Auto-cascade Refrigeration Research Articles

00/03641 Thermodynamic analysis of binary and ternary silicate systems by a structural model

The cubic equation of state/excess Gibbs free energy (CEoS/GE) model is a new idea to predict non-ideal systems. In this study, the Peng-Robinson (PR) EoS combined with the Wong-Sandler (WS) mixing rule and the modified UNIFAC group contribution activity model was used to calculate the vapor liquid equilibrium (VLE) data. The average absolute relative deviations (AARD) of pressure and the average absolute deviations (AAD) of the vapor phase mass fraction between the calculated results and experimental data are 0.87% and 0.005 for fluoroethane (R161) + 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) over the temperature range of (283.15–323.15 K) and at pressures varying from 0.4 MPa to 1.8 MPa, respectively. The liquid and vapor phase mass fraction deviations are within ±0.028 and ±0.025 for difluoromethane (R32) + pentafluoroethane (R125) + 1,1,1,2-tetrafluoroethane (R134a) system at temperatures of (205–350 K), respectively. The VLE behavior for the strongly-zeotropic mixture of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) + trifluoromethane (R23) + tetrafluoromethane (R14) which is suitable for the three-stage auto cascade refrigeration system was calculated at pressures of (0.2–2.2 MPa) and the corresponding three-dimensional phase diagrams were constructed. It was found that the sliding temperature increases with the decrease of pressure and the maximum predicted sliding temperature reached 73 K.

Refrigerant conversion of auto-refrigerating cascade (ARC) systems

This paper describes converting Auto-Refrigerating Cascade (ARC) ultra-low temperature systems from a multicomponent zeotropic working fluid containing CFS to a CFC-free mixture. The differences between azeotropes, mixtures and blends with minimal glides used in conventional refrigeration systems and the steep glide (wide span) zeotropes required for ARC system operation are compared. The design tools used include the Carnahan-Starling-DeSantis and the Peng-Robinson equations of state and relationships of components based upon Raoult's law. Some comparisons of prep and post-conversion operating data are presented. A brief history of ARC cycle cooling systemsis included.