Auxiliary system for low-temperature starting of heat pump system and control method

Abstract

The invention belongs to the technical field of heat pumps, and discloses an auxiliary system for low-temperature starting of a heat pump system and a control method.The auxiliary system for low-temperature starting of the heat pump system comprises a preheating bypass loop, a pressure difference bypass valve, an electromagnetic two-way valve and an injection nozzle. The pre-heating bypass loop is arranged at the outlet end of the pre-heating bypass loop, so that during low-temperature starting, part of high-temperature refrigerant is directly conveyed into the gas-liquid separator through the compressor, liquid refrigerant accumulated in the gas-liquid separator is heated, and the injection nozzle used for injecting multiple strands of rotating refrigerant into the bottom of the gas-liquid separator is arranged at the outlet end of the pre-heating bypass loop. Therefore, the contact area is increased, the heat transfer efficiency is remarkably improved by forming turbulent flow, the preheating time is shortened, the starting efficiency is improved, the evaporation rate is improved, the probability that a liquid refrigerant directly enters the compressor to cause liquid impact is reduced, and the safety protection performance of the compressor is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pumps, and in particular to an auxiliary system and a control method for low-temperature startup of a heat pump system. Background Art

[0002] A heat pump system is a device that transfers low-temperature heat energy to high-temperature heat energy by using a small amount of electrical energy to drive based on the reverse Carnot cycle principle. Its core functions include highly efficient and energy-saving heating, cooling, and hot water supply, and it is widely used in fields such as construction, industry, and transportation. The main components of the system mainly include core components such as an evaporator, a compressor, a condenser, and an expansion valve.

[0003] When starting the heat pump system in a low-temperature environment, the refrigerant is prone to accumulating at the bottom of the gas-liquid separator. The core function of the gas-liquid separator is to prevent liquid refrigerant from entering the compressor. During low-temperature startup, the heat exchange efficiency of the evaporator is insufficient, resulting in incomplete evaporation of the refrigerant and a relatively high proportion of liquid refrigerant. At this time, too much liquid refrigerant accumulates at the bottom of the gas-liquid separator, and the liquid may enter the compressor with the gas, causing liquid slugging and damaging the compressor. Moreover, since the liquid refrigerant enters the compressor directly without being fully vaporized, the suction superheat of the compressor is insufficient, affecting the heating performance of the heat pump, thus greatly reducing the startup efficiency.

[0004] Therefore, there is an urgent need for a control method and an auxiliary system for low-temperature startup of a heat pump system to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide an auxiliary system and a control method for low-temperature startup of a heat pump system, which have a short preheating time, a high startup efficiency, and high safety protection.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] On the one hand, an auxiliary system for low-temperature startup of a heat pump system is provided. The auxiliary system for low-temperature startup of a heat pump system is used to preheat the liquid refrigerant accumulated at the bottom of the gas-liquid separator in the heat pump system. The heat pump system also includes a compressor for supplying refrigerant. The auxiliary system for low-temperature startup of a heat pump system includes:

[0008] A preheating bypass circuit, the preheating bypass circuit includes an inlet end and an outlet end. The inlet end is connected to the outlet of the compressor, and the outlet end is connected to the bottom of the gas-liquid separator;

[0009] A differential pressure bypass valve, the differential pressure bypass valve is provided on the preheating bypass circuit;

[0010] An electromagnetic two-way valve, the electromagnetic two-way valve is provided between the differential pressure bypass valve and the gas-liquid separator;

[0011] An injection nozzle, which is connected to the outlet end of the preheating bypass circuit, and is used to inject multiple rotating refrigerant streams into the bottom of the gas-liquid separator.

[0012] Optionally, a filter element is provided at the connection between the injection nozzle and the outlet end.

[0013] Optionally, the auxiliary system for low-temperature startup of the heat pump system further includes a check valve, which is arranged between the injection nozzle and the solenoid two-way valve.

[0014] Optionally, the auxiliary system for low-temperature startup of the heat pump system further includes a capillary tube, which is arranged between the differential pressure bypass valve and the solenoid two-way valve.

[0015] On the other hand, a control method for low-temperature startup of a heat pump system is provided. The control method for low-temperature startup of the heat pump system is used to control the auxiliary system for low-temperature startup of the heat pump system as described in any one of the above, and the control method for low-temperature startup of the heat pump system includes the following steps:

[0016] S1. Start the heat pump system in a low-power mode;

[0017] S2. Adjust the opening degree of the differential pressure bypass valve to 50%;

[0018] S3. Operate the solenoid two-way valve in an intermittent pulse mode, inject the refrigerant into the bottom of the gas-liquid separator, and continue for the first time t1;

[0019] S4. After the first time ends, operate the solenoid two-way valve in a normally open mode;

[0020] S5. The heat pump system further includes a temperature sensor, which is used to detect the temperature value T of the gas-liquid separator 气分 , when T 气分 ≥25 °C, switch the solenoid two-way valve back to the intermittent pulse mode and maintain for the second time t2;

[0021] S6. After the second time ends, close the preheating bypass circuit, exit the low-temperature mode, and the heat pump system starts normal heating cycle.

[0022] Optionally, the heat pump system further includes a pressure sensor, which is used to detect the pressure value P of the gas-liquid separator 气分 , according to the formula ; dynamically adjust the opening degree of the differential pressure bypass valve, where:

[0023] Q 旁通 is the opening degree of the differential pressure bypass valve;

[0024] K is a system constant, and its value range satisfies 0.8 ≤ K ≤ 1.2;

[0025] T 环境 is the temperature of the current environment;

[0026] T 基准 is the set environmental temperature reference value, and satisfies T 基准 = -35°C.

[0027] Optionally, in step S3, the intermittent pulse mode is specifically to open the electromagnetic two-way valve for 2 seconds and close the electromagnetic two-way valve for 1 second.

[0028] Optionally, in step S1, the following steps are further included:

[0029] S11. Turn on the compressor and operate it in a low-frequency mode of 10 Hz;

[0030] S12. The heat pump system includes an evaporator, a condenser, and an electronic expansion valve connected between the evaporator and the condenser. Adjust the opening of the electronic expansion valve to 70%.

[0031] Optionally, in step S3, the first time t1 satisfies 2 min ≤ t1 ≤ 3 min.

[0032] Optionally, in step S5, the second time t2 satisfies t2 = 30 s.

[0033] Advantages of the present invention:

[0034] The present invention provides an auxiliary system for low-temperature startup of a heat pump system. The auxiliary system for low-temperature startup of the heat pump system enables a part of the high-temperature refrigerant to be directly transported from the compressor to the gas-liquid separator during low-temperature startup by providing a preheating bypass circuit with a differential pressure bypass valve and an electromagnetic two-way valve between the compressor and the gas-liquid separator, thereby heating the liquid refrigerant accumulated in the gas-liquid separator. And by providing an injection nozzle for injecting multiple rotating refrigerant jets into the bottom of the gas-liquid separator at the outlet end of the preheating bypass circuit, not only the contact area is increased, but also by forming a turbulent flow, the heat transfer efficiency is significantly improved. It not only shortens the preheating time, improves the startup efficiency, but also increases the evaporation rate, reduces the probability of liquid slugging when the liquid refrigerant directly enters the compressor, and improves the safety protection for the compressor.

[0035] The present invention also provides a control method for controlling the above-mentioned auxiliary system for low-temperature startup of a heat pump system. The electromagnetic two-way valve is controlled in an intermittent pulse mode to inject high-temperature refrigerant, so that when injecting, the surface tension of the liquid refrigerant accumulated at the bottom of the gas-liquid separator is destroyed by the shock wave, thereby increasing the contact area between the high-temperature refrigerant and the liquid refrigerant accumulated at the bottom of the gas-liquid separator, accelerating the temperature rise of the liquid refrigerant accumulated at the bottom of the gas-liquid separator, further shortening the preheating time, and improving the startup efficiency. Brief Description of the Drawings

[0036] Figure 1 is a schematic diagram of a heat pump system applying the auxiliary system for low-temperature startup of a heat pump system provided by the present invention;

[0037] Figure 2 is a schematic diagram of the installation position of the injection nozzle in the gas-liquid separator in the auxiliary system for low-temperature startup of a heat pump system provided by the present invention;

[0038] Figure 3 is a flowchart of the steps of the control method for low-temperature startup of a heat pump system provided by the present invention.

[0039] In the figure:

[0040] 100, compressor; 200, gas-liquid separator; 300, temperature sensor; 400, pressure sensor; 500, evaporator; 600, condenser; 700, electronic expansion valve; 800, accumulator; 900, economizer;

[0041] 1, preheating bypass circuit;

[0042] 2, differential pressure bypass valve;

[0043] 3, electromagnetic two-way valve;

[0044] 4, injection nozzle;

[0045] 5, filter element;

[0046] 6, check valve. Detailed Embodiments

[0047] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that for the sake of description, only parts related to the present invention are shown in the drawings, rather than all structures.

[0048] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected to", and "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0049] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

[0050] In the description of this embodiment, the orientation or positional relationships such as "above", "below", "right", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description and simplifying the operation, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0051] During low-temperature startup, the heat exchange efficiency of the evaporator is insufficient, resulting in incomplete evaporation of the refrigerant and a relatively high proportion of liquid refrigerant. At this time, too much liquid refrigerant accumulates at the bottom of the gas-liquid separator, and the liquid may enter the compressor with the gas, causing liquid hammer and damaging the compressor. Moreover, since the liquid refrigerant enters the compressor directly without being fully vaporized, the suction superheat of the compressor is insufficient, affecting the heating performance of the heat pump, thereby greatly reducing the startup efficiency.

[0052] Therefore, in order to shorten the preheating time, improve the startup efficiency, and enhance the safety protection performance, this embodiment provides an auxiliary system for the low-temperature startup of a heat pump system. The auxiliary system for the low-temperature startup of a heat pump system is used to preheat the liquid refrigerant accumulated at the bottom of the gas-liquid separator in the heat pump system, and the heat pump system further includes a compressor for supplying the refrigerant.

[0053] Such as Figures 1 to 2As shown in the figure, the auxiliary system for low-temperature startup of the heat pump system includes a preheating bypass circuit 1, a differential pressure bypass valve 2, an electromagnetic two-way valve 3, and an injection nozzle 4. The preheating bypass circuit 1 includes an inlet end and an outlet end. The inlet end is connected to the outlet of the compressor 100, and the outlet end is connected to the bottom of the gas-liquid separator 200. The differential pressure bypass valve 2 is arranged on the preheating bypass circuit 1. The electromagnetic two-way valve 3 is arranged between the differential pressure bypass valve 2 and the gas-liquid separator 200. The injection nozzle 4 is connected to the outlet end of the preheating bypass circuit 1. The injection nozzle 4 is used to inject multiple rotating refrigerant streams into the bottom of the gas-liquid separator 200.

[0054] The auxiliary system for low-temperature startup of the heat pump system is provided with a preheating bypass circuit 1 having a differential pressure bypass valve 2 and an electromagnetic two-way valve 3 between the compressor 100 and the gas-liquid separator 200. During low-temperature startup, a part of the high-temperature refrigerant is directly transported from the compressor 100 to the gas-liquid separator 200, thereby heating the liquid refrigerant accumulated in the gas-liquid separator 200. And by arranging an injection nozzle 4 for injecting multiple rotating refrigerant streams into the bottom of the gas-liquid separator 200 at the outlet end of the preheating bypass circuit 1, not only the contact area is increased, but also by forming a turbulent flow, the heat transfer efficiency is significantly improved. This not only shortens the preheating time, improves the startup efficiency, but also increases the evaporation rate, reduces the probability of liquid slugging when the liquid refrigerant directly enters the compressor 100, and improves the safety protection for the compressor 100.

[0055] In this embodiment, the injection nozzle 4 is designed based on a self-priming nozzle, and a honeycomb porous ceramic layer is provided thereon, which is convenient for dividing the refrigerant into multiple fine streams, thereby increasing the contact area with the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200. The porosity of the honeycomb porous ceramic layer is 30% to 40%, and its pore diameter is 1 mm to 2 mm. The self-priming nozzle is a nozzle with a special structure. Its main feature is that a spiral channel and a water flow rotating member are provided inside the nozzle, so that the ejected water jet is a rotating water jet, which has the advantages of strong diffusion ability and large impact area. Therefore, the injection nozzle 4 designed based on the self-priming nozzle makes the refrigerant have a certain rotational force when injecting the refrigerant, thereby forming a turbulent flow and significantly improving the heat transfer efficiency. Since the self-priming nozzle is a conventional solution in the prior art, no more details will be described here.

[0056] Optionally, a filter element 5 is provided at the connection between the injection nozzle 4 and the outlet end. By arranging the filter element 5 at the connection between the injection nozzle 4 and the outlet end, impurities in the refrigerant are intercepted. In this embodiment, the filter element 5 is a double-layer stainless steel filter screen, and its thickness range is 50 μm to 100 μm.

[0057] Optionally, the auxiliary system for the low-temperature startup of the heat pump system further includes a check valve 6, and the check valve 6 is arranged between the injection nozzle 4 and the electromagnetic two-way valve 3. By arranging the check valve 6 between the electromagnetic two-way valve 3 and the injection nozzle 4, the high-temperature refrigerant can only flow from the compressor 100 to the gas-liquid separator 200, avoiding the liquid refrigerant accumulated in the gas-liquid separator 200 from flowing back to the compressor 100 in reverse and causing liquid hammer, which may damage the compressor 100.

[0058] Optionally, the auxiliary system for the low-temperature startup of the heat pump system further includes a capillary tube, and the capillary tube is arranged between the differential pressure bypass valve 2 and the electromagnetic two-way valve 3. By arranging the capillary tube between the differential pressure bypass valve 2 and the electromagnetic two-way valve 3, the flow rate and pressure of the refrigerant are adjusted to ensure the stable operation of the system. In this embodiment, the inner diameter of the capillary tube is 1.0 mm.

[0059] In this embodiment, as Figures 1 to 3 shown, a control method for the low-temperature startup of the heat pump system is also provided. The control method for the low-temperature startup of the heat pump system is used to control the above-mentioned auxiliary system for the low-temperature startup of the heat pump system, and the control method for the low-temperature startup of the heat pump system includes the following steps:

[0060] S1. Start the heat pump system in the low-power mode;

[0061] S2. Adjust the opening degree of the differential pressure bypass valve 2 to 50%;

[0062] S3. Operate the electromagnetic two-way valve 3 in an intermittent pulse mode, inject the refrigerant into the bottom of the gas-liquid separator 200, and continue for the first time t1;

[0063] S4. After the first time ends, operate the electromagnetic two-way valve 3 in the normally open mode;

[0064] S5. The heat pump system further includes a temperature sensor 300, and the temperature sensor 300 is used to detect the temperature value T of the gas-liquid separator 200 气分 , when T 气分 ≥25 °C, switch the electromagnetic two-way valve 3 back to the intermittent pulse mode and maintain the second time t2;

[0065] S6. After the second time ends, close the preheating bypass circuit 1, exit the low-temperature mode, and the heat pump system starts the normal heating cycle.

[0066] The electromagnetic two-way valve 3 is controlled by an intermittent pulse mode to inject high-temperature refrigerant, so that the surface tension of the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200 is destroyed by the shock wave during injection, thereby increasing the contact area between the high-temperature refrigerant and the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, accelerating the temperature rise of the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, further shortening the preheating time, and improving the starting efficiency.

[0067] Among them, in this embodiment, in step S3, the electromagnetic two-way valve 3 operates in a pulse mode for the first time. In step S4, the electromagnetic two-way valve 3 is in an always-open mode. In step S5, the electromagnetic two-way valve 3 switches back to the pulse mode and continues for the second time. The main reason is that in the initial stage, it is necessary to use the shock wave formed by the pulse mode to destroy the surface tension of the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, so that the high-temperature refrigerant and the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200 are quickly mixed and heated up. After continuing for the first time, the preliminary heating of the liquid refrigerant is realized. At this time, there is no need to accelerate the heating by forming a shock wave. Therefore, the pulse mode is switched to the always-open mode, and the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200 is continuously heated by continuously inputting high-temperature refrigerant. As the temperature gradually rises, when the temperature satisfies T 气分 ≥25 °C, at this time, the requirements for the normal circulation operation of the heat pump system have been met, and there is no need to heat up anymore. At this time, the electromagnetic two-way valve 3 is switched back to the pulse mode. Its main purpose is to intermittently cut off the refrigerant flow through the pulse mode, so that the total amount of refrigerant entering the gas-liquid separator 200 per unit time is reduced, thereby reducing the heat input rate, maintaining the temperature, and maintaining it for the second time. After determining that its temperature is in a stable state, the low-temperature mode can be exited and the normal working mode of the heat pump system can be carried out.

[0068] Optionally, the heat pump system further includes a pressure sensor 400. The pressure sensor 400 is used to detect the pressure value P 气分 of the gas-liquid separator 200, and dynamically adjusts the opening of the differential pressure bypass valve 2 according to the formula ; where:

[0069] Q 旁通 is the opening of the differential pressure bypass valve 2;

[0070] K is a system constant, and its value range satisfies 0.8 ≤ K ≤ 1.2;

[0071] T 环境 is the temperature of the current environment;

[0072] T 基准 is the set ambient temperature reference value, and it satisfies T 基准 = -35 °C.

[0073] By detecting the pressure of the gas-liquid separator 200 and using the detected pressure value P 气分 , according to the formula , the opening degree of the differential pressure bypass valve 2 is dynamically adjusted to protect the pressure of the gas-liquid separator 200, avoiding excessive pressure values and damaging the gas-liquid separator 200.

[0074] It should be noted that when Q 旁通 ≥1, it is default that the differential pressure bypass valve 2 is fully opened.

[0075] Optionally, in step S3, the intermittent pulse mode is specifically to open the solenoid two-way valve for 2 seconds and close the solenoid two-way valve for 1 second. By opening for 2 seconds, refrigerant injection is allowed, and by closing for 1 second, flow truncation is achieved through interruption, so that the high-temperature refrigerant forms a "pulsed" transport mode to form a shock wave, breaking the surface tension of the liquid refrigerant accumulated at the bottom of the gas-liquid separator 200, thereby improving the heat transfer efficiency. And by using 2 seconds of opening and 1 second of closing as a cycle, when the high-temperature refrigerant is injected, it has a high injection frequency, thus ensuring the impact effect.

[0076] Optionally, in step S1, the following steps are further included:

[0077] S11. Start the compressor 100 and operate it in a low-frequency mode of 10 Hz;

[0078] S12. The heat pump system includes an evaporator 500, a condenser 600, and an electronic expansion valve 700 connected between the evaporator 500 and the condenser 600. Adjust the opening degree of the electronic expansion valve 700 to 70%.

[0079] By starting the compressor 100 at a low frequency of 10 Hz during low-temperature startup, the initial load of the compressor 100 is reduced, avoiding overload or overheating of the compressor 100 caused by a high compression ratio in a low-temperature environment, extending the equipment life. And by opening the electronic expansion valve 700 with an opening degree of 70%, on the one hand, it avoids insufficient heat absorption of the evaporator 500 or liquid refrigerant entering the compressor 100 due to too low evaporation pressure at low temperature, causing liquid hammer and damaging the compressor 100. On the other hand, by moderately throttling, the superheat degree of the refrigerant in the evaporator 500 is increased, ensuring sufficient evaporation and heat absorption, and enhancing the heat exchange effect in a low-temperature environment.

[0080] In this embodiment, the heat pump system further includes a liquid accumulator 800 and an economizer 900. The liquid accumulator 800 is connected between the economizer 900 and the evaporator 500, and the economizer 900 is connected between the liquid accumulator 800 and the condenser 600. By providing the liquid accumulator 800, the excess liquid in the refrigerant after condensation in the condenser 600 is stored, thereby avoiding liquid slugging, which may damage the compressor 100. By providing the economizer 900 in the heat pump circuit, the economizer 900 includes two circuits that divide the refrigerant into two paths. An electronic expansion valve 700 is provided on one of the circuits. The refrigerant throttles and evaporates by itself to absorb heat, thereby cooling the refrigerant in the other circuit. The cooled refrigerant in the other path enters the evaporator 500, improving the heat absorption efficiency of the evaporator 500. The refrigerant that throttles and evaporates by itself through the electronic expansion valve 700 directly returns to the compressor 100 to supply gas to the compressor 100.

[0081] Optionally, in step S3, the first time t1 satisfies 2 min ≤ t1 ≤ 3 min. By limiting the first time of the intermittent pulse mode of the electromagnetic two-way valve 3, the operation time is sufficient to ensure that the evaporation rate of the liquid refrigerant accumulated in the gas-liquid separator 200 reaches more than 95%.

[0082] Optionally, in step S5, the second time t2 satisfies t2 = 30 s. By limiting the second time t2 of the intermittent pulse mode of the electromagnetic two-way valve 3 in step S5 to satisfy t2 = 30 s, the temperature in the gas-liquid separator 200 is ensured to be stably maintained above 25°C, enabling the normal startup of the heat pump system. When the heat pump system is normally started, the operating frequency of the compressor 100 is increased to 45 Hz.

[0083] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments, and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. An auxiliary system for low-temperature startup of a heat pump system, characterized in that, The auxiliary system for low-temperature startup of the heat pump system is used to preheat the liquid refrigerant accumulated at the bottom of the gas-liquid separator (200) in the heat pump system. The heat pump system further includes a compressor (100) for supplying refrigerant. The auxiliary system for low-temperature startup of the heat pump system includes: A preheating bypass circuit (1), the preheating bypass circuit (1) including an inlet end and an outlet end, the inlet end being connected to the outlet of the compressor (100), and the outlet end being connected to the bottom of the gas-liquid separator (200); A differential pressure bypass valve (2), the differential pressure bypass valve (2) being provided on the preheating bypass circuit (1); An electromagnetic two-way valve (3), the electromagnetic two-way valve (3) being provided between the differential pressure bypass valve (2) and the gas-liquid separator (200); An injection nozzle (4), the injection nozzle (4) being connected to the outlet end of the preheating bypass circuit (1), and the injection nozzle (4) being used to inject multiple swirling streams of the refrigerant into the bottom of the gas-liquid separator (200).

2. The auxiliary system for low-temperature startup of a heat pump system according to claim 1, characterized in that, A filter element (5) is provided at the connection between the injection nozzle (4) and the outlet end.

3. The auxiliary system for low-temperature startup of a heat pump system according to claim 1, characterized in that The auxiliary system for low-temperature startup of the heat pump system further includes a check valve (6), the check valve (6) being provided between the injection nozzle (4) and the electromagnetic two-way valve (3).

4. The auxiliary system for low-temperature startup of a heat pump system according to claim 1, characterized in that, The auxiliary system for low-temperature startup of the heat pump system further includes a capillary tube, the capillary tube being provided between the differential pressure bypass valve (2) and the electromagnetic two-way valve (3).

5. Control method for low-temperature startup of heat pump system, characterized in that, The control method for low-temperature startup of the heat pump system is used to control the auxiliary system for low-temperature startup of the heat pump system according to any one of claims 1-4. The control method for low-temperature startup of the heat pump system includes the following steps: S1. Start the heat pump system in a low-power mode; S2. Adjust the opening degree of the differential pressure bypass valve (2) to 50%; S3. Operate the electromagnetic two-way valve (3) in an intermittent pulse mode, inject the refrigerant into the bottom of the gas-liquid separator (200), and continue for a first time t1; S4. After the first time ends, operate the electromagnetic two-way valve (3) in an always-open mode; S5. The heat pump system further includes a temperature sensor (300), and the temperature sensor (300) is used to detect the temperature value T of the gas-liquid separator (200). 气分 , when T 气分 ≥ 25°C, switch the electromagnetic two-way valve (3) back to the intermittent pulse mode and maintain it for a second time t2; S6. When the second time ends, close the preheating bypass circuit (1), exit the low-temperature mode, and the heat pump system starts a normal heating cycle.

6. The control method for low-temperature startup of a heat pump system according to claim 5, characterized in that, The heat pump system further includes a pressure sensor (400) for detecting the pressure value P of the gas-liquid separator (200). 气分 , according to the formula ; dynamically adjust the opening degree of the differential pressure bypass valve (2), where: Q 旁通 is the opening degree of the differential pressure bypass valve (2); K is a system constant, and the value range satisfies 0.8 ≤ K ≤ 1.2; T 环境 is the temperature of the current environment; T 基准 is the set reference value of the ambient temperature, and satisfies T 基准 = -35°C.

7. The control method for low-temperature startup of a heat pump system according to claim 5, characterized in that, In step S3, the intermittent pulse mode is specifically to open the electromagnetic two-way valve (3) for 2 seconds and close the electromagnetic two-way valve (3) for 1 second.

8. The control method for low-temperature startup of a heat pump system according to claim 5, characterized in that In step S1, the following steps are further included: S11. Start the compressor (100) and operate it in a low-frequency mode of 10 Hz; S12. The heat pump system includes an evaporator (500), a condenser (600), and an electronic expansion valve (700) connected between the evaporator (500) and the condenser (600). Adjust the opening degree of the electronic expansion valve (700) to 70%.

9. The control method for low-temperature startup of a heat pump system according to claim 5, wherein In step S3, the first time t1 satisfies 2 min ≤ t1 ≤ 3 min.

10. The control method for low-temperature startup of a heat pump system according to claim 5, characterized in that, In step S5, the second time t2 satisfies t2 = 30 s.

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