Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 1: Single-Phase Ejectors

Abstract

Ejectors used in refrigeration systems as entrainment and compression components or expanders, alone or in combination with other equipment devices, have gained renewed interest from the scientific community as a means of low temperature heat recovery and more efficient energy use. This paper summarizes the main findings and trends, in the area of heat-driven ejectors and ejector-based machines, using low boiling point working fluids, which were reported in the literature for a number of promising applications. An overall view of such systems is provided by discussing the ejector physics principles, as well as a review of the main developments in ejectors over the last few years. Recent achievements on thermally activated ejectors for single-phase compressible fluids are the main focus in this part of the review. Aspects related to their design, operation, theoretical and experimental approaches employed, analysis of the complex interacting phenomena taking place within the device, and performance are highlighted. Conventional and improved ejector refrigeration cycles are discussed. Some cycles of interest employing ejectors alone or boosted combinations are presented and their potential applications are indicated.

CFD Analysis of an Ejector Operating in an Experimental Cooling System

“…Ejectors used in refrigeration systems as components or drag and compression expanders, alone or in combination with other equipment devices, have gained renewed interest from the scientific community as a means of recovering heat at low temperature and a more efficient use of energy, where the numerical approach is increasingly available at affordable costs and has become necessary for flow evaluation, design refinement and precise predictions of ejector design conditions [2]. In [3] it is mentioned that few approaches have tried to optimize the geometric parameters that define the ejectors, and even less to optimize the back pressure and the drag ratio, which are key parameters in the ejector efficiency and therefore results in the efficiency of the whole system.…”

Refrigerant selection for ejector refrigeration systems: a multiscale evaluation

“…[1]). Moreover, COP depends on the ejector-component performance, which is determined by the local-scale flow phenomena; in turn, the flow phenomena are imposed by the ejector design, refrigerant properties and inlet/outlet boundary conditions [2,3]. For the sake of clarity, a discussion regarding ejector-component performance is proposed, based on the ejector operating curve ( Figure 1b -note that Figure 1b is valid under the assumption of T3 in saturation conditions), which displays the relationship between the entrainment ratio (ω, Eq.…”

Prediction of Performance for an Ejector Refrigeration Cycle Working with R245fa Using Artificial Neural Network

“…It is thermally activated by a high-temperature fluid stream, transferring energy to a low-pressure stream, propelling it in the process to intermediate conditions through the partial transfer of momentum. The resulting flow discharges at a stagnation pressure halfway between the primary and the secondary pressures [1]. A general schematics of a typical ejector geometry is shown in Figure 1.…”

“…These, in general, assess the effects of operating conditions, different geometries, and working fluids on the performance of the device. Depending on the role of the device within the cycle, different configurations with varying performance and complexity have been proposed in the literature [1]. There has been a great interest in recent years concerning the use of artificial neural networks in other fields [3] [4].…”