Application of Binary Fluid Ejector in Thermal Vapor Compression Distillation Systems

Abstract

Ejector Refrigeration Systems (ERS) offer the use of low grade energy sources. These systems are simple in principle; however, suffer from relatively low COP, mainly due to inefficient energy exchange between the primary and secondary fluid flows in the ejector. The use of two chemically distinct fluids in forward and reversed Rankine cycles of such systems has been shown to improve COP. These systems are known as Binary Fluid ERS (BFERS). This paper focuses on the application of BFERS for the purpose of water distillation. First, a model for an ideal ejector was developed and the maximum theoretical COP of the system was determined. Actual COP of the system was also estimated by computing the entrainment ratio in the ejector using computational fluid dynamic modeling (CFD). The effects of certain fluid properties such as molecular masse and specific heat ratio of the two fluids were investigated with respect to mass entrainment ratio. A number of guidelines for the selection of suitable primary and secondary fluids were developed based on research literature and the potential for increasing COP through the use of chemically distinct fluids, i.e. binary operating fluids.