Investigation of dry ice blockage in an ultra-low temperature cascade refrigeration system using CO2 as a working fluid

Dry ice blockage in a CO2-solid–gas-flow-based ultra-low temperature cascade refrigeration system is investigated experimentally by a visualization test and a system study of the liquid CO2 blew into an expansion tube through a Throttle needle valve. The visualization test shows that dry ice sedimentation occurs in low flow velocity and the dry ice formation makes the heat transfer behavior of CO2 complicated. The sedimentation also occurs at low condensation temperature and low heating power input. Based on the present investigation, it is found that the present ultra-low temperature cascade refrigeration system is better to work at heating power input above 900 W and condensation temperature above −20 °C. At suitable operating condition, the present ultra-low temperature cascade refrigeration system has been shown the capability of achieving ultra-low temperature −62 °C continuously and stably.