scholarly journals Numerical Study On The Internal Irreversible Flow Loss of Single Screw Expanders

2021 ◽  
Author(s):  
Lili Shen ◽  
Yuting Wu ◽  
Wei Wang ◽  
Biao Lei ◽  
Wei Duan ◽  
...  
Keyword(s):  
Energy Loss ◽  
Loss Factor ◽  
Waste Heat ◽  
Numerical Study ◽  
Great Influence ◽  
Volume Ratio ◽  
Turbulent Fluctuation ◽  
Turbulent Dissipation ◽  
Single Screw ◽  
Flow Loss

Abstract As a type of positive displacement expander, single screw expander (SSEs) can be widely applied in the energy storage systems and waste heat recovery field. The irreversible losses (such as leakage, flow, heat transfer, intake and exhaust pressure loss…) have great influence on the expander performance. However, irreversible flow loss in the expander is nearly impossible to investigate experimentally and theoretically. In this paper, a three-dimensional computational fluid dynamics (CFD) study of SSE using mesh deformation approach was presented. The CFD model was validated by the experimental results. Field distribution of pressure, temperature and velocity of SSE were carried out. An energy loss factor based on entropy production principle was used to measure the irreversible flow (including leakage) loss. The energy loss caused by direct dissipation and turbulent fluctuation dissipation was compared. The energy loss of different region was investigated. Results show that energy loss of the turbulent dissipation is far more than that of direct dissipation. The energy loss factor decreases from 0.547 to 0.221 when the rotation speed changes from 2000rpm to 4000rpm. The shaft efficiency increases from 39.8% to 52.1% with the internal volume ratio from 3 to 5.

scholarly journals A Numerical Study of Separation Performance of Vibrating Flip-Flow Screens for Cohesive Particles

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 631
Author(s):  
Chi Yu ◽  
Runhui Geng ◽  
Xinwen Wang
Keyword(s):  
Surface Energy ◽  
Numerical Study ◽  
Energy Levels ◽  
Great Influence ◽  
Rigid Motion ◽  
Separation Performance ◽  
Gravitational Acceleration ◽  
Screening Process ◽  
Vibration Intensity ◽  
Screen Surface

Vibrating flip-flow screens (VFFS) are widely used to separate high-viscosity and fine materials. The most remarkable characteristic is that the vibration intensity of the screen frame is only 2–3 g (g represents the gravitational acceleration), while the vibration intensity of the screen surface can reach 30–50 g. This effectively solves the problem of the blocking screen aperture in the screening process of moist particles. In this paper, the approximate state of motion of the sieve mat is realized by setting the discrete rigid motion at multiple points on the elastic sieve mat of the VFFS. The effects of surface energy levels between particles separated via screening performance were compared and analyzed. The results show that the flow characteristics of particles have a great influence on the separation performance. For 8 mm particle screening, the particle’s velocity dominates its movement and screening behavior in the range of 0–8 J/m2 surface energy. In the feeding end region (Section 1 and Section 2), with the increase in the surface energy, the particle’s velocity decreases, and the contact time between the particles and the screen surface increases, and so the passage increases. When the surface energy level continues to increase, the particles agglomerate together due to the effect of the cohesive force, and the effect of the particle’s agglomeration is greater than the particle velocity. Due to the agglomeration of particles, the difficulty of particles passing through the screen increases, and the yields of various size fractions in the feeding end decrease to some extent. In the transporting process, the agglomerated particles need to travel a certain distance before depolymerization, and the stronger the adhesive force between particles, the larger the depolymerization distance. Therefore, for the case of higher surface energy, the screening percentage near the discharging end (Section 3 and Section 4) is greater. The above research is helpful to better understand and optimize the screening process of VFFS.

Numerical Study on Flow Characteristics in High Multi-Stage Pressure Reducing Valve

2017 ◽  
Author(s):  
Fu-qiang Chen ◽  
Zhi-xin Gao ◽  
Jin-yuan Qian ◽  
Zhi-jiang Jin
Keyword(s):  
Energy Consumption ◽  
Numerical Study ◽  
Research Work ◽  
Flow Characteristics ◽  
Temperature Fields ◽  
Turbulent Dissipation ◽  
Technological Support ◽  
Multi Stage ◽  
Valve Opening ◽  
Pressure Reducing Valve

In this paper, a new high multi-stage pressure reducing valve (HMSPRV) is proposed. The main advantages include reducing noise and vibration, reducing energy consumption and dealing with complex conditions. As a new high pressure reducing valve, its flow characteristics need to be investigated. For that the valve opening has a great effect on steam flow, pressure reduction and energy consumption, thus different valve openings are taken as the research points to investigate the flow characteristics. The analysis is conducted from four aspects: pressure, velocity, temperature fields and energy consumption. The results show that valve opening has a great effect on flow characteristics. No matter for pressure, velocity or temperature field, the changing gradient mainly reflects at those throttling components for all valve openings. For energy consumption, in the study of turbulent dissipation rate, it can be found that the larger of valve opening, the larger of energy consumption. It can be concluded that the new high multi-stage pressure reducing valve works well under complex conditions. This study can provide technological support for achieving pressure regulation, and benefit the further research work on energy saving and multi-stage design of pressure reducing devices.

scholarly journals Performance Characteristics of Solid-Desiccant Evaporative Cooling Systems

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2574 ◽  
Author(s):  
Ramadas Narayanan ◽  
Edward Halawa ◽  
Sanjeev Jain
Keyword(s):  
Air Conditioning ◽  
Natural Ventilation ◽  
Waste Heat ◽  
Numerical Study ◽  
Evaporative Cooling ◽  
Peak Load ◽  
Dew Point ◽  
Low Grade ◽  
Subtropical Climate ◽  
Cooling Systems

Air conditioning accounts for up to 50% of energy use in buildings. Increased air-conditioning-system installations not only increase total energy consumption but also raise peak load demand. Desiccant evaporative cooling systems use low-grade thermal energy, such as solar energy and waste heat, instead of electricity to provide thermal comfort. This system can potentially lead to significant energy saving, reduction in carbon emissions, and it has a low dew-point operation and large capacity range. Their light weight, simplicity of design, and close-to-atmospheric operation make them easy to maintain. This paper evaluates the applicability of this technology to the climatic conditions of Brisbane, Queensland, Australia, specifically for the residential sector. Given the subtropical climate of Brisbane, where humidity levels are not excessively high during cooling periods, the numerical study shows that such a system can be a potential alternative to conventional compression-based air-conditioning systems. Nevertheless, the installation of such a system in Brisbane’s climate zone requires careful design, proper selection of components, and a cheap heat source for regeneration. The paper also discusses the economy-cycle options for this system in such a climate and compares its effectiveness to natural ventilation.

scholarly journals Experimental and Numerical Study on the Effect of Creep Behavior on Epoxy Composites Reinforced with Yttrium Oxide Powder

2020 ◽  
Vol 25 (4) ◽  
pp. 203-213
Author(s):  
B.H. Abed ◽  
K.J. Jadee ◽  
A.A. Battawi
Keyword(s):  
Mechanical Properties ◽  
Composite Material ◽  
Elasticity Modulus ◽  
Epoxy Composite ◽  
Numerical Study ◽  
Creep Behaviour ◽  
Weight Ratio ◽  
Volume Ratio ◽  
Epoxy Composites ◽  
Creep Characteristics

AbstractThe creep test is one of the important approaches to determining some mechanical properties of composite materials. This study was carried out to investigate the creep behaviour of an epoxy composite material that was reinforced with Y2O3 powder at weight ratios of 2%, 7%, 12%, 17% and 22%. Each volume ratio was subjected to five loads over the range of 1N to5N at a constant temperature of 16 ± 2°C. In this work, creep behaviour, stress and elasticity modulus were studied through experimental and numerical analyses. Results showed that increasing the weight ratio of Y2O3 powder enhanced creep characteristics.

scholarly journals A Study of ZVS, ZCS and ZVZCS Techniques in Reducing the Energy Loss and Improving the Soft Switching Range

2020 ◽  
Author(s):  
Ratil H Ashique ◽  
Zainal Salam
Keyword(s):  
Energy Loss ◽  
Loss Factor ◽  
Recent Literature ◽  
Soft Switching ◽  
Low Loss ◽  
Turn On ◽  
Switching Losses ◽  
Extended Range ◽  
Simulation Results ◽  
Switch Voltage

This paper presents a comparative analysis of the ZVZCS soft switching technique with the ZVS and the ZCS counterpart. The generalization of the voltage-current crossover or the energy loss factor obtained from simulation of the prototype converter shows that the ZVZCS significantly reduces the loss and helps to improve the efficiency of the converter as compared to the ZVS or the ZCS. On the other hand, it is also found that the soft switching range of operation of the ZVS and the ZCS are largely affected by the maximum switch voltage and switch current respectively. In contrary, these factors have a negligible effect on the ZVZCS operation which results in an extended range of soft switching operation. Additionally, a detailed LTPICE simulation is performed for selected ZVS, ZCS and ZVSCS topologies from the recent literature and the switching losses in the main switches of the converters are measured. It is observed that the energy losses in the ZVZCS mode are reduced on average by approximately 26 % at turn on and 20 % at the turn off as compared to the ZVS and the ZCS. Besides, the low standard deviation in this mode confirms a stable low loss profile which renders extended soft switching range. An experimental test is also conducted by building the prototype converter to verify the simulation results. It is found that the switching losses are minimum while the converter is operated in the ZVZCS mode. Besides, the efficiency drop remains consistently low as compared to the ZVS and the ZCS in the whole operating range. Resultantly, the simulation and the experimental results are both found to be consistent.

scholarly journals Influence of Clandestine Connections on Energy Loss Evaluation in Electrical Distribution Networks

2020 ◽  
Author(s):  
Clainer B. Donadel ◽  
Gilberto C. D. Sousa ◽  
Flávio M. Varejão
Keyword(s):  
Artificial Intelligence ◽  
Developing Countries ◽  
Energy Loss ◽  
Loss Factor ◽  
Distribution Systems ◽  
Distribution Network ◽  
Distribution Networks ◽  
Operation Costs ◽  
Electrical Distribution ◽  
Electrical Distribution Networks

In the literature, there are several methodologies to estimate technical losses in electrical distribution networks. The range of techniques is broad, ranging from basic techniques (based on loss factor, for example) to sophisticated ones (based on artificial intelligence). These methodologies are important, because the costs of technical losses represent a huge part of the total operation costs of distribution network operators (DNOs). However, the presence of clandestine connections, common in developing countries, was not considered in the methodologies encountered in the literature. Clandestine connections occur when a consumer has made his/her connection without DNO permission. In these cases, the amount of energy consumed by a clandestine "consumer" is a nontechnical loss (and, therefore, should be correctly computed as nonbilled energy). Therefore, a new methodology is proposed to consider the presence of clandestine connections in energy loss estimation in distribution systems.

Numerical Study of a Micro Gas Turbine Integrated With a Supercritical CO2 Brayton Cycle Turbine

2018 ◽  
Author(s):  
Fabrizio Reale ◽  
Vincenzo Iannotta ◽  
Raffaele Tuccillo
Keyword(s):  
Gas Turbines ◽  
Waste Heat ◽  
Numerical Study ◽  
Organic Rankine Cycle ◽  
Energy Systems ◽  
Rankine Cycle ◽  
Energy System ◽  
Small Scale ◽  
Brayton Cycle ◽  
Integrated Energy System

The primary need of reducing pollutant and greenhouse gas emissions has led to new energy scenarios. The interest of research community is mainly focused on the development of energy systems based on renewable resources and energy storage systems and smart energy grids. In the latter case small scale energy systems can become of interest as nodes of distributed energy systems. In this context micro gas turbines (MGT) can play a key role thanks to their flexibility and a strategy to increase their overall efficiency is to integrate gas turbines with a bottoming cycle. In this paper the authors analyze the possibility to integrate a MGT with a super critical CO2 Brayton cycle turbine (sCO2 GT) as a bottoming cycle (BC). A 0D thermodynamic analysis is used to highlight opportunities and critical aspects also by a comparison with another integrated energy system in which the waste heat recovery (WHR) is obtained by the adoption of an organic Rankine cycle (ORC). While ORC is widely used in case of middle and low temperature of the heat source, s-CO2 BC is a new method in this field of application. One of the aim of the analysis is to verify if this choice can be comparable with ORC for this operative range, with a medium-low value of exhaust gases and very small power values. The studied MGT is a Turbec T100P.

Experimental and numerical study of energy loss through double-glazed windows

2019 ◽  
Vol 56 (3) ◽  
pp. 727-747
Author(s):  
Mohammadhassan Bitaab ◽  
Reza Hosseini Abardeh ◽  
Saeid Movahhed
Keyword(s):  
Energy Loss ◽  
Numerical Study

Numerical Study of Coal Composition Effects on the Performance of Gasification Through Computational Fluid Dynamic

2019 ◽  
Vol 17 (7) ◽  
Author(s):  
Imran Nazir Unar ◽  
Suhail Ahmed Soomro ◽  
Ghulamullah Maitlo ◽  
Shaheen Aziz ◽  
Rasool Bux Mahar ◽  
...  
Keyword(s):  
Computational Fluid Dynamic ◽  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Great Influence ◽  
Electricity Production ◽  
Combustion Model ◽  
Heating Value ◽  
Coal Composition ◽  
Coal Reserves

Abstract Pakistan is very rich in coal reserves specifically after exploration of Thar coal reserves. At the same time country is facing energy crises due to shortage or unavailability of sustainable fuel supply at a cheaper rate. One potential solution is coal gasification which gives clean synthetic gas usually called syngas for use as an alternative fuel source for electricity production at a cheaper rate as well as a source of recovering different chemicals used as basic raw materials in other industries. Numerical simulations have been performed in this work for the gasification process of indigenous coal on a 2D computational fluid dynamic (CFD) model of downdraft entrained-flow gasifier using commercial CFD software FLUENT®6.3.26. Navier-stokes equations along with transport equations for species have been solved using eddy-dissipation combustion model. The compositions of indigenous coals (Thar, Lakhra, and Sonda) were used in simulations as gasification feedstock. Rich oxidant conditions 95 % O2 and 5 % N2 were set for gasification. The gasification performance was studied by comparing efficiencies of gasification and quality of syngas produced for three types of coal feedings. The temperature and pressure profiles inside the gasifier were also studied. From simulation results, the great influence of coal composition was observed in the performance of gasification. Lakhra coal produced syngas with a maximum heating value of 20.55 MJ/kg whereas sonda coal produced syngas with a minimum heating value of 17.96 MJ/kg.

Parametric Study of Beam to Column Extended Endplate Connection in Fire

2012 ◽  
Vol 594-597 ◽  
pp. 779-784
Author(s):  
Meng Wang
Keyword(s):  
Cross Section ◽  
Failure Modes ◽  
Numerical Study ◽  
Numerical Models ◽  
Great Influence ◽  
Load Ratio ◽  
Simulation Methodology ◽  
Study Results ◽  
Endplate Connection ◽  
In Fire

In this paper, numerical study results using ABAQUS are presents to demonstrate the failure modes and the behaviour of endplate connection with different parameters at elevated temperature. Numerical models and simulation methodology are first validated by the comparison to experimental data. Then the behaviour of beam and the failure modes endplate connection with different parameters- including beam span, beam load ratio, column cross section, endplate type- are studied. It can be concluded that all these parameters has a effects on the behaviour of the connection, while some parameters has a great influence on the survivability of the joint.

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