Abstract
A one-dimensional mathematical model of the R744 two-phase ejector for expansion work recovery is presented in this paper. Governing equations were formulated for all passages of the ejector based on the differential equations for mass, momentum, and energy balance as well as a differential representation for the equation of state. For two-flow sections (mixer and diffuser) closing equations for mass, momentum and energy transfer between the primary and secondary flow were introduced. This model utilises the Delayed Equilibrium Model along with the Homogeneous Nucleation Theory for the purpose of the metastable state analysis for a transcritical flow with delayed flashing over the motive nozzle. The thermal properties model was based on a real fluid approach, where the REFPROP 8.0 database was used. Based on the results of experimental tests performed at SINTEF Energi Laboratory, the model was validated for a typical range of operating conditions. The range of available simulation output allowed for the creation of 1D profiles of local values for the flow variables and the computation of the overall indicators, such as pressure lift and expansion work recovery efficiency. Copyright © 2012 Elsevier B.V. All rights reserved.