Cold storage cascade instant freezer system and control method thereof

Abstract

The invention discloses a cold accumulation cascade instant freezer system and a control method thereof, and the system comprises a cold accumulation system which is sequentially connected with a cold accumulation unit, a cold accumulation condenser, a first expansion valve and a cold accumulation device through a pipeline to form a cold accumulation loop; the quick-freezing system is sequentially connected with a quick-freezing unit, a cold storage device, a second expansion valve and a quick-freezing evaporator through pipelines to form a quick-freezing loop, and the quick-freezing evaporator is arranged in the heat preservation warehouse body; the cold storage device comprises an ice pool with a built-in phase change medium, the ice pool serves as a cold storage evaporator in the cold storage system to enable the phase change medium to be solidified and store cold, and the ice pool serves as a quick-freezing condenser in the quick-freezing system to enable the phase change medium to be melted and release cold. According to the invention, night valley electricity cold storage and daytime peak electricity cold release are utilized to assist quick freezing, so that the electric charge is greatly reduced, and the energy consumption is saved; the cold storage temperature in the cold storage device is high, compared with an existing scheme that the cold storage temperature must be lower than the quick-freezing temperature, energy consumption of cold storage is lower, the cold storage temperature and the quick-freezing temperature are decoupled and are not limited by the quick-freezing temperature, and application is more flexible.

Description

Technical Field

[0001] This invention relates to the field of quick-freezing technology, and in particular to a cold storage cascade quick-freezing system and its control method. Background Technology

[0002] Currently, the food quick-freezing industry commonly uses traditional single-stage or two-stage Freon compression refrigeration systems (such as Hanbell single-unit two-stage units LT-S-83 / 41 and LT-S-65 / 32). While these systems can meet basic freezing requirements, they suffer from high energy consumption, high electricity costs, and increased grid load during peak electricity consumption periods. They cannot utilize electricity price differences for peak shaving and valley filling, resulting in poor overall operational economics. Furthermore, existing technologies combine cold storage technology with refrigeration equipment, but these solutions also have significant limitations. For example, the cold storage medium after cold storage is placed in the same cold storage as the goods for quick-freezing, or the stored cold energy is directly used to assist in cooling within the cold storage. These technologies require the cold storage temperature to be lower than the target quick-freezing temperature, limiting the cold storage temperature to the quick-freezing temperature of the system. Additionally, low cold storage temperatures significantly increase energy consumption.

[0003] A "cold storage quick-freezing machine" disclosed in Chinese patent literature, publication number CN206803578U, published on 2017-12-26, includes a horizontal, top-opening box. The box contains a refrigeration system, a cold storage mechanism, and an air-cooled circulation mechanism. The refrigeration system and the air-cooled circulation mechanism are connected to a control system. The cold storage mechanism includes a wire basket containing a cold storage container filled with a cold storage agent. The air-cooled circulation mechanism includes two fan wheels diagonally arranged within the box, each connected to an AC motor via a coupling. The AC motors are mounted on the outside of the box's insulation layer. In this technology, after pre-cooling the cold storage medium, the cold storage medium and goods are stacked in the same space, and cold air flows through them for cooling. However, this quick-freezing method requires the cold storage temperature to be much lower than the quick-freezing temperature of the goods, and it cannot achieve stable and accurate control of the quick-freezing temperature. Summary of the Invention

[0004] The present invention aims to overcome the problem in the prior art that the cold storage temperature during quick freezing is limited by the quick freezing temperature of the quick freezing system, and the cold storage temperature must be lower than the quick freezing temperature, which greatly increases the cold storage energy consumption at low cold storage temperatures. The present invention provides a cold storage cascade quick freezing machine system and its control method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A cold storage cascade freezer system includes: The cold storage system is formed by connecting the cold storage unit, the cold storage condenser, the first expansion valve and the cold storage device in sequence through pipelines to form a cold storage circuit. The quick-freezing system is formed by connecting the quick-freezing unit, the cold storage device, the second expansion valve and the quick-freezing evaporator in sequence through pipelines. The quick-freezing evaporator is installed inside the heat preservation warehouse. The cold storage device includes an ice pool with a built-in phase change medium. In the cold storage system, it acts as a cold storage evaporator to solidify and store cold in the phase change medium, and in the quick-freezing system, it acts as a quick-freezing condenser to melt and release cold in the phase change medium.

[0006] The cold storage cascade quick-freezing system of this invention mainly consists of two cascaded parts: a cold storage system and a quick-freezing system. These two parts are coupled through a shared cold storage device. Its core objective is to utilize off-peak electricity at night to store cold energy and release it during the daytime quick-freezing period to lower the condensation temperature in the quick-freezing circuit, thereby assisting in quick-freezing and reducing energy consumption. The cold storage medium of this invention does not directly participate in the cooling of goods inside the insulated storage room. Instead, it achieves quick-freezing by lowering the condensation temperature in the quick-freezing system through the cascade structure. Therefore, the cold storage temperature does not change with different quick-freezing temperature requirements. When using a relatively high cold storage temperature, cold storage energy consumption can be saved. Simultaneously, because the condensation temperature decreases while the evaporation temperature remains constant, quick-freezing energy consumption is saved. Furthermore, with the condensation temperature remaining stable, the operating parameters of the quick-freezing unit can be adjusted in real time according to the different quick-freezing requirements of the goods and the quantity to be frozen, allowing for rapid and flexible operation.

[0007] Preferably, the cold storage cascade freezer system further includes: The status monitoring module monitors the temperature of the ice pool in the cold storage device, the temperature inside the insulated storage chamber, the temperature and pressure of the refrigerant in the cold storage circuit, and the temperature and pressure of the refrigerant in the quick-freezing circuit. The mode control module switches control modes based on the data monitored by the status monitoring module and the peak and valley periods. The control modes include cold storage mode, quick-freezing mode and combined operation mode.

[0008] Preferably, a precooler is installed on the pipeline between the quick-freezing unit and the cold storage device in the quick-freezing circuit.

[0009] As a preferred embodiment, a first gas-liquid separator is installed on the pipeline between the cold storage device and the cold storage unit in the cold storage circuit; In the quick-freezing circuit, a second gas-liquid separator is installed on the pipeline between the quick-freezing evaporator and the quick-freezing unit.

[0010] Preferably, a first temperature sensor and a first pressure sensor are installed near the refrigerant inlet of the cold storage device in the cold storage circuit, and a second temperature sensor and a second pressure sensor are installed near the refrigerant outlet of the cold storage device. A third temperature sensor and a third pressure sensor are installed near the refrigerant inlet of the cold storage device in the quick-freezing circuit, and a fourth temperature sensor and a fourth pressure sensor are installed near the refrigerant outlet of the cold storage device.

[0011] Preferably, a fifth temperature sensor and a sixth temperature sensor are respectively installed in the ice pool near the refrigerant inlet and outlet; a seventh temperature sensor is installed inside the insulated chamber.

[0012] A control method for a cold storage cascade freezer system includes: During off-peak electricity hours, the cold storage mode is activated, and the ice pool acts as a cold storage evaporator in the cold storage system to solidify the phase change medium and store cold. When there is a need for quick freezing, the quick freezing mode is activated. The ice pool acts as a quick freezing condenser in the quick freezing system to melt and release the phase change medium, providing low-temperature condensation conditions for the quick freezing circuit and quick freezing the goods in the insulated warehouse. In quick-freezing mode, when the conditions for joint operation are met, the joint operation mode is activated, and cold storage and quick-freezing are carried out simultaneously.

[0013] Preferably, the cold storage mode includes: Control the operating parameters of the cold storage mode so that the refrigerant entering the cold storage device is in a subcooled liquid state and the refrigerant flowing out of the cold storage device is in a superheated gas state; Real-time monitoring of the ice pool temperature and the refrigerant status entering and exiting the cold storage device in the cold storage circuit; When the heat exchange temperature difference between the ice pool and the refrigerant is less than the first temperature difference threshold, and the evaporation temperature of the cold storage circuit is lower than the second temperature threshold, the cold storage is considered complete.

[0014] Preferably, the quick-freezing mode includes: Control the operating parameters of the quick-freezing mode so that the refrigerant entering the cold storage device is in a superheated gaseous state and the refrigerant flowing out of the cold storage device is in a subcooled liquid state; By maintaining the ice pool in a state of ice-water mixture, a low-temperature condensation source is provided for the quick-freezing circuit; The system monitors the temperature of the ice pool and the insulated storage room in real time, as well as the refrigerant status entering and exiting the ice pool in the quick-freezing circuit; when the conditions for joint operation are met, it enters the joint operation mode.

[0015] Preferably, the joint operating conditions include: The temperature inside the ice pool exceeds the first temperature threshold; or Temperature fluctuations within the insulated storage chamber exceed a preset fluctuation threshold; or The temperature of the refrigerant entering or leaving the cold storage device in the quick-freezing circuit increases by more than a preset percentage threshold relative to the stable operating value.

[0016] This invention offers the following advantages: It utilizes off-peak electricity for cold storage at night and peak electricity for cold release during the day to assist in quick-freezing, significantly reducing electricity costs and saving energy. The ice pool in the cold storage device acts as a stable low-temperature cold source (ice-water mixture), keeping the condensation temperature of the quick-freezing unit constant at a low level, thus ensuring the stability of the evaporation temperature and the temperature inside the storage chamber, and improving the quality of quick-frozen products. The cold storage temperature in the cold storage device is relatively high. Compared to existing solutions where the cold storage temperature must be lower than the quick-freezing temperature, the cold storage itself consumes less energy, and the cold storage temperature is decoupled from the quick-freezing temperature, not being limited by the latter, making its application more flexible. It employs direct expansion heat exchange, where the refrigerant directly expands and evaporates (during cold storage) and directly condenses (during quick-freezing) within the ice pool, resulting in higher heat exchange efficiency compared to traditional cold storage methods that use a refrigerant for indirect heat exchange. It features a combined operation mode, automatically starting the cold storage unit to supplement cooling when the ice pool's cooling capacity is insufficient, ensuring uninterrupted quick-freezing production, and demonstrating strong system resilience to load fluctuations. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a cold storage cascade quick-freezing system in this invention.

[0018] Figure 2 This is a flowchart of the control method for the cold storage cascade quick-freezing machine system in this invention.

[0019] In the diagram: 1. Cold storage device; 2. First gas-liquid separator; 3. Cold storage unit; 4. Cold storage condenser; 5. First expansion valve; 6. Second expansion valve; 7. Insulated storage body; 71. Quick-freezing evaporator; 8. Second gas-liquid separator; 9. Quick-freezing unit. Detailed Implementation

[0020] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 The cold storage cascade freezer system shown includes: The cold storage system is formed by connecting the cold storage unit 3, the cold storage condenser 4, the first expansion valve 5 and the cold storage device 1 in sequence through pipelines to form a cold storage circuit; The quick-freezing system is connected in sequence through pipelines to quick-freezing unit 9, cold storage device 1, second expansion valve 6 and quick-freezing evaporator 71 to form a quick-freezing circuit. The quick-freezing evaporator 71 is installed inside the heat preservation body 7. The cold storage device 1 includes an ice pool with a built-in phase change medium. In the cold storage system, it acts as a cold storage evaporator to solidify and store cold in the phase change medium, and in the quick-freezing system, it acts as a quick-freezing condenser to melt and release cold in the phase change medium.

[0022] The cold storage cascade quick-freezing system of this invention mainly consists of two cascaded parts: a cold storage system and a quick-freezing system. These two parts are coupled through a shared cold storage device. Its core objective is to utilize off-peak electricity at night to store cold energy and release it during the daytime quick-freezing period to lower the condensation temperature in the quick-freezing circuit, thereby assisting in quick-freezing and reducing energy consumption. The cold storage medium of this invention does not directly participate in the cooling of goods inside the insulated storage room. Instead, it achieves quick-freezing by lowering the condensation temperature in the quick-freezing system through the cascade structure. Therefore, the cold storage temperature does not change with different quick-freezing temperature requirements. When using a relatively high cold storage temperature, cold storage energy consumption can be saved. Simultaneously, because the condensation temperature decreases while the evaporation temperature remains constant, quick-freezing energy consumption is saved. Furthermore, with the condensation temperature remaining stable, the operating parameters of the quick-freezing unit can be adjusted in real time according to the different quick-freezing requirements of the goods and the quantity to be frozen, allowing for rapid and flexible operation.

[0023] Specifically, a cold storage system is used to generate and store cold energy during periods of low electricity prices. Its main equipment includes a cold storage unit (compressor, such as RC2-410B, RC2-580B, etc., using R22 refrigerant), a cold storage condenser, and a first expansion valve. The core component is the cold storage device. Under cold storage conditions, the ice pool in the cold storage device acts as the evaporator of the cold storage unit, where the phase change medium is cooled and solidified, storing the phase change cold energy.

[0024] The quick-freezing system is used to rapidly freeze goods during the day. Its main equipment includes a quick-freezing unit (compressor, such as RC2-370DL, RC2-470DL, etc., using R507 refrigerant), an insulated storage unit (a tunnel-type quick-freezing production line for quick-freezing goods, with a quick-freezing evaporator inside to cool the storage unit), and a second expansion valve. The core component is the same cold storage device as in a cold storage system. Under quick-freezing conditions, the ice pool in the cold storage device acts as a condenser for the quick-freezing unit, absorbing heat from the compressor exhaust and condensing it.

[0025] The cold storage device serves as a crucial coupling hub in the entire system. Its ice pool can be filled with water as the phase change material (ice / water). It has an internal heat exchanger (such as stainless steel tubes) and an external insulation layer. Its design volume is calculated based on the required cold storage capacity.

[0026] As a specific embodiment, in the cold storage circuit, a first gas-liquid separator 2 is installed on the pipeline between the cold storage device 1 and the cold storage unit 3; after the refrigerant flowing out of the cold storage device 1 undergoes gas-liquid separation in the first gas-liquid separator 2, the gas part enters the cold storage unit 3 for subsequent cold storage process, while the liquid part remains at the bottom of the first gas-liquid separator 2. When it accumulates to a certain amount, it is recycled or replenished back into the cold storage circuit.

[0027] In the quick-freezing circuit, a second gas-liquid separator 8 is installed on the pipeline between the quick-freezing evaporator 71 and the quick-freezing unit 9. After the refrigerant flowing out of the quick-freezing evaporator 71 is separated into gas and liquid by the second gas-liquid separator 8, the gas part enters the quick-freezing unit 9 for the subsequent quick-freezing process, while the liquid part remains at the bottom of the second gas-liquid separator 8. When it accumulates to a certain amount, it is recycled or replenished into the cold storage circuit.

[0028] When the refrigeration system is running, the refrigerant at the evaporator outlet may not completely vaporize due to load fluctuations, improper expansion valve adjustment, or frequent start-stop cycles, causing liquid refrigerant to enter the return gas line along with the gaseous refrigerant. If this liquid refrigerant is directly drawn into the compressor, it may cause liquid slugging. Therefore, a gas-liquid separator is placed between the evaporator and the compressor in the circuit. Its core purpose is to prevent liquid refrigerant from entering the compressor and avoiding liquid slugging damage.

[0029] Optionally, a precooler is installed on the pipeline between the quick-freezing unit 9 and the cold storage device 1 in the quick-freezing circuit. That is, the refrigerant compressed by the quick-freezing unit 9 can be pre-cooled by the precooler before entering the ice pool of the cold storage device 1 for further cooling, thereby saving the cooling capacity of the ice pool. The precooler can adopt various existing cooling methods such as air coolers, air cooling, and water cooling, without affecting the effect of the present invention, and therefore will not be described in detail.

[0030] As a specific embodiment, the cold storage cascade freezer system, in addition to the cold storage system and the freezer system coupled together by the cold storage device 1, also includes: The status monitoring module monitors the temperature of the ice pool in the cold storage device 1, the temperature inside the insulated storage body 7, the temperature and pressure of the refrigerant in the cold storage circuit, and the temperature and pressure of the refrigerant in the quick-freezing circuit. The mode control module switches control modes based on the data monitored by the status monitoring module and the peak and valley periods. The control modes include cold storage mode, quick-freezing mode and combined operation mode.

[0031] It should be noted that the temperature and pressure of the refrigerant in the cold storage circuit are used to confirm whether the refrigerant entering the cold storage device 1 is entirely liquid, and whether the refrigerant flowing out of the cold storage device 1 has completely evaporated into gas. The temperature and pressure of the refrigerant in the quick-freezing circuit are used to confirm whether the refrigerant entering the cold storage device 1 is entirely gas, and whether the refrigerant flowing out of the cold storage device 1 has completely condensed into liquid. Temperature detection in the ice pool is used to determine the cold storage status within the cold storage device 1. When the temperature in the ice pool is greater than 0 degrees Celsius, it indicates that cold storage is needed; when it is less than or equal to 0 degrees Celsius, it indicates that there is stored cold energy that can be used to lower the condensation temperature of the quick-freezing circuit. Temperature detection inside the insulated storage chamber is used to determine the stability of the quick-freezing temperature during operation of the quick-freezing circuit.

[0032] Specifically, a first temperature sensor T1 and a first pressure sensor P1 are installed near the inlet of the refrigerant flowing into the cold storage device 1 in the cold storage circuit to detect the temperature and pressure of the refrigerant before it flows into the cold storage device 1; a second temperature sensor T2 and a second pressure sensor P2 are installed near the outlet of the refrigerant flowing out of the cold storage device 1 to detect the temperature and pressure of the refrigerant after it flows out of the cold storage device 1.

[0033] A third temperature sensor T3 and a third pressure sensor P3 are installed near the inlet of the refrigerant flowing into the cold storage device 1 in the quick-freezing circuit to detect the temperature and pressure of the refrigerant before it flows into the cold storage device 1; a fourth temperature sensor T4 and a fourth pressure sensor P4 are installed near the outlet of the refrigerant flowing out of the cold storage device 1 to detect the temperature and pressure of the refrigerant after it flows out of the cold storage device 1.

[0034] A fifth temperature sensor T5 and a sixth temperature sensor T6 are respectively installed near the refrigerant inlet and outlet of the ice pool to detect the temperature status inside the ice pool; a seventh temperature sensor T7 is installed inside the insulation chamber to detect the temperature status inside the insulation chamber 7.

[0035] Compared to existing cold storage quick-freezing technologies, this invention achieves an economical, energy-saving, and flexible quick-freezing effect through a cascade system. Unlike existing technologies where the cold storage temperature must be lower than the quick-freezing temperature (e.g., a quick-freezing temperature of -20 degrees Celsius necessitates a cold storage temperature below -20 degrees Celsius to ensure good quick-freezing results), the cold storage temperature of this invention is not limited by the quick-freezing temperature but is maintained at a stable temperature level relatively higher than the quick-freezing temperature. Therefore, the energy consumption for cold storage is lower. Furthermore, the cold storage medium in this invention does not directly contact the goods to produce a cooling effect. Instead, it achieves a cooling temperature of -42 degrees Celsius by lowering the condensing temperature of the quick-freezing unit (the condensing temperature of a traditional quick-freezing unit is generally 35 degrees Celsius, while the condensing temperature of this invention's quick-freezing unit is 4-10 degrees Celsius). Because the condensing temperature is significantly reduced while the evaporation temperature remains unchanged, the refrigeration energy consumption also decreases significantly.

[0036] In addition to a cold storage cascade freezer system, this invention also provides, for example, a cold storage cascade freezer system. Figure 2 The control method of a cold storage cascade freezer system shown includes: During off-peak electricity hours, the cold storage mode is activated, and the ice pool acts as a cold storage evaporator in the cold storage system to solidify the phase change medium and store cold. When there is a need for quick freezing, the quick freezing mode is activated. The ice pool acts as a quick freezing condenser in the quick freezing system to melt and release the phase change medium, providing low-temperature condensation conditions for the quick freezing circuit and quick freezing the goods in the insulated warehouse. In quick-freezing mode, when the conditions for joint operation are met, the joint operation mode is activated, and cold storage and quick-freezing are carried out simultaneously.

[0037] Specifically, in this invention, the condensing temperature of the cold storage unit can be set to 35 degrees Celsius, the evaporation temperature of the cold storage unit is -10 degrees Celsius to -6 degrees Celsius, the cold storage temperature of the ice pool is -6 degrees Celsius to 0 degrees Celsius, the cold release temperature of the ice pool is 4 degrees Celsius to 10 degrees Celsius, the condensing temperature of the quick-freezing unit is 4 degrees Celsius to 10 degrees Celsius, and the evaporation temperature of the quick-freezing unit is -42 degrees Celsius.

[0038] First, assess the operating conditions of the cold storage cascade freezer system to determine if there is a need for quick-freezing.

[0039] If there is no demand for quick-freezing, the quick-freezing mode is not required. In this case, it is further determined whether it is during off-peak electricity hours. If it is not during off-peak hours, the system will not enter cold storage mode and will not operate until there is a demand for quick-freezing or the system returns to off-peak hours. If it is during off-peak hours, the cold storage unit will be activated and enter cold storage mode. Cold storage mode will be maintained until the cold storage shutdown conditions are met, at which point cold storage will cease operation. After cold storage is complete, the system will not operate until there is a demand for quick-freezing.

[0040] When there is a need for quick-freezing, the quick-freezing unit is activated and enters quick-freezing mode. During quick-freezing mode, the ice-water mixture in the ice tank is maintained at a temperature of approximately 0 degrees Celsius, and the condensing temperature of the quick-freezing circuit is maintained between 4 and 10 degrees Celsius to quickly freeze the goods inside the insulated warehouse. During the operation of quick-freezing mode, when the conditions for combined operation are met, the cold storage unit and the quick-freezing unit are activated simultaneously, entering a combined operation mode.

[0041] During the combined operation mode, the combined operation mode will be exited when the temperature of the ice pool in the cold storage unit returns to below 0 degrees Celsius, or when the goods have been quick-frozen. There are two scenarios: First, if the ice pool temperature returns to below 0 degrees Celsius, the combined operation mode will be exited and the system will revert to quick-freezing mode for refrigeration. Second, if the goods have been quick-frozen, both the quick-freezing unit and the cold storage unit will stop operating after exiting the combined operation mode. The decision to re-enter the cold storage mode will then be based on whether it is during off-peak electricity hours.

[0042] This invention creates a stable cold source inside the ice pool, unaffected by the quantity of goods or fluctuations in ambient temperature. The temperature inside the insulated storage unit is uniform and stable, resulting in a higher quality quick-freezing effect. Compared to traditional quick-freezing systems, this invention lowers the condensing temperature in quick-freezing mode, allowing the ice pool to provide more cooling capacity in the same amount of time, or achieve the same cooling effect with less energy consumption. The refrigerant directly expands inside the ice pool (evaporation and heat absorption), resulting in higher heat exchange efficiency compared to traditional cold storage methods that use indirect methods like ethylene glycol. The cold storage temperature is higher (making cold storage more energy-efficient), and it overcomes the limitation that the quick-freezing temperature of the goods must be higher than the cold storage temperature (the low-temperature cold storage medium absorbs heat from the high-temperature goods). Peak electricity pricing is also optimized, significantly enhancing operational economics and feasibility. Operating parameters are stable and control is simple. The ice pool ensures that the evaporation temperature of the cold storage unit and the condensing temperature of the quick-freezing unit remain constant. Therefore, regardless of the operating conditions, the quick-freezing system always operates with stable parameters, and in extreme situations, the cold storage unit can be activated to supplement the ice pool's cooling capacity.

[0043] As a specific embodiment, the cold storage mode includes: Control the operating parameters of the cold storage mode so that the refrigerant entering the cold storage device is in a subcooled liquid state and the refrigerant flowing out of the cold storage device is in a superheated gas state; Real-time monitoring of the ice pool temperature and the refrigerant status entering and exiting the cold storage device in the cold storage circuit; When the heat exchange temperature difference between the ice pool and the refrigerant is detected to be less than the second temperature difference threshold, the operating parameters are adjusted to gradually reduce the evaporation temperature so that the heat exchange temperature difference is always greater than or equal to the first temperature difference threshold; the first temperature difference threshold is less than the second temperature difference threshold. When the heat exchange temperature difference between the ice pool and the refrigerant is less than the first temperature difference threshold, and the evaporation temperature of the cold storage circuit is lower than the second temperature threshold, the cold storage is considered complete.

[0044] Specifically, during off-peak electricity hours or the nighttime peak electricity hours, the cold storage unit is turned on to store cold energy. The high-temperature exhaust gas from the cold storage unit enters the cold storage condenser for condensation and heat dissipation (+35℃). The condensed refrigerant liquid is throttled by the first expansion valve and becomes a low-temperature refrigerant liquid (-6℃), which enters the ice pool of the cold storage device to evaporate and absorb heat. At this time, the water (phase change medium) in the ice pool continuously freezes into ice as the low-temperature refrigerant evaporates. The evaporated refrigerant gas returns to the cold storage unit after passing through the first gas-liquid separator, completing the cycle of the entire cold storage circuit.

[0045] Initially, the ice pool contains little or no ice, and its temperature is greater than or equal to 0 degrees Celsius (monitored by the fifth temperature sensor T5 and the sixth temperature sensor T6). Due to the large heat exchange temperature difference (the temperature difference between the water in the ice pool and the cryogenic refrigerant is greater than or equal to the second temperature difference threshold of 6 degrees Celsius, i.e., the temperature difference ΔT1 between T5 and T1 is greater than or equal to 6 degrees Celsius and the temperature difference ΔT2 between T6 and T2 is greater than or equal to 6 degrees Celsius), the cryogenic refrigerant entering the ice pool quickly evaporates into gas. As time progresses, the ice content in the ice pool increases, and the ice pool temperature drops below 0 degrees Celsius (monitored by the fifth temperature sensor T5 and the sixth temperature sensor T6). As the temperature difference between the water and the cryogenic refrigerant in the ice pool gradually decreases (the temperature difference between the water and the cryogenic refrigerant in the ice pool is less than the second temperature difference threshold of 6 degrees Celsius, that is, the temperature difference ΔT1 between T5 and T1 is less than 6 degrees Celsius and the temperature difference ΔT2 between T6 and T2 is less than 6 degrees Celsius), the cryogenic refrigerant entering the ice pool no longer completely evaporates into gas. At this time, the chilled water storage unit adjusts its operating parameters, and the evaporation temperature gradually decreases (starting from -6 degrees Celsius), so that the water and the cryogenic refrigerant in the ice pool still maintain a certain temperature difference (greater than or equal to the first temperature difference threshold of 5 degrees Celsius), and the cryogenic refrigerant entering the ice pool can still completely evaporate into gas. Finally, when the temperature difference is less than the first temperature difference threshold of 5 degrees Celsius and the evaporation temperature is less than the second temperature threshold of -10 degrees Celsius, the chilled water storage is considered complete, and the chilled water storage unit is shut down.

[0046] Furthermore, the method for determining whether the refrigerant entering the cold storage device is in a subcooled liquid state is as follows: Monitoring is performed using a first temperature sensor T1 and a first pressure sensor P1. The saturated liquid / gas temperature of the refrigerant at that pressure can be determined based on the reading of the first pressure sensor P1 (saturation temperature is a function of pressure and is existing technology, therefore not described in detail). When the unit is running, the first temperature sensor T1 is lower than the saturated liquid temperature, indicating that the refrigerant is in a subcooled liquid state. If the first temperature sensor T1 is equal to the saturated liquid temperature, it cannot be confirmed in actual engineering that the refrigerant is always in a liquid or gas-liquid mixture state.

[0047] Furthermore, the method for determining that the refrigerant flowing out of the cold storage device is a superheated gas is as follows: by monitoring with the second temperature sensor T2 and the second pressure sensor P2, the saturated liquid / gas temperature of the refrigerant at that pressure can be determined based on the reading of the second pressure sensor P2. When the unit is running, the second temperature sensor T2 is greater than the saturated gas temperature, which means that it is considered that all of it has evaporated into gas, because the refrigerant gas temperature is greater than the saturated gas temperature and reaches the superheated gas state. At this time, all the refrigerant is in a gaseous state.

[0048] As a specific embodiment, the quick-freezing mode includes: Control the operating parameters of the quick-freezing mode so that the refrigerant entering the cold storage device is in a superheated gaseous state and the refrigerant flowing out of the cold storage device is in a subcooled liquid state; By maintaining the ice pool in a state of ice-water mixture, a low-temperature condensation source is provided for the quick-freezing circuit; The system monitors the temperature of the ice pool and the insulated storage room in real time, as well as the refrigerant status entering and exiting the ice pool in the quick-freezing circuit; when the conditions for joint operation are met, it enters the joint operation mode.

[0049] Specifically, during peak or off-peak electricity periods (daytime), the blast freezer is turned on for production and processing, at which time the ice pool releases heat. The high-temperature exhaust from the blast freezer enters the ice pool for condensation and heat dissipation (the recommended temperature range is 4 to 10 degrees Celsius, set according to requirements; the lower the condensation temperature, the greater the heat release during condensation, which also means more heat release). At this time, the ice in the ice pool continuously melts into water as the high-temperature exhaust from the blast freezer is condensed. The condensed refrigerant liquid passes through the second expansion valve and becomes a low-temperature refrigerant liquid (-42°C), which enters the insulated storage room to evaporate and absorb heat to blast freeze the goods. The evaporated refrigerant gas returns to the blast freezer after passing through the second gas-liquid separator, completing the entire blast freezer cycle.

[0050] During quick-freezing production, the ice in the ice pool gradually melts, but always remains a mixture of ice and water, thus forming a stable cold source at or below 0 degrees Celsius (monitored by the fifth temperature sensor T5 and the sixth temperature sensor T6). Before the high-temperature exhaust gas from the quick-freezing unit enters the ice pool for condensation and heat dissipation, an additional air cooler can be added to utilize air to remove some heat in advance, saving the cold energy stored in the ice pool and extending its service life.

[0051] During operation of the quick-freezing unit, the ice pool is maintained at a temperature of 0 degrees Celsius or less. The high-temperature exhaust gas from the quick-freezing unit enters the ice pool in a superheated gaseous state and condenses into a saturated / subcooled liquid. The entire quick-freezing process operates under stable conditions and parameters, unaffected by external environmental factors or the quantity of goods. A stable low-temperature environment is formed within the insulated storage room (monitored by the seventh temperature sensor T7, its fluctuation range is less than or equal to 0.5 degrees Celsius), which helps improve the quality of quick-frozen products.

[0052] Furthermore, the method for determining whether the refrigerant entering the cold storage device is a superheated gas is as follows: by monitoring with the third temperature sensor T3 and the third pressure sensor P3, the saturated liquid / gas temperature of the refrigerant at that pressure can be determined based on the reading of the third pressure sensor P3. When the unit is running, the third temperature sensor T3 is greater than the saturated gas temperature, which means that all of it has evaporated into gas, because the refrigerant gas temperature is greater than the saturated gas temperature and reaches the superheated gas state. At this time, all the refrigerant is in a gaseous state.

[0053] Furthermore, the method for determining whether the refrigerant flowing out of the cold storage device is in a subcooled liquid state is as follows: Monitoring is performed using the fourth temperature sensor T4 and the fourth pressure sensor P4. The reading of the fourth pressure sensor P4 indicates the saturated liquid / gas temperature of the refrigerant at that pressure. During unit operation, if the reading of the fourth temperature sensor T4 is lower than the saturated liquid temperature, the refrigerant is in a subcooled liquid state. If the fourth temperature sensor T4 equals the saturated liquid temperature, it cannot be confirmed in practical engineering that the refrigerant is in a liquid or gas-liquid mixture state.

[0054] It should be noted that the conditions for joint operation include: The temperature inside the ice pool exceeds the first temperature threshold; or Temperature fluctuations within the insulated storage chamber exceed a preset fluctuation threshold; or The temperature of the refrigerant entering or leaving the cold storage device in the quick-freezing circuit increases by more than a preset percentage threshold relative to the stable operating value.

[0055] Specifically, when the quick-freezing unit runs for too long, or when the quick-freezing unit operates under overload for an extended period, and the ice storage capacity of the ice pool is consumed too quickly, the cold storage unit will start up and initiate a combined operation mode.

[0056] The determination method includes: monitoring by the fifth temperature sensor T5 and the sixth temperature sensor T6, and determining the temperature when the reading of at least one of the temperature sensors is greater than the first temperature threshold of 0.5 degrees Celsius; or When the reading increase of either the third temperature sensor T3 or the fourth temperature sensor T4 exceeds a preset percentage threshold of 10% for stable operation, or The joint operation is triggered when the temperature reading of the seventh temperature sensor T7 fluctuates more than the preset fluctuation threshold of 1 degree Celsius.

[0057] In the combined operation mode, the cold storage unit operates with a condensing temperature of 35 degrees Celsius and an evaporating temperature of -6 degrees Celsius, under which its cooling capacity is at its maximum. The quick-freezing unit operates with a condensing temperature of 4 degrees Celsius and an evaporating temperature of -42 degrees Celsius, under which its cooling capacity is also at its maximum, fully guaranteeing the quick-freezing processing needs. During the operation of the combined mode, the combined operation mode will exit when the temperature of the ice pool in the cold storage device returns to below 0 degrees Celsius (when the temperatures of the fifth temperature sensor T5 and the sixth temperature sensor T6 are both below 0 degrees Celsius), or after the quick-freezing of the goods is completed.

[0058] Example 1: This example uses a quick-freezing machine with a capacity of 1 ton of fish and shrimp per hour as an example, comparing it with a traditional quick-freezing machine. Calculations are based on 9 hours of operation per day and 330 operating days per year. A direct-in, direct-out feeding method is used, with an inlet temperature of 15 degrees Celsius, an outlet temperature of -18 degrees Celsius, and an internal temperature of 35 degrees Celsius ± 2 degrees Celsius. Freon (R507) is used as the refrigerant.

[0059] The traditional quick-freezing unit uses the Hanbell LT-S-83 / 41 single-unit two-stage unit with a cooling capacity of 228kW and a power of 143kW, operating at -42 / 35 degrees Celsius. The annual operating electricity cost, including the main unit and evaporator cooling electricity cost, is: (143+10)*9 hours*0.84 yuan / kWh*330 days = 1157 yuan / day*330 days = 381810 yuan / year.

[0060] The quick-freezing system used in this embodiment consists of two RC2-470DL quick-freezing units with a cooling capacity of 225kW (cooling conditions -42 / +4 degrees Celsius) and a power of 68kW. The chilled water storage unit is RC2-580B with a cooling capacity of 400kW (cooling conditions -10 / +35 degrees Celsius) and a power of 114kW. The chilled water storage tank requires a storage capacity of approximately 3000kWh and has a designed effective volume of 36m³. 3 (divided into two 18m units) 3 equipment).

[0061] Operating electricity costs: 8 hours of nighttime cold storage costs 0.24 yuan / kWh, for a daily cost of 242 yuan; 9 hours of daytime production costs 0.84 yuan / kWh, for a daily cost of 514 yuan, for a total daily cost of 756 yuan. Compared to traditional quick-freezing machines, this saves 401 yuan per day and approximately 132,330 yuan per year (330 days).

[0062] Example 2: This example uses a quick-freezing machine with a capacity of 1 ton of meat per hour as an example, comparing it with a traditional quick-freezing machine. Calculations are based on 9 hours of operation per day and 330 operating days per year. A direct-in, direct-out feeding method is used, with an inlet temperature of 15 degrees Celsius, an outlet temperature of -18 degrees Celsius, and an internal temperature of 35 degrees Celsius ± 2 degrees Celsius. Freon (R507) is used as the refrigerant.

[0063] The traditional quick-freezing machine uses a Hanbell LT-S-65 / 32 single-unit two-stage chiller with a cooling capacity of 178kW and a power of 111kW, operating at -42 / 35 degrees Celsius. The annual operating electricity cost, including the main unit and evaporator cooling electricity cost, is: (111+9)*9 hours*0.84 yuan / kWh*330 days = 907 yuan / day*330 days = 299,310 yuan / year.

[0064] The quick-freezing system used in this embodiment consists of two RC2-370DL quick-freezing units, each with a cooling capacity of 180kW (cooling conditions -42 / +4 degrees Celsius) and a power of 53kW. A chilled water storage unit (RC2-410B) has a cooling capacity of 263kW (cooling conditions -10 / +35 degrees Celsius) and a power of 77kW. The required chilled water storage tank has a capacity of approximately 2400kWh and a designed effective volume of 27m³. 3 (divided into two 14.4m units) 3 equipment).

[0065] Operating electricity costs: 8 hours of nighttime cooling storage costs 167 yuan per day; 9 hours of daytime production costs 401 yuan per day, totaling 568 yuan per day. Compared to the traditional system, this saves 339 yuan per day and approximately 111,870 yuan per year.

[0066] The above embodiments are further elaborations and descriptions of the present invention to facilitate understanding, and are not intended to limit the present invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cold storage cascade quick-freezing system, characterized in that, include: The cold storage system is formed by connecting the cold storage unit, the cold storage condenser, the first expansion valve and the cold storage device in sequence through pipelines to form a cold storage circuit. The quick-freezing system is formed by connecting the quick-freezing unit, the cold storage device, the second expansion valve and the quick-freezing evaporator in sequence through pipelines. The quick-freezing evaporator is installed inside the heat preservation warehouse. The cold storage device includes an ice pool with a built-in phase change medium. In the cold storage system, it acts as a cold storage evaporator to solidify and store cold in the phase change medium, and in the quick-freezing system, it acts as a quick-freezing condenser to melt and release cold in the phase change medium.

2. The cold storage cascade quick-freezing system according to claim 1, characterized in that, Also includes: The status monitoring module monitors the temperature of the ice pool in the cold storage device, the temperature inside the insulated storage chamber, the temperature and pressure of the refrigerant in the cold storage circuit, and the temperature and pressure of the refrigerant in the quick-freezing circuit. The mode control module switches control modes based on the data monitored by the status monitoring module and the peak and valley periods. The control modes include cold storage mode, quick-freezing mode and combined operation mode.

3. A cold storage cascade quick-freezing system according to claim 1 or 2, characterized in that, In the quick-freezing circuit, a precooler is installed on the pipeline between the quick-freezing unit and the cold storage device.

4. A cold storage cascade quick-freezing system according to claim 1 or 2, characterized in that, In the cold storage circuit, a first gas-liquid separator is installed on the pipeline between the cold storage device and the cold storage unit; In the quick-freezing circuit, a second gas-liquid separator is installed on the pipeline between the quick-freezing evaporator and the quick-freezing unit.

5. A cold storage cascade quick-freezing system according to claim 1 or 2, characterized in that, A first temperature sensor and a first pressure sensor are installed near the refrigerant inlet of the cold storage device in the cold storage circuit, and a second temperature sensor and a second pressure sensor are installed near the refrigerant outlet of the cold storage device. A third temperature sensor and a third pressure sensor are installed near the refrigerant inlet of the cold storage device in the quick-freezing circuit, and a fourth temperature sensor and a fourth pressure sensor are installed near the refrigerant outlet of the cold storage device.

6. The cold storage cascade quick-freezing system according to claim 5, characterized in that, A fifth temperature sensor and a sixth temperature sensor are respectively installed in the ice pool near the refrigerant inlet and outlet; a seventh temperature sensor is installed inside the insulated chamber.

7. A control method for a cold storage cascade freezer system, applicable to the cold storage cascade freezer system as described in any one of claims 1-6, characterized in that, include: During off-peak electricity hours, the cold storage mode is activated, and the ice pool acts as a cold storage evaporator in the cold storage system to solidify the phase change medium and store cold. When there is a need for quick freezing, the quick freezing mode is activated. The ice pool acts as a quick freezing condenser in the quick freezing system, causing the phase change medium to melt and release cold, providing low-temperature condensation conditions for the quick freezing circuit, and quick freezing the goods in the insulated warehouse. In quick-freezing mode, when the conditions for joint operation are met, the joint operation mode is activated, and cold storage and quick-freezing are carried out simultaneously.

8. The control method for a cold storage cascade freezer system according to claim 7, characterized in that, The cold storage mode includes: Control the operating parameters of the cold storage mode so that the refrigerant entering the cold storage device is in a subcooled liquid state and the refrigerant flowing out of the cold storage device is in a superheated gas state; Real-time monitoring of the ice pool temperature and the refrigerant status entering and exiting the cold storage device in the cold storage circuit; When the heat exchange temperature difference between the ice pool and the refrigerant is less than the first temperature difference threshold, and the evaporation temperature of the cold storage circuit is lower than the second temperature threshold, the cold storage is considered complete.

9. A control method for a cold storage cascade freezer system according to claim 7 or 8, characterized in that, The quick-freezing mode includes: Control the operating parameters of the quick-freezing mode so that the refrigerant entering the cold storage device is in a superheated gaseous state and the refrigerant flowing out of the cold storage device is in a subcooled liquid state; By maintaining the ice pool in a state of ice-water mixture, a low-temperature condensation source is provided for the quick-freezing circuit; The system monitors the temperature of the ice pool and the insulated storage room in real time, as well as the refrigerant status entering and exiting the ice pool in the quick-freezing circuit; when the conditions for joint operation are met, it enters the joint operation mode.

10. The control method for a cold storage cascade freezer system according to claim 9, characterized in that, The joint operating conditions include: The temperature inside the ice pool exceeds the first temperature threshold; or Temperature fluctuations within the insulated storage chamber exceed a preset fluctuation threshold; or The temperature of the refrigerant entering or leaving the cold storage device in the quick-freezing circuit increases by more than a preset percentage threshold relative to the stable operating value.

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