Characteristics of Sustainable Cooling by Cryogenic Dry Ice Sublimation Flow

Sustainable cooling technologies are in increasing demand with the fast development in food processing technology, medical technology and various industrial processes. Generally it is difficult to maintain stable cryogenic cooling process and the utilization of cryogenic thermal cycles are also limited due to high cost and application feasibility. This study presents a novel cryogenic refrigeration process achieved by low temperature sublimation phase change of CO2 (dry ice) below its triple point of -56.6°C. By expanding liquid CO2 from -20°C to below the triple point value of -56.6 °C, a solid-gas two phase sublimation flow can be generated and a cryogenic environment below the triple point of CO2 obtained. In this method, latent heat is utilized as a stable source and the cooling/refrigeration temperature can be quickly achieved and easily maintained in real applications. In the current study, fundamental experiments show that by utilizing the latent heat of sublimation, a stable refrigeration temperature below -62.0°C can be obtained. By utilizing visualization apparatus in this study, the detailed two phase flow process and evolution of parameters are obtained and analyzed. For system feasibility purpose, a cascade refrigeration system which simultaneously uses rejected cycle heat and provides cooling capacity, are proposed and tested. On the basic sublimation flow, the effects of different expansion strategies and off-design cooling capacities are also tested.