Low-energy-consumption refrigerating system suitable for direct expansion liquid supply and hot gas defrosting

Abstract

The invention discloses a low-energy-consumption refrigerating system suitable for direct expansion liquid supply and hot gas defrosting. The refrigerating system comprises a refrigerating branch and a defrosting branch. A liquid drainage tank is arranged above a liquid reservoir of the refrigerating system, the internal pressure of the liquid drainage tank is lower than the exhaust pressure of the high-pressure side of the refrigerating system, and the pressure difference between the internal pressure and the exhaust pressure is a constant difference value. And a detection system and a liquid level control system which are used for stabilizing a constant difference value are connected with the liquid discharge tank. Hot gas defrosting provided by the system is well applied to a refrigerating system for direct expansion liquid supply, operation is stable and reliable, the system can be used for installation and transformation of existing projects and can also be used for being matched with new equipment for project application, and the increased cost is limited.

Description

Technical Field

[0001] The invention relates to the technical field of refrigeration systems, and in particular to a low-energy consumption refrigeration system suitable for direct expansion liquid supply and hot air defrosting. Background Art

[0002] Due to stricter environmental protection requirements, the limited use of HFC refrigerants such as R404A, R507A, and 134a in domestic industrial and commercial refrigeration systems has been implemented since 2024. The above refrigerants will be increasingly restricted in their application in large and medium-sized refrigeration systems due to their large charge volume; in addition, natural refrigerants such as ammonia and carbon dioxide are considered low-carbon and environmentally friendly, but the safety hazards brought by the large charge volume of such refrigerants cannot be ignored. Therefore, no matter which type of refrigerant is used, low refrigerant charge volume is a direction for the future development of the refrigeration field. In low refrigerant charge refrigeration systems, direct expansion liquid supply refrigeration systems are considered to be the most suitable and currently the most common.

[0003] However, while direct expansion liquid supply brings the advantage of low refrigerant charge to the refrigeration system, it is also accompanied by some unavoidable defects, one of which is that the hot air defrosting of the air cooler is not ideal.

[0004] There are usually three ways to defrost a cold air machine: 1. Electric defrosting; 2. Water defrosting; 3. Hot air defrosting. Considering the system cost and energy consumption, the advantage of hot air defrosting is obvious. Therefore, how to apply hot air defrosting to the direct expansion liquid supply refrigeration system is a question worth exploring.

[0005] See also Figure 1 As shown in FIG. 1 , the most common hot gas defrosting principle used in the prior art for direct expansion liquid supply refrigeration system is as follows: Figure 1As shown. The specific principle is: under the normal operation of the compressor and condenser, when the air cooler-1 is cooling (its fan is running at this time), the electromagnetic pressure difference valve is opened, and there is almost no pressure difference before and after the valve, the 1-1 expansion valve is open, the 1-2 electromagnetic valve is open, and the 1-3 electromagnetic valve is closed; the refrigerant net compressor exhaust pipe is sucked into the compressor through the 5-1 electromagnetic pressure difference valve, the condenser, the liquid storage tank, the 1-1 expansion valve, the air cooler-1, and the 1-2 electromagnetic valve to complete the refrigeration cycle; when the air cooler-1 is defrosting (its fan stops at this time, and other air coolers are in normal refrigeration operation), the 5-1 electromagnetic pressure difference valve is opened (the pressure difference function is turned on at this time, and the pressure difference before and after the valve is about 2bar), the 1-1 expansion valve is closed, the 1-2 electromagnetic valve is closed, and the 1-3 electromagnetic valve is opened. The high-pressure and high-temperature refrigerant discharged from the compressor passes through the 1-3 electromagnetic, the air cooler-1, the 1-4 check valve, the 4-3 check valve, and the liquid storage tank to complete the defrosting cycle. From the above, it is not difficult to find that as long as any of the air coolers is defrosting, the compressor of the entire refrigeration system has to raise the exhaust pressure by about 2 bar. If there are a large number of air coolers in the refrigeration system, they may have to "queue" one after another to defrost. In this way, the system has to operate continuously under high exhaust pressure, which greatly increases the energy consumption of the system.

[0006] Therefore, based on the above technical problems, technicians in this field urgently need to develop a low-energy refrigeration system suitable for direct expansion liquid supply and hot air defrosting. Summary of the invention

[0007] The purpose of the present invention is to provide a low-energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting. The system is suitable for direct expansion liquid supply refrigeration systems of various refrigerants, and the hot gas defrosting mode of the air cooler is completely changed. In order to make the defrosting efficient, stable and safe, and thus improve the efficiency of the entire refrigeration system, a drain tank device is also set in the system, and the pressure in the drain tank is accurately controlled at a constant difference of about 2 Bar below the system exhaust pressure (condensing pressure). .

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A low-energy refrigeration system suitable for direct expansion liquid supply and hot gas defrosting of the present invention comprises a refrigeration branch and a defrosting branch;

[0010] A drain tank is provided above the liquid storage tank of the refrigeration system, and the internal pressure of the drain tank is lower than the exhaust pressure on the high-pressure side of the refrigeration system, and the pressure difference between the two is a constant difference;

[0011] A detection system and a liquid level control system for stabilizing a constant difference are connected to the liquid drainage tank.

[0012] Furthermore, the refrigeration system comprises:

[0013] Compressor, liquid receiver, condenser;

[0014] The compressor is connected with an exhaust pipe and an intake pipe;

[0015] The condenser is connected to the compressor via the exhaust pipe, and the liquid outlet of the condenser is connected to the liquid receiver via the condenser drain pipe;

[0016] One end of the refrigeration branch is connected to the discharge pipe of the liquid storage device, and the other end of the refrigeration branch is connected to the suction pipe of the compressor;

[0017] One end of the defrost branch is communicated with the exhaust pipe of the compressor, and the other end of the defrost branch is communicated with the liquid inlet pipe of the drain tank.

[0018] Furthermore, the refrigeration system has multiple defrost branches, and the multiple defrost branches are arranged in parallel;

[0019] The refrigeration system has multiple refrigeration branches, and the multiple refrigeration branches are arranged in parallel.

[0020] Further, the bottom of the drain tank is connected to the liquid reservoir through a first drain tank pipeline, the upper part of the drain tank is provided with a second drain tank pipeline connected to the suction pipe of the compressor, the second drain tank pipeline is connected to a third drain tank pipeline, and the other end of the third drain tank pipeline is connected to the liquid reservoir;

[0021] A liquid discharge check valve is installed on the first pipeline of the liquid discharge tank;

[0022] An electronic expansion valve and a pressure reducing solenoid valve are installed on the second pipeline of the drainage tank;

[0023] A pressurizing solenoid valve is installed on the third pipeline of the drainage tank;

[0024] A liquid inlet check valve is installed on the liquid inlet pipe of the liquid discharge tank;

[0025] The drain tank is equipped with an electronic expansion valve controller.

[0026] Furthermore, the refrigeration branch includes:

[0027] a refrigeration pipeline connected to the liquid discharge pipe of the liquid receiver;

[0028] An air cooler installed in the refrigeration pipeline, wherein the air cooler is equipped with a fan;

[0029] A liquid supply expansion valve is installed at one end of the refrigeration pipeline connected to the liquid discharge pipe of the liquid storage device, and a defrost liquid discharge check valve is installed at one end of the refrigeration pipeline connected to the liquid inlet pipe of the liquid discharge tank.

[0030] Furthermore, the defrost branch includes:

[0031] a first defrost pipeline connected to the exhaust pipe of the compressor;

[0032] a second defrost pipeline connected to the suction pipe of the compressor;

[0033] A defrost hot gas solenoid valve is installed on the first defrost pipeline, and a return air solenoid valve is installed on the second defrost pipeline.

[0034] Furthermore, when the air cooler of any refrigeration branch of the refrigeration system performs refrigeration operation, the liquid supply expansion valve is opened, the air return solenoid valve is opened, and the defrost hot air solenoid valve is closed;

[0035] The refrigerant enters the condenser through the exhaust pipe of the compressor, and the refrigerant is converted into liquid after releasing heat in the condenser and flows into the liquid receiver. At this time, the liquid flows from the liquid receiver to the liquid supply expansion valve, and enters the corresponding air cooler after being throttled by the liquid supply expansion valve. After the liquid is vaporized in the air cooler, it passes through the return air solenoid valve and is sucked into the compressor to complete the refrigeration cycle.

[0036] Furthermore, when the cold air blower of any defrost branch of the refrigeration system performs a defrosting operation, the liquid supply expansion valve is closed, the return air solenoid valve is closed, the defrost hot gas solenoid valve is opened, the pressurizing solenoid valve is closed, and the decompression solenoid valve is opened, the electronic expansion valve controller measures the difference between the condensing pressure and the drain tank pressure, and controls the electronic expansion valve to be at a certain opening to maintain a constant pressure difference value;

[0037] The high-pressure and high-temperature refrigerant discharged from the compressor enters the air cooler through the defrost hot gas solenoid valve and is converted into liquid after releasing heat in the air cooler. The liquid enters the drain tank after passing through the defrost drain check valve and the liquid inlet check valve.

[0038] Furthermore, when the liquid level of the drain tank reaches an upper limit, the liquid level sensor of the drain tank triggers the decompression solenoid valve to close and the pressurization solenoid valve to open, and the liquid in the drain tank is discharged to the liquid reservoir.

[0039] Furthermore, when any one of the air coolers is performing defrosting or refrigeration operations, the other air coolers can perform refrigeration or defrosting operations.

[0040] In the above technical solution, the present invention provides a low-energy refrigeration system suitable for direct expansion liquid supply and hot gas defrosting, which has the following beneficial effects:

[0041] The refrigeration system of the present invention overcomes the drawbacks of the hot air defrosting currently used, and improves the refrigeration system, wherein a drain tank with a very small volume is added above the system liquid storage tank, and the pressure in the drain tank is appropriately reduced during defrosting (1.5 to 2 bar lower than the exhaust pressure), while the refrigeration system operates normally with the exhaust pressure unchanged, and the condensate discharged during the defrosting of the air cooler is discharged to the drain tank, and when the liquid level of the drain tank reaches a certain height, the liquid level control device detects the high liquid level and uses gravity and siphon principles to discharge the liquid to the liquid storage tank. Therefore, when the air cooler defrosts, there is almost no additional increase in the energy consumption of the refrigeration system, and the increase in system cost is also very limited. This will play a positive role in the popularization and promotion of green, energy-saving and safe refrigeration systems.

[0042] The hot gas defrost provided by the system of the present invention is well applied to the direct expansion liquid supply refrigeration system, and the operation is stable and reliable. The system can be used for installation and modification of existing projects, and can also be used in projects supporting new equipment, and the increase in cost is limited. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. It is obvious that the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0044] Figure 1 It is a system flow chart of a refrigeration system in the prior art;

[0045] Figure 2 A system flow chart of a low-energy refrigeration system suitable for direct expansion liquid supply and hot gas defrosting disclosed in an embodiment of the present invention;

[0046] Figure 3 The invention discloses a constant difference detection system and a liquid level control system for a drain tank of a low-energy refrigeration system with direct expansion liquid supply and hot gas defrosting.

[0047] Description of reference numerals:

[0048] 1. Compressor; 2. Liquid storage tank; 3. Condenser; 4. Drain tank;

[0049] 101, exhaust pipe; 102, intake pipe;

[0050] 201. Drain pipe;

[0051] 401, the first pipeline of the liquid drain tank; 402, the second pipeline of the liquid drain tank; 403, the third pipeline of the liquid drain tank; 404, the liquid inlet pipe;

[0052] 501, liquid supply expansion valve; 502, air return solenoid valve; 503, defrost hot gas solenoid valve; 504, defrost discharge check valve;

[0053] 601, electronic expansion valve; 602, pressure reducing solenoid valve; 603, liquid inlet check valve; 604, pressurizing solenoid valve; 605, liquid discharge check valve; 606, electronic expansion valve controller; 607, sight glass. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0055] See also Figures 2 to 3 As shown;

[0056] A low-energy refrigeration system suitable for direct expansion liquid supply and hot gas defrosting in this embodiment, the refrigeration system includes a refrigeration branch and a defrosting branch;

[0057] A drain tank 4 is provided above the liquid storage tank 2 of the refrigeration system, and the internal pressure of the drain tank 4 is lower than the high-pressure side exhaust pressure of the refrigeration system, and the pressure difference between the two is a constant difference;

[0058] A detection system and a liquid level control system for stabilizing a constant difference are provided in connection with the drain tank 4 .

[0059] Specifically, the present embodiment discloses a low-energy refrigeration system suitable for direct expansion liquid supply and hot air defrosting, which is divided into a refrigeration branch and a defrost branch; first, the present embodiment adds a drain tank 4, and a detection system and a liquid level control system connected to the drain tank 4 and the liquid storage tank 2 on the basis of the refrigeration system of the prior art. The system of the present embodiment mainly applies hot air defrosting to the refrigeration system of direct expansion liquid supply, reduces the transformation cost, operates reliably and stably, and will not affect the defrosting or refrigeration of other branches when cooling or defrosting.

[0060] Preferably, the refrigeration system of this embodiment includes a compressor 1, a liquid receiver 2, and a condenser 3;

[0061] The compressor 1 is connected with an exhaust pipe 101 and an intake pipe 102;

[0062] The condenser 3 is connected to the compressor 1 through the exhaust pipe 101, and the liquid outlet of the condenser 3 is connected to the liquid storage tank 2 through the condenser drain pipe;

[0063] One end of the refrigeration branch is connected to the discharge pipe 201 of the liquid storage tank 2, and the other end of the refrigeration branch is connected to the suction pipe 102 of the compressor 1;

[0064] One end of the defrost branch is communicated with the exhaust pipe 101 of the compressor 1 , and the other end of the defrost branch is communicated with the liquid inlet pipe 404 of the drain tank 4 .

[0065] The refrigeration system of this embodiment has the function of hot gas defrosting the air cooler, that is, the high-temperature and high-pressure gaseous refrigerant on the high-pressure side enters the heat exchange coil of the air cooler and defrosts the air cooler. The high-temperature and high-pressure gas releases heat and is converted into liquid, which is discharged into the drainage tank 4 of the system. The internal pressure of the drainage tank 4 of this embodiment is lower than the exhaust pressure on the high-pressure side, and the pressure difference between the two is a constant difference, generally 2Bar (which can be adjusted according to actual process requirements). The constant difference of this embodiment can be adjusted and maintained by the above-mentioned detection system and liquid level control system.

[0066] As an expanded implementation method, the refrigeration system of this embodiment is applicable to refrigeration systems using other refrigerants, such as HFC, HC, NH3, CO2, etc., with direct expansion liquid supply and a cold air blower for hot gas defrosting.

[0067] The refrigeration system of this embodiment has multiple defrost branches, and the multiple defrost branches are arranged in parallel;

[0068] The refrigeration system has multiple refrigeration branches, and the multiple refrigeration branches are arranged in parallel.

[0069] Preferably, the drain tank 4 of this embodiment is arranged above the liquid reservoir 2, and its position is higher than the liquid reservoir 2. The liquid refrigerant discharged to the drain tank 4 by defrosting is discharged to the liquid reservoir 2 below by gravity and siphon action using the static liquid column of the liquid refrigerant. Specifically, the bottom of the drain tank 4 of this embodiment is connected to the liquid reservoir 2 through the first drain tank pipeline 401, and the upper part of the drain tank 4 is provided with a second drain tank pipeline 402 connected to the suction pipe 102 of the compressor 1, and the second drain tank pipeline 402 is connected to the third drain tank pipeline 403, and the other end of the third drain tank pipeline 403 is connected to the liquid reservoir 2;

[0070] A liquid discharge check valve 605 is installed on the first pipeline 401 of the liquid discharge tank;

[0071] An electronic expansion valve 601 and a pressure reducing solenoid valve 602 are installed on the second pipeline 402 of the drain tank;

[0072] A pressurizing solenoid valve 604 is installed on the third pipeline 403 of the drain tank;

[0073] A liquid inlet check valve 603 is installed on the liquid inlet pipe 404 of the drain tank;

[0074] The drain tank 4 is provided with an electronic expansion valve controller 605 .

[0075] Based on the above system composition, the refrigeration branch of this embodiment includes a refrigeration pipeline connected to the discharge pipe 201 of the liquid storage tank 2;

[0076] An air cooler installed in the refrigeration pipeline, the air cooler is equipped with a fan;

[0077] A liquid supply expansion valve 501 is installed at one end of the refrigeration pipeline connected to the discharge pipe 201 of the liquid storage tank 2, and a defrost discharge check valve 504 is installed at one end of the refrigeration pipeline connected to the liquid inlet pipe 404 of the discharge tank 4.

[0078] Based on the above system composition, the defrost branch of this embodiment includes a first defrost pipeline connected to the exhaust pipe 101 of the compressor 1; a second defrost pipeline connected to the suction pipe 102 of the compressor 1;

[0079] A defrost hot air solenoid valve 503 is installed on the first defrost pipeline, and a return air solenoid valve 502 is installed on the second defrost pipeline.

[0080] The volume of the drain tank 4 of this embodiment is determined according to the size of the air cooler of the refrigeration system. In general, its volume is proportional to the volume of the coil of the air cooler. Taking the condensation temperature of 35°C as an example, the pressure in the drain tank 4 during defrosting is 1.5 bar to 2.0 bar lower than the condensation pressure. At this time, the corresponding saturation temperature inside is 30°C to 31°C. Therefore, the drain tank 4 does not need to be insulated.

[0081] The specific implementation method of the refrigeration operation of the refrigeration system of this embodiment is as follows:

[0082] When the air cooler of any refrigeration branch of the refrigeration system performs refrigeration operation, the liquid supply expansion valve 501 is opened, the return air solenoid valve 502 is opened, and the defrost hot air solenoid valve 503 is closed;

[0083] The refrigerant enters the condenser 3 through the exhaust pipe 101 of the compressor 1, and after releasing heat in the condenser 3, the refrigerant gas is converted into liquid and flows into the liquid receiver 2. At this time, the liquid flows from the liquid receiver 2 to the liquid supply expansion valve 501, and enters the corresponding air cooler after being throttled by the liquid supply expansion valve 501. After the liquid is vaporized in the air cooler, it passes through the return air solenoid valve 502 and is sucked into the compressor 1 to complete the refrigeration cycle.

[0084] The specific implementation method of the defrosting operation of the refrigeration system of this embodiment is as follows:

[0085] When the cold air blower of any defrost branch of the refrigeration system performs defrosting operation, the liquid supply expansion valve 501 is closed, the return air solenoid valve 502 is closed, the defrost hot gas solenoid valve 503 is opened, the pressurizing solenoid valve 604 is closed, the decompression solenoid valve 602 is opened, and the electronic expansion valve controller 605 measures the difference between the condensing pressure and the pressure of the drain tank 4, and controls the electronic expansion valve 601 to be at a certain opening to maintain a constant pressure difference value;

[0086] The high-pressure and high-temperature refrigerant discharged from the compressor 1 enters the air cooler through the defrost hot gas solenoid valve 503 and is converted into liquid after releasing heat in the air cooler. The liquid enters the drain tank 4 after passing through the defrost drain check valve 504 and the liquid inlet check valve 603.

[0087] When the liquid level of the drain tank 6 reaches the upper limit, the liquid level sensor of the drain tank 4 triggers the pressure reducing solenoid valve 602 to close and the pressure increasing solenoid valve 604 to open, and the liquid in the drain tank 4 is discharged to the liquid reservoir 2 .

[0088] As a preferred embodiment, the pressurizing solenoid valve 604 of this embodiment should be a solenoid valve that opens with zero pressure difference to ensure that the pressure in the tank and the pressure in the reservoir 2 are completely balanced during the discharge. Secondly, the discharge check valve 605 is preferably opened with a small pressure difference, and the resistance of the connected riser is as small as possible, and a siphon effect can be formed during the discharge, so that the discharge tank 4 and the reservoir 2 can be emptied smoothly even if the height difference is small, and the emptying time is reduced.

[0089] When any air cooler is performing defrosting or refrigeration operation, the other air coolers can perform refrigeration or defrosting operation.

[0090] In the above technical solution, the present invention provides a low-energy refrigeration system suitable for direct expansion liquid supply and hot gas defrosting, which has the following beneficial effects:

[0091] The refrigeration system of the present invention overcomes the drawbacks of the hot air defrosting currently used, and improves the refrigeration system, wherein a drain tank 4 with a very small volume is added above the system liquid reservoir 2, and the pressure in the drain tank 4 is appropriately reduced during defrosting (1.5 to 2 bar lower than the exhaust pressure), while the exhaust pressure of the refrigeration system remains unchanged when the air cooler is running. The condensate discharged during defrosting is discharged to the drain tank 4, and when the liquid level of the drain tank 4 reaches a certain height, the liquid level control device detects the high liquid level and uses gravity and siphon principle to discharge the liquid to the liquid reservoir 2. Therefore, the energy consumption of the refrigeration system will hardly be increased when the air cooler is defrosting, and the increase in system cost is also very limited. This will play a positive role in the popularization and promotion of green, energy-saving and safe refrigeration systems.

[0092] The hot gas defrost provided by the system of the present invention is well applied to the direct expansion liquid supply refrigeration system, and the operation is stable and reliable. The system can be used for installation and modification of existing projects, and can also be used in projects supporting new equipment, and the increase in cost is limited.

[0093] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting, the refrigeration system comprising a refrigeration branch and a defrosting branch; It is characterized in that A drain tank (4) is arranged above the liquid storage tank (2) of the refrigeration system, and the internal pressure of the drain tank (4) is lower than the high-pressure side exhaust pressure of the refrigeration system, and the pressure difference between the two is a constant difference; A detection system and a liquid level control system for stabilizing a constant difference are connected to the liquid drainage tank (4).

2. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 1, characterized in that: The refrigeration system comprises: Compressor (1), liquid receiver (2), condenser (3); The compressor (1) is connected to an exhaust pipe (101) and an intake pipe (102); The condenser (3) is connected to the compressor (1) via the exhaust pipe (101), and the liquid outlet end of the condenser (3) is connected to the liquid storage container (2) via a condenser liquid discharge pipe; One end of the refrigeration branch is in communication with a liquid discharge pipe (201) of the liquid storage device (2), and the other end of the refrigeration branch is in communication with a suction pipe (102) of the compressor (1); One end of the defrost branch is in communication with the exhaust pipe (101) of the compressor (1), and the other end of the defrost branch is in communication with the liquid inlet pipe (404) of the liquid drain tank (4).

3. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 2, characterized in that: The refrigeration system has multiple defrost branches, and the multiple defrost branches are arranged in parallel; The refrigeration system has multiple refrigeration branches, and the multiple refrigeration branches are arranged in parallel.

4. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 2, characterized in that: The bottom of the drain tank (4) is connected to the liquid reservoir (2) via a first drain tank pipeline (401); the upper part of the drain tank (4) is provided with a second drain tank pipeline (402) connected to the suction pipe (102) of the compressor (1); the second drain tank pipeline (402) is connected to a third drain tank pipeline (403); and the other end of the third drain tank pipeline (403) is connected to the liquid reservoir (2); A liquid discharge check valve (605) is installed on the first pipeline (401) of the liquid discharge tank; An electronic expansion valve (601) and a pressure reducing solenoid valve (602) are installed on the second pipeline (402) of the drainage tank; A pressurizing solenoid valve (604) is installed on the third pipeline (403) of the drainage tank; A liquid inlet check valve (603) is installed on the liquid inlet pipe (404) of the liquid discharge tank (4); The drainage tank (4) is equipped with an electronic expansion valve controller (605).

5. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 4, characterized in that: The refrigeration branch comprises: a refrigeration pipeline connected to the liquid discharge pipe (201) of the liquid storage container (2); An air cooler installed in the refrigeration pipeline, wherein the air cooler is equipped with a fan; A liquid supply expansion valve (501) is installed at one end of the refrigeration pipeline that is connected to the liquid discharge pipe (201) of the liquid storage device (2), and a defrost liquid discharge check valve (504) is installed at one end of the refrigeration pipeline that is connected to the liquid inlet pipe (404) of the liquid discharge tank (4).

6. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 5, characterized in that: The defrost branch comprises: a first defrost pipeline connected to the exhaust pipe (101) of the compressor (1); a second defrost pipeline connected to the suction pipe (102) of the compressor (1); A defrost hot air solenoid valve (503) is installed on the first defrost pipeline, and a return air solenoid valve (502) is installed on the second defrost pipeline.

7. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 6, characterized in that: When the air cooler of any refrigeration branch of the refrigeration system performs refrigeration operation, the liquid supply expansion valve (501) is opened, the air return solenoid valve (502) is opened, and the defrost hot air solenoid valve (503) is closed; The refrigerant enters the condenser (3) through the exhaust pipe (101) of the compressor (1), and the refrigerant is converted from gas to liquid after releasing heat in the condenser (3), and flows into the liquid storage tank (2). At this time, the liquid flows from the liquid storage tank (2) to the liquid supply expansion valve (501), and enters the corresponding air cooler after being throttled by the liquid supply expansion valve (501). After the liquid is vaporized in the air cooler, it passes through the return air solenoid valve (502) and is sucked into the compressor (1), completing the refrigeration cycle.

8. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 6, characterized in that: When the cold air blower of any defrost branch of the refrigeration system performs a defrosting operation, the liquid supply expansion valve (501) is closed, the return air solenoid valve (502) is closed, the defrosting hot air solenoid valve (503) is opened, the pressurizing solenoid valve (604) is closed, the pressure reducing solenoid valve (602) is opened, and the electronic expansion valve controller (605) measures the difference between the condensing pressure and the pressure of the drain tank (4), and controls the electronic expansion valve (601) to be at a certain opening to maintain a constant pressure difference value; The high-pressure and high-temperature refrigerant discharged from the compressor (1) enters the air cooler through the defrost hot gas solenoid valve (503) and is converted into liquid after releasing heat in the air cooler. The liquid enters the drain tank (4) after passing through the defrost liquid discharge check valve (504) and the liquid inlet check valve (603).

9. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 8, characterized in that: When the liquid level of the drainage tank (4) reaches the upper limit, the liquid level sensor of the drainage tank (4) triggers the pressure reducing solenoid valve (602) to close and the pressure increasing solenoid valve (604) to open, thereby discharging the liquid in the drainage tank (4) into the liquid storage container (2).

10. A low energy consumption refrigeration system suitable for direct expansion liquid supply and hot gas defrosting according to claim 8 or 9, characterized in that: When any air cooler is performing defrosting or refrigeration operation, the other air coolers can perform refrigeration or defrosting operation.

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