A low temperature oil return device for cascade refrigeration system

Abstract

The present invention discloses a low-temperature oil return device for a cascade refrigeration system, including an evaporator, a condenser, a compressor, an oil separator, a fine filter, a return air pipeline and a liquid supply pipeline. The evaporator is connected to the compressor, the oil separator and the condenser in sequence through the return air pipeline, and the condenser is connected to the evaporator through the liquid supply pipeline and the fine filter to form a heat exchange cycle. The return air pipeline is connected in parallel with the compressor and the oil separator through a bypass pipeline, and the fine filter is connected in series on the bypass pipeline. The present invention connects a fine filter in parallel to the liquid supply pipeline of the evaporator to intercept solid oil. By switching valves at a fixed time, the solidified oil can be melted by hot air and brought back to the compressor. The oil return time is adjustable. A throttling hand valve is installed on the bypass pipeline to adjust the flow pressure of the hot air. The device can effectively prevent or minimize the lubricating oil from entering the evaporator of the cascade low-temperature system, ensuring the long-term stable operation of the cascade unit and the continuous operation requirements of ultra-low temperature applications.

Description

Technical Field

[0001] The invention relates to the technical field of refrigeration systems, and in particular to a low-temperature oil return device for a cascade refrigeration system. Background Art

[0002] Cascade refrigeration systems are often used in ultra-low temperature (≤-60℃) applications, such as environmental testing equipment, oil and gas recovery, and drug freeze-drying. When the evaporation temperature of the low-temperature stage of the cascade system is lower than -50℃~-60℃ (depending on the pour point of the lubricant), the lubricant entering the evaporator will become solid and remain in the evaporator, slowly causing the compressor to lack oil and the evaporator to increase thermal resistance and reduce its refrigeration capacity. Summary of the invention

[0003] The purpose of the present invention is to provide a low-temperature oil return device for a cascade refrigeration system to solve the problems existing in the above-mentioned prior art. The oil is melted and brought back to the compressor through a hot gas liquid supply pipeline to prevent the lubricating oil from entering the evaporator, thereby ensuring long-term ultra-low temperature stable operation of the cascade unit.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a low-temperature oil return device for a cascade refrigeration system, comprising an evaporator, a condenser, a compressor, an oil separator, a fine filter, an air return pipeline and a liquid supply pipeline. The evaporator is connected to the compressor, the oil separator and the condenser in sequence through the air return pipeline, and the condenser is connected to the fine filter and the evaporator in sequence through the liquid supply pipeline to form a heat exchange cycle. The air return pipeline is connected in parallel with the compressor and the oil separator through a bypass pipeline, and the bypass pipeline can be connected in series with the fine filter.

[0006] Preferably, a solenoid valve and an expansion valve are provided on the liquid supply pipeline.

[0007] Preferably, a valve is provided at both ends of the compressor and the oil separator.

[0008] Preferably, two of the fine filters are arranged in parallel on the liquid supply pipeline, and a three-way solenoid valve is respectively arranged at both ends of the pipeline at the parallel connection to communicate with the liquid supply pipeline.

[0009] Preferably, the bypass pipeline is divided into two parallel bypass branches through a tee, and each of the bypass branches is connected to one of the fine filters.

[0010] Preferably, a throttle valve is provided at the inlet end of the bypass pipeline.

[0011] Preferably, two solenoid valves are provided on each of the bypass branches, and the solenoid valves are located on the pipeline between the fine filter and the three-way solenoid valve.

[0012] Preferably, the compressor, the three-way solenoid valve, the throttle valve and the solenoid valve are electrically connected to a controller respectively.

[0013] Compared with the prior art, the present invention has achieved the following technical effects:

[0014] The present invention connects a fine filter in parallel to the liquid supply pipeline of the evaporator to intercept the solid oil. By switching the valve at a fixed time, the solidified oil can be melted by hot gas and brought back to the compressor. The oil return time is adjustable. A throttling hand valve is installed on the bypass pipeline for hot gas circulation to adjust the flow and pressure of the hot gas. The invention can effectively prevent or minimize the lubricating oil from entering the evaporator of the cascade low-temperature system, ensure the long-term stable operation of the cascade unit, and meet the requirements of continuous operation of its ultra-low temperature application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a structural schematic diagram of a low temperature oil return device of a cascade refrigeration system of the present invention;

[0017] Among them: 1-evaporator, 2-compressor, 3-oil separator, 4-condenser, 5-return air pipeline, 6-liquid supply pipeline, 7-fine filter, 8-bypass pipeline, 9-bypass branch, 10-throttle valve, 11-three-way solenoid valve, 12-solenoid valve, 13-expansion valve. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The purpose of the present invention is to provide a low-temperature oil return device for a cascade refrigeration system to solve the problems existing in the prior art. The oil is melted and brought back to the compressor through a hot gas liquid supply pipeline to prevent the lubricating oil from entering the evaporator, thereby ensuring long-term ultra-low temperature stable operation of the cascade unit.

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown: This embodiment provides a low-temperature oil return device for a cascade refrigeration system, including an evaporator 1, a condenser 4, a compressor 2, an oil separator 3, a fine filter 7, a return air pipeline 5 and a liquid supply pipeline 6. The evaporator 1 is connected to the compressor 2, the oil separator 3 and the condenser 4 in sequence through the return air pipeline 5, and the condenser 4 is connected to the fine filter 7 and the evaporator 1 in sequence through the liquid supply pipeline 6 to form a heat exchange cycle. The return air pipeline 5 is connected in parallel with the compressor 2 and the oil separator 3 through the bypass pipeline 8, and the bypass pipeline 8 can be connected in series with the fine filter 7 through a valve. In this embodiment, one end of the bypass pipeline 8 at the hot gas end is connected to the exhaust outlet of the oil separator 3, and the other end is connected to the inlet of the fine filter 7. One end of the bypass pipeline 8 at the oil return end is connected to the outlet of the fine filter 7, and the other end is connected to the return air pipeline 5 of the compressor 2.

[0022] The liquid supply pipeline 6 is provided with a solenoid valve 12 and an expansion valve 13. A valve is provided at both ends of the compressor 2 and the oil separator 3. Two fine filters 7 are provided in parallel on the liquid supply pipeline 6, and a three-way solenoid valve 11 is provided at both ends of the pipeline at the parallel connection to communicate with the liquid supply pipeline 6. The fine filter 7 can intercept the solid oil, and then melt the solidified oil through hot air and bring it back to the compressor 2, reducing the lubricating oil entering the evaporator 1 of the cascade low-temperature system, ensuring the long-term stable operation of the cascade unit, and meeting the requirements of continuous operation of the equipment in ultra-low temperature applications.

[0023] The bypass pipeline 8 is divided into two parallel bypass branches 9 through a three-way valve, and each bypass branch 9 is connected to a fine filter 7. A throttle valve 10 is provided at the inlet end of the bypass pipeline 8 to control the flow and pressure of the hot gas. Two solenoid valves 12 are provided on each bypass branch 9, and the solenoid valve 12 is located on the pipeline between the fine filter 7 and the three-way solenoid valve 11.

[0024] The compressor 2, the three-way solenoid valve 11, the throttle valve 10 and the solenoid valve 12 are electrically connected to a controller respectively, so as to realize automatic control. The controller can control the timing switching of the three-way reversing valve, the opening and closing of the solenoid valve 12, and the setting of the oil return time, which is generally set within 5-10 minutes.

[0025] The working principle of the low temperature oil return device of the cascade refrigeration system of this embodiment is as follows:

[0026] After the compressor 2 is started, when the evaporation temperature drops to -50°C, the controller starts timing, and when the set time (such as 120 minutes, adjustable) for opening the bypass line 8 is reached, the three-way solenoid valves 11 on both sides of the fine filter 7 are controlled to switch synchronously, so that the liquid supply line 6 can be switched between the two fine filters 7 to ensure that there is a connection of the liquid supply line 6. After switching the three-way solenoid valve 11, the controller controls the two solenoid valves 12 on the bypass branch 9 of the inoperative fine filter 7 to open, and uses hot air to melt the solidified oil and bring it back to the compressor 2. The oil return time is set at 5-10 minutes.

[0027] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A low temperature oil return device for a cascade refrigeration system, characterized in that: The heat exchanger comprises an evaporator, a condenser, a compressor, an oil separator, a fine filter, a return air pipeline and a liquid supply pipeline. The evaporator is connected to the compressor, the oil separator and the condenser in sequence through the return air pipeline. The condenser is connected to the fine filter and the evaporator in sequence through the liquid supply pipeline to form a heat exchange cycle. Two fine filters are arranged in parallel on the liquid supply pipeline, and a three-way solenoid valve is arranged at both ends of the pipeline at the parallel connection to communicate with the liquid supply pipeline. The return air pipeline is connected in parallel with the compressor and the oil separator through a bypass pipeline, and the bypass The pipeline can be connected in series with the fine filter; the bypass pipeline connected to the two ends of the fine filter is respectively arranged between the evaporator and the compressor, and between the oil separator and the condenser, and the bypass pipeline is divided into two parallel bypass branches through a three-way valve, and each of the bypass branches is connected to a fine filter, and a throttle valve is arranged at the inlet end of the bypass pipeline; two solenoid valves are arranged on each of the bypass branches, and the solenoid valve is located on the pipeline between the fine filter and the three-way solenoid valve; the liquid supply pipeline is provided with a solenoid valve and an expansion valve.

2. The low temperature oil return device of the cascade refrigeration system according to claim 1, characterized in that: A valve is arranged at both ends of the compressor and the oil separator.

3. The low temperature oil return device of the cascade refrigeration system according to claim 1, characterized in that: The compressor, the three-way solenoid valve, the throttle valve and the solenoid valve are electrically connected to a controller respectively.

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