'Siirt Universitesi Sosyal Bilimler Enstitusu Dergisi'
Abstract
A refrigeration temperature below −50.0°C is highly required for the storage of vaccines and fishery catches using natural refrigerants such as CO2 (carbon dioxide). In this study, we have proposed and developed a unique refrigeration system using solid-state CO2 (dry ice) to achieve ultra-low temperatures below −70°C. The initial challenge was the evaporator blockage due to dry ice aggregation, causing system instability. A stainless-steel spiral coil (swirl promoter) was introduced at the evaporator/sublimator inlet to enhance heat transfer and alleviate the blockage problem. The system, which operates effectively at the triple point of approximately −60°C and 0.5 MPa, is further advanced to its limits by using a cyclone separator/evaporator in its latest stage. By integrating a cold recovery heat exchanger in a cylindrical vessel, the system can maintain ultra-low temperatures of approximately −70°C inside the recovery section, achieving a coefficient of performance of this system (COPsystem) of 1.2. Keywords: Natural Refrigerant, CarbonDdioxide, CO2 Refrigeration System, Dry Ice, Ultra-low TemperatureDevelopment of CO2 dry ice heat pump systemacceptedVersio
