A CFD analysis of the flow structure inside a steam ejector to identify the suitable experimental operating conditions for a solar-driven refrigeration system

2014 ◽  
Vol 39 ◽  
pp. 186-195 ◽  
Author(s):  
Yosr Allouche ◽  
Chiheb Bouden ◽  
Szabolcs Varga
Keyword(s):  
Flow Structure ◽  
Operating Conditions ◽  
Cfd Analysis ◽  
Refrigeration System ◽  
Steam Ejector

scholarly journals A Steam Ejector Refrigeration System Powered by Engine Combustion Waste Heat: Part 1. Characterization of the Internal Flow Structure

2019 ◽  
Vol 9 (20) ◽  
pp. 4275 ◽  
Author(s):  
Yu Han ◽  
Lixin Guo ◽  
Xiaodong Wang ◽  
Anthony Chun Yin Yuen ◽  
Cuiling Li ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Flow Structure ◽  
Waste Heat ◽  
Mixing Layer ◽  
Internal Flow ◽  
Fluid Temperature ◽  
Refrigeration System ◽  
Shock Train ◽  
Steam Ejector ◽  
Primary Fluid

With the escalating production of automobiles, energy efficiency and environmental friendliness have always been a major concern in the automotive industry. In order to effectively lower the energy consumption of a vehicle, it is essential to develop air-conditioning systems that can make good use of combustion waste heat. Ejector refrigeration systems have become increasingly popular for this purpose due to their energy efficiency and ability to recycle waste heat. In this article, the elements affecting the performance of a typical ejector refrigeration system have been explored using both experimental and numerical approaches. For the first time, the internal flow structure was characterized by means of comprehensive numerical simulations. In essence, three major sections of the steam ejector were investigated. Two energy processes and the shock-mixing layer were defined and analyzed. The results indicated that the length of the choking zone directly affects the entertainment ratio under different primary fluid temperature. The optimum enterainment ratio was achieved with 138 °C primary fluid temperature. The shock-mixing layer was greatly affected by secondary fluid temperature. With increasing of back pressure, the normal shock gradually shifted from the diffuser towards the throat, while the shock train length remains lunchanged.

scholarly journals Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector

2021 ◽  
Vol 11 (13) ◽  
pp. 6111
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Jiuxin Ning ◽  
Pengfei Zhang ◽  
Hailong Huang
Keyword(s):  
Flow Structure ◽  
Mass Fraction ◽  
Internal Flow ◽  
Working Fluid ◽  
Physical Parameters ◽  
Entrainment Ratio ◽  
Air Mass ◽  
Steam Ejector ◽  
Primary Fluid ◽  
Mass Fractions

This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system.

Prediction of the Flow and Force Characteristics of Safety Relief Valves

2006 ◽  
Author(s):  
W. Dempster ◽  
C. K. Lee ◽  
J. Deans
Keyword(s):  
Operating Conditions ◽  
Cfd Analysis ◽  
Flow Conditions ◽  
Relief Valve ◽  
Good Correspondence ◽  
Geometry Modeling ◽  
Valve Opening ◽  
Satisfactory Prediction ◽  
Force Characteristics

The design of safety relief valves depends on knowledge of the expected force-lift and flow-lift characteristics at the desired operating conditions of the valve. During valve opening the flow conditions change from seal-leakage type flows to combinations of sub-sonic and supersonic flows It is these highly compressible flow conditions that control the force and flow lift characteristics. This paper reports the use of computational fluid dynamics techniques to investigate the valve characteristics for a conventional spring operated 1/4” safety relief valve designed for gases operating between 10 and 30 bar. The force and flow magnitudes are highly dependent on the lift and geometry of the valve and these characteristics are explained with the aid of the detailed information available from the CFD analysis. Experimental determination of the force and flow lift conditions has also been carried out and a comparison indicates good correspondence between the predictions and the experiment. However, attention requires to be paid to specific aspects of the geometry modeling including corner radii and edge chamfers to ensure satisfactory prediction.

Influence of Flow Structure on Shaped Hole Film Cooling Performance

2010 ◽  
Author(s):  
Benoit Laveau ◽  
Reza S. Abhari
Keyword(s):  
Flow Structure ◽  
Thermal Performance ◽  
Turbine Blades ◽  
Density Ratio ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Infrared Measurements ◽  
Cylindrical Holes ◽  
Shaped Hole ◽  
Adiabatic Effectiveness

Shaped holes are used on modern turbine blades for their higher performance and greater lateral coolant spreading compared to classic streamwise angled holes. This study incorporates measurements and observations from a shaped hole geometry undertaken at ETH Zurich in which a row of laterally expanded diffusely shaped holes is compared to the classic row of streamwise round holes. Infrared measurements provide high-resolution data of the adiabatic effectiveness and three dimensional velocity measurements are carried out through stereoscopic Particle Image Velocimetry. Both experiments are run for similar operating conditions allowing a comparison to be made between the flow structure and the thermal performance. The adiabatic effectiveness is seen to be higher for shaped holes compared to cylindrical holes: in particular the laterally averaged values are higher due to a larger lateral spreading of the coolant. The work presented here shows the first results on the limited influence of the density ratio on the thermal performance. The performance is also influenced by the vortical structure. The typical counter-rotating vortex pair which is completed by another pair of anti-kidney vortices is observed with their strength being clearly reduced compared to the example with cylindrical holes. The doubled structure and the reduced strength change the behavior of the jet, explaining the higher performance of a jet with shaped holes. The vertical motion leading to lift-off is reduced, so the jet remains close to the surface even at high blowing rates. The goal of this article is to present data for the thermal performance and flow field of shaped holes and then explain the relationship between the two.

An Experimental Investigation on Vapor Compression Refrigeration System Cascaded with Ejector Refrigeration System

2021 ◽  
pp. 2150028
Author(s):  
Vikas Kumar ◽  
Gulshan Sachdeva ◽  
Sandeep Tiwari ◽  
Parinam Anuradha ◽  
Vaibhav Jain
Keyword(s):  
Experimental Investigation ◽  
Thermal Equilibrium ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Compression System ◽  
Vapor Compression System ◽  
Vapor Compression Refrigeration ◽  
Cascaded System

A conventional vapor compression refrigeration system (VCRS) cascaded with a heat-assisted ejector refrigeration system (ERS) has been experimentally analyzed. Cascading allows the VCRS to operate at lower condenser temperatures and thus achieve a higher coefficient of performance. In this cascaded system, the condenser of the vapor compression system does not dissipate its heat directly to the evaporator of the ERS; instead, water circulates between the condenser of VCRS and the evaporator of ERS to exchange the heat. Seven ejectors of different geometries have been used in the ERS; however, all the ejectors could not maintain thermal equilibrium at the desired operating conditions. The compressor of the cascaded VCRS consumed 1.3 times less power than the noncascaded VCRS. Furthermore, the cascaded system provided a maximum 87.74% improvement in COP over the noncascaded system for the same operating conditions. The performance of the system remained constant until the critical condenser pressure of the ERS.

scholarly journals Parametric analysis of a combined ejector-vapor compression refrigeration cycle

2020 ◽  
Vol 15 (3) ◽  
pp. 398-408
Author(s):  
I Ouelhazi ◽  
Y Ezzaalouni ◽  
L Kairouani
Keyword(s):  
Current Model ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Refrigeration Cycle ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Entrainment Ratio ◽  
Constant Area ◽  
Vapor Compression Refrigeration Cycle ◽  
Vapor Compression Refrigeration

Abstract From the last few years, the use of efficient ejector in refrigeration systems has been paid a lot of attention. In this article a description of a refrigeration system that combines a basic vapor compression refrigeration cycle with an ejector cooling cycle is presented. A one-dimensional mathematical model is developed using the flow governing thermodynamic equations based on a constant area ejector flow model. The model includes effects of friction at the constant-area mixing chamber. The current model is based on the NIST-REFPROP database for refrigerant property calculations. The model has basically been used to determine the effect of the ejector geometry and operating conditions on the performance of the whole refrigeration system. The results show that the proposed model predicts ejector performance, entrainment ratio and the coefficient of performance of the system and their sensitivity to evaporating and generating temperature of the cascade refrigeration cycle. The simulated performance has been then compared with the available experimental data from the literature for validation.

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

2019 ◽  
Vol 9 (20) ◽  
pp. 4435 ◽  
Author(s):  
Yu Han ◽  
Xiaodong Wang ◽  
Lixin Guo ◽  
Anthony Chun Yin Yuen ◽  
Hengrui Liu ◽  
...  
Keyword(s):  
Shock Wave ◽  
Waste Heat ◽  
Wave Structure ◽  
Back Pressure ◽  
Normal Shock ◽  
Engine Fuel ◽  
Refrigeration System ◽  
Shock Wave Structure ◽  
Steam Ejector ◽  
Shock Region

In general, engine fuel combustion generates 30% waste heat, which is disposed to the environment. The use of the steam ejector refrigeration to recycle the waste heat and transfer them to useful energy source could be an environmentally friendly solution to such an issue. The steam ejector is the main component of the ejector refrigeration system, which can operate at a low-temperature range. In this article, the internal shock wave structure of the ejector is comprehensively studied through the computation fluid dynamics (CFD) approach. The shock wave structure can be subdivided into two regions: firstly the pseudo-shock region consisting of shock train and co-velocity region; secondly the oblique-shock region composed of a single normal shock and a series of oblique shocks. The effect of the shock wave structure on both pumping performance and the critical back pressure were investigated. Numerical predictions indicated that the entrainment ratio is enhanced under two conditions including (i) a longer pseudo-shock region and (ii) when the normal shock wave occurs near the outlet. Furthermore, the system is stabilized as the back pressure and its disturbance is reduced. A critical range of the primary fluid pressure is investigated such that the pumping is effectively optimized.

Assessment of CFD Approaches for Next-Generation Combustor Design

2014 ◽  
Author(s):  
Kumud Ajmani ◽  
Hukam C. Mongia ◽  
Phil Lee
Keyword(s):  
Experimental Data ◽  
Direct Injection ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Cfd Analysis ◽  
Next Generation ◽  
Lean Direct Injection ◽  
Liquid Spray ◽  
Exit Temperature ◽  
Computational Predictions

An effort was undertaken to perform CFD analysis of fluid flow in Lean-Direct Injection (LDI) combustors with axial swirl-venturi elements for next-generation LDI-2 design. The National Combustion Code (NCC) developed at NASA Glenn Research Center was used to perform reacting flow computations on an LDI-2 combustor configuration with thirteen injector elements arranged in four fuel stages. Reacting computations were performed with a consistent approach for mesh-optimization, liquid spray modeling and kinetics modeling. Computational predictions of Emissions Index (EINOx) and combustor exit temperature were compared with two sets of experimental data at medium and high-power operating conditions, for two different pressure-drop conditions in the combustor. The NCC simulations predicted the combustor exit temperature to within 1–2% of experimental data. The accuracy of the EINOx predictions from the NCC simulations was within 10% to 30% of experimental data.

scholarly journals Experimental and CFD analysis of rotary multi vane expander for small capacity generation

2018 ◽  
Vol 204 ◽  
pp. 06007
Author(s):  
Mohammad Mahardika
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Energy Demand ◽  
Energy Production ◽  
Energy Content ◽  
Operating Conditions ◽  
Volumetric Efficiency ◽  
Population Increase ◽  
Cfd Analysis

Every year, Indonesia's population increase so as energy demand. To fulfill Indonesia's energy needs, the capacity of energy production should be increased. Indonesia government has made a solution by propose 35.000 MW program to increase energy production and electrification ratio in Indonesia. An insulated area where electricity did not reach, has many problem to get electricity such as limited infrastructure, low fuel energy content, and expensive turbine. To solve these problem, multi-vane expander (MVE) can be used to extract the low energy and is cheap. MVE have many advantages such as cheap, easy to manufacture, able to operate with 2 phase, and able to low speed operation. But, the disadvantage of this type of expander is leakage. In this paper, experimental and CFD analysis of MVE are conducted. The experiment generated power of 25.7 watt with isentropic and volumetric efficiency of 11.6% and 11.7% by using operating condition of 1.5 bar, 115.6 °C, 626 rpm, and mass flow rate of 80 kg/h. The CFD model of the expander is created with the same dimension and operating conditions as experimental. The result for isentropic efficiency is inversely proportional with mass flow rate and for volumetric efficiency, power, and expander rotation are directly proportional with mass flow rate.

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