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选择R404A、R23作为复叠式制冷系统的高、低温级循环制冷剂,构建了冲击试验箱的低温箱制冷系统,高温箱采用电加热控制方法,高、低温箱均采用PID控制。实验结果表明,高温箱经过约12.8min达到预热温度210℃,偏差±0.3℃。低温箱经过约57min可达到预冷温度-70℃,偏差±0.5℃。冲击试验在-55℃~+200℃时,转换时间为5s,温度恢复时间不大于5min,温度偏差不大于±0.5℃。测试过程中,两级压缩机进、排气压力值稳定,说明系统达到设计要求。
R404A and R23 were selected as the high and low temperature circulating refrigerants in the cascade refrigeration system, and the cryogenic chamber refrigeration system of the impact chamber was constructed. The electrical heating control method was adopted for the high temperature chamber. PID control was adopted for the high and low temperature chambers. The experimental results show that the temperature of the oven reaches about 210 ℃ and the deviation of ± 0.3 ℃ after about 12.8min. Cryogenic box after about 57min can reach pre-cooling temperature -70 ℃, deviation ± 0.5 ℃. Impact test at -55 ℃ ~ +200 ℃, the conversion time of 5s, the temperature recovery time is not greater than 5min, the temperature deviation is not greater than ± 0.5 ℃. During the test, two-stage compressor inlet and outlet pressure values are stable, indicating that the system meets the design requirements.