CFD Simulation of a Supersonic Steam Ejector for Refrigeration Application

Abstract

Supersonic steam ejectors are widely used in many industrial applications, for example for refrigeration and desalination. The experimental evaluation of the flow field inside the ejector is relatively difficult and costly due to the occurrence of shock after the velocity of the steam reaches over the sonic level in the ejector. In this paper, numerical simulations are conducted to investigate the detailed flow field inside a supersonic steam (water vapor being the working fluid) ejector. The commercial computational fluid dynamics (CFD) flow solver ANSYS-Fluent and the mesh generation software ANSYS-ICEM are used to predict the steam performance during the mixing inside the ejector by employing two turbulence models, the k-ω SST and the k-ε realizable models. The computed results are validated against the experimental data. The effects of operating conditions on the efficiency of the ejector such as the primary fluid pressure and condenser pressure are studied to obtain a better understanding of the mixing process and entrainment. Velocity contours, pressure plots and shock region analyses provide a good understanding for optimization of the ejector performance, in particular how to increase the entrainment ratio.

Design and Performance Analysis of Double-Flux Supersonic Air Ejector

“…In the first instance, a geometry / a supersonic ejector model is taken from the literature, [39] which is shown in Figure 18 indicating the dimensions and geometry of the ejector used for this study [16].…”

“…In addition to dimensional and geometrical properties ( Figure 18), operating conditions as well as the non-dimensional design parameters of the present system is also given in Table 1 and Table 2. For the test case used in this study, the system operates with a primary flow of pressure 743000 Pa, a secondary flow of pressure 86300 Pascal and a discharge pressure of 137000 Pa, same as used in the literature [39]. Figure 18.…”

“…This section presents the method and the computer programs that are used to validate the computational results for the present study. As a validation of the methods and tools, two different geometries are taken from the literature [12] and [39]. Then the 1-D and the CFD results are compared with the corresponding results given in [12], [15], [16], [39] and [40].…”

CFD simulation of ejector: is it worth to use real gas models?

“…Figure 3 showed the contours of ejector's Mach number at on-design regime. Many researchers claimed that the length of mixing chamber does not significantly affect to performance of ejector [2] [13]. However, it was observed that the length of mixing chamber help stabilize ejector's entrainment ratio, means the performance remains stable while working pressures change in a limited values.…”

A Steam Ejector Refrigeration System Powered by Engine Combustion Waste Heat: Part 2. Understanding the Nature of the Shock Wave Structure

“…Sriveerakul et al [35,36], Yuan et al [26] and Aly et al [37] comprehensively analysed and discussed the variation of the pumping performance under different geometric and operating parameters. A better understanding of the mixing process of the working steam and the pumped steam under different back pressure was studies by Su and Agarwal [38]. According to the work of Dong et al [27], a higher COP can be obtained by decreasing the temperature of primary steam and raising the temperature of secondary steam.…”