable-frequency water pump (15), and the water tank (16) is connected to the water supply side of the water-cooled heat exchanger (8).;

[0023] The multi-functional internal pressure ratio variable direct expansion solar air source heat pump system of the present invention can achieve a two-stage compression intermediate imperfect cooling heating cycle, a single-stage compression heat pump cycle for directly collecting solar energy under low ambient temperature conditions, and a single-stage compression refrigeration cycle under high ambient temperature conditions, and can provide hot air, hot water, cold air, and cold water for users; it has diverse functions, convenient mode switching, high equipment utilization rate, and high energy efficiency ratio.

[0024] In winter, when the temperature is between -15°C and -25°C and the sunshine is sufficient, when the high internal pressure ratio mode is used to operate the two-stage compression cycle to produce hot air, the second normally open solenoid valve (K2) and the fifth normally open solenoid valve (K5) are opened; the fourth normally closed solenoid valve (B4) and the seventh normally closed solenoid valve (B7) are opened; the first normally closed solenoid valve (B1), the third normally closed solenoid valve (B3), the sixth normally closed solenoid valve (B6) and the eighth normally closed solenoid valve (B8) are closed; the first expansion valve (P1) and the third expansion valve (P3) are opened, and the second expansion valve (P2) is closed. The first manual valve (S1), the third manual valve (S3), and the second manual valve (S2) are opened; the D interface of the regulating four-way reversing valve is connected to the C interface, and the E interface of the regulating four-way reversing valve is connected to the S interface; the second variable frequency compressor (4) compresses the working medium into a high-temperature gas state and then enters the air-cooled heat exchanger (7) through the regulating four-way reversing valve for condensation, thereby generating a heating phenomenon. The condensed working medium enters the air-cooled heat exchanger (7) through the fifth normally open solenoid valve (K5), the liquid storage device (9), the intermediate cooler (10) pipe, the first expansion valve (P1), the first manual valve (S1), and the first manual valve (S1). The intermediate cooler (10) absorbs heat in the shell process by evaporation, reducing the superheat of the medium-pressure superheated steam, and then enters the solar thermal evaporator (14) through the drying filter (11), the third expansion valve (P3), and the third manual valve (S3) to evaporate and absorb solar radiation heat, and then enters the return air port of the low-pressure first variable frequency compressor (1) of the heat pump unit through the seventh normally closed solenoid valve (B7) and the E interface and S interface of the regulating four-way reversing valve; after the low-pressure first variable frequency compressor (1) compresses the working fluid, it passes through the first oil separator (2), the first check valve (3), The second normally open solenoid valve (K2) enters the shell side of the intercooler (10) and mixes with the low-temperature gaseous working medium to release heat, thereby reducing the superheat, and then enters the suction port of the second variable frequency compressor (4) to be compressed into a high-temperature gaseous state, and then enters the air-cooled heat exchanger (7) to be condensed, thereby generating a heating phenomenon, and this reciprocating cycle provides a continuous and stable heat supply; the eighth normally closed solenoid valve (B8) is an oil return valve, which is connected to the return port by a capillary tube and is opened for 10 minutes every 8 hours of operation; the high and low pressure level system variable flow regulation is achieved by controlling the rotation speed of the two variable frequency compressors in the heat pump unit.

[0025] In winter, when the temperature is between -15°C and -25°C and the sunshine is sufficient, when the high internal pressure ratio mode is used to operate the two-stage compression cycle to produce hot water, the second normally open solenoid valve (K2) in the heat pump unit is opened, and the fifth normally open solenoid valve (K5) is closed; the fourth normally closed solenoid valve (B4), the sixth normally closed solenoid valve (B6), and the seventh normally closed solenoid valve (B7) are opened; the first normally closed solenoid valve (B1), the third normally closed solenoid valve (B3), and the eighth normally closed solenoid valve (B8) are closed; the first expansion valve (P1) and the third expansion valve (P3) are opened, and the second expansion valve (P2) is closed; The first hand valve (S1), the third hand valve (S3), and the second hand valve (S2) are opened; the D interface of the regulating four-way reversing valve is connected to the C interface, and the E interface of the regulating four-way reversing valve is connected to the S interface; the first variable frequency compressor (1) serves as a low-pressure compressor, and the variable frequency compressor (4) serves as a high-pressure compressor; the second variable frequency compressor (4) compresses the working fluid into a high-temperature gas state, and then enters the water-cooled heat exchanger (8) through the regulating four-way reversing valve to condense, thereby generating a heating phenomenon, and the condensed working fluid is intermediately cooled by the normally open solenoid valve, the sixth normally closed solenoid valve (B6), and the liquid storage device (9). The steam passes through the tube side of the intercooler (10), the first expansion valve (P1), and the first manual valve (S1) to enter the shell side of the intercooler (10) to absorb heat in the process of evaporation, thereby reducing the superheat of the medium-pressure superheated steam. The steam then passes through the drying filter (11), the third expansion valve (P3), and the third manual valve (S3) to enter the solar heat collection evaporator (14) to evaporate and absorb solar radiation heat. The steam then passes through the seventh normally closed solenoid valve (B7) and the E interface and the S interface of the regulating four-way reversing valve to enter the return air port of the first variable frequency compressor (1) of the heat pump unit. After the working medium is compressed by the first variable frequency compressor (1), the working medium passes through the first oil separator. (2), the first non-return valve (3), the second normally open solenoid valve (K2) and the low-temperature gaseous working medium in the shell side of the intercooler (10) are mixed to release heat, reduce the superheat, and then enter the suction port of the second variable frequency compressor (4) to be compressed into a high-temperature gas, and then enter the water-cooled heat exchanger (8) to condense, thereby generating a heating phenomenon, and this reciprocating cycle provides a continuous and stable heat supply; the eighth normally closed solenoid valve (B8) is an oil return valve, which is connected to the return port by a capillary tube and is opened for 10 minutes every 8 hours of operation; the high and low pressure level system variable flow regulation is achieved by controlling the rotation speed of the two variable frequency compressors in the heat pump unit.

[0026] In winter, when the temperature is between -15°C and -25°C and the sunshine is insufficient, when the high internal pressure ratio mode is adopted to operate the two-stage compression cycle to heat the air, the solar heat collection evaporator (14) and the tube-fin heat exchanger (13) are connected in parallel to absorb heat. The second normally open solenoid valve (K2) and the fifth normally open solenoid valve (K5) in the heat pump unit are opened; the fourth normally closed solenoid valve (B4) and the seventh normally closed solenoid valve (B7) are opened; the first normally closed solenoid valve (B1), the third normally closed solenoid valve (B3), the sixth normally closed solenoid valve (B6), and the eighth normally closed solenoid valve (B8) are closed; the first expansion valve (P1), the second expansion valve (P2), and the third expansion valve (P3) are opened; the first hand valve (S1), the second hand valve (S2), and the third hand valve (S3) are opened; the D interface of the regulating four-way reversing valve is connected to the C interface, and the regulating four-way reversing valve The E interface is connected to the S interface; the first variable frequency compressor (1) serves as a low-pressure compressor, and the variable frequency compressor (4) serves as a high-pressure compressor; the second variable frequency compressor (4) compresses the working medium into a high-temperature gas state, and then enters the air-cooled heat exchanger (7) through the regulating four-way reversing valve for condensation, thereby generating a heating phenomenon; the condensed working medium enters the shell side of the intercooler (10) through the fifth normally open solenoid valve (K5), the liquid storage device (9) intercooler (10) pipe side, the first expansion valve (P1), and the first manual valve (S1) to evaporate and absorb heat, thereby reducing the superheat of the medium-pressure superheated steam, and then passes through the drying filter (11) to be divided into two paths, one of which is The first path passes through the third expansion valve (P3) and the third hand valve (S3) to enter the solar thermal evaporator (14) for evaporation, and then passes through the seventh normally closed solenoid valve (B7) to enter the E interface of the regulating four-way reversing valve after absorbing the heat of solar radiation; the other path passes through the second expansion valve (P2) and the second hand valve (S2) to enter the tube-fin heat exchanger (13) for evaporation, and then passes through the E interface of the regulating four-way reversing valve through the S interface to enter the return air port of the first variable frequency compressor (1) of the heat pump unit; the first variable frequency compressor (1) compresses the working fluid, and then passes through the first oil separator (2), the first check valve (3), the second normally open solenoid valve ( K2) mixes with the low-temperature gaseous working fluid in the shell side of the intercooler (10) to release heat, reduce the superheat, and then enters the suction port of the second variable frequency compressor (4) to be compressed into a high-temperature gas, enters the second oil separator (5), passes through the fourth normally closed solenoid valve (B4), adjusts the four-way reversing valve (6), and then enters the air-cooled heat exchanger (7) for condensation, thereby generating a heating phenomenon. This reciprocating cycle provides a continuous and stable heat supply; the eighth normally closed solenoid valve (B8) is an oil return valve, which is connected to a capillary tube and communicates with the return port, and is opened for 10 minutes every 8 hours of operation; the high and low pressure level system variable flow regulation is achieved by controlling the rotation speed of the two variable frequency compressors in the heat pump unit.

[0027] When the winter temperature is between -15°C and -25°C and the sunlight is insufficient, when operating the double-stage compression cycle to produce hot water in the high internal pressure ratio mode, the solar collector evaporator (14) and the finned tube heat exchanger (13) operate in parallel to absorb heat. The second normally open solenoid valve (K2) in the heat pump unit is opened, and the fifth normally open solenoid valve (K5) is closed; the fourth normally closed solenoid valve (B4), the sixth normally closed solenoid valve (B6), and the seventh normally closed solenoid valve (B7) are opened; the first normally closed solenoid valve (B1), the third normally closed solenoid valve (B3), and the eighth normally closed solenoid valve (B8) are closed; the first expansion valve (P1), the second expansion valve (P2), and the third expansion valve (P3) are opened; the first manual valve (S1), the second manual valve (S2), and the third manual valve (S3) are opened; the D port of the regulating four-way reversing valve is connected to the C port, and the E port of the regulating four-way reversing valve is connected to the S port; the first variable frequency compressor (1) serves as the low-pressure stage compressor, and the variable frequency compressor (4) serves as the high-pressure stage compressor; the second variable frequency compressor (4) compresses the working medium into high-temperature gaseous state and then enters the water-cooled heat exchanger (8) through the regulating four-way reversing valve to condense, generating a heating phenomenon. The condensed working medium passes through the sixth normally closed solenoid valve (B6), the liquid receiver (9), the tube side of the intercooler (10), the first expansion valve (P1), and the first manual valve (S1) and enters the shell side of the intercooler (10) to evaporate and absorb heat, reducing the superheat of the medium-pressure superheated steam. Then it passes through the dryer filter (11) and is divided into two paths. One path passes through the third expansion valve (P3) and the third manual valve (S3) and enters the solar collector evaporator (14) to evaporate. After absorbing the solar radiation heat, it then passes through the seventh normally closed solenoid valve (B7) and merges into the E port of the regulating four-way reversing valve; the other path passes through the second expansion valve (P2) and the second manual valve (S2) and enters the finned tube heat exchanger (13) to evaporate. After absorbing the outdoor air heat, it merges into the E port of the regulating four-way reversing valve and enters the suction port of the first variable frequency compressor (1) of the heat pump unit through the S port; after the first variable frequency compressor (1) compresses the working medium, it passes through the first oil separator (2), the first one-way valve (3), the second normally open solenoid valve (K2) and mixes with the low-temperature gaseous working medium in the shell side of the intercooler (10) to release heat and reduce the superheat, and then enters the suction port of the second variable frequency compressor (4) and is compressed into high-temperature gaseous state, enters the second oil separator (5), passes through the fourth normally closed solenoid valve (B4), the regulating four-way reversing valve (6) and then enters the air-cooled heat exchanger (7) to condense, generating a heating phenomenon. Such a cycle is repeated to continuously and stably supply heat; the eighth normally closed solenoid valve (B8) is an oil return valve, and a capillary tube is connected behind it and communicates with the suction port. It is opened for 10 minutes every 8 hours of operation; the variable flow regulation of the high and low pressure stage systems is achieved by controlling the rotational speeds of the two variable frequency compressors in the heat pump unit.

[0028] In winter, when the temperature is between -15°C and -25°C and the sunshine is insufficient, a high internal pressure ratio mode is used to operate a two-stage compression cycle to simultaneously produce hot air and hot water, and a solar heat collection evaporator (14) and a tube-fin heat exchanger (13) are used to absorb heat in parallel. The second normally open solenoid valve (K2) and the fifth normally open solenoid valve (K5) in the heat pump unit are opened; the fourth normally closed solenoid valve (B4), the sixth normally closed solenoid valve (B6), and the seventh normally closed solenoid valve (B7) are opened, and the first normally closed solenoid valve (B1), the third normally closed solenoid valve (B3), and the eighth normally closed solenoid valve (B8) are closed; the first expansion valve (P1), the second expansion valve (P2), and the third expansion valve (P3) are opened; the first manual valve (S1), the second manual valve (S2), and the third manual valve (S3) are opened; the D interface of the regulating four-way reversing valve is connected to the C interface, and the E interface of the regulating four-way reversing valve is connected to the S interface The first variable frequency compressor (1) serves as a low-pressure compressor, and the variable frequency compressor (4) serves as a high-pressure compressor; the second variable frequency compressor (4) compresses the working fluid into a high-temperature gas state, and then enters the air-cooled heat exchanger (7) and the water-cooled heat exchanger (8) through the regulating four-way reversing valve for condensation, thereby generating a heating phenomenon; the condensed working fluid respectively flows into the liquid storage tank (9) and the intermediate cooler (10) pipe side, the first expansion valve (P1), and the first manual valve (S1) through the fifth normally open solenoid valve (K5) and the sixth normally closed solenoid valve (B6), and enters the intermediate cooler (10) shell side to evaporate and absorb heat, thereby reducing the superheat of the medium-pressure superheated steam, and then passes through the drying filter (11) The heat exchanger is divided into two paths, one of which is to enter the solar heat collection evaporator (14) through the third expansion valve (P3) and the third manual valve (S3) for evaporation, and then enter the E interface of the regulating four-way reversing valve through the seventh normally closed solenoid valve (B7) after absorbing the solar radiation heat; the other path is to enter the tube-fin heat exchanger (13) through the second expansion valve (P2) and the second manual valve (S2) for evaporation, and then enter the E interface of the regulating four-way reversing valve through the S interface to enter the return air port of the first variable frequency compressor (1) of the heat pump unit after absorbing the outdoor air heat; the first variable frequency compressor (1) compresses the working fluid, and then enters the return air port of the first oil separator (2), the first check valve (3), and the second normally open solenoid valve (K 2) Mixed with the low-temperature gaseous working fluid in the shell side of the intercooler (10) to release heat, reduce the superheat, and then enter the suction port of the second variable frequency compressor (4) to be compressed into a high-temperature gas, enter the second oil separator (5), pass through the fourth normally closed solenoid valve (B4), adjust the four-way reversing valve (6), and then enter the air-cooled heat exchanger (7) and the water-cooled heat exchanger (8) for condensation, thereby generating a heating phenomenon. This reciprocating cycle provides a continuous and stable heat supply; the eighth normally closed solenoid valve (B8) is an oil return valve, which is connected to a capillary tube and communicates with the return port, and is opened for 10 minutes every 8 hours of operation; the high and low pressure level system variable flow regulation is achieved by controlling the rotation speed of the two variable frequency compressors in the heat pump unit.

[0029] When the winter temperature is between 0°C and -15°C and there is sufficient sunlight, when operating the single-stage compression cycle to produce hot air in the low internal pressure ratio mode, the first variable-frequency compressor (1) operates alone, and the solar collector evaporator (14) is used to absorb heat. The fifth normally open solenoid valve (K5) in the heat pump unit is opened, and (K2) is closed; the first normally closed solenoid valve (B1) and the seventh normally closed solenoid valve (B7) are opened; the third normally closed solenoid valve (B3), the fourth normally closed solenoid valve (B4), the sixth normally closed solenoid valve (B6), and the eighth normally closed solenoid valve (B8) are closed; the third expansion valve (P3) is opened, and the first expansion valve (P1) and the second expansion valve (P2) are closed; the first manual valve (S1), the third manual valve (S3), and the second manual valve (S2) are opened; the D port of the adjustable four-way reversing valve is connected to the C port, and the E port of the adjustable four-way reversing valve is connected to the S port; the first variable-frequency compressor (1) operates alone to compress the working medium into a high-temperature gas state and then enters the air-cooled heat exchanger (7) through the adjustable four-way reversing valve for condensation, generating a heating phenomenon. The condensed working medium passes through the fifth normally open solenoid valve (K5), the liquid receiver (9), the tube side of the intermediate cooler (10), then through the drying filter (11), the third expansion valve (P3), and the third manual valve (S3) to enter the solar collector evaporator (14) for evaporation, absorbing solar radiation heat, and then enters the suction port of the first variable-frequency compressor (1) of the heat pump unit through the seventh normally closed solenoid valve (B7) and the E port and S port of the adjustable four-way reversing valve (6); after the first variable-frequency compressor (1) compresses the working medium, it passes through the first oil separator (2), the first check valve (3), the first normally closed solenoid valve (B1), and then enters the air-cooled heat exchanger (7) through the C port and C port of the adjustable four-way reversing valve (6) for condensation, generating a heating phenomenon, and so on in a cycle, continuously and stably supplying heat; the eighth normally closed solenoid valve (B8) is an oil return valve, and a capillary tube is connected to the suction port and is opened for 10 minutes every 8 hours of operation; by controlling the speed of the first variable-frequency compressor of the heat pump unit, variable flow regulation of the system can be achieved.

[0030] When the winter temperature is between 0°C and -15°C and there is sufficient sunlight, when operating a single-stage compression cycle to produce hot water in a low internal pressure ratio mode, the low-pressure first variable-frequency compressor (1) operates alone, and the solar collector evaporator (14) is used to absorb heat. The second normally open solenoid valve (K2) and the fifth normally open solenoid valve (K5) in the heat pump unit are closed; the first normally closed solenoid valve (B1), the sixth normally closed solenoid valve (B6), and the seventh normally closed solenoid valve (B7) are opened; the third normally closed solenoid valve (B3), the fourth normally closed solenoid valve (B4), and the eighth normally closed solenoid valve (B8) are closed; the third expansion valve (P3) is opened, and the first expansion valve (P1) and the second expansion valve (P2) are closed; the first manual valve (S1), the third manual valve (S3), and the second manual valve (S2) are opened; the D port of the regulating four-way reversing valve is connected to the C port, and the E port of the regulating four-way reversing valve is connected to the S port; the first variable-frequency compressor (1) operates alone to compress the working medium into a high-temperature gas state, and then enters the water-cooled heat exchanger (8) through the D port and C port of the regulating four-way reversing valve (6) for condensation, generating a heating phenomenon. After condensation, the working medium passes through the sixth normally closed solenoid valve (B6), the liquid receiver (9), the tube side of the intermediate cooler (10), then through the drying filter (11), the third expansion valve (P3), and the third manual valve (S3) to enter the solar collector evaporator (14) for evaporation, absorbing solar radiation heat, and then enters the suction port of the first variable-frequency compressor (1) of the heat pump unit through the seventh normally closed solenoid valve (B7) and the E port and S port of the regulating four-way reversing valve (6); after the first variable-frequency compressor (1) compresses the working medium, it passes through the first oil separator (2), the first one-way valve (3), the first normally closed solenoid valve (B1), and then enters the air-cooled heat exchanger (7) through the D and C of the regulating four-way reversing valve (6) for condensation, generating a heating phenomenon, and so on in a reciprocating cycle, continuously and stably supplying heat; the eighth normally closed solenoid valve (B8) is an oil return valve, and is connected with a capillary tube to communicate with the suction port, and is opened for 10 minutes every 8 hours of operation; by controlling the speed of the first variable-frequency compressor of the heat pump unit, variable flow regulation of the system can be achieved.

[0031] When the winter temperature is between 0°C and -15°C and there is no sunlight, when operating a single-stage compression cycle to produce hot air in the low internal pressure ratio mode, the low-pressure first variable-frequency compressor (1) operates alone, and the finned tube heat exchanger (13) is used to absorb heat. The fifth normally open solenoid valve (K5) in the heat pump unit is opened, and the second normally open solenoid valve (K2) is closed; the first normally closed solenoid valve (B1), the sixth normally closed solenoid valve (B6), and the seventh normally closed solenoid valve (B7) are opened; the third normally closed solenoid valve (B3), the fourth normally closed solenoid valve (B4), and the eighth normally closed solenoid valve (B8) are closed; the second expansion valve (P2) is opened, and the first expansion valve (P1) and the third expansion valve (P3) are closed; the first manual valve (S1), the third manual valve (S3), and the second manual valve (S2) are opened; the D port of the adjustable four-way reversing valve is connected to the C port, and the E port of the adjustable four-way reversing valve is connected to the S port; the first variable-frequency compressor (1) operates alone to compress the working medium into a high-temperature gas state, and then enters the air-cooled heat exchanger (7) through the adjustable four-way reversing valve for condensation, generating a heating phenomenon. The condensed working medium passes through the fifth normally open solenoid valve (K5), the liquid receiver (9), the tube side of the intercooler (10), then through the drying filter (11), the second expansion valve (P2), and the second manual valve (S2) to enter the finned tube heat exchanger (13) for evaporation, absorbing the heat in the outdoor air, and then entering the suction port of the first variable-frequency compressor (1) of the heat pump unit through the E port and the S port of the adjustable four-way reversing valve (6); after the first variable-frequency compressor (1) compresses the working medium, it passes through the first oil separator (2), the first one-way valve (3), the first normally closed solenoid valve (B1), and then through the D and C of the adjustable four-way reversing valve (6) to enter the air-cooled heat exchanger (7) for condensation, generating a heating phenomenon, and so on in a reciprocating cycle to continuously and stably supply heat; the eighth normally closed solenoid valve (B8) is an oil return valve, and a capillary tube is connected to the suction port and is opened for 10 minutes every 8 hours of operation; by controlling the speed of the first variable-frequency compressor of the heat pump unit, variable flow regulation of the system can be achieved.

[0032] When the winter temperature is between 0°C and 15°C and there is sufficient sunlight, when operating a single-stage compression cycle to produce hot air in a low internal pressure ratio mode, the low-pressure variable-frequency compressor (4) operates alone, and the solar collector evaporator (14) is used to absorb heat. The fifth normally open solenoid valve (K5) in the heat pump unit is opened, and the second normally open solenoid valve (K2) is closed; the third normally closed solenoid valve (B3), the fourth normally closed solenoid valve (B4), and the seventh normally closed solenoid valve (B7) are opened; the first normally closed solenoid valve (B1), the sixth normally closed solenoid valve (B6), and the eighth normally closed solenoid valve (B8) are closed; the third expansion valve (P3) is opened, and the first expansion valve (P1) and the second expansion valve (P2) are closed; the first manual valve (S1), the third manual valve (S3), and the second manual valve (S2) are opened; the D port of the regulating four-way reversing valve (6) is connected to the C port, and the E port of the regulating four-way reversing valve is connected to the S port; the variable-frequency compressor (4) operates alone to compress the working medium into a high-temperature gas state, and then enters the regulating four-way reversing valve (6) through the second oil separator (5) and the fourth normally closed solenoid valve (B4), and then enters the air-cooled heat exchanger (7) to condense, generating a heating phenomenon. The condensed working medium passes through the fifth normally open solenoid valve (K5), the liquid receiver (9), the tube side of the intercooler (10), then through the drying filter (11), the third expansion valve (P3), and the third manual valve (S3) to enter the solar collector evaporator (14) to evaporate, absorbing solar radiation heat, and then through the seventh normally closed solenoid valve (B7), the E port and S port of the regulating four-way reversing valve (6), and the third normally closed solenoid valve (B3), and enters the suction port of the second variable-frequency compressor (4) of the heat pump unit; after the second variable-frequency compressor (4) compresses the working medium, it passes through the second oil separator (5) and the fourth normally closed solenoid valve (B4), and then through the D and C of the regulating four-way reversing valve (6) to enter the air-cooled heat exchanger (7) to condense, generating a heating phenomenon, and so on in a reciprocating cycle to continuously and stably supply heat; the system variable flow regulation is achieved by controlling the speed of the second variable-frequency compressor in the heat pump unit.

[0033] When the winter temperature is between 0°C and 15°C and there is no sunlight, when using a single-stage compression cycle with a low internal pressure ratio mode to produce hot water, the low-pressure first variable-frequency compressor (1) operates alone, and the finned tube heat exchanger (13) is used to absorb heat. The second normally open solenoid valve (K2) and the fifth normally open solenoid valve (K5) in the heat pump unit are closed; the first normally closed solenoid valve (B1) and the sixth normally closed solenoid valve (B6) are opened; the third normally closed solenoid valve (B3), the fourth normally closed solenoid valve (B4), the seventh normally closed solenoid valve (B7), and the eighth normally closed solenoid valve (B8) are closed; the second expansion valve (P2) is opened, and the first expansion valve (P1) and the third expansion valve (P3) are closed; the first manual valve (S1), the third manual valve (S3), and the second manual valve (S2) are opened; the D port of the regulating four-way reversing valve is connected to the C port, and the E port of the regulating four-way reversing valve is connected to the S port; the first variable-frequency compressor (1) compresses the working medium into a high-temperature gas state and then enters the water-cooled heat exchanger (8) through the regulating four-way reversing valve for condensation, generating a heating phenomenon. The condensed working medium passes through the sixth normally closed solenoid valve (B6), the liquid receiver (9), the tube side of the intercooler (10), then through the drying filter (11), the second expansion valve (P2), and the second manual valve (S2) to enter the finned tube heat exchanger (13) for evaporation, absorbing heat from the outdoor air, and then entering the suction port of the first variable-frequency compressor (1) of the heat pump unit through the E and S ports of the regulating four-way reversing valve (6); after the first variable-frequency compressor (1) compresses the working medium, it passes through the first oil separator (2), the first one-way valve (3), the first normally closed solenoid valve (B1), and then enters the water-cooled heat exchanger (8) through the D and C ports of the regulating four-way reversing valve (6) for condensation, generating a heating phenomenon, and so on in a reciprocating cycle to continuously and stably supply heat; the eighth normally closed solenoid valve (B8) is an oil return valve, and there is a capillary tube connected to the suction port and it is opened for 10 minutes every 8 hours of operation; the system variable flow regulation is achieved by controlling the rotational speed of the first variable-frequency compressor in the heat pump unit.

[0034] When the temperature in summer is higher than 35°C, the low internal pressure ratio mode can meet the cooling demand. When the single-stage compression cycle cooling wind is running, the first variable frequency compressor (1) and the second variable frequency compressor (4) are operated in parallel, the air-cooled heat exchanger (7) is used for cooling, and the tube-fin heat exchanger (13) releases heat. The second normally open solenoid valve (K2) in the heat pump unit is closed, and the fifth normally open solenoid valve (K5) is opened; the first normally closed solenoid valve (B1), the third normally closed solenoid valve (B3), and the fourth normally closed solenoid valve (B4) are opened; the sixth normally closed solenoid valve (B6), the seventh normally closed solenoid valve (B7), and the eighth normally closed solenoid valve (K8) are opened. The normally closed solenoid valve (B8) is closed; the second expansion valve (P2) is opened, and the first expansion valve (P1) and the third expansion valve (P3) are closed; the first manual valve (S1), the third manual valve (S3), and the second manual valve (S2) are opened; the D interface of the regulating four-way reversing valve is connected to the E interface, and the C interface of the regulating four-way reversing valve is connected to the S interface; the first variable frequency compressor (1) and the second variable frequency compressor (4) are operated in parallel to compress the working fluid into a high-temperature gas state, which then passes through the regulating four-way reversing valve and enters the tube-fin heat exchanger (13) for condensation, releasing heat to the outdoor air, and the condensed working fluid passes through the second The fluid passes through the hand valve (S2), the drying filter (11), the intermediate cooler (10) pipe line, and then enters the air heat exchanger (7) through the liquid storage device (9) to evaporate, thereby generating a refrigeration phenomenon to cool the indoor air, and then passes through the C and S of the regulating four-way reversing valve (6) to be divided into two paths, one of which enters the return air port of the first variable frequency compressor (1) of the heat pump unit; after the first variable frequency compressor (1) compresses the working fluid, it passes through the first oil separator (2), the first non-return valve (3), and the first normally closed solenoid valve (B1), and then enters the D and E of the regulating four-way reversing valve (6); the other path passes through the third normally closed solenoid valve (B3) and enters the heat pump unit. The return air port of the second variable frequency compressor (4) of the pump unit compresses the working fluid, passes through the second oil separator (5) and the fourth normally closed solenoid valve (B4), and then enters the D and E of the regulating four-way reversing valve (6), and then enters the tube-fin heat exchanger (13) for condensation, releasing the waste heat to the outdoor air, and repeats this cycle to provide a continuous and stable cooling supply; the eighth normally closed solenoid valve (B8) is an oil return valve, which is connected to the return air port by a capillary tube and is opened for 10 minutes every 8 hours of operation; the cooling capacity can be adjusted by controlling the parallel operation and single operation of the two variable frequency compressors in the heat pump unit and the rotation speed of the two compressors.

[0035] In the multifunctional variable internal pressure ratio direct expansion solar air source heat pump experimental system of the present invention, the switching between the heat pump cycle and the refrigeration cycle can be achieved by reversing the regulating four-way reversing valve; the switching between collecting solar energy and collecting air energy can be achieved by turning on and off the solenoid valve; furthermore, by turning on and off the solenoid valve and starting, stopping, and adjusting the speed of the compressor, the change of the internal pressure ratio of the heat pump unit and the change of the gas volume ratio of the high and low pressure stages can be realized, thereby improving the energy efficiency ratio of the system. The production of hot air, hot water, cold air, and cold water can be achieved by turning on and off the solenoid valve. Although the present invention has been described above in conjunction with the drawings, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many variations without departing from the purpose of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A multifunctional variable internal pressure ratio direct expansion solar air source heat pump system, characterized in that, Including a first variable-frequency compressor (1), a first oil separator (2), a first check valve (3), a second variable-frequency compressor (4), a second oil separator (5), a four-way reversing valve (6), an air-cooled heat exchanger (7), a water-cooled heat exchanger (8), a liquid receiver (9), an intermediate cooler (10), a dryer filter (11), a second check valve (12), a tube-fin heat exchanger (13), a solar collector evaporator (14), a variable-frequency water pump (15), a water tank (16), a first variable-frequency fan (17), a second variable-frequency fan (18), a first normally-closed solenoid valve (B1), a third normally-closed solenoid valve (B3), a fourth normally-closed solenoid valve (B4), a sixth normally-closed solenoid valve (B6), a seventh normally-closed solenoid valve (B7), an eighth normally-closed solenoid valve (B8), a second normally-open solenoid valve (K2), a fifth normally-open solenoid valve (K5), a first expansion valve (P1), a second expansion valve (P2), a third expansion valve (P3), a first manual valve (S1), a second manual valve (S2), a third manual valve (S3); The exhaust port of the first variable-frequency compressor (1) is divided into two paths through the first oil separator (2). One path is connected to the suction port of the first variable-frequency compressor (1) through the eighth normally-closed solenoid valve (B8), and the other path is further divided into two branches through the first check valve (3) and connected to the second normally-open solenoid valve (K2) and the first normally-closed solenoid valve (B1) respectively. At the same time, the first normally-closed solenoid valve (B1) is connected to port D of the four-way reversing valve (6), and the second normally-open solenoid valve (K2) is connected to the suction port of the second variable-frequency compressor (4); the exhaust port of the variable-frequency compressor (4) is successively connected to port D of the four-way reversing valve (6) through the second oil separator (5) and the fourth normally-closed solenoid valve (B4); port C of the four-way reversing valve (6) is divided into two paths and connected to the inlet of the air-cooled heat exchanger (7) and the refrigerant-side inlet of the water-cooled heat exchanger (8) respectively; the outlet of the air-cooled heat exchanger (7) is connected to the accumulator (9) through the fifth normally-open solenoid valve (K5); the refrigerant-side outlet of the water-cooled heat exchanger (8) is connected to the accumulator (9) through the sixth normally-closed solenoid valve (B6); at the same time, the accumulator (9) is connected to the tube-side inlet of the shell-and-tube heat exchanger (10). The tube-side outlet of the shell-and-tube heat exchanger (10) is divided into two paths. One path is connected to the inlet of the dryer filter (11), and the other path is successively connected to the inlet of the shell side of the shell-and-tube heat exchanger (10) through the first expansion valve (P1) and the first manual valve (S1); the shell-side outlet of the shell-and-tube heat exchanger (10) is connected to the suction of the second variable-frequency compressor (4) through the second check valve (12); the outlet of the dryer filter (11) is divided into two paths. One path is successively connected to the inlet of the finned-tube heat exchanger (13) through the second expansion valve (P2) and the second manual valve (S2), and the other path is successively connected to the inlet of the solar collector evaporator (14) through the third expansion valve (P3) and the third manual valve (S3); the outlet of the finned-tube heat exchanger (13) is connected to port E of the four-way reversing valve (6); at the same time, the solar collector evaporator (14) is connected to port E of the four-way reversing valve (6) through the seventh normally-closed solenoid valve (B7); port S of the four-way reversing valve (6) is divided into two paths. One path is connected to the suction port of the second variable-frequency compressor (4) through the third normally-closed solenoid valve (B3), and the other path is connected to the suction port of the first variable-frequency compressor (1); the return water side of the water-cooled heat exchanger (8) is connected to the water tank (16) through the variable-frequency water pump (15), and at the same time, the water tank (16) is connected to the water supply side of the water-cooled heat exchanger (8).

2. A multifunctional variable internal pressure ratio direct expansion solar air source heat pump system according to claim 1, characterized in that, The first variable-frequency fan (17) is matched with the air-cooled heat exchanger (7), and the second variable-frequency fan (18) is matched with the finned-tube heat exchanger (13).

3. A multifunctional variable internal pressure ratio direct expansion solar air source heat pump system according to claim 1, characterized in that The air-cooled heat exchanger (7), the water-cooled heat exchanger (8), and the water tank (16) are located indoors; The first variable-frequency compressor (1), the first oil separator (2), the variable-frequency compressor (4), the second oil separator (5), the four-way reversing valve (6), the accumulator (9), the intermediate cooler (10), the dryer filter (11), the finned-tube heat exchanger (13), and the solar collector evaporator (14) are located outdoors.

4. A multifunctional variable internal pressure ratio direct expansion solar air source heat pump system according to claim 1, characterized in that The variable-frequency compressor in the heat pump compressor unit is any one of piston type, scroll type, rotor type, screw type, and vane type compressors.

5. A multifunctional variable internal pressure ratio direct expansion solar air source heat pump system according to claim 1, characterized in that, The first expansion valve (P1), the second expansion valve (P2), and the third expansion valve (P3) are any one of an electronic expansion valve, a thermostatic expansion valve, a capillary tube, an orifice throttling device, and a manual throttle valve.

6. A multifunctional variable internal pressure ratio direct expansion solar air source heat pump system according to claim 1, characterized in that, It is possible to control different pairwise connections inside C, S, D, and E of the four-way reversing valve (6) to achieve different function switches; when CD is connected and SE is connected, the heating mode is achieved, and when CS is connected and DE is connected, the cooling mode is achieved.

7. The operation mode of a multifunctional variable internal pressure ratio direct expansion solar air source heat pump system according to any one of claims 1-6, characterized in that, It includes 33 operating modes, including 27 during heating and 6 during cooling; two variable-frequency compressors are used. When a two-stage compression cycle is adopted, the compressors operate in series, and different gas transmission ratios can be achieved by adjusting the speed ratio, which can improve the energy efficiency ratio.

8. According to the operation mode of claim 7, characterized in that, According to different outdoor ambient temperature conditions and required heating capacities, the high-pressure and low-pressure stage compressors are selected to operate in series or separately; it is used to supply warm air and cold air indoors, and can also produce hot water and cold water and utilize the water tank to store heat and cold.

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