Parameter Optimization And Experimental Study On Ultra Low Temperature Box Using Auto-Cascade Refrigeration System With Mixed Refrigerant

Auto-cascade refrigeration system is a kind of single stage refrigeration in which mixed refrigerant is used. According to the difference of boiling points of components, it can obtain low temperature with a large working temperature range. This thesis conducts theoretical and experimental studies on a low temperature refrigerator using auto-cascade refrigeration system with a rectification column which can enlarge the contacting area of liquids and gases, and prevent oil from entering the low temperature part of the system, therefore, improving the efficiency and reliability of the system. The main research contents of this thesis are as follow:1. The research history and present status of auto-cascade refrigeration system at home and abroad are reviewed. The problems that will be confronted in future research are also pointed out.2. By the numerical optimization, the thesis obtained the optimum compositions of the mixture refrigerant for the rectification cycle at the temperature range of -60℃ —100℃. It provides theoretical basis for the experiment and reduces the time of experiment.3. A series of experiments were conducted with three, four and five components mixed refrigerants. The relationship between the performance of system and the proportion of each component has been obtained. The compositions of mixed refrigerant which can be used in -80℃, -90℃ and -100℃ temperature range have been recommended.4. The relationship between opening of expansion valves and the performance of...