Visualization and Measurement of Swirling Flow of Dry Ice Particles in Cyclone Separator-Sublimator

The dry ice sublimation process of carbon dioxide (CO₂
) is a unique, environmentally
friendly technology that can achieve a temperature of −56 ◦C or lower, which is a triple point of
CO₂
in CO₂ refrigeration systems. In this study, a cyclone separator-evaporator was proposed
to separate dry ice particles in an evaporator. As an initial step before introducing the cyclone
separator-evaporator into an actual refrigeration system, a prototype cyclone separator-evaporator
was constructed to visualize dry ice particles in a separation chamber. A high-speed camera was used
to visualize the non-uniform flow of dry ice particles that repeatedly coalescence and collision in a
swirl section. Consequently, the dry ice particle size and the circumferential and axial velocities of
dry ice were measured. The results show that the equivalent diameter of the most abundant dry ice
particles in the cyclone separation chamber is 2.0 mm. As the inner diameter of the separation section
decreases, dry ice particles coalesce and grow from an equivalent diameter of 4 mm to a maximum of
40 mm. In addition, the comparison of the experimental and simulation results shows that the drag
force due to CO₂ gas flow is dominant in the circumferential velocity of dry ice particles.
Keywords: dry ice; carbon dioxide; cyclone separator-sublimator; swirling flow; visualization