A control method for cooling the temperature of a carbon dioxide refrigeration system in stages

Abstract

The invention discloses a step-by-step cooling control method for a carbon dioxide refrigeration system, and relates to the technical field of carbon dioxide refrigeration. The system includes a low-temperature stage circuit and a medium-temperature stage circuit. A first solenoid valve group is provided in the low-temperature stage circuit. The first solenoid valve group includes a first solenoid valve and a second solenoid valve connected in parallel, and the diameter of the first solenoid valve is larger than The diameter of the second solenoid valve; the second solenoid valve group is provided in the middle temperature stage circuit, the second solenoid valve group includes the third solenoid valve and the fourth solenoid valve in parallel, and the diameter of the third solenoid valve is larger than that of the fourth solenoid valve The diameter of the solenoid valve. The method includes: when the system is switching the cooling mode, first open the solenoid valve with the smaller diameter in the solenoid valve group, and then open the solenoid valve with the larger diameter after the pressure difference between the two sides of the solenoid valve is reduced to the preset pressure difference , to complete the cooling mode switch. The invention can improve the overall energy efficiency of the system, reduce equipment cost and operating cost, and solve the problem of impact on pipelines and valve parts when the temperature of the system changes.

Description

technical field [0001] The invention relates to the technical field of carbon dioxide refrigeration, in particular to a method for controlling the temperature reduction of a carbon dioxide refrigeration system in stages. Background technique [0002] Because carbon dioxide refrigeration has significant energy efficiency advantages in the low temperature range of -25°C to -45°C, and has superior safety and environmental protection, it has gradually become the preferred refrigerant for freezing and refrigeration in the low temperature range. [0003] Carbon dioxide refrigeration is widely used in the quick-freezing field of cold storage or quick-freezing machines. The operating temperature of cold storage and quick-freezing machines is very low, generally around -30°C to -40°C. Taking the cold storage as an example, the carbon dioxide refrigeration system of the cold storage is usually composed of a carbon dioxide loop, a carbon dioxide unit and a cooling fan. The carbon dioxi...

AI Technical Summary

Problems solved by technology

[0005] The above-mentioned carbon dioxide refrigeration system used in the field of quick freezing has the following defects: First, because the operating temperature of the cold storage or quick freezer is very low, the efficiency of the compressor in the carbon dioxide unit is very low at this time, resulting in low overall operating efficiency of the refrigeration system; Second, the cooling range in the quick-freezing field is large, and the temperature difference is often above 30K. At the same time, it is required to cool down quickly and pass through the ice crystal area quickly. Therefore, all components of the entire carbon dioxide refrigeration system are configured with an evaporation temperature of -40°C to -45°C. This will lead to high equipment cost, and the operating cost and energy efficiency during operation are also higher than the actual demand, resulting in the unreasonable and uneconomical existing carbon dioxide refrigeration system

[0006] To sum up, in the prior art, the carbon dioxide refrigeration system used in the field of quick freezing has the disadvantages of low energy efficiency, high equipment cost and high operating cost

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