Refrigeration system, defrost control method and refrigeration equipment

Abstract

The present invention discloses a refrigeration system, a defrost control method and a refrigeration device. The refrigeration system includes: a refrigeration cycle loop, which is formed by connecting a compressor unit, a condenser and an evaporator unit, the compressor unit includes a first compressor and a second compressor arranged in series, and the refrigerant discharged from the first compressor is sent to the air intake of the second compressor; a heat recovery defrost loop, which is formed by connecting a compressor unit, an evaporator unit, an auxiliary heat exchanger and a heat regenerator, the refrigerant flowing out of the condenser is sent to the evaporator unit for refrigeration through the first heat exchange pipeline of the heat regenerator, and the refrigerant flowing out of the defrost of the evaporator unit is sent back to the air intake of the first compressor through the auxiliary heat exchanger and the second heat exchange pipeline of the heat regenerator, and the auxiliary heat exchanger is used to cool the refrigerant discharged from the first compressor. The present invention introduces the liquid refrigerant that undergoes phase change after defrosting into the auxiliary heat exchanger and the heat regenerator, eliminates the hidden danger of liquid hammer, and reduces the exhaust temperature of the compressor unit, reduces the work of the compressor, and improves the refrigeration efficiency.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration technology, and in particular to a refrigeration system, a defrost control method and a refrigeration device. Background Art

[0002] In the refrigeration system of large industrial cold storage, frosting is a very common phenomenon. It is generally believed that when air flows over the surface of the evaporator and the surface temperature of the evaporator is lower than 0°C, surface frost will occur. Since the thermal conductivity of the formed frost layer is low, the heat exchange performance of the evaporator is reduced, which not only increases energy consumption but also causes liquid inhalation to a certain extent. Usually, the industry uses hot fluorine defrosting as the defrosting method for low-temperature cold storage. Hot fluorine defrosting requires sufficient heat source - gaseous high-pressure and high-temperature refrigerant. The high-temperature gas generated when the compressor unit is working is introduced into the evaporator in the evaporator group in the defrosting condition through the diversion, and the heat of the high-temperature gas is used to melt the frost layer on the surface of the evaporator.

[0003] This defrosting method has a great advantage in defrosting rate. The high-temperature gas absorbs the cold of the frost layer and condenses into liquid while defrosting the evaporator. The existing technology for handling the liquid refrigerant generated by defrosting is to introduce the liquid refrigerant into the regenerator, and the liquid refrigerant absorbs the heat of the refrigerant flowing out of the condenser through the regenerator, and then sends it to the suction port of the compressor unit. However, due to factors such as the low temperature of the refrigerant flowing out of the condenser and incomplete heat exchange, the liquid refrigerant cannot be completely converted into gaseous refrigerant after absorbing heat, and there is still a risk of liquid hammer.

[0004] Therefore, how to overcome the shortcomings of existing hot fluorine defrosting solutions is a technical problem that the industry urgently needs to solve. Summary of the invention

[0005] In order to solve the defect of the existing hot fluorine defrost technology that has the risk of liquid hammer, the present invention proposes a refrigeration system, a defrost control method and a refrigeration equipment. The refrigeration system introduces the liquid refrigerant that undergoes phase change after defrosting into an auxiliary heat exchanger and a regenerator. The liquid refrigerant and the gaseous refrigerant discharged from the first compressor are heat exchanged with each other through the auxiliary heat exchanger, which eliminates the risk of liquid hammer and reduces the exhaust temperature of the second compressor, thereby reducing the work of the compressor under the same pressure ratio and improving the refrigeration efficiency.

[0006] The technical solution adopted by the present invention is to design a refrigeration system, including:

[0007] A refrigeration cycle loop is formed by connecting a compressor unit, a condenser and an evaporator unit, wherein the compressor unit comprises a first compressor and a second compressor arranged in series, and the refrigerant discharged from the first compressor is sent to the suction port of the second compressor;

[0008] The heat recovery defrost circuit is formed by connecting the compressor unit, the evaporator unit, the auxiliary heat exchanger and the regenerator. The refrigerant flowing out of the condenser is sent to the evaporator unit for refrigeration through the first heat exchange pipeline of the regenerator. The refrigerant flowing out of the evaporator unit for defrosting is sent back to the suction port of the first compressor through the auxiliary heat exchanger and the second heat exchange pipeline of the regenerator. The auxiliary heat exchanger is used to cool the refrigerant discharged from the first compressor.

[0009] Furthermore, a bypass branch is provided on the outlet side of the first heat exchange pipeline of the regenerator, and the bypass branch is used to return part of the refrigerant flowing out of the first heat exchange pipeline to the inlet of the condenser. The bypass branch is installed with a bypass valve for adjusting its flow rate.

[0010] Further, the evaporator group is composed of at least two evaporators arranged in parallel;

[0011] The first heat exchange pipeline of the regenerator is connected to the refrigeration inlet end of the evaporator group through the liquid supply header, and the refrigeration outlet end of the evaporator group is connected to the exhaust port of the second compressor through the defrost header;

[0012] The second heat exchange pipeline of the regenerator is connected to the refrigeration inlet end of the evaporator group through the liquid return header, and the refrigeration outlet end of the evaporator group is connected to the suction port of the first compressor through the gas return header;

[0013] The liquid supply manifold, liquid return manifold, defrost manifold and gas return manifold are all provided with liquid distribution ports connected to each evaporator in a one-to-one correspondence, and each liquid distribution port is installed with an independently working valve.

[0014] Furthermore, when the evaporator is in a refrigeration condition, the valves corresponding to the evaporator on the liquid supply header and the gas return header are opened, and the valves corresponding to the evaporator on the defrost header and the liquid return header are closed;

[0015] When the evaporator is in the defrosting condition, the valves corresponding to the evaporator on the liquid supply header and the gas return header are closed, and the valves corresponding to the evaporator on the defrost header and the liquid return header are opened.

[0016] Furthermore, the refrigeration inlet end of each evaporator is connected to the liquid supply manifold and the liquid return manifold through two parallel branches, one branch is equipped with a throttle valve and a switching valve, and the other branch is equipped with a one-way valve. The switching valve is only opened when the evaporator is in a refrigeration condition, and the one-way valve only allows the refrigerant to flow out of the refrigeration inlet end of the evaporator.

[0017] Furthermore, a heat recovery control valve is installed on the inlet side of the second heat exchange pipeline of the heat exchanger. The heat recovery control valve remains closed when all evaporators of the evaporator group are in refrigeration condition, and remains open when an evaporator is in defrosting condition.

[0018] The present invention also proposes a defrost control method using the above refrigeration system, comprising:

[0019] Determine whether any evaporator has reached the defrost start condition;

[0020] If so, the evaporator that has reached the defrost start-up conditions will be used as the standby evaporator, and the evaporator that is in the refrigeration condition but has not reached the defrost start-up conditions will be used as the refrigeration evaporator. It is determined whether the ratio of the sum of the number of standby evaporators to the sum of the number of refrigeration evaporators exceeds the set ratio. If so, some evaporators are selected from the standby evaporators to be forced into the refrigeration condition, and then all the standby evaporators are turned on to enter the defrost condition. If not, all the standby evaporators are directly turned on to enter the defrost condition.

[0021] In some embodiments, selecting some of the evaporators in standby mode to enter the defrosting state includes:

[0022] The sum of the number of target refrigeration evaporators is obtained by calculating and rounding up according to the sum of the number of evaporators to be determined and the set ratio;

[0023] calculating a difference between the sum of the numbers of target refrigeration evaporators and the sum of the numbers of refrigeration evaporators;

[0024] According to the difference, the corresponding evaporator is selected randomly or according to the priority from the standby evaporators to force it into the refrigeration state.

[0025] Furthermore, the defrost control method further includes:

[0026] After all pending evaporators are turned on and enter defrosting conditions;

[0027] Determine whether the throttle valve opening of more than half of the refrigeration evaporators is less than the set opening;

[0028] If yes, the bypass valve is opened to send part of the refrigerant flowing out of the first heat exchange pipeline of the regenerator back to the inlet of the condenser;

[0029] If not, close the bypass valve.

[0030] Furthermore, the defrost control method further includes:

[0031] After all pending evaporators are turned on and enter defrosting conditions;

[0032] Determine whether any pending evaporator has reached defrost end conditions;

[0033] If so, the pending evaporator ends the defrost condition, and the refrigeration evaporator that is forced to enter the refrigeration condition resumes standby, and determines whether all pending evaporators end the defrost condition. If not, return to determine whether the ratio of the sum of the number of remaining pending evaporators to the sum of the number of refrigeration evaporators exceeds the set ratio. If so, return to determine whether any evaporator meets the defrost start condition.

[0034] In some embodiments, determining whether an evaporator has reached a defrost start condition includes:

[0035] Monitor the evaporator current in refrigeration mode to determine whether the evaporator current exceeds the set current value;

[0036] If yes, the evaporator reaches the defrost start condition;

[0037] If not, the evaporator has not reached the defrost start condition.

[0038] Furthermore, before determining whether any evaporator reaches the defrost start condition, the indoor ambient temperature of each evaporator in the evaporator group is monitored to determine whether the indoor ambient temperature of the evaporator drops to the set temperature value. If not, the evaporator is turned on to enter the refrigeration condition.

[0039] The present invention also proposes a refrigeration device, comprising: a refrigeration system and a controller for controlling the operating state of the refrigeration system, and the controller executes the above-mentioned defrost control method.

[0040] In some embodiments, the refrigeration equipment is a cold storage.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. Add an auxiliary heat exchanger in the heat recovery defrost circuit. The liquid refrigerant that undergoes phase change after defrosting flows through the auxiliary heat exchanger and the regenerator in sequence. The liquid refrigerant and the gaseous refrigerant discharged from the first compressor exchange heat through the auxiliary heat exchanger, eliminating the hidden danger of liquid hammer while reducing the exhaust temperature of the second compressor, increasing the subcooling of the liquid supply, reducing the work of the compressor under the same pressure ratio, and reducing the energy consumption of the refrigeration system;

[0043] 2. A bypass branch is set between the outlet side of the first heat exchange pipe of the regenerator and the inlet of the condenser. When the heat load of the refrigeration system is not large, the bypass valve of the bypass branch is opened to return part of the refrigerant flowing out of the first heat exchange pipe to the inlet of the condenser, and the excess cooling capacity is used to reduce the load of the condenser and improve the refrigeration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0045] Figure 1 It is a connection diagram of the refrigeration system in the present invention;

[0046] Figure 2 It is a flow chart of the defrost control method in the present invention. DETAILED DESCRIPTION

[0047] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this patent and are not used to limit this patent.

[0048] like Figure 1 As shown, the refrigeration system proposed in the present invention is suitable for refrigeration equipment, especially cold storage, etc. The refrigeration system includes: a compressor unit, a condenser 5, an evaporator unit 6, a regenerator 11, and an auxiliary heat exchanger 12, etc. The compressor unit, the condenser 5, and the evaporator unit 6 are connected to form a refrigeration cycle loop, and the compressor unit, the evaporator unit 6, the auxiliary heat exchanger 12, and the regenerator 11 are connected to form a heat recovery defrosting loop.

[0049] The compressor unit includes a first compressor 1 and a second compressor 2 which are arranged in series. The first compressor 1 is a low-pressure compressor, and the second compressor 1 is a high-pressure compressor. The refrigerant discharged from the first compressor 1 is sent to the suction port of the second compressor 2. The exhaust port of the first compressor 1 is connected to a first oil separator 3, and the exhaust port of the second compressor 2 is connected to a second oil separator 4. The refrigerant discharged from the exhaust port of the first compressor 1 is separated by the first oil separator 3 and sent to the suction port of the second compressor 2. The refrigerant discharged from the exhaust port of the second compressor 2 is separated by the second oil separator 4 and sent to the condenser 5.

[0050] The regenerator 11 and the auxiliary heat exchanger 12 each have two sets of heat exchange pipelines. The first heat exchange pipeline of the regenerator 11 is connected between the outlet of the condenser and the refrigeration inlet of the evaporator group 6. The first heat exchange pipeline of the regenerator 11 is part of the refrigeration cycle. The second heat exchange pipeline of the regenerator 11 is connected between the outlet of the second heat exchange pipeline of the auxiliary heat exchanger 12 and the air intake of the first compressor 1. The second heat exchange pipeline of the regenerator 11 is part of the heat recovery defrosting circuit. The first heat exchange pipeline of the auxiliary heat exchanger 12 is connected between the exhaust port of the first compressor 1 and the air intake of the second compressor 2, or more precisely, between the air outlet of the first oil separator 3 and the air intake of the second compressor 2. The first heat exchange pipeline of the auxiliary heat exchanger 12 is part of the refrigeration cycle. The second heat exchange pipeline of the auxiliary heat exchanger 12 is connected between the refrigeration inlet of the evaporator group and the inlet of the second heat exchange pipeline of the regenerator 11. The second heat exchange pipeline of the auxiliary heat exchanger 12 is part of the heat recovery defrosting circuit.

[0051] The refrigerant flowing out of the condenser 5 is sent to the evaporator in the refrigeration condition in the evaporator group 6 through the first heat exchange pipeline of the regenerator 11 for refrigeration, and the refrigerant flowing out of the evaporator in the defrosting condition in the evaporator group 6 after defrosting is sent back to the air intake port of the first compressor 1 through the second heat exchange pipeline of the auxiliary heat exchanger 12 and the second heat exchange pipeline of the regenerator 11 in sequence. In other words, the liquid refrigerant that undergoes phase change after defrosting and the gaseous refrigerant discharged from the first compressor 1 perform heat exchange through the auxiliary heat exchanger 12 to complete the first heat absorption, and the refrigerant flowing out of the auxiliary heat exchanger 12 and the refrigerant flowing out of the condenser 5 perform heat exchange through the regenerator 11 to complete the second heat absorption. This design has the following advantages. First, the liquid refrigerant generated by defrosting absorbs heat twice through the auxiliary heat exchanger 12 and the regenerator 11, so that the liquid refrigerant is vaporized and enters the air intake of the compressor unit, ensuring the normal operation of the system and avoiding liquid hammer. Second, the gaseous refrigerant discharged from the first compressor 1 is cooled by the auxiliary heat exchanger 12, thereby reducing the exhaust temperature of the compressor unit and the heat load of the condenser 5, thereby reducing the work done by the compressor unit under the same pressure ratio, reducing system energy consumption and improving refrigeration efficiency. Third, the refrigerant in the second heat exchange pipeline absorbs the heat of the refrigerant in the first heat exchange pipeline, increasing the supercooling of the refrigerant flowing out of the first heat exchange pipeline and optimizing the refrigeration effect. Fourth, the lubricating oil temperature of the compressor unit is reduced, which is beneficial to the oil return of the compressor unit.

[0052] In some embodiments, a bypass branch is provided at the outlet side of the first heat exchange pipeline of the regenerator 11, and the bypass branch is used to send part of the refrigerant flowing out of the first heat exchange pipeline back to the inlet of the condenser 5. The bypass branch is installed with a bypass valve 13 for adjusting its flow rate. When the heat load of the refrigeration system is not large, the bypass valve 13 of the bypass branch is opened to send part of the refrigerant flowing out of the first heat exchange pipeline back to the inlet of the condenser 5, and the excess cold is used to reduce the load of the condenser 5 and improve the refrigeration efficiency. For example, the heat load of the refrigeration system is judged by the opening of the refrigeration evaporator. When the throttle valve opening of more than half of the refrigeration evaporators is less than the set opening, it means that the current heat load of the refrigeration system is not large, and the cold provided by the first heat exchange pipeline of the regenerator is surplus. At this time, the bypass valve is opened to send part of the refrigerant flowing out of the first heat exchange pipeline of the regenerator back to the inlet of the condenser. This part of the refrigerant is mixed with the high-temperature refrigerant discharged by the second compressor to reduce the temperature, so as to reduce the load of the condenser.

[0053] In some embodiments, the evaporator group 6 is composed of at least two evaporators arranged in parallel. The evaporators can be installed in different rooms, and each evaporator can be independently switched to connect to the refrigeration cycle circuit or the heat recovery defrost circuit. The two ends of the evaporator group 6 are respectively the refrigeration inlet end and the refrigeration outlet end. Since the refrigerant flow direction of the evaporator in the heat recovery defrost circuit or the refrigeration cycle circuit is opposite, the refrigeration inlet end of the evaporator group 6 is actually the defrost outlet end, and the refrigeration outlet end is actually the defrost inlet end.

[0054] The connection structure of the refrigeration system is described in detail below. The first heat exchange pipeline of the regenerator 11 is connected to the refrigeration inlet end of the evaporator group 6 through the liquid supply header 7, and the refrigeration outlet end of the evaporator group 6 is connected to the exhaust port of the second compressor 2 through the defrost header 9. The second heat exchange pipeline of the regenerator 11 is connected to the refrigeration inlet end of the evaporator group 6 through the liquid return header 8, and the refrigeration outlet end of the evaporator group 6 is connected to the suction port of the first compressor 1 through the gas return header 10. The end of each header connected to the evaporator group 6 is provided with a plurality of liquid separation ports, which are the same as the number of evaporators. The liquid separation ports are connected to each evaporator one by one, and each liquid separation port is installed with an independently working valve. When the evaporator is in refrigeration condition, the valve components on the liquid supply manifold 7 and the return air manifold 10 corresponding to the evaporator are opened, and the valve components on the defrost manifold 9 and the return liquid manifold 8 corresponding to the evaporator are closed; when the evaporator is in defrost condition, the valve components on the liquid supply manifold 7 and the return air manifold 10 corresponding to the evaporator are closed, and the valve components on the defrost manifold 9 and the return liquid manifold 8 corresponding to the evaporator are opened.

[0055] Specifically, each liquid distribution port of the liquid supply manifold 7 is installed with a liquid supply solenoid valve, each liquid distribution port of the return liquid manifold 8 is installed with a liquid return solenoid valve, each liquid distribution port of the defrost manifold 9 is installed with a defrost solenoid valve, and each liquid distribution port of the return air manifold 10 is installed with a return air solenoid valve. Independent control of each evaporator is achieved through valve components and liquid distribution ports, and even distribution of refrigerant is ensured.

[0056] In some embodiments, the refrigeration inlet of each evaporator is connected to the liquid supply manifold 7 and the liquid return manifold 8 through two parallel branches, one branch is equipped with a throttle valve and a switching valve, and the other branch is equipped with a one-way valve, the switching valve is only opened when the evaporator is in a refrigeration condition, and the one-way valve only allows the refrigerant to flow out of the refrigeration inlet of the evaporator. A regenerative control valve 14 is installed at the inlet of the second heat exchange pipeline of the regenerator 11, and the regenerative control valve 14 remains closed when all evaporators of the evaporator group 6 are in a refrigeration condition.

[0057] like Figure 1 As shown, taking the evaporator group consisting of four evaporators 6-1~6-4 as an example, the liquid supply solenoid valves of the four evaporators are 7-1~7-4 from left to right, the liquid return solenoid valves are 8-1~8-4 from left to right, the defrost solenoid valves are 9-1~9-4 from left to right, and the return air solenoid valves are 10-1~10-4 from right to left. The working process of the refrigeration system is as follows.

[0058] All evaporators are in cooling mode, liquid supply solenoid valves 7-1~7-4 are open, liquid return solenoid valves 8-1~8-4 are closed, defrost solenoid valves 9-1~9-4 are closed, return air solenoid valves 10-1~10-4 are open, and the reheat control valve and bypass valve are closed. The refrigerant flow direction is: high-temperature and high-pressure gaseous refrigerant discharged from the second compressor 2 → second oil separator 4 → condenser 5 → reheater 11 → liquid supply solenoid valve → throttle valve → evaporator → return air solenoid valve → suction port of the first compressor 1 → first oil separator 3 → suction port of the second compressor 2.

[0059] Some evaporators enter the defrosting condition and the other evaporators are in the cooling mode. Take the evaporator 5-1 defrosting and the evaporators 5-2, 5-3, and 5-4 cooling as an example: the defrost solenoid valve 9-1 is opened, and the defrost solenoid valves 9-2, 9-3, and 9-4 are closed; the liquid supply solenoid valve 7-1 is closed, and the liquid supply solenoid valves 7-2, 7-3, and 7-4 are opened; the liquid return solenoid valve 8-1 is opened, and the liquid return solenoid valves 8-2, 8-3, and 8-4 are closed, the heat recovery control valve 14 is opened, and the bypass valve 13 is opened when the heat load of the refrigeration system is not large. The refrigerant flow direction in the refrigeration mode is: high-temperature and high-pressure gaseous refrigerant discharged from the second compressor 2 → second oil separator 4 → condenser 5 → regenerator 11 → liquid supply solenoid valve → throttle valve → evaporator → return air solenoid valve → air intake port of the first compressor 1 → first oil separator 3 → air intake port of the second compressor 2; the refrigerant flow direction in the defrost condition is: high-temperature and high-pressure gaseous refrigerant discharged from the second compressor 2 → second oil separator 4 → defrost solenoid valve → evaporator → check valve → liquid return solenoid valve → heat recovery control valve → auxiliary heat exchanger 12 → regenerator 11 → air intake port of the first compressor 1 → first oil separator 3 → air intake port of the second compressor 2.

[0060] The present invention also proposes a defrost control method for the above refrigeration system, comprising:

[0061] Determine whether any evaporator has reached the defrost start condition;

[0062] If so, the evaporator that has reached the defrost start-up conditions will be used as the standby evaporator, and the evaporator that is in the refrigeration condition but has not reached the defrost start-up conditions will be used as the refrigeration evaporator. It is determined whether the ratio of the sum of the number of standby evaporators to the sum of the number of refrigeration evaporators exceeds the set ratio. If so, some evaporators are selected from the standby evaporators to be forced into the refrigeration condition, and then all the standby evaporators are turned on to enter the defrost condition. If not, all the standby evaporators are directly turned on to enter the defrost condition.

[0063] The defrost control method is based on the ratio of the sum of the number of pending evaporators that meet the defrost start conditions to the sum of the number of refrigeration evaporators. When the ratio exceeds the set ratio, it means that the current number of refrigeration evaporators is insufficient and the cooling capacity provided is insufficient to maintain the temperature of the cold storage stable. Therefore, some evaporators are selected from the standby evaporators to force them into the refrigeration condition, and then all pending evaporators are turned on to enter the defrost condition, which speeds up the defrosting speed while ensuring the temperature of the cold storage is stable, thereby improving the use effect of the cold storage. More importantly, it is easy to count the number of pending evaporators and refrigeration evaporators, without the need to add additional sensors and other detection parts. The calculation logic is simple, the cost is low, and it is easy to implement and promote.

[0064] In some embodiments, selecting some of the evaporators in standby mode to enter the defrosting state includes:

[0065] A preliminary result is calculated by dividing the sum of the number of evaporators to be determined by the set ratio, and the preliminary result is rounded up to obtain the sum of the number of target refrigeration evaporators;

[0066] calculating a difference between the sum of the numbers of target refrigeration evaporators and the sum of the numbers of refrigeration evaporators;

[0067] According to the difference, the corresponding evaporator is selected randomly or according to the priority from the standby evaporators to force the refrigeration condition. It should be understood that when the corresponding evaporator is selected from the standby evaporators according to the priority, the priority can be a pre-designed fixed priority, or a dynamic priority sorted according to the temperature difference between the ambient temperature in the room where the evaporator is located and the set temperature value, or a dynamic priority sorted according to the size of other operating parameters of the evaporator, and the present invention does not impose any special restrictions on this.

[0068] In some embodiments, the defrost control method further includes:

[0069] After all pending evaporators are turned on and enter defrosting conditions;

[0070] Determine whether any pending evaporator has reached defrost end conditions;

[0071] If so, the pending evaporator ends the defrost condition, and the refrigeration evaporator that is forced to enter the refrigeration condition resumes standby, and determines whether all pending evaporators end the defrost condition. If not, return to determine whether the ratio of the sum of the number of remaining pending evaporators to the sum of the number of refrigeration evaporators exceeds the set ratio. If so, return to determine whether any evaporator meets the defrost start condition.

[0072] It should be understood that in the defrost control method, as the pending evaporators gradually complete defrosting, the number of remaining pending evaporators becomes smaller and smaller, and the ratio of the sum of the number of all remaining pending evaporators to the sum of the number of refrigeration evaporators will inevitably be less than or equal to the set ratio, that is, in the later stage of defrosting, all the remaining pending evaporators are directly opened to enter the defrost condition.

[0073] In some embodiments, the defrost control method further includes:

[0074] After all pending evaporators are turned on and enter defrosting conditions;

[0075] Determine whether the throttle valve opening of more than half of the refrigeration evaporators is less than the set opening;

[0076] If yes, it means that the heat load of the current refrigeration system is not large, and the cooling capacity provided by the first heat exchange pipeline of the regenerator is surplus. At this time, the bypass valve is opened to send part of the refrigerant flowing out of the first heat exchange pipeline of the regenerator back to the inlet of the condenser. This part of the refrigerant is mixed with the high-temperature refrigerant discharged from the second compressor to reduce the temperature, so as to reduce the load of the condenser;

[0077] If not, it means that the current heat load of the refrigeration system is large. At this time, the bypass valve is closed, and the refrigerant flowing out of the first heat exchange pipeline of the regenerator is all distributed to the refrigeration evaporator to meet the refrigeration demand of the refrigeration system.

[0078] The set ratio and set opening mentioned above can be designed according to the actual situation of the refrigeration system. Generally speaking, the best value is when the set ratio is one-third, and the best value is when the set opening is 30%.

[0079] In some embodiments, determining whether an evaporator has reached a defrost start condition includes:

[0080] Monitor the evaporator current in refrigeration mode to determine whether the evaporator current exceeds the set current value;

[0081] If yes, it means that the heat exchange state of the evaporator is poor, the frost layer on the evaporator surface is thick, and the evaporator has reached the defrost start condition;

[0082] If not, it means that the heat exchange state of the evaporator is still good, there is no frost on the evaporator surface or the frost layer is thin, and the evaporator has not reached the defrost start condition.

[0083] It should be pointed out that the current value is easy to collect and has a small error, and it is a preferred implementation to use it to judge whether the evaporator has reached the defrost start condition. Of course, the defrost start condition and defrost end condition mentioned above can adopt existing judgment conditions, such as the duration of the evaporator's refrigeration operation as the defrost start condition, and the duration of the heat recovery defrost operation as the defrost exit condition. It can also be used to detect whether the parameters such as the evaporator's tube temperature have reached the corresponding target temperature as a judgment condition, and the present invention is not limited to this.

[0084] by Figure 2 Taking the illustrated embodiment as an example, the implementation process of the defrost control method is described in detail.

[0085] Step 1: Turn on the refrigeration system;

[0086] Step 2, monitoring the indoor ambient temperature of each evaporator in the evaporator group, and determining whether the indoor ambient temperature of any evaporator drops to the set temperature value, if so, executing step 3, if not, executing step 4;

[0087] Step 3: The evaporator of the room whose temperature drops to the set temperature value enters standby mode, the liquid supply solenoid valve of the standby evaporator is closed, the air return solenoid valve is closed, the liquid return solenoid valve is closed, and the defrost solenoid valve is closed, and the process returns to step 2;

[0088] Step 4: The evaporator of the room whose temperature exceeds the set temperature value enters the refrigeration condition, the liquid supply solenoid valve of the refrigeration evaporator is opened, the liquid return solenoid valve is closed, the defrost solenoid valve is closed, and the air return solenoid valve is opened, and step 5 is executed;

[0089] Step 5, monitor the evaporator current in the refrigeration condition, and determine whether the evaporator current exceeds the set current value. If so, execute step 6, if not, return to step 2;

[0090] Step 6: The evaporators whose current exceeds the set current value are regarded as pending evaporators, and the evaporators in the refrigeration condition and whose current does not exceed the set current value are regarded as refrigeration evaporators, and it is determined whether the ratio of the sum of the number of pending evaporators to the sum of the number of refrigeration evaporators exceeds the set ratio. If so, step 7 is executed; if not, step 8 is executed;

[0091] Step 7, select some evaporators from the standby evaporators to force them into refrigeration conditions, open the liquid supply solenoid valve of the refrigeration evaporator, close the liquid return solenoid valve, close the defrost solenoid valve, and open the air return solenoid valve, then open all the pending evaporators to enter the defrost condition, close the liquid supply solenoid valve of the pending evaporator, open the liquid return solenoid valve, open the defrost solenoid valve, and close the air return solenoid valve, and execute step 9;

[0092] Step 8, directly open all pending evaporators to enter the defrost condition, close the liquid supply solenoid valve of the pending evaporator, open the liquid return solenoid valve, open the defrost solenoid valve, and close the air return solenoid valve, and execute step 9;

[0093] Step 9, determining whether the throttle valve openings of more than half of the refrigeration evaporators are less than the set openings, if so, executing step 10, if not, executing step 11;

[0094] Step 10, open the bypass valve;

[0095] Step 11, close the bypass valve;

[0096] Step 12, determining whether any pending evaporator has reached the defrost end condition, forcing the refrigeration evaporator in the refrigeration state to resume standby, and executing step 13;

[0097] Step 13, determine whether all pending evaporators have completed the defrosting condition, return to step 6, and determine whether the ratio of the sum of the number of remaining pending evaporators to the sum of the number of the refrigeration evaporators exceeds the set ratio. If so, return to step 5.

[0098] The present invention also proposes a refrigeration device, comprising: a refrigeration system and a controller for controlling the operating state of the refrigeration system, and the controller executes the above-mentioned defrost control method.

[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A refrigeration system, characterized in that: include: A refrigeration cycle loop is formed by connecting a compressor unit, a condenser and an evaporator unit, wherein the compressor unit comprises a first compressor and a second compressor arranged in series, and the refrigerant discharged by the first compressor is sent to the suction port of the second compressor; A heat recovery defrost circuit is formed by connecting the compressor group, the evaporator group, the auxiliary heat exchanger and the regenerator. The refrigerant flowing out of the condenser is sent to the evaporator in the evaporator group in a refrigeration state through the first heat exchange pipeline of the regenerator for refrigeration. The refrigerant flowing out of the evaporator in the evaporator group in a defrost state is successively sent back to the suction port of the first compressor through the auxiliary heat exchanger and the second heat exchange pipeline of the regenerator. The auxiliary heat exchanger is used to cool the refrigerant discharged from the first compressor. A bypass branch is provided at the outlet side of the first heat exchange pipeline of the regenerator, and the bypass branch is used to send part of the refrigerant flowing out of the first heat exchange pipeline back to the inlet of the condenser. The bypass branch is installed with a bypass valve for adjusting its flow rate. After all the pending evaporators are opened to enter the defrosting condition, when the throttle valve opening of more than half of the refrigeration evaporators is less than the set opening, the bypass valve is opened; Among them, the evaporator group is composed of at least two evaporators arranged in parallel, and each evaporator can be independently switched to connect to the refrigeration cycle circuit or the heat recovery defrost circuit. The evaporator that meets the defrost start conditions will be used as the pending evaporator, and the evaporator that is in the refrigeration condition and has not met the defrost start conditions will be used as the refrigeration evaporator.

2. The refrigeration system according to claim 1, characterized in that: The first heat exchange pipeline of the regenerator is connected to the refrigeration inlet end of the evaporator group through the liquid supply header, and the refrigeration outlet end of the evaporator group is connected to the exhaust port of the second compressor through the defrost header; The second heat exchange pipeline of the regenerator is connected to the refrigeration inlet end of the evaporator group through the liquid return header, and the refrigeration outlet end of the evaporator group is connected to the suction port of the first compressor through the gas return header; The liquid supply manifold, liquid return manifold, defrost manifold and gas return manifold are all provided with liquid separation ports connected to the respective evaporators in a one-to-one correspondence, and each liquid separation port is installed with an independently working valve.

3. The refrigeration system according to claim 2, characterized in that: When the evaporator is in a refrigeration condition, the valves on the liquid supply header and the gas return header corresponding to the evaporator are opened, and the valves on the defrost header and the liquid return header corresponding to the evaporator are closed; When the evaporator is in a defrosting condition, the valves on the liquid supply header and the gas return header corresponding to the evaporator are closed, and the valves on the defrost header and the liquid return header corresponding to the evaporator are opened.

4. The refrigeration system according to claim 2, characterized in that: The refrigeration inlet end of each evaporator is connected to the liquid supply manifold and the liquid return manifold through two parallel branches. One branch is equipped with a throttle valve and a switching valve, and the other branch is equipped with a one-way valve. The switching valve is only opened when the evaporator is in a refrigeration condition, and the one-way valve only allows the refrigerant to flow out of the refrigeration inlet end of the evaporator.

5. The refrigeration system according to claim 1, characterized in that: A heat recovery control valve is installed on the inlet side of the second heat exchange pipeline of the heat regenerator. The heat recovery control valve remains closed when all evaporators of the evaporator group are in a refrigeration condition, and remains open when an evaporator is in a defrosting condition.

6. A defrost control method for a refrigeration system, wherein the refrigeration system is a refrigeration system according to any one of claims 1 to 5, characterized in that: The defrost control method comprises: Determine whether any evaporator has reached the defrost start condition; If so, determine whether the ratio of the sum of the number of pending evaporators to the sum of the number of refrigeration evaporators exceeds the set ratio. If so, select some evaporators from the standby evaporators to force them into the refrigeration condition, and then turn on all the pending evaporators to enter the defrost condition. If not, directly turn on all the pending evaporators to enter the defrost condition.

7. The defrost control method according to claim 6, characterized in that: Selecting some of the evaporators in standby mode to force them into cooling mode includes: The sum of the number of target refrigeration evaporators is obtained by calculating and rounding up according to the sum of the number of the pending evaporators and the set ratio; Calculating a difference between the sum of the numbers of the target refrigeration evaporators and the sum of the numbers of the refrigeration evaporators; According to the difference, a corresponding evaporator is selected randomly or according to priority from the standby evaporators to be forced to enter the refrigeration state.

8. The defrost control method according to claim 6, characterized in that: Also includes: After all the pending evaporators are turned on to enter the defrosting state; Determine whether any of the pending evaporators has reached the defrost end condition; If so, the pending evaporator ends the defrost condition, and the refrigeration evaporator that is forced to enter the refrigeration condition resumes standby, and it is determined whether all the pending evaporators end the defrost condition. If not, it returns to determine whether the ratio of the sum of the number of remaining pending evaporators to the sum of the number of refrigeration evaporators exceeds the set ratio. If so, it returns to determine whether any evaporator meets the defrost start condition.

9. The defrost control method according to claim 6, characterized in that: Determining whether an evaporator has reached the defrost start condition includes: Monitoring the evaporator current in a refrigeration condition to determine whether the evaporator current exceeds a set current value; If yes, the evaporator reaches the defrost start condition; If not, the evaporator does not meet the defrost start condition.

10. The defrost control method according to claim 9, characterized in that: Before determining whether any evaporator reaches the defrost start condition, monitor the indoor ambient temperature of each evaporator in the evaporator group to determine whether the indoor ambient temperature of the evaporator drops to the set temperature value. If not, turn on the evaporator to enter the refrigeration state.

11. Refrigeration equipment, including: A refrigeration system and a controller for controlling the operating state of the refrigeration system, characterized in that the controller executes the defrost control method according to any one of claims 6 to 10.

12. The refrigeration device according to claim 11, characterized in that: The refrigeration equipment is a cold storage.

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