CN104061705B - Two-stage compression air conditioning system and control method thereof - Google Patents

Abstract

The invention discloses a two-stage compression air conditioning system and a control method thereof, wherein the air conditioning system comprises a two-stage compressor, a four-way reversing valve, an outdoor heat exchanger, a first throttling device, a flash evaporator, a second throttling device and an indoor heat exchanger, and the opening degrees of the first throttling device and the second throttling device are adjustable; the heat exchanger comprises an outdoor heat exchanger, a first heat exchange pipe of the heat exchanger, a second heat exchange pipe of the heat exchanger and a control valve, wherein the first heat exchange pipe of the heat exchanger is connected in series with a pipeline between an exhaust port of the two-stage compressor and a first end interface of the indoor heat exchanger, the second heat exchange pipe of the heat exchanger is connected in series with the bypass pipeline, and the control valve is used for selectively connecting or disconnecting the pipeline between the first end interface of the outdoor heat exchanger and the air suction port of the two-stage compressor and the bypass pipeline. The two-stage compression air-conditioning system can improve the operation efficiency of the system; and moreover, the defrosting speed is high, and the refrigerant which is not completely evaporated during defrosting can be prevented from entering the compressor.

Description

Two-stage compression air-conditioning system and its control method

technical field

The invention relates to the technical field of air conditioning, in particular to a two-stage compression air conditioning system and a control method thereof.

Background technique

At present, the intermediate air supply volume of the two-stage compression air conditioning system with a flash evaporator cannot be adjusted. When the compressor uses the same frequency, changes in other parameters in the system may cause fluctuations in the intermediate air supply volume, which will make the compressor run from the optimal state. efficiency point, causing the compressor not to operate at the best efficiency point.

In addition, the conventional defrosting method of the two-stage compression air-conditioning system is that during the heating process, when the defrosting condition is reached, the compressor is first stopped, and then turned on to the cooling mode for defrosting. When the defrosting is over, stop the machine, and then turn it back on to the heating mode. In this defrosting method, the compressor starts and stops twice, and the defrosting takes a long time. In addition, in the cooling mode, heat will be absorbed from the indoor environment, causing the indoor temperature to drop rapidly during the defrosting process, affecting the comfort of users. In order to solve the above problems in the traditional defrosting method, the prior art proposes a thermal storage defrosting method, which uses a heat accumulator installed on the compressor housing as the main low-temperature heat source in the defrosting working condition . When cooling or heating, the accumulator absorbs the waste heat of the compressor. When heating and defrosting, the four-way reversing valve does not change direction. After the refrigerant flows out of the indoor heat exchanger, it passes through the bypass pipeline connected in parallel with the electronic expansion valve. into the outdoor heat exchanger for defrosting. Although this defrosting method can solve the above-mentioned problems existing in the traditional defrosting method, since the defrosting method uses the heat generated by the compressor to store heat, the phase change temperature point of the phase change heat storage material used will inevitably be If the temperature is lower, the heat absorption and heat release speed of the heat storage material will be slower, so that the defrosting speed will be slower, and the defrosting time will be prolonged, which will also affect the heating effect and comfort. Especially for the two-stage compression air conditioning system with defrosting function, when heating, due to the existence of the flash evaporator, the refrigerant must be subcooled again when it flows through the flash evaporator, that is, the refrigerant flowing into the outdoor heat exchanger must be at At lower temperatures than with single-stage compression, frosting will be more severe and frequent, and therefore defrost slower. Moreover, defrosting when the heat stored in the heat accumulator is insufficient will cause a large amount of refrigerant that cannot be evaporated to enter the compressor, thereby posing a fatal threat to the reliability of the compressor.

Contents of the invention

Aiming at the current state of the art above, the technical problem to be solved by the present invention is to provide a two-stage compression air-conditioning system, in which the amount of air supply in the middle can be adjusted, and the defrosting speed is fast, which can avoid the refrigerant that cannot be completely evaporated during defrosting. Entering the compressor can adversely affect the compressor.

In order to solve the above technical problems, a two-stage compression air conditioning system provided by the present invention includes a two-stage compressor, a four-way reversing valve, an outdoor heat exchanger, a first throttling device, a flash evaporator, and a second throttling device and the indoor heat exchanger, the exhaust port and the suction port of the two-stage compressor are connected to the first port of the outdoor heat exchanger and the first port of the indoor heat exchanger through the four-way reversing valve. The second port of the outdoor heat exchanger communicates with the first port of the flash evaporator through the first throttling device, and the second port of the flash evaporator passes through the second section The flow device is connected with the second end interface of the indoor heat exchanger, and the third interface of the flash evaporator is connected with the air supply port of the two-stage compressor through the air supply pipeline;

The openings of the first throttling device and the second throttling device are adjustable;

It also includes a bypass line, a heat accumulator and a control valve, the bypass line is connected between the first port of the outdoor heat exchanger and the suction port of the two-stage compressor, the accumulator The heat exchanger has a first heat exchange tube and a second heat exchange tube, the first heat exchange tube is connected in series between the exhaust port of the two-stage compressor and the first end interface of the indoor heat exchanger On the road, the second heat exchange pipe is connected in series on the bypass pipe, and the control valve is used to selectively connect or disconnect the first port of the outdoor heat exchanger from the two-stage compressor. The pipeline between the suction port and the bypass pipeline.

In one of the embodiments, the two-stage compression air-conditioning system further includes a third throttling device, and the third throttling device is connected in series with the on the bypass line.

In one of the embodiments, the third throttling device is a capillary.

In one of the embodiments, the channel aperture of the control valve is smaller than the aperture of the refrigerant pipe, so that the refrigerant passing through the control valve is throttled and flows into the second heat exchange pipe of the heat accumulator.

In one of the embodiments, one end of the bypass pipeline is connected to the pipeline between the four-way reversing valve and the first port of the outdoor heat exchanger, and the other end is connected to the four-way reversing valve. On the pipeline between the reversing valve and the suction port of the two-stage compressor.

In one embodiment, both ends of the bypass pipeline are connected to the pipeline between the four-way reversing valve and the suction port of the two-stage compressor.

In one of the embodiments, the control valve is a three-way valve.

In one of the embodiments, both the first throttling device and the second throttling device are electronic expansion valves.

In one of the embodiments, an air supply valve is arranged on the air supply pipeline.

A control method for a two-stage compression air-conditioning system provided by the present invention includes:

During cooling or heating operation, the control valve connects the pipeline between the first end interface of the outdoor heat exchanger and the suction port of the two-stage compressor, disconnects the bypass pipeline, adjusting the flow rate of the refrigerant passing through the air supply pipeline by adjusting the opening of the first throttling device and/or the second throttling device;

During the defrosting operation, the control valve disconnects the pipeline between the first end interface of the outdoor heat exchanger and the suction port of the two-stage compressor, and connects the bypass pipeline.

In one of the embodiments, when the defrosting is running, the air supply line is disconnected.

Compared with the prior art, the two-stage compression air-conditioning system and its control method of the present invention, since the opening of the first throttling device and the second throttling device can be adjusted, by adjusting the first throttling device and/or the second throttling device The opening of the throttling device can adjust the flow rate of the refrigerant passing through the air supply pipeline, so that it can effectively adjust the intake air volume in the middle air supply section, so that the system can run near the best efficiency point and improve the operation of the system. efficiency; moreover, the two-stage compression air-conditioning system uses the high-temperature refrigerant directly discharged from the compressor to store heat, so a phase change heat storage material with a higher phase change temperature can be used, so that during defrosting, the phase change heat storage The temperature difference between the material and the refrigerant increases, the heat release speed of the phase change heat storage material is fast, and the corresponding defrosting speed will also be accelerated, ensuring the comfort of the user. Moreover, the accumulator has sufficient heat storage capacity during defrosting, which prevents the refrigerant from evaporating into the compressor and causing liquid shock, which poses a fatal threat to the reliability of the compressor.

The beneficial effects of the additional technical features of the present invention will be described in the specific embodiments of this specification.

Description of drawings

Fig. 1 is a system diagram of a two-stage compression air-conditioning system in one of the embodiments of the present invention;

Fig. 2 is a schematic flow chart of the two-stage compression air-conditioning system in Fig. 1 during refrigeration;

Fig. 3 is a schematic flow chart of the two-stage compression air-conditioning system in Fig. 1 during heating;

FIG. 4 is a schematic flow chart of the two-stage compression air-conditioning system in FIG. 1 during defrosting.

Explanation of reference signs: 1. Two-stage compressor; 2. Indoor heat exchanger; 3. Second throttling device; 4. Flash evaporator; 5. First throttling device; 6. Outdoor heat exchanger; 7. Three Through valve; 8. Four-way reversing valve; 9. Air supply valve; 10. Third throttling device; 11. Regenerator; 11a. First heat exchange tube; 11b. Second heat exchange tube; 12. Supplement 13. Bypass pipeline.

detailed description

The present invention will be described in detail below with reference to the accompanying drawings and examples. It should be noted that, in the case of no conflict, the following embodiments and features in the embodiments can be combined with each other.

As shown in Figure 1, the two-stage compression air conditioning system in one of the embodiments of the present invention includes a two-stage compressor 1, a four-way reversing valve 8, an outdoor heat exchanger 6, a first throttling device 5, a flash evaporator 4, The second throttling device 3, the indoor heat exchanger 2, the bypass pipeline 13, the heat accumulator 11 and the control valve.

Wherein, the exhaust port and the suction port of the two-stage compressor 1 are connected to the first port 6a of the outdoor heat exchanger 6 and the first port of the indoor heat exchanger 2 through the four-way reversing valve 8 . One end interface 2a is connected, the second end interface 6b of the outdoor heat exchanger 6 is communicated with the first interface of the flash evaporator 4 through the first throttling device 5, and the second end interface 6b of the flash evaporator 4 The interface communicates with the second end interface 2b of the indoor heat exchanger 2 through the second throttling device 3, and the third interface of the flash evaporator 4 communicates with the two-stage compressor 1 through the air supply pipeline 12. The gas supply port is connected. The opening of the first throttling device 5 and the second throttling device 3 can be adjusted, so that the passage can be adjusted by adjusting the opening of the first throttling device 5 and/or the second throttling device 3 The flow rate of the refrigerant in the air supply pipeline 12 can effectively adjust the intake air volume in the middle air supply section, so that the system can operate near the optimum efficiency point, and the operating efficiency of the system can be improved.

The bypass pipeline 13 is connected between the first end interface 6a of the outdoor heat exchanger 6 and the suction port of the two-stage compressor 1. In this embodiment, the bypass pipeline 13 One end is connected to the pipeline between the four-way reversing valve 8 and the first port of the outdoor heat exchanger 6, and the other end is connected to the four-way reversing valve 8 and the two-stage compressor 1 on the pipeline between the suction ports. Of course, both ends of the bypass pipeline 13 can also be connected to the pipeline between the four-way reversing valve 8 and the suction port of the two-stage compressor 1 .

The heat accumulator 11 has a first heat exchange pipe 11a and a second heat exchange pipe 11b, and the first heat exchange pipe 11a is connected in series between the exhaust port of the two-stage compressor 1 and the four-way reversing valve. 8, the first heat exchange tube 11a can also be connected to the pipeline between the four-way reversing valve 8 and the first end interface of the indoor heat exchanger 2; the second heat exchange tube 11b connected in series to the bypass line 13.

The control valve is used to selectively connect or disconnect the pipeline between the first port of the outdoor heat exchanger 6 and the suction port of the two-stage compressor 1 and the bypass pipeline 13. Preferably, the control valve is a three-way valve 7, and the three-way valve 7 can also be replaced by two two-way valves.

The two-stage compression air-conditioning system of this embodiment uses the high-temperature refrigerant directly discharged from the compressor to store heat, so a phase change heat storage material with a higher phase change temperature can be used, so that when defrosting, the phase change heat storage material As the temperature difference with the refrigerant increases, the heat release speed of the phase change heat storage material is fast, and the corresponding defrosting speed will also be accelerated, ensuring the comfort of the user. Moreover, the heat accumulator 11 has sufficient heat storage during defrosting, which prevents the incompletely evaporated refrigerant from entering the compressor and causing liquid hammer, thereby posing a fatal threat to the reliability of the compressor.

Preferably, a third throttling device 10 is further included, and the third throttling device 10 is connected in series on the bypass line 13 on the inlet side of the second heat exchange tube 11b. Further preferably, the third throttling device 10 is a capillary. In this way, the refrigerant at the outlet of the outdoor heat exchanger 6 is throttled by the capillary tube, and then enters the accumulator 11 to absorb heat and evaporate, which is conducive to the complete evaporation of the liquid refrigerant, and avoids the liquid shock caused by the endlessly evaporated refrigerant entering the two-stage compressor 1 . Of course, the capillary tube can also be replaced by a three-way valve 7 with a channel aperture smaller than that of the refrigerant pipe, so that the three-way valve 7 can also play a throttling role.

Preferably, the air supply line 12 is provided with an air supply valve 9 , and the conduction and disconnection of the air supply line 12 are controlled by the air supply valve 9 .

The present invention also provides a control method for a two-stage compression air-conditioning system, comprising the following steps:

Step 1. During cooling or heating operation, the three-way valve 7 connects the pipeline between the first end interface of the outdoor heat exchanger 6 and the suction port of the two-stage compressor 1, disconnects In the bypass pipeline 13, the supplementary air valve 9 is opened, and the gas passing through the supplementary supplementary pipeline 12 is adjusted by adjusting the opening of the first throttling device 5 and/or the second throttling device 3 . The flow rate of refrigerant. The specific process is as follows:

When the system is in cooling operation, as shown in Figure 2, the high-temperature and high-pressure gas from the exhaust port of the two-stage compressor 1 passes through the first heat exchange tube 11a of the heat accumulator 11 to exchange heat with the phase-change heat storage material, and the phase-change heat storage material It absorbs heat and undergoes a phase change to store the heat, then the refrigerant enters the outdoor heat exchanger 6 through the four-way reversing valve 8, and exchanges heat with the outdoor environment to release heat. The refrigerant first flows through the first throttling device 5, and then Enter the flash evaporator 4 to vaporize, the liquid refrigerant separated from the flash evaporator 4 enters the indoor heat exchanger 2 after being throttled by the second throttling device 3, exchanges heat with the indoor environment, absorbs indoor heat and environmental heat, and finally passes through the four-way reversing The valve 8 enters the suction port of the two-stage compressor 1 to complete a refrigeration cycle; the gaseous refrigerant separated from the flash evaporator 4 enters the air supply port of the two-stage compressor 1 through the air supply valve 9 . When it is necessary to increase the amount of supplementary air, open the opening degree of the first throttling device 5, close or maintain the opening degree of the second throttling device 3, so that the amount of refrigerant entering the flash evaporator 4 increases, and the amount of refrigerant flowing out decreases. If it is small or unchanged, the amount of supplementary air in the middle will increase; or, turn down the opening degree of the first throttling device 5 and at the same time turn down the opening degree of the second throttling device 3 more. The refrigerant decreases, but the amount of refrigerant flowing out of the flash evaporator 4 decreases even more, and the amount of air supplemented in the middle increases. Conversely, when it is necessary to reduce the amount of supplementary air, close the opening of the first throttling device 5, and close or maintain the opening of the second throttling device 3, so that the amount of refrigerant entering the flash evaporator 4 is reduced, and the refrigerant flowing out If the air volume increases or remains unchanged, the amount of intermediate supplementary air will decrease; or, increase the opening degree of the first throttling device 5 and at the same time increase the opening degree of the second throttling device 3 more, even though it enters the flasher 4 The amount of refrigerant increased, but the amount of refrigerant flowing out of the flash evaporator 4 increased even more, and the amount of air replenishment in the middle decreased.

When the system is in heating operation, as shown in Figure 3, the high-temperature and high-pressure gas from the exhaust port of the two-stage compressor 1 passes through the first heat exchange tube 11a of the heat accumulator 11 to exchange heat with the phase-change heat storage material, and the phase-change heat storage The material absorbs heat and undergoes a phase change to store the heat, then the refrigerant enters the indoor heat exchanger 2 through the four-way reversing valve 8, condenses and releases heat in the indoor heat exchanger 2, and then throttles through the second throttling device 3 After entering the flash evaporator 4 for gas-liquid separation, the liquid refrigerant separated from the flash evaporator 4 is throttled by the first throttling device 5 and then enters the outdoor heat exchanger 6, where it evaporates and absorbs heat, and finally passes through three The one-way valve 7 and the four-way reversing valve 8 enter the suction port of the two-stage compressor 1 to complete a heating cycle; the gaseous refrigerant separated from the flash evaporator 4 enters the air supply port of the two-stage compressor 1 through the air supply valve 9 . When it is necessary to increase the amount of supplementary air, open the opening degree of the second throttling device 3, close or maintain the opening degree of the first throttling device 5, so that the amount of refrigerant entering the flash evaporator 4 increases, and the amount of refrigerant flowing out decreases. If it is small or unchanged, the amount of air supply in the middle will increase; or, turn down the opening degree of the second throttling device 3 and at the same time turn down the opening degree of the first throttling device 5 more. The refrigerant decreases, but the amount of refrigerant flowing out of the flash evaporator 4 decreases even more, and the amount of air supplemented in the middle increases. Conversely, when it is necessary to reduce the amount of supplementary air, close the opening of the second throttling device 3 small, and close or maintain the opening of the first throttling device 5, so that the amount of refrigerant entering the flash evaporator 4 is reduced, and the refrigerant flowing out If the air volume increases or does not change, the amount of air supply in the middle will decrease; or, increase the opening of the second throttling device 3 and at the same time increase the opening of the first throttling device 5 more, even though it enters the flasher 4 The amount of refrigerant increased, but the amount of refrigerant flowing out of the flash evaporator 4 increased even more, and the amount of air replenishment in the middle decreased.

It can be seen that, since the openings of the first throttling device 5 and the second throttling device 3 can be adjusted, by adjusting the opening degree of the first throttling device 5 and/or the second throttling device 3, it is possible to adjust the The flow rate of the refrigerant in the air pipeline 12 can be controlled so as to realize the control of the amount of air supply in the middle, so that the system can operate near the best efficiency point.

Step 2. During defrosting operation, the three-way valve 7 disconnects the pipeline between the first end interface of the outdoor heat exchanger 6 and the suction port of the two-stage compressor 1, and conducts the Bypass pipeline 13, the gas supplement valve 9 is closed. The specific process is as follows:

When the system enters defrosting from heating operation, as shown in Figure 4, the high-temperature refrigerant discharged from the exhaust port of the two-stage compressor 1 flows through the first heat exchange tube 11a of the heat accumulator 11 to exchange heat with the phase change heat storage material, The phase change heat storage material absorbs heat and undergoes phase change to store the heat, and then the refrigerant enters the indoor heat exchanger 2 through the four-way reversing valve 8. In order to reduce heat loss, the indoor fan is turned off or in a low windshield state. After flowing through the indoor heat exchanger 2, the refrigerant has only a small amount of heat loss, and then flows through the second throttling device 3, the flash evaporator 4, and the first throttling device 5. The loss is minimized, the openings of the second throttling device 3 and the first throttling device 5 are opened to the maximum, and the air supplement valve 9 is closed. Then the high-temperature refrigerant enters the outdoor heat exchanger 6 for defrosting; after condensing and exchanging heat in the outdoor heat exchanger 6, it is then reversed through the three-way valve 7 and enters the second heat exchange tube 11b of the heat accumulator 11 to absorb the heat of the heat accumulator. The heat accumulated in 11 is evaporated, and then enters the suction port of the two-stage compressor 1 to complete the defrosting cycle.

It can be seen that the two-stage compression air-conditioning system of the embodiment of the present invention uses the high-temperature refrigerant directly discharged from the compressor to store heat, so a phase-change heat storage material with a higher phase-change temperature can be used. In this way, when defrosting , The temperature difference between the phase change heat storage material and the refrigerant increases, the heat release speed of the phase change heat storage material is fast, and the corresponding defrosting speed will also be accelerated, ensuring the comfort of the user. Moreover, the accumulator has sufficient heat storage capacity during defrosting, which prevents the refrigerant from evaporating into the compressor and causing liquid shock, which poses a fatal threat to the reliability of the compressor.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims (11)

1. A two-stage compression air-conditioning system, comprising a two-stage compressor, a four-way reversing valve, an outdoor heat exchanger, a first throttling device, a flash evaporator, a second throttling device and an indoor heat exchanger, the two-stage The exhaust port and the suction port of the stage compressor are connected with the first end interface of the outdoor heat exchanger and the first end interface of the indoor heat exchanger through the four-way reversing valve, and the outdoor heat exchanger The second port of the heater communicates with the first port of the flasher through the first throttling device, and the second port of the flasher communicates with the indoor heat exchanger through the second throttling device The second port of the flash evaporator is connected to the second port, and the third port of the flasher is connected to the gas supply port of the two-stage compressor through the gas supply pipeline; It is characterized in that the openings of the first throttling device and the second throttling device are adjustable; It also includes a bypass line, a heat accumulator and a control valve, the bypass line is connected between the first port of the outdoor heat exchanger and the suction port of the two-stage compressor, the accumulator The heat exchanger has a first heat exchange tube and a second heat exchange tube, the first heat exchange tube is connected in series between the exhaust port of the two-stage compressor and the first end interface of the indoor heat exchanger On the road, the second heat exchange tube is connected in series on the bypass pipeline; During cooling or heating operation, the control valve connects the pipeline between the first end interface of the outdoor heat exchanger and the suction port of the two-stage compressor, disconnects the bypass pipeline, adjusting the flow rate of the refrigerant passing through the air supply pipeline by adjusting the opening of the first throttling device and/or the second throttling device; During the defrosting operation, the control valve disconnects the pipeline between the first end interface of the outdoor heat exchanger and the suction port of the two-stage compressor, and connects the bypass pipeline. 2. The two-stage compression air-conditioning system according to claim 1, further comprising a third throttling device connected in series to the inlet of the second heat exchange tube of the heat accumulator side of the bypass line. 3. The two-stage compression air-conditioning system according to claim 2, wherein the third throttling device is a capillary tube. 4. The two-stage compression air-conditioning system according to claim 1, wherein the channel aperture of the control valve is smaller than the aperture of the refrigerant pipe, so that the refrigerant passing through the control valve flows into the accumulator after throttling. The second heat exchange tube. 5. The two-stage compression air-conditioning system according to claim 1, wherein one end of the bypass pipeline is connected between the four-way reversing valve and the first port of the outdoor heat exchanger On the pipeline, the other end is connected on the pipeline between the four-way reversing valve and the suction port of the two-stage compressor. 6. The two-stage compression air-conditioning system according to claim 1, wherein both ends of the bypass pipeline are connected between the four-way reversing valve and the suction port of the two-stage compressor on the pipeline between them. 7. The two-stage compression air-conditioning system according to claim 1, wherein the control valve is a three-way valve. 8. The two-stage compression air-conditioning system according to any one of claims 1 to 7, characterized in that both the first throttling device and the second throttling device are electronic expansion valves. 9. The two-stage compression air-conditioning system according to any one of claims 1 to 7, wherein an air supply valve is arranged on the air supply pipeline. 10. A control method for the two-stage compression air-conditioning system according to any one of claims 1 to 9, characterized in that it comprises: During cooling or heating operation, the control valve connects the pipeline between the first end interface of the outdoor heat exchanger and the suction port of the two-stage compressor, disconnects the bypass pipeline, adjusting the flow rate of the refrigerant passing through the air supply pipeline by adjusting the opening of the first throttling device and/or the second throttling device; During the defrosting operation, the control valve disconnects the pipeline between the first end interface of the outdoor heat exchanger and the suction port of the two-stage compressor, and connects the bypass pipeline. 11. The control method of the two-stage compression air-conditioning system according to claim 10, characterized in that, during the defrosting operation, the air supply pipeline is disconnected.