Control system for cooling of rectification type auto-cascade refrigeration system

Abstract

The invention discloses a control system for cooling of a rectification type auto-cascade refrigeration system. The rectification type auto-cascade refrigeration system comprises a compressor, an oilseparator, a condenser, a rectification kettle, a high-temperature heat regenerator, a low-temperature heat regenerator, a first main throttle valve, a second main throttle valve, an evaporator, a cold box, an auxiliary throttle valve, a gas storage tank and a control system which are connected through pipelines. The control system is composed of a temperature controller, a pressure controller andan electromagnetic valve. Input parameters of the pressure controller and the temperature controller are exhaust pressure of the system and a temperature of the cold box. Opening and closing of the electromagnetic valve are controlled through the input parameters and setting parameters of the pressure controller and the temperature controller. According to the control system for cooling of the rectification type auto-cascade refrigeration system, an exhaust pressure range and a working medium concentration change in a cooling process can be controlled at the same time to meet concentration requirements of different temperature positions, and a cooling rate is higher; and compressor power consumption and heating power consumption under maintenance conditions are reduced.

Description

technical field [0001] The invention belongs to the technical field of refrigeration, in particular to a control system for cooling a rectification type self-cascading refrigeration system. Background technique [0002] With the continuous development of refrigeration technology, the application of refrigeration equipment in the industrial field is becoming more and more extensive. In recent years, some refrigeration equipment with system cooling rate as the main index have appeared in the industry, such as high and low temperature test equipment, freeze drying equipment, etc. [0003] In practical industrial applications, equipment such as high and low temperature test chambers and freeze dryers require a higher cooling rate (20°C to -70°C cooling time ≤ 70min) and a lower evaporation temperature (-60°C to - 120°C). Due to the high-efficiency internal heat exchange of the mixed working fluid single-stage compression cycle, a single compressor can be used to reach the temp...

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Problems solved by technology

[0004] There are still some technical problems in the current mixed working medium single-stage compression cycle: (1) The exhaust pressure of the refrigeration system is high during the start-up process, which will pose a safety threat to the pipeline pressure. At the same time, as the system temperature drops, the system suction and discharge The air pressure also gradually decreases, which will lead to a decrease in cooling capacity. Therefore, pressure control is required during system start-up and cooling; (2) The optimal concentration required for different evaporation temperature levels is different, and it needs to be carried out during the cooling process; (3) ) For products such as high and low temperature test chambers and freeze dryers, when the system cools down to the target temperature, it is necessary to maintain the working condition. In order to ensure a high cooling rate for such products, when the target temperature is reached, the cooling capacity is often Larger, the system has the potential to further decrease, at this time, the heating capacity required to maintain the target temperature constant and the power consumption of the compressor are relatively large

The disadvantages of this solution are: there are many variable concentration circuits, and multiple storage tanks are used, which increases the complexity of control; at the same time, there is no suitable control system and clear switching conditions, which is not conducive to the use of standardized and commercial products.

The disadvantage of this solution is that the electric or manual opening adjustment valve is used to change, and the manual opening adjustment is not suitable for automatic control and standardized operation. The automatic control of the electric opening adjustment valve is more convenient than the on-off solenoid valve control. Complicated and at the same time more expensive

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