Binary and Multicomponent Fluids for Ejector Refrigeration System

Low energy efficiency and limitations of cooling temperatures in the ejector refrigerating systems (ERS) are major obstacles for its widespread use. Application of binary or multicomponent fluids may prove to be one of the successful ways to increase ERS performance. Presented paper describes principles how to raise COP by 30-50% on example of binary fluid ERS (BERS). Three classes of blended fluids are possible candidates to be applied in BERS: 1) azeotropic fluids, which behave like new pure substances with pre-assigned properties; 2) heteroazeotropic fluids with limited solubility in the liquid state that defines the condensation pressure equal to the sum of pure components pressures; 3) zeotropic mixtures which have unlimited solubility and evaporates at certain pressures and temperatures. Ideal candidate working fluid should exhibit high molecular weight, low latent heat of evaporation, high normal boiling temperature and high compressibility factor. Refrigerant should have a low molecular weight, high heat of vaporization, a low boiling point and the compressibility factor. BERS provides an opportunity for simultaneous achievement of three goals: increase of COP, production of cold at two temperature levels, increase the condensation point up to 45-55 C° at fixed COP, i.e. apply air-cooling of the condenser. The paper presents schematic diagrams of multicomponent fluid ERS (MERS); its cascade principle enables to achieve several temperature ranges, using low grade heat. This system can be applied for air conditioning with simultaneous cooling and freezing. Such solutions could be also used for cryoengineering and gas separation. Research outcomes from this paper could promote effective application of ejector technologies.