scispace - formally typeset
Search or ask a question
Author

Khaled Ameur

Bio: Khaled Ameur is an academic researcher from Natural Resources Canada. The author has contributed to research in topics: Subcooling & Maximum power principle. The author has an hindex of 4, co-authored 5 publications receiving 82 citations.

Papers
More filters
Journal ArticleDOI
06 Mar 2019
TL;DR: A review of the main developments in ejectors over the last few years can be found in this article, where the main findings and trends in the area of heat-driven ejectors and ejector-based machines using low boiling point working fluids are summarized.
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.

70 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a modeling procedure of liquid-vapour ejectors for refrigeration, heat pumps and several other potential industrial applications based on a thermodynamic approach where conservation equations and properties of real refrigerants are used.

36 citations

Journal ArticleDOI
TL;DR: In this paper, an experimental study of a liquid-vapour ejector operated under various conditions encountered in refrigeration and other cooling processes with R134a as the working fluid is presented.

10 citations

Journal ArticleDOI
TL;DR: In this article, an experimental study of R134a refrigerant expansion in a two-phase ejector with no induced flux has been performed under a number of conditions commonly encountered in refrigerators and heat pumps.

7 citations

Journal ArticleDOI
18 Jun 2020
TL;DR: In this paper, the authors present the results of an experimental study on a two-phase ejector and assess the effects of the nozzle's divergent and the throat diameter on performance under various working conditions.
Abstract: This paper presents the results of an experimental study on a two-phase ejector The main objective is to assess the effects of the nozzle’s divergent and the throat diameter on performance under various working conditions Under the same conditions, ejector operation with a convergent nozzle, results in higher critical primary mass flow rate and lower critical pressure than with a convergent-divergent nozzle version Experiments show as well that the flow expansion is higher in the convergent-divergent nozzle The throat diameter turns out to have an important impact only on the amount of the critical mass flow rate The nozzle geometry has no impact on its optimal position in the ejector Globally, the ejector with the convergent-divergent nozzle provides a higher entrainment ratio, due to a reduced primary mass flow rate and an increased secondary flow induction Tests also show that the ejector with a lower throat diameter provides a higher entrainment ratio, due to better suction with less primary flow Unlike the convergent-divergent nozzle, the convergent nozzle permits an entrainment ratio almost insensitive to a wide range of primary inlet sub-cooling levels Primary and secondary mass flow rates increase proportionally with the subcooling level and result in a quasi-constant entrainment ratio

3 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: The objective of this work is to provide a literature survey on the research attempts made in the field of ejector refrigeration systems and the studies made on the ejector as a component.

202 citations

01 Jan 2014
TL;DR: In this paper, an analysis of the performance of the ERS using dry and isentropic fluids has been carried out, and the results show that the dry fluids have generally better performance than the wet fluids.
Abstract: Refrigeration systems, air-conditioning units and heat pumps have been recognized as indispensable machines in human life, and are used for e.g. food storage, provision of thermal comfort. These machines are dominated by the vapor compression refrigeration system and consume a large percentage of world-wide electricity output. Moreover, CO2 emissions related to the heating and cooling processes contribute significantly to the total amount of CO2 emission from energy use. The ejector refrigeration system (ERS) has been considered as a quite interesting system that can be driven by sustainable and renewable thermal energy, like solar energy, and low-grade waste heat, consequently, reducing the electricity use. The system has some other remarkable merits, such as being simple and reliable, having low initial and running cost with long lifetime, and providing the possibility of using environmentally-friendly refrigerants, which make it very attractive. The ERS has received extensive attention theoretically and experimentally.This thesis describes in-depth investigations of vapor ejectors in the ERS to discover more details. An ejector model is proposed to determine the system performance and obtain the required area ratio of the ejector by introducing three ejector efficiencies. Based on this ejector model, the characteristics of the vapor ejector and the ERS are investigated from different perspectives.The working fluid significantly influences the ejector behavior and system performance as well as the ejector design. No perfect working fluid that satisfies all the criteria of the ERS can be found. The performance of nine refrigerants has been parametrically compared in the ERS. Based on the slope of the vapor saturation curve in a T-s diagram, the working fluids can be divided into three categories: wet, dry and isentropic. A wet fluid has a negative slope of the vapor saturation curve in the T-s diagram. An isentropic expansion process from a saturated vapor state will make the state after the expansion to fall inside the liquid-vapor area of the T-s diagram which will result in droplet formation. Generally, an isentropic expansion for a dry fluid will not occur inside the liquid-vapor area, and consequently no droplets will form. An isentropic fluid has a vertical slope of the vapor saturation curve in the T-s diagram and an isentropic expansion process will hence follow the vapor saturation curve in the T-s diagram, ideally without any droplet formation. However, when the saturation condition is close to the critical point, it is possible that the isentropic expansion process of a dry fluid and an isentropic fluid occurs inside the liquid-vapor area of the T-s diagram, resulting in formation of droplets. In order to avoid droplet formation during the expansion, a minimum required superheat of the primary flow has been introduced before the nozzle inlet. Results show that the dry fluids have generally better performance than the wet fluids and the isentropic fluid. Hence the thesis mostly focuses on the features of vapor ejectors and the ERS using dry fluids.Exergy analysis has been proven to be very useful to identify the location, magnitude, and sources of exergy destruction and exergy loss, and to determine the possibilities of system performance improvement. This method is applied to the ejector and the ERS. The ejector parameters are closely interacting. The operating condition and the ejector area ratio have a great impact on the ejector overall efficiency and system COP. The ejector efficiencies are sensitive to the operating conditions, and they significantly influence the system performance. A so-called advanced exergy analysis is adopted to quantify the interactions among the ERS components and to evaluate the realistic potential of improvement. The results indicate that, at the studied operating condition, the ejector should have the highest priority to be improved, followed by the condenser, and then the generator.Thermoeconomics, which combines the thermodynamic analysis and economic principles, is applied to reveal new terms of interest of the ERS. The economic costs of the brine side fluids (fluids that supply heat to the generator and evaporator and remove heat from the condenser) play very essential roles in the thermoeconomic optimization of the ERS. Depending on different economic conditions, the system improvement from a thermodynamic point of view could be quite different from the thermoeconomic optimization. The ERS is economically sound when using free heat sources and heat sink.An ejector test bench has been built to test the entrainment ratio of different ejectors. Although the experiments do not achieve the desired results, they could still be discussed. The insignificant effect of the superheat of the secondary flow found in the theoretical study is validated. The assumption of neglecting the velocities at the ejector inlets and outlet are confirmed. The quantification of the ejector efficiencies shows that they largely depend on the operating conditions and the ejector dimensions.

115 citations

Journal ArticleDOI
06 Mar 2019
TL;DR: A review of the main developments in ejectors over the last few years can be found in this article, where the main findings and trends in the area of heat-driven ejectors and ejector-based machines using low boiling point working fluids are summarized.
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.

70 citations

Journal ArticleDOI
TL;DR: In this article, a novel ejector-expansion refrigeration cycle (EERC) is proposed, analyzed and optimized in a detailed and comprehensive thermodynamic analysis, based on the first and second laws, is conducted and the system performance is investigated for six proper refrigerants.
Abstract: A novel ejector-expansion refrigeration cycle (EERC) is proposed, analyzed and optimized in this paper. Assuming a constant-pressure mixing model for ejector simulation, a detailed and comprehensive thermodynamic analysis, based on the first and second laws, is conducted and the system performance is investigated for six proper refrigerants. The proposed system is then optimized considering the exergy efficiency as the objective function and a comparison is made with the standard EERC and conventional vapor compression refrigeration system at the optimized conditions. The results indicated that, among the six investigated refrigerants, R1234ze is the best one for which the proposed system has 5.7% and 15.5% higher exergy efficiency values than the standard EERC and conventional vapor compression refrigeration cycle, respectively, at condensing temperature of 40 ∘C and evaporation temperature of 5 ∘C. Also, it is concluded that for higher condensing and lower evaporating temperatures the value of performance improvement is higher.

63 citations

Journal ArticleDOI
TL;DR: The use of an expansion energy recovery ejector has been given great concern owing to virtues of no moving elements, cost-effectiveness, high reliability, and comparable efficiency as mentioned in this paper.

55 citations