Experimental observation of sedimentation phenomena of CO₂ dry ice in model channel

In development of a refrigeration system with ultra-low temperature below the triple point of CO₂, an investigation of the dry ice sedimentation in CO₂ solid-gas two-phase flow is essential. In order to understand the sedimentation mechanism, dynamic behavior of dry ice particles are studied experimentally by horizontally placed observation system with varying the shape of expansion channel. As the results, the visualization test reveals that the sedimentation phenomena are greatly eased in the observation system when the shape of expansion channel is changed from a sudden expansion to a tapered channel. On the basis of the visualization test, it is found that the practical ultra-low temperature cascade refrigeration system works continuously and stably without the dry ice blockage when the shape of evaporator is changed from a sudden expansion to a tapered channel