Performance improvement of the R744 two-phase ejector with an implemented suction nozzle bypass

Abstract

In this study, the concept of an R744 ejector with a bypass duct of a suction nozzle was presented. The design of the geometry and bypass positioning in a mixing section, and the idea of regulation, as well as integration, with a suction nozzle duct was described. A preliminary numerical analysis of the proposed bypass geometry was also presented. The computational platform ejectorPL integrated with an extensively validated mathematical model of transcritical R744 two-phase flow was used. Motive nozzle inlet and suction nozzle inlet conditions reflecting gas cooler and evaporator conditions characteristic of large systems, such as supermarket refrigeration units, were examined. Three different separation pressures in liquid receivers were assumed for two bypass geometries and six bypass inlet positions. The bypass positioning as a function of a mixer length was presented. Uniquely positive results were obtained for the lowest pressure conditions. Namely, the increment of the suction mass flow rate was substantial and equal to 36.9% for the bypass angle of 19°. Hence, the bypass implementation resulted in distinct potential of an efficiency improvement-from 22.2% to 30.4%. A higher pressure lift case did not result in any improvement of the ejector work. The influence of the bypass geometry on the overall ejector efficiency was preliminarily characterised. Finally, the pressure distribution in the bypass type ejector was described.

Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors

“…It is equipped with two nozzles and will be further discussed in a later section (5.2.1). Recent work by Bodys et al [44] proposed a two-phase ejector for CO2 with a bypass on the suction nozzle duct (Figure 4). The study assessed numerically the bypass positioning and its angle of incidence under several working conditions.…”

“…This represents a limitation for comparing ejector design alternatives in practical conditions. As a result, ways were sought to represent ejector performance by a single characteristic factor, accounting for both aspects Recent work by Bodys et al [44] proposed a two-phase ejector for CO 2 with a bypass on the suction nozzle duct (Figure 4). The study assessed numerically the bypass positioning and its angle of incidence under several working conditions.…”

Effect of Closure Characteristics of Annular Jet Mixed Zone on Inspiratory Performance and Bubble System

“…In addition, the diameter of the droplet size and the existence of microbubbles greatly influence the characteristics of the jet flow [21]. Some experts have conducted extensive simulations and experiments on the outlet structure, mixing zone structure, and positioning design of the bypass suction pipe of the R77 ejector, in an effort to realize better nozzle suction performance and efficiency [22,23]. Similarly, other researchers have studied the evolution process in the gas-liquid submerged jet.…”

Performance analysis of a two-stage ejector in an ejector refrigeration system using computational fluid dynamics

“…The design process of a TSE can be classified into two stages, namely the annular primary at the second stage that was first invented by Grazzini in 1998; simulation results showed that a miniature geometrical arrangement, with low entrainment, can produce a high compression ratio of an ejector (Grazzini & Mariani, 1998;Grazzini & Rocchetti, 2002); the next stage is the annular secondary at the second stage. It affects the performance improvement of a conventional single-stage ejector (SSE) in refrigeration system (Kong & Kim, 2015Yan et al, 2018;Yu et al, 2013), increasing production and recovery from natural gas fields (Chen et al, 2016), a bypass implementation to the transcritical carbon dioxide ejector cycles could have a great impact on the COP of the system (Bodys et al, 2018), a rocket-based combined-cycle (RBCC) engine in propulsion ejector system (Dong et al, 2019).…”