Investigation on flow pattern, particle size and clogging during the expansion of CO2 into the solid-gaseous region below the triple point.

In this study, we experimentally investigated the throttling of preconditioned liquid carbon dioxide (CO2) to atmospheric pressure. As throttling devices a standard thermostatic expansion valve, a capillary tube and other non-standard geometries were used. It can be shown that the outflow patterns of the produced solid CO2 particles are strongly dependent on the type of used expansion device and the temperature as well as pressure conditions at the inlet. Additionally, we measured the distribution of CO2 solid particles size under various boundary conditions. The obtained averaged particle size in finest dispersed solid-gaseous fluid flow can be expected to be in the range of a few microns.