Refrigeration energy efficiency improvement scheme of CO2 cascade and cold carrier block

Abstract

The application discloses a CO2 cascade refrigeration energy efficiency improvement scheme, and belongs to the technical field of CO2 cascade refrigeration. The scheme is characterized by optimizing the structure of a condenser-evaporator falling liquid pipe, setting spiral flow guides that are uniformly distributed along the length direction on the inner wall of the falling liquid pipe, the spiral angle of the spiral flow guides being 30-45 degrees, and the pitch of the spiral flow guides being 2 times the diameter of the falling liquid pipe. The structure can guide carbon dioxide to form a vortex flow, avoid wall hanging and liquid accumulation, increase the falling liquid speed from 0.5 m / s to 1.2 m / s, and shorten the falling liquid time by 58%. After the scheme is applied, the CO2 cascade refrigeration system has an 8-15% increase in refrigerating capacity and a 5-10% reduction in energy consumption, and has the advantages of simple structure, low modification difficulty, no need for overall replacement of equipment, and suitability for various scenes such as cold chain logistics, industrial refrigeration and commercial refrigeration, and can meet the requirements of efficient and stable refrigeration, and has extremely high popularization and application value.

Description

Technical Field

[0001] This invention relates to the field of CO2 cascade (cooling) refrigeration technology, specifically to a refrigeration energy efficiency improvement scheme for CO2 cascade (cooling) skids. It is applicable to various scenarios such as cold chain logistics (e.g., cold chain transportation for fresh food e-commerce) and industrial refrigeration (e.g., chemical production, meat processing) that rely on CO2 cascade (cooling) refrigeration skids. It can effectively improve the operating efficiency, stability and safety of refrigeration systems and provide technical support for the development of related industries. Background Technology

[0002] In CO2 cascade (cooled) refrigeration skid systems, the condenser-evaporator, as the core heat exchanger, directly determines the overall system performance through the liquid state of carbon dioxide within it, much like the heart's crucial role in blood circulation in the human body. However, existing CO2 cascade (cooled) refrigeration skid condensers and evaporators suffer from several prominent problems in actual operation:

[0003] On the one hand, vapor blockage in the liquid receiver is frequent, and a gas-liquid mixture is easily formed in the condenser and evaporator. Similar to traffic congestion, this causes the CO2 to fall into the liquid, and the liquid occupies the condensation area, which greatly reduces the heat exchange area. For example, in the refrigeration system of cold chain logistics warehouses, this problem leads to a significant decrease in refrigeration efficiency and seriously affects the preservation effect of goods.

[0004] On the other hand, the exhaust pressure of the CO2 compressor increases accordingly, and the operating current of the equipment rises simultaneously. This not only increases the energy consumption of the equipment, but also further deteriorates the heat exchange effect of the condenser and evaporator, ultimately resulting in insufficient cooling capacity of the system. In the field of industrial refrigeration, some factories need to run refrigeration equipment for a long time to meet the low-temperature environment required for production. However, due to the above problems, the cooling capacity cannot meet the production requirements, and energy consumption continues to rise, significantly increasing the production costs of enterprises.

[0005] These problems severely restrict the performance of CO2 cascade (cooled) refrigeration skid systems. Therefore, developing a refrigeration efficiency improvement solution that can solve problems such as slow liquid drop speed, high exhaust temperature, and increased energy consumption is crucial for improving the overall system performance and meeting the urgent needs of various fields for efficient and stable refrigeration. Summary of the Invention

[0006] This invention aims to overcome the technical challenges of slow liquid drop rate, high exhaust temperature, and increased energy consumption in the condenser-evaporator of existing CO2 cascade (cooled) refrigeration skids. Slow liquid drop rate is like poor blood circulation in the human body, resulting in low system operating efficiency; high exhaust temperature is like a fever in the human body, affecting the stability of equipment operation; increased energy consumption not only wastes energy but also increases operating costs.

[0007] This invention innovates the structure of the liquid drop pipe in the condenser evaporator, allowing carbon dioxide to flow more smoothly within the pipe. This increases the liquid drop rate, reduces exhaust pressure, and significantly improves the operating efficiency and stability of the CO2 cascade refrigeration system. At the same time, it enhances energy efficiency, achieves rational energy utilization, reduces environmental pressure and enterprise operating costs, brings new development opportunities to related industries, and promotes the industry towards high efficiency, stability, and energy conservation.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] The CO2 cascade and cooling skid-mounted refrigeration energy efficiency improvement scheme includes structural optimization of the liquid drop pipe of the condenser evaporator in the CO2 cascade and cooling skid-mounted refrigeration system. The liquid drop pipe is equipped with a spiral acceleration structure, which can guide the falling carbon dioxide to form a rotating flow state in the liquid drop pipe, thereby accelerating the descent speed of the falling carbon dioxide and avoiding poor liquid drop, which would lead to a reduction in condensation and evaporation area, a decrease in heat exchange efficiency, an increase in pressure, and an increase in energy consumption of refrigeration equipment.

[0010] Furthermore, the spiral acceleration structure is a spiral guide plate evenly distributed along the length of the inner wall of the liquid discharge pipe. The spiral angle of the spiral guide plate is 30-45°, and the pitch is set to twice the diameter of the liquid discharge pipe.

[0011] Furthermore, the liquid discharge pipe is made of carbon steel, and its inner diameter can be 150mm depending on the container capacity; the spiral guide plate is a stainless steel spiral guide plate with a pitch of 150mm and a lead of 120mm.

[0012] Furthermore, the spiral guide vane is fully welded to the inner wall of the liquid dropper to ensure a leak-free seal.

[0013] Furthermore, when liquid carbon dioxide at a temperature of -12℃ and a pressure of 2.5-3.5MPa enters the drop pipe, it forms a rotating flow under the guidance of the spiral acceleration structure, with a rotational angular velocity of about 5rad / s. The drop velocity can be increased from 0.5m / s to 1.2m / s, and the drop time is shortened by 58%.

[0014] Furthermore, the condenser-evaporator using this scheme can increase the cooling capacity of a CO2 cascade refrigeration system by 8-15% and reduce energy consumption by 5-10%.

[0015] Furthermore, it includes a condenser-evaporator body and a liquid-fall optimization structure disposed within the body, wherein the liquid-fall optimization structure is the spiral acceleration structure as described in any one of claims 1-6.

[0016] The technical solution of this invention brings significant and comprehensive benefits:

[0017] 1. Significantly improved liquid discharge effect:

[0018] The spiral guide plate guides the carbon dioxide to form a vortex flow, which greatly accelerates the drop speed, increasing it from 0.5m / s to 1.2m / s and shortening the drop time by 58%. This effectively avoids the problems of carbon dioxide sticking to the wall, accumulating, and accumulating liquid in the drop pipe, improves the uniformity and efficiency of the drop, and provides a strong guarantee for the optimized operation of the refrigeration system.

[0019] 2. Optimization of refrigeration system performance:

[0020] The improved liquid flow efficiency directly leads to an increase in the heat exchange efficiency of the condenser-evaporator, significantly increasing the cooling capacity of the CO2 cascade refrigeration system by 8-15% while reducing energy consumption by 5-10%, achieving the dual goals of high efficiency and energy saving. In cold chain logistics scenarios, it can provide a suitable low-temperature environment for goods more quickly and efficiently, ensuring product quality. In the field of industrial refrigeration, it can meet the stringent requirements of the production process for low-temperature environments, reducing enterprise production costs. In commercial refrigeration, it can provide a more comfortable cooling environment for shopping malls, supermarkets, and other venues, reducing energy consumption and aligning with the concept of sustainable development.

[0021] 3. Strong applicability and scalability:

[0022] The overall structural design is simple and reasonable, and the technical path is mature. Upgrades and transformations can be achieved without replacing the entire core equipment. It is especially suitable for the integrated configuration of new production equipment and can be directly integrated into the design and production process of new CO2 cascade (cooled) refrigeration skids without additional adjustments to the overall architecture, which greatly reduces the deployment cost and cycle of new systems. For old systems that need to be upgraded, although the transformation process requires a short shutdown, targeted upgrades can still be carried out based on the existing condenser and evaporator without eliminating the original main equipment. Compared with the overall replacement, it can still significantly save transformation costs and time costs. Its applicable scenarios cover both new refrigeration systems and upgrades of old systems, and its application value is extremely high. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the liquid drop pipe of the CO2 cascade, cold skid-mounted condenser-evaporator in this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] The proposed solution for improving the refrigeration efficiency of CO2 cascade and cooling skid includes structural optimization of the liquid drop pipe of the condenser evaporator in the CO2 cascade and cooling skid. The liquid drop pipe is equipped with a spiral acceleration structure inside, which can guide the falling carbon dioxide to form a rotating flow state in the liquid drop pipe, thereby accelerating the falling speed of the carbon dioxide and preventing the liquid from accumulating in the liquid drop pipe.

[0026] Furthermore, the spiral acceleration structure is a spiral guide plate evenly distributed along the length of the inner wall of the liquid discharge pipe. The spiral angle of the spiral guide plate is 30-45°, and the pitch is set to twice the diameter of the liquid discharge pipe.

[0027] Furthermore, the liquid discharge pipe is made of carbon steel, and its inner diameter can be 150mm depending on the container capacity; the spiral guide plate is a stainless steel spiral guide plate with a pitch of 150mm and a lead of 120mm.

[0028] Furthermore, the spiral guide vane is fully welded to the inner wall of the liquid dropper to ensure a leak-free seal.

[0029] Furthermore, when liquid carbon dioxide at a temperature of -12℃ and a pressure of 2.5-3.5MPa enters the drop pipe, it forms a rotating flow under the guidance of the spiral acceleration structure, with a rotational angular velocity of about 5rad / s. The drop velocity can be increased from 0.5m / s to 1.2m / s, and the drop time is shortened by 58%.

[0030] Furthermore, the condenser-evaporator using this scheme can increase the cooling capacity of the CO2 cascade refrigeration system by 8-15% and reduce energy consumption by 5-10%.

[0031] Furthermore, it includes a condenser-evaporator body and a liquid-fall optimization structure disposed within the body, wherein the liquid-fall optimization structure is the spiral acceleration structure as described in any one of claims 1-6.

[0032] Specifically:

[0033] A spiral acceleration structure is installed inside the liquid dropper of the condenser-evaporator. This spiral acceleration structure consists of spiral guide plates evenly distributed along the length of the inner wall of the liquid dropper. The processing and fitting of the spiral guide plates must strictly adhere to the principle of precision. Laser cutting technology is used to form the stainless steel plate to ensure that the spiral angle error of the guide plates is controlled within ±0.5° and the pitch error does not exceed ±2mm, so as to avoid the CO2 flow trajectory being disordered due to insufficient processing precision. The spiral angle and pitch are not set arbitrarily, but are dynamically adapted according to the diameter of the liquid dropper and the flow rate of carbon dioxide: when the diameter of the liquid dropper is 60mm, the pitch is adjusted to 90-120mm accordingly; when the system CO2 flow rate is increased to 1.2 times the original, the pitch can be reduced to 1.2-1.5 times the diameter of the liquid dropper. Through dynamic adjustment of parameters, efficient flow guidance can be achieved under different operating conditions. The preferred spiral angle is 30-45° and the pitch is set to 2 times the diameter of the liquid dropper.

[0034] Preferably, the dropper is made of carbon steel, with an inner diameter of 150mm depending on the container capacity, ensuring structural strength to withstand the high pressure of CO2. The spiral guide plate is made of the same 304 stainless steel, with a thickness of 3mm, a pitch of 150mm, and a lead of 120mm. The cross-section of the guide plate is an isosceles trapezoid with an upper base width of 10mm and a lower base width of 15mm. This structural design reduces local resistance during CO2 flow and increases the contact area between the guide plate and the liquid, improving the guiding effect. The spiral guide plate is fully welded to the inner wall of the dropper. Argon arc welding is used during welding, with the welding current controlled at 80-100A and the welding speed at 50mm / min. After welding, the weld is pickled and passivated to remove oxide scale and form a corrosion-resistant protective film, ensuring a leak-free seal and preventing impurities from corrosion at the weld from affecting CO2 flow.

[0035] As carbon dioxide falls through the downpipe, a spiral guide plate directs it into a vortex-like flow similar to that of flushing water in a toilet. The guide plate's edges are rounded with a 1.5mm radius to prevent sharp edges from creating shear resistance to the CO2 liquid and to reduce liquid buildup at the edges. This vortex flow generates a stable centrifugal force, reaching up to 1.2N under standard operating conditions of -30℃ and 2.0MPa. This ensures a uniform circumferential distribution of carbon dioxide on the inner wall of the downpipe, preventing localized film thickening caused by adhering to the walls. On the other hand, it can accelerate the falling speed of carbon dioxide, shortening the residence time of liquid in the drop pipe from the original 4s to 1.7s, improving the drop efficiency and reducing the residence time of carbon dioxide in the drop pipe, laying a solid foundation for improving the heat exchange effect of the condenser-evaporator. In addition, at the connection between the inlet end of the drop pipe and the spiral acceleration structure, a 50mm long conical transition section with a taper of 1:10 is set to guide the CO2 liquid smoothly into the spiral guide area, avoiding cavitation caused by sudden changes in flow rate at the inlet, and further ensuring the stability of system operation. Specific implementation examples:

[0037] 1. Preliminary preparations

[0038] Before modifying the CO2 cascade condenser-evaporator with a cooling skid, a comprehensive assessment of the overall condition of the equipment is required. This includes checking the model and specifications of the condenser-evaporator, and determining key parameters such as the diameter and material of the liquid drop pipe to provide accurate data support for subsequent modification work. At the same time, prepare the necessary materials and tools, such as stainless steel materials for making spiral guide plates, as well as welding tools, measuring tools, and special installation fixtures.

[0039] 2. Fabrication and installation of spiral guide vanes

[0040] The spiral guide plate is precisely machined according to design requirements: the spiral angle is strictly controlled within the range of 30-45°, and the pitch is 1.5-2 times the diameter of the discharge pipe; for a discharge pipe with an inner diameter of 80mm, the preferred pitch is 150mm, the lead is 120mm, and the thickness of the spiral guide plate is controlled at 3mm to ensure compliance with design standards.

[0041] During installation, welding is used to firmly install the spiral guide plate on the inner wall of the liquid drop pipe and make a full weld connection. During the welding process, the welding process must be strictly controlled to ensure the welding quality and avoid problems such as false welding or missing welding. This ensures that there is no leakage and that the guide plate does not loosen or fall off during long-term use.

[0042] 3. System debugging and optimization

[0043] After the installation of the spiral guide plate is completed, the entire CO2 cascade and cooling skid system is fully debugged: the refrigeration system is started, the flow state of carbon dioxide in the drop pipe is observed, and the system's pressure, flow rate, drop velocity and other parameters are monitored in real time through pressure sensors, flow sensors and other equipment.

[0044] The system should be optimized and adjusted based on the monitoring data: if the drop velocity is not as expected (e.g., it does not increase from about 0.5 m / s to about 1.2 m / s), the installation of the spiral guide plate can be further checked to see if it is correct, or the spiral angle, pitch and other parameters can be adjusted appropriately to achieve the best drop effect; during the commissioning process, the system safety should be the focus to ensure that the equipment operates without any abnormalities.

[0045] 4. Regular maintenance and inspection

[0046] After the system is put into use, a regular maintenance and inspection system should be established: regularly check whether the spiral guide plate is damaged, deformed or detached, and repair or replace it in time if any problems are found; at the same time, conduct a comprehensive inspection of other components of the condenser and evaporator (such as pipes, valves, etc.) to ensure the normal operation of the entire refrigeration system; in addition, the system should be cleaned regularly to remove internal impurities and dirt, ensure smooth carbon dioxide flow, and maintain the efficient operation of the system.

[0047] 5. Common Problems and Solutions

[0048] The installation of spiral guide plates is difficult: Due to the limited internal space of the drop pipe, special installation clamps can be used to assist in the installation process, so as to accurately position and fix the guide plates to the inner wall of the drop pipe; at the same time, professional training should be provided to the installation personnel to improve their operating skills and ensure that the installation work is carried out smoothly.

[0049] Unstable parameters in the early stage of system operation: When parameters such as pressure and flow rate are unstable in the early stage of commissioning, it may be because the gas inside the system has not been completely discharged or the effect of the spiral guide plate has not been fully exerted. The system can be vented to remove the internal gas. At the same time, the system running time can be extended appropriately to allow the spiral guide plate to fully adapt to the flow of carbon dioxide and gradually stabilize the system parameters.

[0050] Corrosion of the spiral guide plate: If the carbon dioxide contains corrosive impurities that cause the guide plate to corrode, corrosion-resistant materials can be selected to make the spiral guide plate, or an anti-corrosion coating can be applied to its surface for anti-corrosion treatment; at the same time, the purification treatment of carbon dioxide should be strengthened to reduce the content of corrosive impurities and extend the service life of the spiral guide plate.

[0051] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A scheme for improving the refrigeration efficiency of CO2 cascade and refrigerated skid-mounted units, characterized by: This includes structural optimization of the liquid drop pipe of the condenser evaporator in the CO2 cascade and cooling skid. The liquid drop pipe is equipped with a spiral acceleration structure inside, which can guide the falling carbon dioxide to form a rotating flow state in the liquid drop pipe, thereby accelerating the falling speed of the carbon dioxide and avoiding poor liquid drop, which would lead to a reduction in condensation and evaporation area, a decrease in heat exchange efficiency, an increase in pressure, and an increase in energy consumption of refrigeration equipment.

2. The CO2 cascade and refrigerated skid-mounted cooling energy efficiency improvement scheme according to claim 1, characterized in that: The spiral acceleration structure is a spiral guide plate evenly distributed along the length of the inner wall of the liquid discharge pipe. The spiral angle of the spiral guide plate is 30-45°, and the pitch is set to twice the diameter of the liquid discharge pipe.

3. The CO2 cascade and refrigeration skid-mounted cooling energy efficiency improvement scheme according to claim 2, characterized in that: The drop pipe is made of carbon steel, and its inner diameter can be 150mm depending on the container capacity; the spiral guide plate is a stainless steel spiral guide plate with a pitch of 150mm and a lead of 120mm.

4. The CO2 cascade and refrigerated skid-mounted cooling energy efficiency improvement scheme according to claim 3, characterized in that: The spiral guide vane is fully welded to the inner wall of the liquid dropper to ensure a leak-free seal.

5. The CO2 cascade and refrigeration skid-mounted cooling energy efficiency improvement scheme according to claim 1, characterized in that: When liquid carbon dioxide at a temperature of -12℃ and a pressure of 2.5-3.5MPa enters the drop pipe, it forms a rotating flow under the guidance of the spiral acceleration structure. The rotational angular velocity is about 5rad / s, and the drop velocity can be increased from 0.5m / s to 1.2m / s, and the drop time is shortened by 58%.

6. The CO2 cascade and refrigeration skid-mounted cooling energy efficiency improvement scheme according to any one of claims 1-5, characterized in that: The condenser-evaporator using this scheme can increase the cooling capacity of a CO2 cascade refrigeration system by 8-15% and reduce energy consumption by 5-10%.

7. A CO2 cascade, refrigerated skid-mounted condenser-evaporator employing any one of the solutions described in claims 1-6, characterized in that: It includes a condenser-evaporator body and a liquid-fall optimization structure disposed within the body, wherein the liquid-fall optimization structure is the spiral acceleration structure as described in any one of claims 1-6.

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