Air conditioning system capable of realizing quick oil return in starting process of compressor and design method of air conditioning system

Abstract

The invention relates to an air-conditioning system capable of realizing quick oil return in a compressor starting process and a design method thereof, and solves the technical problems of oil shortage or oil shortage of a compressor in the starting process of an existing air-conditioning system and the like. The air conditioning system comprises a compressor, an oil separator, a four-way reversing valve, a first heat exchanger, a second heat exchanger, a liquid storage device and corresponding connecting pipelines. The liquid storage device comprises a barrel body, an inlet pipe and an outlet pipe; one end of the inlet pipe is connected with the four-way reversing valve, and the other end of the inlet pipe extends into the barrel and is of a bent structure bent towards the outlet pipe. One end of the outlet pipe is connected with an air suction port of the compressor, and the other end of the outlet pipe extends into the cylinder and is of a U-shaped structure with one high end and one low end; a first oil return hole is formed in the bottom of the U-shaped structure in the horizontal direction; and the effective volume between the bottom of the cylinder body and the bottom of the U-shaped structure is 1 / 4-3 / 4 of the volume of an oil pool of the compressor. The oil return time of the air conditioning system is greatly shortened, the quality of lubricating oil in the compressor is improved, and the reliability of the compressor is improved.

Description

Technical Field

[0001] The invention relates to an air conditioning system, and in particular to an air conditioning system capable of realizing rapid oil return during a compressor startup process and a design method thereof. Background Art

[0002] With the development of society and the improvement of living standards, people's demand for air-conditioning products is increasing day by day, and the application of air-conditioning, heat pumps and other products is becoming more and more extensive, which also puts higher requirements on the quality and reliability of air-conditioning products. Among them, the compressor is the core component of the air-conditioning system. Its performance directly affects the reliability, safety and energy saving of the entire air-conditioning system. Therefore, how to ensure the reliability of the compressor has always been a concern.

[0003] The researchers found that when the air conditioning system is shut down, the difference in temperature and pressure between the compressor and the evaporator drives the refrigerant to flow to a colder place. At the same time, due to the dissolution and adsorption effect of the lubricant on the refrigerant, the refrigerant is driven to flow to places with more lubricant. Under low temperature conditions, the refrigerant migration phenomenon is particularly obvious. When the temperature is high, the solubility of the refrigerant is very small; when the temperature remains unchanged, the solubility of the refrigerant increases rapidly with the increase in pressure until it reaches the saturated solubility when it approaches the critical pressure at that temperature. When the air conditioning system is in a long-term shutdown state, the solubility of the refrigerant in the lubricant increases with the decrease in temperature, causing the refrigerant to migrate continuously and mix fully with the lubricant inside the compressor. If the air conditioning system is started at this time, due to the small system pressure difference at the initial startup, a large amount of refrigerant gathers on the high-pressure side of the compressor, causing the exhaust pressure to rise; and the increase in the solubility of the refrigerant also causes the liquid level of the compressor oil pool to rise. At the same time, as the compressor exhaust pressure increases, the saturation temperature increases accordingly. Since the initial temperature of the compressor housing, oil pool, motor and other components is the ambient temperature, and the refrigerant continuously dissipates heat outward during the compression and discharge process, the exhaust temperature is in a saturated state for a long time (that is, the exhaust superheat is not established), which easily causes a large amount of liquid refrigerant to fall into the oil pool, causing the oil pool liquid level to rise further. Afterwards, the lubricating oil is blown into the upper cavity of the motor by the refrigerant brought out of the muffler, causing a large amount of lubricating oil to be discharged along with the refrigerant, thereby reducing the reliability of the compressor.

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

[0005] 1. During the startup process, due to the fact that the internal pressure of the compressor rises quickly and the temperature rises slowly, the compressor discharges a large amount of oil and the liquid level of the compressor oil pool decreases, resulting in the compressor running without oil.

[0006] 2. After the lubricating oil is discharged from the compressor, it has to pass through the condenser, evaporator, liquid storage tank and system pipelines before returning to the compressor. The required oil return time is relatively long. Especially for multi-split systems, the compressor return oil pipeline is longer and has a large drop, which makes it more likely to be short of oil or empty oil, further affecting the reliability of the compressor operation.

[0007] 3. When the air-conditioning system is operated in heating mode for a long time under low temperature conditions, the liquid refrigerant and lubricating oil in the reservoir are prone to stratification. Since the density of the liquid refrigerant is greater than that of the lubricating oil, the lubricating oil is placed upward, resulting in a decrease in the lubricating oil returned from the oil return hole of the reservoir, 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] In order to solve the above problems existing in the prior art, the present invention provides an air conditioning system and a design method thereof which can realize rapid oil return during the compressor startup process.

[0009] To achieve the above objectives, the technical solutions provided by the present invention are:

[0010] An air conditioning system capable of realizing 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 storage device, and corresponding connecting pipelines; the system is special in that:

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

[0012] Lubricating oil and liquid refrigerant are stored in the cylinder; the lubricating oil is discharged from the compressor and stored in the liquid reservoir cylinder when the compressor is started for the first time. During the subsequent startup process, the lubricating oil in the cylinder can be replenished to the compressor in time, and the lubricating oil no longer needs to circulate through the compressor, condenser, evaporator and liquid reservoir before returning to the oil, thereby ensuring a high liquid level in the compressor oil pool during the startup process.

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

[0014] The outlet pipe is installed on the top of the cylinder, one end of which is connected to the air inlet of the compressor, and the other end extends into the cylinder, and the outlet pipe extending into the cylinder is a U-shaped structure with one end higher than the other end; a pressure equalizing hole is provided at the higher end of the U-shaped structure than the bending structure; a first oil return hole is provided at the bottom of the U-shaped structure in 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 volume of the compressor oil pool.

[0016] Furthermore, a second oil return hole is provided on the side wall of the lower end 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 circular arc at the bottom 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 volume of the compressor oil pool.

[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 volume of the compressor oil pool.

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

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

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

[0022] Furthermore, it also includes a throttling element, and the throttling element is multiple;

[0023] There are multiple second heat exchangers, which correspond one-to-one to multiple throttling elements. Each throttling element is located on the connecting pipeline between the corresponding first heat exchanger and the second heat exchanger.

[0024] At the same time, the present invention also provides a design method for an air conditioning system capable of realizing rapid oil return during the compressor startup process, comprising the following steps:

[0025] Step [1], according to preset requirements, pre-select a compressor, an oil separator, a four-way reversing valve, a first heat exchanger and a second heat exchanger of corresponding specifications;

[0026] Step [2], according to the preset process requirements, complete the design of the compressor, oil separator, four-way reversing valve, first heat exchanger, second heat exchanger, and pipelines between the liquid accumulator 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], calculating the volume of the accumulator cylinder according to the oil pool volume of the compressor and the maximum refrigerant charge of the air conditioning system;

[0028] Step [4], according to the volume of the cylinder described in step [3], select an inlet pipe and an outlet pipe of corresponding length, and design the portion of the inlet pipe extending into the cylinder into a bent structure, and design the portion of the outlet pipe extending into the cylinder into a U-shaped structure with one end higher than the other end, 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 pool;

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

[0030] Step [6]: Based on step [5], a pressure equalizing hole is designed at a position where the higher end of the U-shaped structure is higher than the bending structure of the inlet pipe, thereby completing the design of the liquid reservoir;

[0031] Step [7] According to the preset process requirements, sufficient lubricating oil is filled into the compressor, thereby completing the design of an air-conditioning system that can achieve rapid oil return during the compressor startup process.

[0032] Furthermore, step [6] also includes the step of 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 aperture of the second oil return hole is the same as the aperture of the first oil return hole.

[0033] Furthermore, in step [7], after the compressor is filled with sufficient lubricating oil, when the compressor is started for the first time, the lubricating oil inside is discharged into the reservoir cylinder, and the lubricating oil above the first oil return hole returns to the compressor through the first oil return hole and the outlet pipe, and 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 an air-conditioning system capable of realizing rapid oil return during the startup process of a compressor provided by the present invention, a liquid reservoir comprises a cylinder, an inlet pipe and an outlet pipe, wherein one end of the outlet pipe is connected to the air intake port of the compressor, and the other end extends into the cylinder, and the outlet pipe extending into the cylinder is a U-shaped structure with one end higher than the other end; a first oil return hole is provided at the bottom of the U-shaped structure in a horizontal direction, 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 volume of the compressor oil pool. This design increases the effective volume below the first oil return hole (i.e., the bottom of the cylinder), and by filling the compressor with an amount of lubricating oil greater than the effective volume of the oil pool, after the compressor is started for the first time, part of the lubricating oil is discharged from the compressor and gradually accumulated in the liquid reservoir. At this time, the oil level inside the compressor will also be within a normal range. In the subsequent startup process, the lubricating oil can be replenished in the compressor oil pool in time, effectively avoiding the oil-free phenomenon of the compressor.

[0036] 2. In the air-conditioning system that can realize rapid oil return during the startup process of the compressor provided by the present invention, lubricating oil and part of the refrigerant are stored in the cylinder. When the compressor is started for the first time, part of the lubricating oil in the compressor is discharged and stored in the liquid reservoir (the effective volume below the first oil return hole provides a storage space for the lubricating oil). In the subsequent startup process of the compressor, for the lubricating oil that is completely miscible with the refrigerant, the liquid reservoir absorbs part of the refrigerant from the first heat exchanger or the second heat exchanger, the solubility in the liquid reservoir increases, the liquid level rises, and the lubricating oil can be timely replenished to the compressor oil pool through the first oil return hole, effectively shortening the oil return time of the compressor.

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

[0038] 4. In the air-conditioning system provided by the present invention that can realize rapid oil return during the startup process of the compressor, since the effective volume of the bottom of the cylinder and the lubricating oil filling amount are increased compared with the prior art, the total oil amount in the air-conditioning system is increased, and the liquid refrigerant entering the liquid reservoir will first be mixed with the lubricating oil stored in the liquid reservoir, thereby 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 can realize rapid oil return during the compressor startup process, is also provided with a second oil return hole. This design can ensure that the lubricating oil in the cylinder body quickly returns to the compressor, 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 capable of realizing rapid oil return during the compressor startup process provided by the present invention is not only applicable to the design of rapid oil return of a single air conditioning system, but also to a multi-connected system.

[0041] 7. The present invention is of great significance for improving the reliability of the compressor during the startup of the air-conditioning system and promoting the application of the air-conditioning system under low temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0043] Figure 2 Schematic diagram of the structure of the liquid storage device in an embodiment of the present invention.

[0044] Figure 3 Schematic diagram of the gas-liquid separation process in the liquid storage device according to an embodiment of the present invention.

[0045] Figure 4 This is the two-layer separation curve of R410A refrigerant and 1# lubricating oil.

[0046] The reference numerals are as follows:

[0047] 1- compressor, 2- oil separator, 3- four-way reversing valve, 4- first heat exchanger, 5- second heat exchanger, 6- liquid reservoir, 61- cylinder, 62- inlet pipe, 63- outlet pipe, 631- pressure equalizing hole, 632- first oil return hole, 633- second oil return hole, 64- lubricating oil, 7- throttling element. DETAILED DESCRIPTION

[0048] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that these embodiments are only 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 can realize rapid oil return during the compressor startup process, 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 reservoir 6, a throttling element 7, and corresponding connecting pipelines. Among them, the liquid reservoir 6 is connected to the air intake 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 reservoir 6 are respectively 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 and high-pressure gas from the outlet of the compressor 1 passes through the oil separator 2 and the four-way reversing valve 3 and enters the second heat exchanger 5 (i.e., the indoor heat exchanger) for condensation, releasing heat to the outside to achieve the heating effect. The temperature and pressure of the condensed liquid are reduced after passing through the throttling element 7. At this time, the refrigerant enters the first heat exchanger 4 (i.e., the outdoor heat exchanger) for heat exchange. The gas-liquid two-phase flow at the outlet of the first heat exchanger 4 passes through the four-way reversing valve 3 and enters the liquid storage 6. After gas-liquid separation, the refrigerant returns to the compressor 1 again. At this time, 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 and high-pressure gas from the outlet of the compressor 1 passes through the oil separator 2 and the four-way reversing valve 3, and then enters the first heat exchanger 4 (i.e., the outdoor heat exchanger) for heat exchange, releasing heat to the outside. The temperature and pressure of the condensed liquid are reduced after passing through the throttling element 7. At this time, the refrigerant enters the second heat exchanger 5 (i.e., the indoor heat exchanger) for heat exchange. The refrigerant evaporates and absorbs heat, which reduces the indoor temperature and achieves the refrigeration effect. The gas-liquid two-phase flow at the outlet of the second heat exchanger 5 passes through the four-way reversing valve 3 and enters the liquid storage tank 6. After gas-liquid separation, the refrigerant returns to the compressor 1 again, and the low-temperature and low-pressure refrigerant gas is compressed into a high-temperature and high-pressure gas again, and enters the system pipeline from the outlet of the compressor 1. At this time, the first heat exchanger 4 acts as a condenser, and the second heat exchanger 5 acts as an evaporator.

[0052] The accumulator 6 is a key device of the air conditioning system, and is mainly installed on the pipeline between the four-way reversing valve 3 and the air intake of the compressor 1. The inlet of the accumulator 6 is generally the gas-liquid two-phase flow from the evaporator, and stores the excess refrigerant / oil liquid mixture before entering the compressor 1. At the same time, the outlet of the accumulator 6 is connected to the air intake of the compressor 1, so that the lubricating oil entrained by the refrigerant can be returned to the compressor 1 to ensure the lubrication of the compressor 1.

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

[0054] Alternatively, there are multiple second heat exchangers 5 and corresponding throttling elements 7, and the two correspond one to one, and each throttling element 7 is located on the connecting pipeline between the corresponding first heat exchanger 4 and the second heat exchanger 5.

[0055] like Figure 2 As shown, the accumulator 6 of 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, protect the compressor 1 from the influence of a large amount of liquid when starting, and ensure that the compressor 1 has sufficient oil supply.

[0056] The inlet pipe 62 is vertically 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 bent toward the outlet pipe 63, and 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 which is connected to the air intake port of the compressor 1, and the other end extends into the cylinder 61. The outlet pipe 63 extending into the cylinder 61 is a U-shaped structure with one end high and the other end low, and the height of the lower end of the U-shaped structure is generally lower than the height of the horizontal part of the bending structure.

[0058] In this embodiment, a pressure equalizing hole 631 is provided at the higher end of the U-shaped structure, which is higher than the bending structure, to balance the internal and external pressures of the outlet pipe 63, so as to prevent the liquid stored at the bottom of the cylinder 61 from being siphoned into the compressor through the oil return hole during the period when the compressor 1 stops running. A first oil return hole 632 is provided at the bottom of the U-shaped structure in the horizontal direction, and the liquid stored at the bottom of the cylinder 61 returns to the compressor 1 together with the refrigerant through the first oil return hole 632. 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 volume of the oil pool of the compressor 1, and this volume can be used to store the lubricating oil 64 discharged from the inside of the compressor 1 when it is started for the first time. On the one hand, this volume design provides storage space for the lubricating oil 64 discharged from the inside of the compressor 1, and on the other hand, it effectively improves the situation that excessive refrigerant enters the compressor 1 and the oil return of the compressor 1 is insufficient due to the stratification of the refrigerant and the lubricating oil 64 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 system components and system pipelines is small, and the cylinder 61 cannot replenish sufficient lubricating oil 64 to the compressor 1 in time during the compressor startup process. In addition, under low temperature conditions, it is easy for the first oil return hole 632 to be located in the refrigerant-rich layer, so that the lubricating oil 64 in the cylinder 1 cannot flow back to the compressor, resulting in oil shortage in the compressor 1. If the effective volume is greater than 3 / 4, the compressor 1 will be filled with excessive lubricating oil 64, which is not conducive to the discharge of refrigerant gas.

[0059] Based on this structural design, during the startup process of the compressor 1, the lubricating oil 64 in the liquid reservoir 6 can be replenished into the compressor 1 in time, and the lubricating oil 64 no longer needs to circulate through the compressor 1, the condenser, the evaporator and the liquid reservoir 6 before returning to the oil, thereby ensuring a high liquid level in the oil pool of the compressor 1 during the startup process and avoiding the oil dry phenomenon.

[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 pool volume of the compressor 1. The liquid reservoir 6 of this solution can be applied to most single-unit air-conditioning systems to 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 volume of the oil pool of the compressor 1. The liquid reservoir 6 of this solution can be applied to air-conditioning systems for long-term low-temperature heating and multi-split systems with large height differences and long system pipelines. Because the long-term low-temperature heating system has stratification of lubricating oil 64 and refrigerant when starting, and the multi-split system with large height differences and long outdoor connection pipelines has a longer oil return time (because the system pipeline is long) and a greater oil return volume requirement (because the lubricating oil 64 is more likely to remain in the pipeline), these two air-conditioning systems are suitable for liquid reservoirs 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 close to the first oil return hole 632. Its function is to increase the oil return amount of the compressor 1 when the liquid level in the liquid reservoir 6 is high, so as to realize rapid oil return of the compressor 1 during the startup process.

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

[0064] The lubricating oil 64 is the lubricating oil 64 that migrates to the reservoir 6 after the compressor 1 is started for the first time after the oil sealing amount of the compressor 1 is increased. The lubricating oil 64 above 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] Because the pressure inside the accumulator 6 is relatively low before the air conditioning system is started, the solubility of the refrigerant is also relatively low. When the air conditioning system is started, part of the lubricating oil 64 is carried out of the compressor 1 by the refrigerant, and the liquid level of the oil pool of the compressor 1 will drop. At this time, the refrigerant in the corresponding heat exchanger enters the accumulator 6, and the solubility of the refrigerant in the accumulator 6 increases, the liquid level rises, and the lubricating oil 64 can be replenished to the compressor in time, thereby avoiding the oil shortage phenomenon of the compressor 1.

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

[0067] The inlet pipe 62 is passed into the cylinder 61, and the gas-liquid two-phase flow from the corresponding heat exchanger enters the cylinder 61 through the inlet pipe 62. The liquid refrigerant and lubricating oil 64 are deposited to the bottom of the cylinder 61 under the action of their own gravity and fully mixed with the lubricating oil 64, thereby improving the lubricating oil / refrigerant ratio entering the compressor 1. At the same time, the liquid level in the cylinder 61 rises and submerges the first oil return hole 632. The gaseous refrigerant forms a rotating airflow in the upper cavity of the cylinder 61, thereby completing the gas-liquid separation. A part of the gaseous refrigerant located in the upper cavity of the cylinder 61 enters the outlet pipe 63 through the lower section of the U-shaped structure, and mixes with the lubricating oil 64 entering the outlet pipe 63 through the first oil return hole 632 to form a gas-liquid two-phase flow. A part enters the outlet pipe 63 through the pressure equalizing hole 631 on the outlet pipe 63, mixes with the gas-liquid two-phase flow, and returns to the compressor 1 together. When the liquid level in 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 interior of 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, a large amount of lubricating oil 64 is filled inside the compressor 1. 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 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 in sequence, and then enters the liquid reservoir 6 through the four-way reversing valve 3 again and is stored in the effective volume at the bottom of the cylinder 61 of the liquid reservoir 6. During the subsequent startup process of the compressor 1, the liquid reservoir 6 absorbs a portion of the refrigerant from the corresponding heat exchanger, so that the solubility of the refrigerant in the cylinder 61 of the liquid reservoir 6 increases, the liquid level rises, and the lubricating oil 64 in the cylinder 61 passes through the first reflux hole 632 and the second reflux hole 633 and enters the outlet pipe 63, and then flows back to the compressor 1, realizing rapid oil return.

[0070] During refrigeration, the lubricating oil 64 discharged from the compressor 1 passes 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 in sequence, and then enters the liquid reservoir 6 through the four-way reversing valve 3 again and is stored in the effective volume at the bottom of the cylinder 61 of the liquid reservoir 6. During the subsequent startup process of the compressor 1, the liquid reservoir 6 absorbs a portion of the refrigerant from the corresponding heat exchanger, so that the solubility of the refrigerant in the cylinder 61 of the liquid reservoir 6 increases, the liquid level rises, and the lubricating oil 64 in the cylinder 61 passes through the first reflux hole 632 and the second reflux hole 633 and enters the outlet pipe 63, and then flows back to the compressor 1, realizing rapid oil return.

[0071] Figure 4 It is a two-layer separation curve diagram of R410A refrigerant and 1# lubricant oil. It can be seen from the figure that the two curves represent the dividing lines of mutual solubility and stratification of refrigerant and lubricant oil at different temperatures, and the area within the two curves indicates that the refrigerant and lubricant oil mixture exists in a two-phase state. In the temperature range between the upper critical temperature corresponding to the upper critical point 01 and the lower critical temperature corresponding to the lower critical point 02, the refrigerant and lubricant oil are single-phase, that is, the two are miscible in any proportion. When the air-conditioning system is in low temperature conditions for a long time, the ambient temperature of the liquid storage tank 6 is much lower than the lower critical temperature corresponding to the lower critical point 02 on the miscibility curve. At this time, the refrigerant and lubricant oil are stratified and separated into a lubricant-rich layer containing more oil and a refrigerant-rich layer containing more refrigerant. At the same time, since the density of the liquid refrigerant is greater than the density of the lubricant, the refrigerant-rich layer is located in the lower layer and the lubricant-rich layer is located in the upper layer. The effective volume below the oil return hole at the bottom of the traditional reservoir is small. After the lubricating oil is placed upward due to stratification, the amount of lubricating oil returning to the compressor from the bottom oil return hole is greatly reduced, which easily causes the compressor to be short of oil and affects the reliability of the compressor. Based on this, the present invention increases the effective volume below the bottom oil return hole (i.e., the effective volume below the U-shaped structure) so that the oil return hole is located in the lubricating oil-rich layer, thereby ensuring timely oil return of the compressor.

[0072] In addition, this embodiment also provides a design method for an air conditioning system that can achieve rapid oil return during the compressor startup process, comprising the following steps:

[0073] Step [1]: According to preset requirements, a compressor 1, an oil separator 2, a four-way reversing valve 3, a first heat exchanger 4 and a second heat exchanger 5 of corresponding specifications are pre-selected.

[0074] Step [2] According to the preset process requirements, complete the piping design between the compressor 1, oil separator 2, four-way reversing valve 3, first heat exchanger 4, second heat exchanger 5, and liquid storage tank 6 selected 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 to be designed.

[0075] Step [3], based on the oil pool volume of the compressor 1 and the maximum refrigerant charge of the air conditioning system to be designed, calculate the effective volume of the cylinder 61 of the liquid storage tank 6.

[0076] The calculation formula of the effective volume V of the cylinder 61 of the liquid storage device 6 is:

[0077]

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

[0079] Step [4], based on the effective volume V of the cylinder 61 calculated in step [3], select the inlet pipe 62 and the outlet pipe 63 of corresponding length, and design the portion of the inlet pipe 62 extending into the cylinder 61 as a bent structure, and design the portion of the outlet pipe 63 extending into the cylinder 61 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 61 and the bottom of the U-shaped structure is 1 / 4 to 3 / 4 of the volume of the oil pool of the compressor 1. The effective volume at the bottom of the cylinder 61 can also be adjusted accordingly according to actual needs.

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

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

[0082] The design of the pressure equalizing hole 631 is to prevent the liquid stored in the liquid reservoir 6 from being siphoned into the compressor 1 through the first oil return hole 632 when the compressor 1 is stopped, thereby preventing liquid hammer from occurring when the compressor 1 is restarted. The height of the pressure equalizing hole 631 is generally slightly higher than the bent structure of the inlet pipe 62.

[0083] According to actual needs, a second oil return hole 633 can be designed at the lower end of the U-shaped structure near the first oil return hole 632 to ensure the efficiency of oil return. 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 aperture of the second oil return hole 633 is the same as the aperture of the first oil return hole 632.

[0084] Step [7] According to the preset process requirements, sufficient lubricating oil 64 is filled into the compressor 1, thereby completing the design of the air-conditioning system that can achieve rapid oil return during the compressor startup process.

[0085] In this embodiment, after the compressor 1 is filled with sufficient lubricating oil 64, when the compressor 1 is started for the first time, the lubricating oil 64 inside is discharged into the cylinder 61 of the liquid reservoir 6 (the effective volume below the first oil return hole 632 provides storage space for the lubricating oil 64), and 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, and the remaining lubricating oil 64 is still stored at the bottom of the cylinder 61. In the subsequent startup process of the compressor 1, the liquid reservoir 6 absorbs a part of the refrigerant from the first heat exchanger 4 or the second heat exchanger 5, the solubility in the liquid reservoir 6 increases, the liquid level rises, and the lubricating oil 64 can be timely replenished to the oil pool of the compressor 1 through the first oil return hole 632, which effectively shortens the oil return time of the compressor.

[0086] In summary, the air conditioning system of the present invention can effectively reduce the oil return time of the compressor, ensure the balance of oil return and liquid return, and thus ensure 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 realizing rapid oil return during the compressor startup process, comprising 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 reservoir (6) and corresponding connecting pipelines; characterized in that: The liquid storage container (6) comprises 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 interior of the compressor (1) and stored in the cylinder (61) when the compressor (1) is started for the first time, and during the subsequent starting process, the lubricating oil (64) in the cylinder (61) is used to replenish the interior of 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), and the inlet pipe (62) extending into the cylinder (61) is a bent structure bent toward the outlet pipe (63); The outlet pipe (63) is installed on the top of the cylinder (61), one end of which is connected to the air intake port of the compressor (1), and the other end of which extends into the cylinder (61), and the outlet pipe (63) extending into the cylinder (61) is a U-shaped structure with one end higher than the other end; a pressure equalizing hole (631) is provided at the higher end of the U-shaped structure near the upper part of the bending structure; and 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 volume of the oil pool of the compressor (1).

2. The air conditioning system capable of realizing rapid oil return during compressor startup according to claim 1, characterized in that: A second oil return hole (633) is provided on the side wall of the lower end of the U-shaped structure, and the height of the central axis of the second oil return hole (633) is at the same height as the center of the circular arc at the bottom of the U-shaped structure.

3. The air conditioning system capable of realizing rapid oil return during compressor startup according to claim 2, 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 volume of the oil pool of the compressor (1).

4. The air conditioning system capable of realizing rapid oil return during compressor startup according to claim 2, 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 volume of the oil pool of the compressor (1).

5. The air conditioning system capable of realizing rapid oil return during compressor startup according to any one of claims 1 to 4, 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 bending structure.

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

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

8. A design method for an air conditioning system capable of realizing rapid oil return during compressor startup, characterized in that: The following steps are involved: Step [1], according to preset requirements, preselect a compressor (1), an oil separator (2), a four-way reversing valve (3), a first heat exchanger (4) and a second heat exchanger (5) of corresponding specifications; Step [2], according to the preset process requirements, complete the design of the pipelines between the compressor (1), the oil separator (2), the four-way reversing valve (3), the first heat exchanger (4), the second heat exchanger (5), and the liquid storage device (6) 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; Step [3], calculating the volume of the cylinder (61) of the liquid accumulator (6) according to the volume of the oil pool of the compressor (1) and the maximum refrigerant charge of the air conditioning system; Step [4], according to the volume of the cylinder (61) described in step [3], selecting an inlet pipe (62) and an outlet pipe (63) of corresponding lengths, and designing the portion of the inlet pipe (62) extending into the cylinder (61) to be a bent structure, and designing the portion of the outlet pipe (63) extending into the cylinder (61) to be a U-shaped structure with one end higher than the other end, 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 volume of the oil pool of the compressor (1); Step [5], based on the diameter of the outlet pipe (63), design a first oil return hole (632) in a horizontal direction on the bottom side wall of the U-shaped structure; Step [6]: Based on step [5], a pressure equalizing hole (631) is designed at a position where the higher end of the U-shaped structure is higher than the bent structure of the inlet pipe, thereby completing the design of the liquid storage device (6); Step [7]: according to the preset process requirements, sufficient lubricating oil (64) is filled into the compressor (1), thereby completing the design of an air conditioning system that can achieve rapid oil return during the compressor startup process.

9. The design method of an air conditioning system capable of realizing rapid oil return during compressor startup according to claim 8, characterized in that: Step [6] also includes the step of designing a second oil return hole (633) at the lower end of the U-shaped structure near 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 aperture of the second oil return hole (633) is the same as the aperture of the first oil return hole (632).

10. The design method of an air conditioning system capable of realizing rapid oil return during compressor startup according to claim 9, characterized in that: In step [7], after the compressor (1) is filled with sufficient lubricating oil (64), 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 reservoir (6), and 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) is still stored at the bottom of the cylinder (61).

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