Air conditioning system capable of realizing quick oil return during compressor starting process and design method thereof

Abstract

This invention relates to an air conditioning system and its design method that enables rapid oil return during compressor startup, solving the technical problems of insufficient or empty oil in existing air conditioning systems during startup. The air conditioning system includes a compressor, an oil separator, a four-way reversing valve, a first heat exchanger, a second heat exchanger, and a liquid receiver, along with corresponding connecting pipes. The liquid receiver includes a cylinder, an inlet pipe, and an outlet pipe. One end of the inlet pipe is connected to the four-way reversing valve, and the other end extends into the cylinder and is a bent structure facing the outlet pipe. One end of the outlet pipe is connected to the compressor's suction port, and the other end extends into the cylinder and is a U-shaped structure with one end higher than the other. A first oil return hole is provided horizontally at the bottom of the U-shaped structure. The effective volume between the bottom of the cylinder and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the compressor's oil sump volume. This invention significantly shortens the oil return time of the air conditioning system, improves the quality of the lubricating oil inside the compressor, and enhances the reliability of the compressor.

Description

Technical Field

[0001] This invention relates to an air conditioning system, and more particularly to an air conditioning system and its design method that enables rapid oil return during compressor startup. Background Technology

[0002] With social development and improved living standards, people's demand for air conditioning products is increasing, and the application of air conditioners, heat pumps, and other similar products is becoming more widespread. This also places higher demands on the quality and reliability of air conditioning products. Among them, the compressor, as the core component of the air conditioning system, directly affects the reliability, safety, and energy efficiency of the entire air conditioning system. Therefore, ensuring the reliability of compressor operation has always been a major concern.

[0003] Researchers have found that when an air conditioning system is shut down, the temperature and pressure difference between the compressor and evaporator drives the refrigerant to flow towards colder areas. Simultaneously, the dissolving and adsorption effect of the lubricating oil on the refrigerant drives it to flow towards areas with more lubricating oil. This refrigerant migration is particularly pronounced at low temperatures. At higher temperatures, the refrigerant's solubility is very low; when the temperature remains constant, the refrigerant's solubility increases rapidly with increasing pressure, reaching saturation solubility near the critical pressure at that temperature. When the air conditioning system is shut down for an extended period, the refrigerant's solubility in the lubricating oil increases with decreasing temperature, causing continuous migration and thorough mixing with the lubricating oil inside the compressor. If the air conditioning system is started at this time, the initial pressure difference is small, causing a large amount of refrigerant to accumulate on the high-pressure side of the compressor, resulting in an increase in discharge pressure; the increased refrigerant solubility also causes the oil level in the compressor's oil sump to rise. Meanwhile, as the compressor's discharge pressure increases, the saturation temperature rises accordingly. Since the initial temperature of components such as the compressor casing, oil sump, and motor is ambient temperature, and the refrigerant continuously dissipates heat during compression and discharge, the discharge temperature remains in a saturated state for a prolonged period (i.e., no discharge superheat is established). This easily leads to a large amount of liquid refrigerant falling into the oil sump, causing the oil level to rise further. Subsequently, the lubricating oil is blown into the upper cavity of the motor by the refrigerant carried out from the muffler, causing a large amount of lubricating oil to be discharged along with the refrigerant, thereby reducing the compressor's reliability.

[0004] Based on this, researchers made a series of improvements to the air conditioning system and compressor, aiming to improve the reliability of the compressor, but the following problems still exist:

[0005] 1. During startup, the compressor's internal pressure rises rapidly while its temperature rises slowly, resulting in a large amount of oil being discharged from the compressor and a decrease in the oil level in the compressor's oil sump, which leads to the compressor operating with insufficient oil.

[0006] 2. After the lubricating oil is discharged from the compressor, it has to pass through the condenser, evaporator, receiver, and system piping before returning to the compressor, which takes a relatively long time. Especially for multi-split systems, the compressor oil return line is longer and has a greater drop, making it more prone to oil shortages or oil depletion, further affecting the reliability of compressor operation.

[0007] 3. When the air conditioning system is running in heating mode for a long time under low temperature conditions, the liquid refrigerant and lubricating oil in the receiver are prone to separation. Since the density of the liquid refrigerant is greater than that of the lubricating oil, the lubricating oil is placed on top, which reduces the amount of lubricating oil returning from the oil return hole of the receiver, thereby reducing the lubrication effect of the compressor. In severe cases, it will threaten the reliability of the compressor operation. Summary of the Invention

[0008] To address the aforementioned problems in the existing technology, this invention provides an air conditioning system and its design method that enables rapid oil return during compressor startup.

[0009] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0010] An air conditioning system capable of rapid oil return during compressor startup includes a compressor, an oil separator, a four-way reversing valve, a first heat exchanger, a second heat exchanger, a liquid receiver, and corresponding connecting pipes; its special feature is that:

[0011] The liquid reservoir includes a cylinder, an inlet pipe, and an outlet pipe;

[0012] The cylinder contains lubricating oil and liquid refrigerant. The lubricating oil is discharged from inside the compressor and stored in the receiver cylinder when the compressor is started for the first time. During subsequent startups, the lubricating oil in the cylinder can be replenished to the compressor in a timely manner. The lubricating oil no longer needs to circulate through the compressor, condenser, evaporator and receiver before returning to the compressor, thus ensuring a high liquid level in the compressor oil sump during startup.

[0013] The inlet pipe is installed on the top of the cylinder, with one end connected to the four-way reversing valve and the other end extending into the cylinder. The inlet pipe extending into the cylinder has a bent structure that bends toward the outlet pipe.

[0014] The outlet pipe is installed on the top of the cylinder, with one end connected to the compressor's suction port and the other end extending into the cylinder. The outlet pipe extending into the cylinder has a U-shaped structure with one end higher than the other. The higher end of the U-shaped structure is provided with a pressure equalization hole at the bending structure. The bottom of the U-shaped structure has a first oil return hole along the horizontal direction.

[0015] The effective volume between the bottom of the cylinder and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the compressor oil sump volume.

[0016] Furthermore, a second oil return hole is provided on the lower side wall of the U-shaped structure, and the height of the central axis of the second oil return hole is at the same height as the center of the bottom arc of the U-shaped structure.

[0017] Furthermore, the effective volume between the bottom of the cylinder and the bottom of the U-shaped structure is 1 / 4 to 1 / 2 of the compressor oil sump volume.

[0018] Furthermore, the effective volume between the bottom of the cylinder and the bottom of the U-shaped structure is 2 / 3 to 3 / 4 of the compressor oil sump volume.

[0019] Furthermore, the height of the lower end of the U-shaped structure is lower than the height of the horizontal portion of the bent structure.

[0020] Furthermore, it also includes a throttling element, and there is only one throttling element;

[0021] The second heat exchanger has one unit, and the throttling element is located on the connecting pipe between the first heat exchanger and the second heat exchanger.

[0022] Furthermore, it also includes throttling elements, and there are multiple throttling elements;

[0023] There are multiple second heat exchangers, and each corresponds to a throttling element. Each throttling element is located on the connecting pipe between the corresponding first heat exchanger and second heat exchanger.

[0024] Meanwhile, the present invention also provides a design method for an air conditioning system that enables rapid oil return during compressor startup, comprising the following steps:

[0025] Step [1]: Select the appropriate specifications of compressor, oil separator, four-way reversing valve, first heat exchanger and second heat exchanger according to the preset requirements;

[0026] Step [2]: According to the preset process requirements, complete the pipeline design between the compressor, oil separator, four-way reversing valve, first heat exchanger, second heat exchanger and liquid receiver mentioned in step [1], and determine the maximum refrigerant charge of the air conditioning system in combination with the design and installation requirements of the air conditioning system.

[0027] Step [3]: Calculate the volume of the receiver cylinder based on the oil sump volume of the compressor and the maximum refrigerant charge of the air conditioning system;

[0028] Step [4]: ​​Based on the volume of the cylinder described in step [3], select the inlet pipe and outlet pipe of appropriate length, and design the part of the inlet pipe that extends into the cylinder as a bent structure, and design the part of the outlet pipe that extends into the cylinder as a U-shaped structure with one end high and the other end low, so that the effective volume between the bottom of the cylinder and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the volume of the compressor oil sump.

[0029] Step [5]: Based on the diameter of the outlet pipe, design the first horizontal return oil hole on the bottom side wall of the U-shaped structure;

[0030] Step [6]: Based on step [5], design a pressure equalization hole at the higher end of the U-shaped structure, which is higher than the bend in the inlet pipe, to complete the design of the liquid reservoir;

[0031] Step [7] According to the preset process requirements, fill the compressor with sufficient lubricating oil to complete the design of an air conditioning system that can realize rapid oil return during compressor start-up.

[0032] Furthermore, step [6] also includes designing a second oil return hole at the lower end of the U-shaped structure near the first oil return hole; the central axis of the second oil return hole is at the same height as the center of the U-shaped structure, and the diameter of the second oil return hole is the same as the diameter of the first oil return hole.

[0033] Furthermore, in step [7], after sufficient lubricating oil is filled into the compressor, when the compressor is started for the first time, the lubricating oil inside is discharged into the reservoir cylinder. The lubricating oil higher than the first oil return hole returns to the compressor through the first oil return hole and the outlet pipe, while the remaining lubricating oil is still stored at the bottom of the cylinder.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. In the air conditioning system for rapid oil return during compressor startup provided by this invention, the receiver includes a cylinder, an inlet pipe, and an outlet pipe. One end of the outlet pipe is connected to the compressor's suction port, and the other end extends into the cylinder. The outlet pipe extending into the cylinder has a U-shaped structure with one end higher than the other. A first oil return hole is provided horizontally at the bottom of the U-shaped structure, and the effective volume between the bottom of the cylinder and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the compressor oil sump volume. This design increases the effective volume below the first oil return hole (i.e., the bottom of the cylinder). By filling the compressor with more lubricating oil than the effective volume of the oil sump, some lubricating oil is discharged from the compressor after the compressor starts for the first time and gradually accumulates in the receiver. At this time, the oil level inside the compressor will also be within the normal range. During subsequent startup processes, the lubricating oil can be replenished to the compressor oil sump in a timely manner, effectively avoiding the phenomenon of compressor running dry.

[0036] 2. In the air conditioning system provided by this invention, which enables rapid oil return during compressor startup, the cylinder contains lubricating oil and a portion of refrigerant. When the compressor starts for the first time, some of the lubricating oil inside the compressor is discharged and stored in the receiver (the effective volume below the first oil return hole provides storage space for the lubricating oil). During subsequent compressor startup, for lubricating oil that is completely miscible with the refrigerant, the receiver absorbs a portion of the refrigerant from the first or second heat exchanger. The solubility in the receiver increases, the liquid level rises, and the lubricating oil can be replenished to the compressor oil sump in a timely manner through the first oil return hole, effectively shortening the compressor oil return time.

[0037] 3. In the air conditioning system provided by this invention that enables rapid oil return during compressor startup, the height of the first oil return hole is relatively increased based on the increase in the effective volume at the bottom of the cylinder. For immiscible or semi-miscible lubricating oils when the air conditioning system is under low-temperature conditions for a long time, the refrigerant and lubricating oil stratification occurs in the receiver. The height of the first oil return hole is in the upper lubricating oil layer and far from the lower refrigerant layer, thereby ensuring oil return to the compressor, reducing excessive liquid refrigerant entering the compressor, and thus improving the reliability of the compressor.

[0038] 4. In the air conditioning system that enables rapid oil return during compressor startup provided by the present invention, the effective volume at the bottom of the cylinder and the amount of lubricating oil charged are increased compared with the prior art, thereby increasing the total amount of oil in the air conditioning system. The liquid refrigerant entering the receiver will first mix with the lubricating oil stored in the receiver, improving the lubricating oil / refrigerant ratio entering the compressor, thereby improving the quality of the lubricating oil inside the compressor.

[0039] 5. The air conditioning system provided by the present invention, which enables rapid oil return during compressor startup, is also provided with a second oil return hole. This design ensures that the lubricating oil in the cylinder returns to the compressor quickly, thereby effectively reducing the oil return time of the air conditioning system and improving the working efficiency of the compressor.

[0040] 6. The design method of the air conditioning system that enables rapid oil return during compressor startup provided by the present invention is applicable not only to the design of rapid oil return in single-unit air conditioning systems, but also to multi-split systems.

[0041] 7. This invention is of great significance for improving the reliability of compressors during the start-up process of air conditioning systems and for promoting the application of air conditioning systems under low-temperature conditions. Attached Figure Description

[0042] Figure 1 This is a structural schematic diagram of an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of the liquid reservoir in an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram of the gas-liquid separation process in the liquid storage tank according to an embodiment of the present invention.

[0045] Figure 4 The graph shows the two-layer separation curves of R410A refrigerant and No. 1 lubricating oil.

[0046] The attached figures are labeled as follows:

[0047] 1-Compressor, 2-Oil separator, 3-Four-way reversing valve, 4-First heat exchanger, 5-Second heat exchanger, 6-Liquid receiver, 61-Cylinder, 62-Inlet pipe, 63-Outlet pipe, 631-Equalizing hole, 632-First oil return hole, 633-Second oil return hole, 64-Lubricating oil, 7-Throttling element. Detailed Implementation

[0048] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0049] like Figure 1 As shown, this embodiment provides an air conditioning system that enables rapid oil return during compressor startup, including a compressor 1, an oil separator 2, a four-way reversing valve 3, a first heat exchanger 4, a second heat exchanger 5, a liquid receiver 6, a throttling element 7, and corresponding connecting pipelines. The liquid receiver 6 is connected to the suction port of the compressor 1, the inlet of the oil separator 2 is connected to the outlet of the compressor 1, the outlet of the oil separator 2, the first heat exchanger 4, the second heat exchanger 5, and the liquid receiver 6 are all connected to the four-way reversing valve 3, and the throttling element 7 is located on the connecting pipeline between the first heat exchanger 4 and the second heat exchanger 5.

[0050] During heating, the high-temperature, high-pressure gas from the compressor 1 outlet passes through the oil separator 2 and the four-way reversing valve 3 before entering the second heat exchanger 5 (i.e., the indoor heat exchanger) for condensation, releasing heat to achieve the heating effect. The condensed liquid, after passing through the throttling element 7, experiences a decrease in both temperature and pressure. At this point, the refrigerant enters the first heat exchanger 4 (i.e., the outdoor heat exchanger) for heat exchange. The gas-liquid two-phase flow from the outlet of the first heat exchanger 4 passes through the four-way reversing valve 3 and enters the receiver 6. After gas-liquid separation, the refrigerant returns to the compressor 1. In this configuration, the second heat exchanger 5 acts as a condenser, and the first heat exchanger 4 acts as an evaporator.

[0051] During refrigeration, the high-temperature, high-pressure gas from the compressor 1 outlet passes through the oil separator 2 and the four-way reversing valve 3 before entering the first heat exchanger 4 (i.e., the outdoor heat exchanger) for heat exchange, releasing heat to the outside. The condensed liquid, after passing through the throttling element 7, experiences a decrease in both temperature and pressure. At this point, the refrigerant enters the second heat exchanger 5 (i.e., the indoor heat exchanger) for heat exchange, absorbing heat through evaporation, thus lowering the indoor temperature and achieving the refrigeration effect. The gas-liquid two-phase flow from the outlet of the second heat exchanger 5 enters the receiver 6 through the four-way reversing valve 3. After gas-liquid separation, the refrigerant returns to the compressor 1, where the low-temperature, low-pressure refrigerant gas is compressed again into a high-temperature, high-pressure gas, entering the system pipeline from the compressor 1 outlet. In this configuration, the first heat exchanger 4 acts as a condenser, and the second heat exchanger 5 acts as an evaporator.

[0052] The receiver 6 is a key component of the air conditioning system, primarily installed on the pipeline between the four-way reversing valve 3 and the suction port of the compressor 1. The inlet of the receiver 6 typically receives a two-phase flow from the evaporator, storing excess refrigerant / oil-liquid mixture before it enters the compressor 1. Simultaneously, the outlet of the receiver 6 connects to the suction port of the compressor 1, allowing the lubricating oil carried away by the refrigerant to return to the compressor 1, ensuring its lubrication.

[0053] In addition, this embodiment has one second heat exchanger 5 and one corresponding throttling element 7, and the throttling element 7 is located on the connecting pipe between the first heat exchanger 4 and the second heat exchanger 5.

[0054] Alternatively, there may be multiple second heat exchangers 5, and multiple corresponding throttling elements 7, with each throttling element 7 located on the connecting pipe between the corresponding first heat exchanger 4 and second heat exchanger 5.

[0055] like Figure 2 As shown, the liquid receiver 6 in this embodiment includes a cylinder 61, an inlet pipe 62, and an outlet pipe 63. The cylinder 61 is used to store lubricating oil 64 and excess liquid refrigerant, protecting the compressor 1 from the influence of a large amount of liquid during startup and ensuring that the compressor 1 has a sufficient oil supply.

[0056] The inlet pipe 62 is vertically installed on the top of the cylinder 61. One end of it is connected to the four-way reversing valve 3, and the other end extends into the cylinder 61. The inlet pipe 62 extending into the cylinder 61 is a bent structure that bends toward the outlet pipe 63. The effective volume above the bent structure is much smaller than the effective volume at the bottom of the cylinder 61.

[0057] The outlet pipe 63 is vertically installed on the top of the cylinder 61. One end of it is connected to the suction port of the compressor 1, and the other end extends into the cylinder 61. The outlet pipe 63 extending into the cylinder 61 has a U-shaped structure with one end higher than the other. The height of the lower end of the U-shaped structure is generally lower than the height of the horizontal part of the bent structure.

[0058] In this embodiment, a pressure equalization hole 631 is provided at the higher end of the U-shaped structure, above the bending structure, to balance the internal and external pressures of the outlet pipe 63 and prevent liquid stored at the bottom of the cylinder 61 from being siphoned back into the compressor through the oil return hole during compressor 1 shutdown. A first oil return hole 632 is provided horizontally at the bottom of the U-shaped structure, through which liquid stored at the bottom of the cylinder 61 returns to the compressor 1 along with the refrigerant. In this embodiment, the effective volume between the bottom of the cylinder 61 and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the oil sump volume of the compressor 1. This volume can be used to store the lubricating oil 64 discharged from the compressor 1 during its first start-up. This volume design provides storage space for the lubricating oil 64 discharged from the compressor 1 and effectively improves the situation of excessive refrigerant entering the compressor 1 and insufficient oil return caused by refrigerant and lubricating oil 64 stratification under low-temperature conditions. If the effective volume is less than 1 / 4, the amount of lubricating oil 64 entering the cylinder 61 after passing through multiple components and pipelines in the system will be insufficient. During compressor startup, the cylinder 61 cannot replenish sufficient lubricating oil 64 to the compressor 1 in a timely manner. In addition, under low temperature conditions, the first oil return hole 632 may be located in a refrigerant-rich layer, preventing the lubricating oil 64 in the cylinder 1 from flowing back to the compressor, resulting in insufficient oil in the compressor 1. If the effective volume is greater than 3 / 4, excessive lubricating oil 64 will be charged inside the compressor 1, which is not conducive to the discharge of refrigerant gas.

[0059] Based on this structural design, during the startup process of compressor 1, the lubricating oil 64 in receiver 6 can be replenished to the inside of compressor 1 in a timely manner. The lubricating oil 64 no longer needs to circulate through compressor 1, condenser, evaporator and receiver 6 before returning to the oil, thereby ensuring a high oil level in the oil sump of compressor 1 during startup and avoiding the phenomenon of empty oil.

[0060] In this embodiment, the effective volume between the bottom of the cylinder 61 and the bottom of the U-shaped structure is 1 / 4 to 1 / 2 of the oil sump volume of the compressor 1. The liquid receiver 6 of this solution can be applied to most single-unit air conditioning systems and meet the compressor oil return requirements during startup.

[0061] Alternatively, the effective volume between the bottom of the cylinder 61 and the bottom of the U-shaped structure can be designed to be 2 / 3 to 3 / 4 of the oil sump volume of the compressor 1. This type of receiver 6 is suitable for air conditioning systems requiring long-term low-temperature heating, as well as multi-split systems with significant height differences and long system piping. Because long-term low-temperature heating systems experience stratification of lubricating oil 64 and refrigerant during startup, and because multi-split systems with large height differences and long outdoor connection pipes require longer oil return times (due to the longer system piping) and higher oil return volumes (because lubricating oil 64 is more likely to remain in the piping), these two types of air conditioning systems are better suited to receiver 6 with a larger effective volume at the bottom of the cylinder 61.

[0062] A second oil return hole 633 is provided at the lower end of the U-shaped structure and near the first oil return hole 632. Its function is to increase the oil return of the compressor 1 when the liquid level in the liquid reservoir 6 is high, so as to realize the rapid oil return of the compressor 1 during the start-up process.

[0063] In this embodiment, the first oil return hole 632 and the second oil return hole 633 have the same diameter, generally Φ1.0mm~Φ1.5mm. The specific diameter can also be adjusted according to the design requirements. The size and location of the diameter can ensure sufficient oil return of the compressor.

[0064] The lubricating oil 64 is the lubricating oil that migrates to the reservoir 6 after the compressor 1 is started for the first time after the increase in the sealing oil volume of the compressor 1. The lubricating oil 64 that is higher than the first oil return hole 632 and the second oil return hole 633 returns to the compressor 1 through the outlet pipe 63, and the remaining lubricating oil 64 is stored in the effective volume at the bottom of the cylinder 61.

[0065] Before the air conditioning system starts, the internal pressure of the receiver 6 is relatively low, so the solubility of the refrigerant is also relatively low. When the air conditioning system starts, some of the lubricating oil 64 is carried out of the compressor 1 by the refrigerant, causing the oil level in the compressor 1 to drop. At this time, the refrigerant in the corresponding heat exchanger enters the receiver 6, increasing the solubility of the refrigerant in the receiver 6 and raising the oil level. The lubricating oil 64 can then be replenished to the compressor in a timely manner, thus preventing the compressor 1 from experiencing oil shortage.

[0066] like Figure 3 As shown, the gas-liquid separation process of the liquid reservoir 6 in this embodiment is as follows:

[0067] Inlet pipe 62 leads into cylinder 61. The gas-liquid two-phase flow from the corresponding heat exchanger enters cylinder 61 through inlet pipe 62. Liquid refrigerant and lubricating oil 64, under their own gravity, deposit at the bottom of cylinder 61, mixing thoroughly with the lubricating oil 64, thus improving the lubricating oil / refrigerant ratio entering compressor 1. Simultaneously, the liquid level inside cylinder 61 rises, submerging the first oil return hole 632. Gaseous refrigerant forms a rotating airflow in the upper cavity of cylinder 61, thus completing gas-liquid separation. A portion of the gaseous refrigerant in the upper cavity of cylinder 61 enters outlet pipe 63 through the lower section of the U-shaped structure, mixing with the lubricating oil 64 entering outlet pipe 63 through the first oil return hole 632 to form a gas-liquid two-phase flow. Another portion enters outlet pipe 63 through equalization hole 631 on outlet pipe 63, mixing with the gas-liquid two-phase flow, and both return to compressor 1. When the liquid level inside the cylinder 61 rises to submerge the second oil return hole 633, the lubricating oil 64 enters the outlet pipe 63 through the first oil return hole 632 and the second oil return hole 633, and then returns to the compressor 1 together.

[0068] Combination Figures 1 to 3The working principle of this embodiment is as follows: Before the compressor 1 is started for the first time, it is filled with a large amount of lubricating oil 64. After the first start, the lubricating oil 64 is discharged from the compressor 1.

[0069] During heating, the lubricating oil 64 discharged from the compressor 1 passes sequentially through the oil separator 2, the four-way reversing valve 3, the second heat exchanger 5, the throttling element 7, and the first heat exchanger 4, before entering the receiver 6 again through the four-way reversing valve 3 and being stored in the effective volume at the bottom of the receiver 6 cylinder 61. During the subsequent start-up process of the compressor 1, the receiver 6 absorbs a portion of the refrigerant from the corresponding heat exchangers, increasing the refrigerant solubility in the receiver 6 cylinder 61 and causing the liquid level to rise. The lubricating oil 64 in the cylinder 61 then enters the outlet pipe 63 through the first return hole 632 and the second return hole 633, and then flows back into the compressor 1, achieving rapid oil return.

[0070] During refrigeration, the lubricating oil 64 discharged from the compressor 1 passes sequentially through the oil separator 2, the four-way reversing valve 3, the first heat exchanger 4, the throttling element 7, and the second heat exchanger 5. It then re-enters the receiver 6 through the four-way reversing valve 3 and is stored in the effective volume at the bottom of the receiver 6's cylinder 61. During the subsequent startup process of the compressor 1, the receiver 6 absorbs some refrigerant from the corresponding heat exchangers, increasing the refrigerant solubility in the receiver 6's cylinder 61 and causing the liquid level to rise. The lubricating oil 64 in the cylinder 61 then enters the outlet pipe 63 through the first return hole 632 and the second return hole 633, and subsequently flows back into the compressor 1, achieving rapid oil return.

[0071] Figure 4 This is a two-layer separation curve of R410A refrigerant and No. 1 lubricating oil. The curves show the boundaries between the miscibility and stratification of the refrigerant and lubricating oil at different temperatures. The area within the two curves indicates that the refrigerant and lubricating oil mixture exists in a two-phase state. Within the temperature range between the upper critical temperature corresponding to the upper critical point O1 and the lower critical temperature corresponding to the lower critical point O2, the refrigerant and lubricating oil are single-phase, meaning they are miscible in any proportion. When the air conditioning system is under low-temperature conditions for an extended period, the ambient temperature of the receiver 6 is much lower than the lower critical temperature corresponding to the lower critical point O2 on the miscibility curve. At this time, the refrigerant and lubricating oil separate into a lubricating oil-rich layer (containing more oil) and a refrigerant-rich layer (containing more refrigerant). Simultaneously, because the density of liquid refrigerant is greater than that of lubricating oil, the refrigerant-rich layer is located at the bottom, and the lubricating oil-rich layer is located at the top. Traditional liquid receivers have a small effective volume below the bottom oil return hole. Because the lubricating oil is layered and placed on top, the amount of lubricating oil returning to the compressor from the bottom oil return hole is greatly reduced, easily causing oil shortage in the compressor and affecting its reliability. Therefore, this invention increases the effective volume below the bottom oil return hole (i.e., the effective volume below the U-shaped structure), placing the oil return hole in a lubricating oil-rich layer, thus ensuring timely oil return to the compressor.

[0072] Furthermore, this embodiment also provides a design method for an air conditioning system that enables rapid oil return during compressor startup, including the following steps:

[0073] Step [1]: Select the appropriate specifications of compressor 1, oil separator 2, four-way reversing valve 3, first heat exchanger 4 and second heat exchanger 5 according to the preset requirements.

[0074] Step [2] Based on the preset process requirements, complete the pipeline design between the compressor 1, oil separator 2, four-way reversing valve 3, first heat exchanger 4, second heat exchanger 5, and liquid receiver 6 selected in step [1]. Combined with the design and installation requirements of the air conditioning system to be designed, determine the maximum refrigerant charge of the air conditioning system.

[0075] Step [3]: Calculate the effective volume of the receiver 6 cylinder 61 based on the oil sump volume of compressor 1 and the maximum refrigerant charge of the air conditioning system to be designed.

[0076] The formula for calculating the effective volume V of the reservoir 6 cylinder 61 is:

[0077]

[0078] Wherein, SG is the specific gravity of the refrigerant in its saturated liquid state at 0°.

[0079] Step [4]: ​​Based on the effective volume V of the cylinder 61 calculated in step [3], select inlet pipe 62 and outlet pipe 63 of appropriate length. Design the part of inlet pipe 62 extending into cylinder 61 as a bent structure, and design the part of outlet pipe 63 extending into cylinder 61 as a U-shaped structure with one end higher than the other, so that the effective volume between the bottom of cylinder 61 and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the oil sump volume of compressor 1. The effective volume at the bottom of cylinder 61 can also be adjusted according to actual needs.

[0080] Step [5]: Based on the diameter of the outlet pipe 63, design the first horizontal return oil hole 632 on the bottom side wall of the U-shaped structure.

[0081] Step [6]: Based on step [4], design a pressure equalization hole 631 at the high end of the U-shaped structure near the bend of the inlet pipe, thereby completing the design of the liquid reservoir 6.

[0082] The equalizing hole 631 is designed to prevent liquid stored in the liquid receiver 6 from being siphoned into the compressor 1 through the first oil return hole 632 when the compressor 1 is stopped, thus preventing liquid slugging when the compressor 1 restarts. The height of the equalizing hole 631 is generally slightly higher than the bend in the inlet pipe 62.

[0083] A second oil return hole 633 can also be designed at the lower end of the U-shaped structure, near the first oil return hole 632, to ensure oil return efficiency, depending on actual needs. The central axis of the second oil return hole 633 is at the same height as the center of the U-shaped structure, and the diameter of the second oil return hole 633 is the same as the diameter of the first oil return hole 632.

[0084] Step [7] According to the preset process requirements, fill the compressor 1 with sufficient lubricating oil 64 to complete the design of an air conditioning system that can realize rapid oil return during compressor start-up.

[0085] In this embodiment, after the compressor 1 is filled with sufficient lubricating oil 64, when the compressor 1 starts for the first time, the lubricating oil 64 inside is discharged into the cylinder 61 of the receiver 6 (the effective volume below the first oil return hole 632 provides storage space for the lubricating oil 64). The lubricating oil 64 above the first oil return hole 632 returns to the compressor 1 through the first oil return hole 632 and the outlet pipe 63, while the remaining lubricating oil 64 remains stored at the bottom of the cylinder 61. During the subsequent start-up process of the compressor 1, the receiver 6 absorbs a portion of the refrigerant from the first heat exchanger 4 or the second heat exchanger 5, increasing the solubility in the receiver 6 and raising the liquid level. The lubricating oil 64 can then be replenished to the oil sump of the compressor 1 in a timely manner through the first oil return hole 632, effectively shortening the compressor oil return time.

[0086] In summary, the air conditioning system of the present invention can effectively reduce the compressor oil return time, ensure balanced oil and liquid return, and thus guarantee the reliable operation of the compressor.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. An air conditioning system capable of rapid oil return during compressor start-up, comprising a compressor (1), an oil separator (2), a four-way reversing valve (3), a first heat exchanger (4), a second heat exchanger (5), and a liquid receiver (6), as well as corresponding connecting pipelines; characterized in that: The liquid reservoir (6) includes a cylinder (61), an inlet pipe (62), and an outlet pipe (63). The cylinder (61) stores lubricating oil (64) and liquid refrigerant. The lubricating oil (64) is discharged from the compressor (1) and stored in the cylinder (61) when the compressor (1) is started for the first time. During subsequent start-up processes, the lubricating oil (64) in the cylinder (61) is used to replenish the compressor (1) in a timely manner. The inlet pipe (62) is installed on the top of the cylinder (61), one end of which is connected to the four-way reversing valve (3), and the other end extends into the cylinder (61). The inlet pipe (62) extending into the cylinder (61) is a bent structure that bends toward the outlet pipe (63). The outlet pipe (63) is installed on the top of the cylinder (61), with one end connected to the suction port of the compressor (1) and the other end extending into the cylinder (61). The outlet pipe (63) extending into the cylinder (61) is a U-shaped structure with one end higher than the other. A pressure equalization hole (631) is provided at the higher end of the U-shaped structure near the upper part of the bending structure. A first oil return hole (632) is provided at the bottom of the U-shaped structure in the horizontal direction. The effective volume between the bottom of the cylinder (61) and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the oil sump volume of the compressor (1); The lower end of the U-shaped structure is provided with a second oil return hole (633), and the height of the central axis of the second oil return hole (633) is at the same height as the center of the bottom arc of the U-shaped structure.

2. The air conditioning system according to claim 1, which enables rapid oil return during compressor startup, is characterized in that: The effective volume between the bottom of the cylinder (61) and the bottom of the U-shaped structure is 1 / 4 to 1 / 2 of the oil sump volume of the compressor (1).

3. The air conditioning system according to claim 1, which enables rapid oil return during compressor startup, is characterized in that: The effective volume between the bottom of the cylinder (61) and the bottom of the U-shaped structure is 2 / 3 to 3 / 4 of the oil sump volume of the compressor (1).

4. The air conditioning system capable of rapid oil return during compressor start-up according to any one of claims 1 to 3, characterized in that: The height of the lower end of the U-shaped structure is lower than the height of the horizontal part of the bent structure.

5. The air conditioning system according to claim 1, which enables rapid oil return during compressor startup, is characterized in that: It also includes a throttling element (7), and there is one throttling element (7); The second heat exchanger (5) has one, and the throttling element (7) is located on the connecting pipe between the first heat exchanger (4) and the second heat exchanger (5).

6. The air conditioning system according to claim 1, which enables rapid oil return during compressor startup, is characterized in that: It also includes a throttling element (7), and there are multiple throttling elements (7); There are multiple second heat exchangers (5), and each of them corresponds to a multiple throttling element (7). Each throttling element (7) is located on the connecting pipe between the corresponding first heat exchanger (4) and second heat exchanger (5).

7. A design method for an air conditioning system capable of rapid oil return during compressor start-up, characterized in that, Includes the following steps: Step [1]: Select the appropriate specifications of compressor (1), oil separator (2), four-way reversing valve (3), first heat exchanger (4), second heat exchanger (5) and liquid receiver (6) according to the preset requirements. Step [2]: According to the preset process requirements, complete the pipeline design between the compressor (1), oil separator (2), four-way reversing valve (3), first heat exchanger (4), second heat exchanger (5), and liquid receiver (6) mentioned in step [1]. Combined with the design and installation requirements of the air conditioning system, determine the maximum refrigerant charge of the air conditioning system. Step [3]: Calculate the volume of the receiver (6) cylinder (61) based on the oil sump volume of the compressor (1) and the maximum refrigerant charge of the air conditioning system; Step [4]: ​​Based on the volume of the cylinder (61) described in step [3], select an inlet pipe (62) and an outlet pipe (63) of appropriate length, and design the part of the inlet pipe (62) that extends into the cylinder (61) as a bent structure, and design the part of the outlet pipe (63) that extends into the cylinder (61) as a U-shaped structure with one end higher than the other, so that the effective volume between the bottom of the cylinder (61) and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the oil sump volume of the compressor (1); Step [5]: Based on the diameter of the outlet pipe (63), design the first horizontal return oil hole (632) on the bottom side wall of the U-shaped structure. Step [6]: Based on step [5], design a pressure equalization hole (631) at the higher end of the U-shaped structure, which is higher than the bend in the inlet pipe, and design a second oil return hole (633) at the lower end of the U-shaped structure, which is close to the first oil return hole (632). The central axis of the second oil return hole (633) is at the same height as the center of the U-shaped structure, and the diameter of the second oil return hole (633) is the same as the diameter of the first oil return hole (632), thereby completing the design of the reservoir (6). Step [7]: According to the preset process requirements, fill the compressor (1) with sufficient lubricating oil (64) to complete the design of an air conditioning system that can realize rapid oil return during compressor start-up.

8. The design method of the air conditioning system that enables rapid oil return during compressor start-up according to claim 7, characterized in that: In step [7], after sufficient lubricating oil (64) is filled into the compressor (1), when the compressor (1) is started for the first time, the lubricating oil (64) inside it is discharged into the cylinder (61) of the liquid receiver (6). The lubricating oil (64) higher than the first oil return hole (632) returns to the compressor (1) through the first oil return hole (632) and the outlet pipe (63), while the remaining lubricating oil (64) is still stored at the bottom of the cylinder (61).

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