Scheme for cascade compressor of cryogenic unit at minus 80 degrees Celsius | Key points for protection of R23 ultra-low temperature working condition system
The ultra-low temperature environment of minus 80 degrees relies on a cascade refrigeration cycle, with R23 compressor used for the low temperature stage and R404A semi closed piston unit used for the high temperature stage, with two-stage independent heat exchange.
The intermediate heat exchange temperature of the cascade cycle is controlled between -32 ℃ and -38 ℃, and the load ratio of high and low pressure stages is about 1:2.2. Imbalance in the ratio will make it difficult to lower the temperature on the low temperature side and result in insufficient cooling rate.
The R23 cryogenic compressor, which is used for material testing and special material storage, is matched with the stacked unit of Xitelide. The working pressure of this refrigerant is high, and the requirements for system weld detection are higher than those of conventional units.
The pour point of refrigeration oil must be below -90 ℃ under extreme cold conditions of minus 80 degrees Celsius. Ordinary low-temperature refrigeration oil solidifies directly at this temperature, blocking oil circulation and causing bearing locking.
The intermediate heat exchanger of the cascade unit is the core component, with a 30% increase in heat exchange area margin. If the intermediate temperature fluctuation exceeds ± 2 ℃, the temperature control stability of the entire cryogenic system will rapidly deteriorate.
The compressor valve plate wears out faster under R23 high pressure differential conditions, and the inspection cycle is shortened to 4500 hours. When disassembling, the operation and maintenance personnel must release the pressure and let it stand for 30 minutes to avoid high pressure risks.
The export order volume of ultra-low temperature units is relatively low, and the purchasing entities are mostly engineering departments of chemical and new material enterprises. Customers have strict requirements for CE certification and pressure vessel qualification document review.
Many engineering companies confuse the solutions of -60 ° C cold storage and -80 ° C deep cooling. Single and double stage piston compression cannot stably maintain -80 ° C, and a cascade cycle refrigeration system must be built.
The temperature in the cryogenic unit room cannot exceed 30 ℃. The high temperature environment will push up the condensation pressure of the high temperature stage. When the exhaust pressure of the high temperature stage exceeds 20 bar, the system will be interlocked and protected to shut down.
When refrigeration parts wholesalers supply spare parts for stacked units, R23 seals and refrigeration oil should not be mixed with R404A accessories, as the material can withstand pressure and there are significant differences in refrigerant properties.
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FAQ
What refrigeration cycle is commonly used for deep freezing at -80 ℃? We need to build an R23 cascade refrigeration cycle.
What is the approximate ratio of high and low temperature loads for the stacked system? The load ratio is approximately 1:2.2.
3. What is the minimum pour point requirement for R23 cryogenic oil? The pour point needs to be below -90 ℃ to prevent solidification.
What is the inspection cycle for valve plates in the stacking unit? It is recommended to inspect the valve disc after 4500 hours under high pressure differential conditions.
Can a two-stage compressor achieve a stable temperature of minus 80 degrees Celsius? Conventional two-stage pistons cannot maintain a stable temperature of -80 ℃.
What is the upper limit of the ambient temperature in the stacked unit room? The recommended temperature for the computer room should not exceed 30 ℃.
Can R23 seals be interchangeable with R404A models? No, the pressure bearing and refrigerant resistant materials are different.
