Low-pressure stand-alone auto-cascade refrigeration system and control method
By connecting a one-way valve in parallel with the capillary tube of the liquid storage tank, and combining it with a pressure controller and a solenoid valve, the problem of compressor starting difficulty in a single-unit self-cascade refrigeration system was solved, achieving system pressure balance and improved stability.
Patent Information
- Application Number
- CN202411252099.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-09
- Publication Date
- 2024-12-10
AI Technical Summary
In existing single-unit self-cascade refrigeration systems, the connection between the liquid receiver and the capillary tube is not conducive to the rapid pressure balance of the refrigeration system, resulting in high pressure when the compressor starts and difficulty in starting.
A one-way valve is connected in parallel at the capillary tube of the receiver tank. When the compressor starts, the refrigerant slowly flows back to the receiver tank, and when the compressor stops, the refrigerant flows quickly to the receiver tank. Combined with the pressure controller and solenoid valve, the flow of refrigerant is controlled to ensure system pressure balance.
It enables the refrigeration system to quickly balance pressure during compressor startup, reduces startup difficulties, reduces the impact of high-pressure refrigerant on the compressor, and improves system stability and efficiency.
Smart Images
Figure CN119103739A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of refrigeration systems, and in particular to a low-pressure single-machine self-cascade refrigeration system and a control method thereof. Background Art
[0002] With the increasing application of ultra-low temperature storage boxes and deep low temperature storage boxes, the single-machine cascade refrigeration system is increasingly used. At present, most single-machine cascade refrigeration systems simply add a liquid storage tank. Setting a liquid storage tank at the return air end of the single-machine cascade refrigeration system is mainly used to reduce the pressure when the compressor starts, which is more conducive to the start-up of the compressor. However, the liquid storage tank currently used is simply connected to the liquid storage tank with a capillary tube, which is not conducive to the rapid balance of pressure in the refrigeration system. If the compressor needs to be started quickly, the pressure will be high at startup, making it difficult to start. Summary of the invention
[0003] In order to overcome the above problems existing in the prior art, the present invention proposes a low-pressure single-machine auto-cascade refrigeration system and a control method.
[0004] The technical solution adopted by the present invention to solve its technical problem is: a low-pressure single-machine self-cascade refrigeration system, including a compressor, a condenser, a gas-liquid separator, a primary filter drier, a primary capillary tube, a heat exchanger, a secondary filter drier, a secondary capillary tube, and an evaporator connected in sequence, the gas-liquid separator separates the refrigerant into a liquid refrigerant and a gas refrigerant, the liquid refrigerant enters the heat exchanger through the primary filter drier and the primary capillary tube and returns to the compressor, the gas refrigerant enters the heat exchanger for condensation, passes through the secondary filter drier, the secondary capillary tube, and the evaporator, and then enters the heat exchanger and returns to the compressor after completion, and also includes A pressure controller, a solenoid valve, a liquid storage tank, a liquid storage tank capillary, and a one-way valve, wherein one end of the pressure controller is connected to the compressor exhaust pipe, and the other end is electrically connected to the solenoid valve, the outlet end of the condenser is connected to the liquid storage tank through a first connecting pipeline, the solenoid valve is installed on the first connecting pipeline, the air inlet end of the compressor is provided with a second connecting pipeline, the second connecting pipeline is connected in parallel with the first connecting pipeline, the second connecting pipeline is connected to the liquid storage tank through a liquid storage tank capillary, the liquid storage tank capillary is connected in parallel with the one-way valve, and the one-way valve controls the refrigerant to flow only from the compressor to the liquid storage tank but not from the liquid storage tank back to the compressor.
[0005] In the above-mentioned low-pressure single-machine self-cascade refrigeration system, the pressure controller is connected to the compressor exhaust pipe through a pressure controller capillary tube.
[0006] In the above-mentioned low-pressure single-machine auto-cascade refrigeration system, the capillary flow rate of the liquid storage tank is determined according to the volume of the liquid storage tank.
[0007] In the above-mentioned low-pressure single-unit self-cascade refrigeration system, when the volume of the liquid storage tank is less than or equal to 3L, the capillary flow rate of the liquid storage tank is a constant flow rate of 5L / min; when the volume of the liquid storage tank is greater than or equal to 13L, the capillary flow rate of the liquid storage tank is a constant flow rate of 10L / min; when the volume of the liquid storage tank is greater than 3L and less than 13L, the capillary flow rate of the liquid storage tank is calculated according to q=V / 2+3.5, wherein q represents the capillary flow rate of the liquid storage tank, and V represents the volume of the liquid storage tank.
[0008] A control method for a low-pressure single-machine self-cascade refrigeration system is based on the above-mentioned low-pressure single-machine self-cascade refrigeration system. The specific process is as follows: when the compressor is started, the refrigerant enters the condenser through the compressor exhaust pipe, and the pressure sensor tests the exhaust pressure in real time. When the exhaust pressure is ≥ a predetermined pressure value, the solenoid valve opens, and part of the refrigerant is diverted through the solenoid valve into the liquid storage tank; part of the refrigerant enters the gas-liquid separator for separation, and the liquid phase refrigerant flows out from the bottom by gravity into the primary drying filter and the primary capillary tube, and then enters the heat exchanger for evaporation and heat absorption, and then returns to the compressor; the gas phase refrigerant enters the heat exchanger for condensation, and then enters the secondary drying filter and the secondary capillary tube, and then enters the evaporator for evaporation, and after completion, enters the heat exchanger again, and then returns to the compressor; at the same time, the refrigerant in the liquid storage tank will slowly flow back to the compressor through the liquid storage tank capillary tube to ensure that there is enough refrigerant in the refrigeration system; When the compressor stops, the refrigerant will quickly enter the liquid storage tank through the one-way valve to achieve pressure balance in the entire refrigeration system.
[0009] The beneficial effect of the present invention is that the present invention connects a one-way valve in parallel at the position of the liquid storage tank capillary, and the flow direction of the one-way valve is from the end of the compressor process pipe to the end of the liquid storage tank. At the initial start-up of the compressor, the refrigerant slowly flows back to the compressor from the liquid storage tank through the liquid storage tank capillary, so that all the refrigerant in the refrigeration system is in the refrigeration cycle, and the refrigeration capacity of the refrigeration system is met. When the compressor stops, the refrigerant quickly flows to the liquid storage tank through the one-way valve, reducing the impact of the high-pressure refrigerant on the compressor. The pressure controller measures the exhaust pressure, and when the exhaust pressure is ≥ the predetermined pressure value, the solenoid valve switch is opened, and the high-pressure refrigerant will enter the liquid storage tank through the solenoid valve to reduce the exhaust pressure. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 It is a schematic diagram of the present invention; FIG. 2 is a capillary flow curve diagram of the liquid storage tank of the present invention.
[0011] Among them, 1. liquid storage tank, 2. solenoid valve, 3. pressure controller, 4. pressure controller capillary, 5. condenser, 6. gas-liquid separator, 7. primary drying filter, 8. primary capillary, 9. plate heat exchanger, 10. secondary drying filter, 11. secondary capillary, 12. evaporator, 13. compressor, 14. one-way valve, 15. liquid storage tank capillary. DETAILED DESCRIPTION
[0012] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0013] This embodiment discloses a low-pressure single-machine self-cascade refrigeration system. Figure 1 As shown, it includes a compressor 13, a condenser 5, a gas-liquid separator 6, a primary filter dryer 7, a primary capillary tube 8, a plate heat exchanger 9, a secondary filter dryer 10, a secondary capillary tube 11, and an evaporator 12 connected in sequence. The gas-liquid separator separates the refrigerant into liquid refrigerant and gas refrigerant, which enter the two systems of the plate heat exchanger respectively. The liquid refrigerant evaporates and absorbs heat, and the gas refrigerant condenses and releases heat. The condensed refrigerant enters the evaporator to evaporate and absorb heat. The liquid refrigerant enters the plate heat exchanger 9 through the primary filter dryer 7 and the primary capillary tube 8 and returns to the compressor 13. After the gas refrigerant enters the plate heat exchanger 9 and condenses, it passes through the secondary filter dryer 10, the secondary capillary tube 11, and the evaporator 12. After completion, it enters the plate heat exchanger 9 and returns to the compressor. The evaporator return gas pipeline exchanges heat with the secondary system refrigerant through the plate heat exchanger and then returns to the compressor, reducing the overall temperature, while appropriately increasing the return gas temperature, reducing the refrigerant liquid accumulation, and thus damaging the compressor.
[0014] It also includes a pressure controller 3, a solenoid valve 2, a liquid storage tank 1, a liquid storage tank capillary 15, and a one-way valve 14. One end of the pressure controller 3 is connected to the compressor exhaust pipe through the pressure controller capillary 4, and the other end is connected to the solenoid valve through a wiring harness. The pressure controller can adjust the pressure switch limit according to the compressor's pressure resistance and the system operating pressure. The outlet end of the condenser 5 is connected to the liquid storage tank 1 through a first connecting pipeline, and the solenoid valve 2 is installed on the first connecting pipeline. The solenoid valve realizes the on and off of the solenoid valve by judging the pressure controller signal. A second connecting pipeline is provided at the air inlet end of the compressor, and the second connecting pipeline is connected in parallel with the first connecting pipeline. The second connecting pipeline is connected to the liquid storage tank 1 through the liquid storage tank capillary 15, and the liquid storage tank capillary 15 is connected in parallel with the one-way valve 14. The one-way valve 14 controls the refrigerant to flow only from the compressor to the liquid storage tank and cannot flow back from the liquid storage tank to the compressor.
[0015] In this embodiment, the capillary flow rate of the liquid storage tank is related to the volume of the liquid storage tank, as shown in Figure 2. When the volume of the liquid storage tank V≤3L, a small volume liquid storage tank should select a smaller flow rate liquid storage tank capillary. At this time, the refrigeration system is relatively small, the volume of the liquid storage tank is small, and the small flow rate liquid storage tank has little effect on the operation of the refrigeration system. Therefore, the capillary flow rate of the liquid storage tank is based on a constant flow rate (flow rate under 1Mpa pressure) q=5L / min.
[0016] When the volume of the liquid storage tank V ≥ 13L, a larger flow rate liquid storage tank capillary should be selected for a large volume liquid storage tank. At this time, the refrigeration system is relatively large and the volume of the liquid storage tank is large. Excessive capillary flow will cause impact on the compressor and thus damage the compressor. Therefore, the liquid storage tank capillary flow rate is based on a constant flow rate (flow rate under 1Mpa pressure) q = 10L / min.
[0017] When the volume of the liquid storage tank is 3L<V<13L, the refrigeration system is more sensitive to the selection of the liquid storage tank size and the capillary flow rate of the liquid storage tank. Therefore, the capillary flow rate of the liquid storage tank is calculated according to (flow rate under 1Mpa pressure) q=V / 2+3.5, where q is the capillary flow rate of the liquid storage tank and V is the volume of the liquid storage tank, in L.
[0018] When the compressor 13 of the system is started, the high-temperature and high-pressure refrigerant enters the condenser 5 through the exhaust pipe of the compressor 13, and the pressure sensor 3 tests the exhaust pressure in real time. When the exhaust pressure is ≥ the predetermined pressure value, the solenoid valve 2 opens, and part of the refrigerant will be diverted through the solenoid valve 2 into the liquid storage tank 1. Part of the refrigerant enters the gas-liquid separator 6 for separation, and the liquid phase refrigerant flows out from the bottom by gravity into the primary drying filter 7 and the primary capillary 8, and then enters the plate heat exchanger 9 for evaporation and heat absorption, and then returns to the compressor 13; the gas phase refrigerant enters the plate heat exchanger 9 for condensation, and then enters the secondary drying filter 10 and the secondary capillary 11, and then enters the evaporator 12 for evaporation, and then enters the plate heat exchanger 9 after completion, and then returns to the compressor 13. At the same time, the refrigeration in the liquid storage tank 1 will slowly flow back to the compressor through the liquid storage tank capillary 8 to ensure that there is enough refrigerant in the refrigeration system.
[0019] When the compressor 13 of the system stops, the refrigerant in the refrigeration system will quickly enter the liquid storage tank 1 through the one-way valve 14, so as to achieve pressure balance of the entire refrigeration system and reduce the delay time of restarting the compressor.
[0020] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.
Claims
1. A low-pressure single-machine self-cascade refrigeration system, comprising a compressor, a condenser, a gas-liquid separator, a primary filter drier, a primary capillary tube, a heat exchanger, a secondary filter drier, a secondary capillary tube, and an evaporator connected in sequence, wherein the gas-liquid separator separates the refrigerant into a liquid-phase refrigerant and a gas-phase refrigerant, the liquid-phase refrigerant passes through the primary filter drier and the primary capillary tube and enters the heat exchanger to return to the compressor, the gas-phase refrigerant enters the heat exchanger for condensation, passes through the secondary filter drier, the secondary capillary tube, and the evaporator, and then enters the heat exchanger to return to the compressor. It is characterized in that It also includes a pressure controller, a solenoid valve, a liquid storage tank, a liquid storage tank capillary, and a one-way valve. One end of the pressure controller is connected to the compressor exhaust pipe, and the other end is electrically connected to the solenoid valve. The condenser outlet is connected to the liquid storage tank through a first connecting pipeline. The solenoid valve is installed on the first connecting pipeline. The compressor inlet end is provided with a second connecting pipeline. The second connecting pipeline is connected in parallel with the first connecting pipeline. The second connecting pipeline is connected to the liquid storage tank through a liquid storage tank capillary. The liquid storage tank capillary is connected in parallel with the one-way valve. The one-way valve controls the refrigerant to flow only from the compressor to the liquid storage tank but not from the liquid storage tank back to the compressor.
2. A low-pressure single-unit auto-cascade refrigeration system according to claim 1, It is characterized in that The pressure controller is connected to the compressor exhaust pipe through a pressure controller capillary.
3. A low-pressure single-unit auto-cascade refrigeration system according to claim 1, It is characterized in that The capillary flow rate of the liquid storage tank is determined according to the volume of the liquid storage tank.
4. A low-pressure single-unit auto-cascade refrigeration system according to claim 3, It is characterized in that When the volume of the liquid storage tank is less than or equal to 3L, the capillary flow rate of the liquid storage tank is a constant flow rate of 5L / min; when the volume of the liquid storage tank is greater than or equal to 13L, the capillary flow rate of the liquid storage tank is a constant flow rate of 10L / min; when the volume of the liquid storage tank is greater than 3L and less than 13L, the capillary flow rate of the liquid storage tank is calculated according to q=V / 2+3.5, where q represents the capillary flow rate of the liquid storage tank and V represents the volume of the liquid storage tank.
5. A control method for a low-pressure single-machine auto-cascade refrigeration system. It is characterized in that A low-pressure single-unit self-cascade refrigeration system based on any one of claims 1 to 4, the specific process is: when the compressor is started, the refrigerant enters the condenser through the compressor exhaust pipe, and the pressure sensor tests the exhaust pressure in real time. When the exhaust pressure is ≥ the predetermined pressure value, the solenoid valve opens, and part of the refrigerant is diverted through the solenoid valve into the liquid storage tank; part of the refrigerant enters the gas-liquid separator for separation, and the liquid refrigerant flows out from the bottom by gravity into the first-level drying filter and the first-level capillary tube, and then enters the heat exchanger for evaporation and heat absorption, and then returns to the compressor; The gas phase refrigerant enters the heat exchanger for condensation, then enters the secondary filter dryer and the secondary capillary tube, and then enters the evaporator for evaporation. After completion, it enters the heat exchanger again, and then returns to the compressor; at the same time, the refrigerant in the liquid storage tank will slowly flow back to the compressor through the liquid storage tank capillary tube to ensure that there is enough refrigerant in the refrigeration system; When the compressor stops, the refrigerant will quickly enter the liquid storage tank through the one-way valve to achieve pressure balance in the entire refrigeration system.