The performance and flow structure in a three-dimensional rectangular ejector have been numerically investigated by using air as the working fluid. Commercial software ANSYS Fluent 15.5 has been used for numerical simulation of supersonic, compressible, turbulent flow ejectors. In order to confirm the appropriate turbulence model, the computed results are validated against indigenous experimental data. The study aims to optimize the convergent-divergent (C-D) nozzle position for each operating condition and to bring out the influence of reflected shock waves and boundary layer in the constant area mixing chamber on the performance of the ejector. Also, the variation of entrainment ratio (ER) for a range of primary, secondary and exit pressure has been investigated. Both the on-design and the off-design characteristics and local flow structure of a rectangular ejector have been considered. © 2017

Shaligram Tiwari

Department of Mechanical Engineering

A Mani

Kodamkayath Mani Arun

Atmospheric thermodynamics

Boundary layers

compressible flow

Computational fluid dynamics

Computer software

EJECTORS (PUMPS)

Flow structure

Shock waves

Turbulence models

Commercial software

ENTRAINMENT RATIO

LOCAL FLOW STRUCTURE

Numerical investigations

Operating condition

RECTANGULAR CROSS-SECTIONS

Reflected shock waves

Shock formation

AIR EJECTORS

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

International Journal of Thermal Sciences

Experimental studies have been conducted to depict the flow patterns in a small rectangular ejector by using schlieren flow visualisation technique. A transparent ejector is designed, fabricated, and operated using air as working fluid. Geometry of the ejector is in form of two-dimensional extrusion with two suction inlets: one on top and other at bottom of the convergent-divergent nozzle. Ejector performance has been analysed by measuring the mass flow rates at primary and secondary inlets. The results of flow visualisation studies have been compared with those obtained using numerical computations. Variation of entrainment ratio with change in primary stream pressure has been presented. Moreover, the shock wave patterns in constant area mixing chamber and diffuser for set of inlet and outlet conditions have been visualised and presented. © 2019 Elsevier Masson SAS

Experimental studies on a rectangular ejector with air

In this endeavor, the transients persisting in a vacuum ejector system are studied by numerically simulating the flowfield and experimentally validating the steady-state results. An inertial effect is discovered in the study due to the recirculation zone moving forward and backward during the transients, and subsequently the pressure in the secondary chamber oscillates. The flow exhibits damped oscillations in which the direction of the mass flux through the secondary chamber keeps changing and finally settles downtoastateinwhich thereisnomass flux intoorfrom the secondary chamber.It isseen that the characteristics ofthe short transientsin pressure and mass fluxinthe secondary chamber depend highlyonthe thicknessesof the primary and secondary jets and the secondary chamber volume. The inertial effect reduces with the reduction in thicknesses of both primary and secondary jets. As the volume of the secondary chamber increases, the inertial effect decreases further. It is also seen that the inertial effect decreases as the primary jet pressure increases, while other parameters remain constant. The movement of the recirculation zone during these initial transients is also studied in detail and found to be closely related to the mentioned ejector parameters. Copyright © 2014 by the American Institute of Aeronautics and Astronautics, Inc.

Journal of Propulsion and Power

Starting transients in vacuum ejector-diffuser system

A vapor ejector refrigeration system has been designed and developed to operate with ammonia. In this paper, performance of ejector refrigeration system has been experimentally studied with three different area ratio ejectors by varying operational parameters namely generator, condenser and evaporator temperatures. Effect of non-dimensional parameters like compression ratio, expansion ratio and area ratio on the system performance is studied. Entrainment ratio and coefficient of performance of the system increase with increase in ejector area ratio and expansion ratio and they increase with decrease in compression ratio. © 2006 Elsevier Ltd. All rights reserved.

Renewable Energy

Experimental investigations on ejector refrigeration system with ammonia

The experimental investigation of the performance of a vapour ejector refrigeration system is described. The system uses R134a as working fluid and has a rated cooling capacity of 0.5 kW. The influence of generator, evaporator and condenser temperatures on the system performance is studied. This kind of system can be operated with low grade thermal energy such as solar energy, waste heat, etc. The operating conditions are chosen accordingly as, generator temperature between 338 K and 363 K, condenser temperature between 299 K and 310.5 K, and evaporator temperature between 275 K and 285.5 K. Six configurations of ejectors of different geometrical dimensions are selected for the parametric study. The performance of the refrigeration system at different operating temperatures is presented. © 2006 Elsevier Ltd and IIR.

International Journal of Refrigeration

Experimental investigation on R134a vapour ejector refrigeration system

Vapour ejector refrigeration system yields better performance when the ejector operates at choking-mode. A computer code based on existing one dimensional ejector theory has been developed to carry out a study on performance of the system. When operating conditions are changed, the critical performance parameters of the system get shifted to different critical values. The code includes effects of change in specific heat of the working fluid and friction at the constant-area mixing chamber besides internal irreversibility of the ejector. The simulated performance results are compared with the available experimental data from the literature for validation. The effects of operational parameters and ejector configurations of the system on critical performance are studied. Also, comparison of performance of the system with environment friendly refrigerants, R134a, R152a, R290, R600a and R717 is made. © 2004 Elsevier SAS. All rights reserved.

Analysis of a vapour ejector refrigeration system with environment friendly refrigerants

A computer simulation of a vapour jet refrigeration system is carried out using a one-dimensional model based on mass, momentum and energy balances. The simulated performance of the system is in good agreement with the available experimental performance from the literature. A comparison of system performance is carried out for the same ejector geometry using the environmentally friendly working fluids R123, R134a, R152a and R717 (ammonia). The results suggest that, for different boiler temperatures, the entrainment ratio and the system efficiency (COP) depend mainly on the ejector geometry and the compression ratio.

Applied Thermal Engineering

Performance comparison of vapour jet refrigeration system with environment friendly working fluids

Three-dimensional numerical investigations on rectangular cross-section ejector

Journal	Data powered by TypesetInternational Journal of Thermal Sciences
Publisher	Data powered by TypesetElsevier Masson SAS
ISSN	12900729
Open Access	No