Active Air Flow Control to Reduce Cavity Receiver Heat Loss

2015 ◽  
Author(s):  
J. Jack Zhang ◽  
John D. Pye ◽  
Graham O. Hughes
Keyword(s):  
Heat Loss ◽  
Thermal Power ◽  
Solar Thermal ◽  
Cfd Simulations ◽  
Air Curtain ◽  
Fluid Physics ◽  
Computational Fluid Dynamics Cfd ◽  
Optimum Velocity ◽  
Solar Receiver ◽  
Good Agreement

Convective air flows are a significant source of thermal loss from tubular cavity receivers in concentrating solar-thermal power (CSP) applications. Reduction in these losses is traditionally achieved by tailoring the cavity geometry, but the potential of this method is limited by the aperture size. The use of active airflow control, in the form of an air curtain, is an established practice to prevent infiltration of cold air through building doorways. Its application in reducing solar receiver convective heat loss is new. In this study, computational fluid dynamics (CFD) simulations are presented for the zero wind case, demonstrating that an optimised air curtain can readily reduce convective losses by more than 45%. A parametric investigation of jet direction and speed indicates that two distinct optimal air curtain flow structures exist. In the first, the jet reduces the size of the convective zone within the cavity by partially sealing the aperture. The optimum velocity range for this case occurs with a low strength jet. At higher jet speeds, the losses are generally set by the flow induced in the cavity and entrainment into the jet. However, a second optimal configuration is discovered for a narrow range of jet parameters, where the entrainment is reduced due to a shift in the stack neutral pressure level, allowing the jet to fully seal the cavity. A physical model is developed, based on the fluid physics of a jet and the ‘deflection modulus’ concept typically used to characterise air curtains in building heating and ventilation applications. The model has been applied to the solar thermal cavity case, and shows good agreement with the computational results.

Vortex-Induced Vibration of a Three-Body Launch Vehicle During Ascent

2002 ◽  
Author(s):  
Kirk W. Dotson ◽  
William A. Engblom
Keyword(s):  
Vortex Pair ◽  
Launch Vehicles ◽  
Cfd Simulations ◽  
Structural Dynamic ◽  
Structural Responses ◽  
Wind Tunnel Data ◽  
Computational Fluid Dynamics Cfd ◽  
Test Instrumentation ◽  
Three Body ◽  
Good Agreement

Launch vehicles composed of three bodies can experience the shedding of vortices due to strong crossflow acceleration towards the center body, or core. Upon formation, the vortices obstruct the freestream flow, which diverts the local angle of attack towards the opposite side of the core, and a new pair of vortices are formed. This alternate vortex-pair shedding can induce significant pitch structural responses during transonic flight. Computational fluid dynamics (CFD) simulations have been used to illustrate the phenomenon and to generate forcing functions for structural dynamic analyses. Structural responses from these analyses are in good agreement with flight responses. This success suggests that CFD can be used for preflight predictions of the phenomenon. It also indicates that CFD can be used to supplement wind tunnel data when the test instrumentation does not adequately resolve the alternate vortex-pair shedding.

Method for Quick Prediction of Windage Power Loss

2014 ◽  
Author(s):  
Qide Zhang ◽  
Kannan Sundaravadivelu ◽  
Ningyu Liu ◽  
Quan Jiang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Empirical Formula ◽  
Power Loss ◽  
Hard Disk Drives ◽  
Measurement Data ◽  
Disk Drives ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

This work introduces a method by using an empirical formula to quickly predict windage caused power loss of hard disk drives. The results obtained by the empirical formula are compared with those obtained by computational fluid dynamics (CFD) simulations and validated by the experimental measurement data. Good agreement is observed among these three sets of data.

Influence of Jordanian zeolite on the performance of a solar still: experiments and CFD simulation studies

2016 ◽  
Vol 16 (6) ◽  
pp. 1700-1709 ◽  
Author(s):  
Yazan Taamneh
Keyword(s):  
Experimental Data ◽  
Phase Change ◽  
Cfd Simulation ◽  
Volume Fraction ◽  
Solar Still ◽  
Cfd Simulations ◽  
Two Phase ◽  
Vof Model ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Computational fluid dynamics (CFD) simulations were performed for experiments carried out with two identical pyramid-shaped solar stills. One was filled with Jordanian zeolite-seawater and the second was filled with seawater only. This work is focused on CFD analysis validation with experimental data conducted using a model of phase change interaction (evaporation-condensation model) inside the solar still. A volume-of-fluid (VOF) model was used to simulate the inter phase change through evaporation-condensation between zeolite-water and water vapor inside the two solar stills. The effect of the volume fraction of the zeolite particles (0 ≤ ϕ ≤ 0.05) on the heat and distillate yield inside the solar still was investigated. Based on the CFD simulation results, the hourly quantity of freshwater showed a good agreement with the corresponding experimental data. The present study has established the utility of using the VOF two phase flow model to provide a reasonable solution to the complicated inter phase mass transfer in a solar still.

Heat Transfer of Springs in Oblique Crossflows

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Daniel B. Biggs ◽  
Christopher B. Churchill ◽  
John A. Shaw
Keyword(s):  
Heat Transfer ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Experimental Program ◽  
Convection Heat ◽  
Computational Tool ◽  
Cfd Simulations ◽  
Nonmonotonic Dependence ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

An experimental program is presented of heated tension springs in an external crossflow over a range of laminar Reynolds numbers, spring stretch ratios, and angles of attack. Extensive measurements of the forced convection heat transfer of helical wire within a wind tunnel reveal an interesting nonmonotonic dependence on angle of attack. Computational fluid dynamics (CFD) simulations, showing good agreement with the experimental data, are used to explore the behavior and gain a better understanding of the observed trends. A dimensionless correlation is developed that well captures the experimental and CFD data and can be used as an efficient computational tool in broader applications.

Numerical Analysis of Smoke Confinement by Means of Air Curtains in High-Rise Buildings

2016 ◽  
Vol 858 ◽  
pp. 287-293 ◽  
Author(s):  
Xiao Tao Zhang ◽  
Chong Tan ◽  
Yu Shi Lu
Keyword(s):  
Pressure Difference ◽  
Critical Pressure ◽  
Discharge Coefficient ◽  
Wind Effect ◽  
Cfd Simulations ◽  
Air Curtain ◽  
High Rise ◽  
Discharge Velocity ◽  
Fire Effect ◽  
Computational Fluid Dynamics Cfd

As an effective approach to confine fire-induced smoke transportation, the application of air curtains is introduced in high-rise buildings during fire. A series of computational fluid dynamics (CFD) simulations were carried out for a full scale corridor in high-rise building, in which different factors such as air curtain discharge velocity (ACDV), human evacuation and pressure difference are considered. The results show that with the ACDV increasing, the smoke flowing resistance of air curtain is greater. The factor of evacuation cause significant impact on the efficiency of air curtain. Compared with the pressure difference caused by wind effect, the fire effect would lead to higher critical pressure difference and discharge coefficient.

scholarly journals Investigating the Effect of Heterogeneous Hull Roughness on Ship Resistance Using CFD

2021 ◽  
Vol 9 (2) ◽  
pp. 202
Author(s):  
Soonseok Song ◽  
Yigit Kemal Demirel ◽  
Claire De Marco Muscat-Fenech ◽  
Tonio Sant ◽  
Diego Villa ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Reynolds Number ◽  
Shear Stress ◽  
Flow Characteristics ◽  
Cfd Simulations ◽  
Ship Resistance ◽  
Wigley Hull ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Research into the effects of hull roughness on ship resistance and propulsion is well established, however, the effect of heterogeneous hull roughness is not yet fully understood. In this study, Computational Fluid Dynamics (CFD) simulations were conducted to investigate the effect of heterogeneous hull roughness on ship resistance. The Wigley hull was modelled with various hull conditions, including homogeneous and heterogeneous hull conditions. The results were compared against existing experimental data and showed a good agreement, suggesting that the CFD approach is valid for predicting the effect of heterogeneous hull roughness on ship resistance. Furthermore, the local distributions of the wall shear stress and roughness Reynolds number on the hull surface were examined to assess the flow characteristics over the heterogeneous hull roughness.

scholarly journals Transient 3D CFD Simulation of a Stationary Vane, Oil Free, Rotary Compressor

2019 ◽  
Vol 63 (4) ◽  
pp. 308-318 ◽  
Author(s):  
Balázs Farkas ◽  
Jenő Miklós Suda
Keyword(s):  
Cfd Simulation ◽  
Piston Compressor ◽  
Working Fluid ◽  
Rotary Compressor ◽  
Heat Sources ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Rolling Piston ◽  
Good Agreement

The evaluation of a newly designed oil-free rotary compressor is presented based on transient 3D Computational Fluid Dynamics (CFD) simulations. The simulations are performed at low compression ratios and low pressure ratios and low rotational speeds. To place the results into context, the data presented in related literature was processed and summarized. The methods related to the CFD model of the newly designed compressor were developed, summarized and evaluated. The accessed CFD data are in good agreement with the results of the former rolling piston compressor related investigations. The oil free operation prevents the contamination of the working fluid from lubricant. Since the compressor is planned to work in open cycle within the sensitive environment of thermal heat sources contamination free operation has to be accomplished. However, oil-free operation also results in significantly lower performance based on the modelling results.

Exergetic Analysis of a Solar Thermal Power Plant

2013 ◽  
Vol 724-725 ◽  
pp. 156-162 ◽  
Author(s):  
Jing Qiu Wu ◽  
Dao Fei Zhu ◽  
Hua Wang ◽  
Yong Zhu
Keyword(s):  
Power Plant ◽  
Energy Saving ◽  
Heat Loss ◽  
Thermal Efficiency ◽  
Thermal Power Plant ◽  
Solar Collector ◽  
Thermal Power ◽  
Exergy Loss ◽  
Solar Thermal ◽  
Solar Thermal Power

The study of heat loss and exergy loss distribution in the power plant system plays a very important role in improving the efficiency of the system. In this paper, a dynamic simulation model of the 5MW solar thermal power system is established. Then, the simulation test with the actual data in a solar thermal power plant is carried out, and we analyze the heat and the exergy loss of the system. The results show that, the heat loss of the condenser is the largest, up to 72%. To increase the thermal efficiency of the system, the energy-saving research for the condenser should be pay attention to. The solar collector field has the most of exergy loss in the system, accounting for approximately 89%. From the exergy efficiency perspective, the solar collector system has huge potential for energy- saving. The thermal efficiency and exergy efficiency of a solar thermal power plant system increases as the load increases, full-load operation of the unit should be maintained as much as possible.

scholarly journals Analysis of Solar Receiver Performance for Chemical-Looping Integration With a Concentrating Solar Thermal System

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Zhiwen Ma ◽  
Janna Martinek
Keyword(s):  
Energy Storage ◽  
Solar Energy ◽  
Thermal Energy ◽  
Thermal Power ◽  
Solar Thermal ◽  
Chemical Looping ◽  
Receiver Design ◽  
Peak Shaving ◽  
Thermochemical Processes ◽  
Solar Receiver

This paper introduces a chemical-looping configuration integrated with a concentrating solar thermal (CST) system. The CST system uses an array of mirrors to focus sunlight, and the concentrated solar flux is applied to a solar receiver to collect and convert solar energy into thermal energy. The thermal energy then drives a thermal power cycle for electricity generation or provides an energy source to chemical processes for material or fuel production. Considerable interest in CST energy systems has been driven by power generation, with its capability to store thermal energy for continuous electricity supply or peak shaving. However, CST systems have other potential to convert solar energy into fuel or to support thermochemical processes. Thus, we introduce the concept of a chemical-looping configuration integrated with the CST system that has potential applications for thermochemical energy storage or solar thermochemical hydrogen production. The chemical-looping configuration integrated with a CST system consists of the following: a solar-receiver reactor for solar-energy collection and conversion, thermochemical energy storage, a reverse reactor for energy release, and system circulation. We describe a high-temperature reactor receiver that is a key component in the chemical-looping system. We also show the solar-receiver design and its performance analyzed by solar-tracing and thermal-modeling methods for integration within a CST system.

Effect of Turbulence and Transition Models on the CFD-Based Performance Prediction of Wind Turbines

2016 ◽  
Author(s):  
Benedikt Ernst ◽  
Joerg R. Seume ◽  
Florian Herbst
Keyword(s):  
Wind Turbines ◽  
Transition Model ◽  
Cfd Simulations ◽  
Correction Model ◽  
Rotor Aerodynamics ◽  
Curvature Correction ◽  
Computational Fluid Dynamics Cfd ◽  
Transition Models ◽  
2D And 3D ◽  
Good Agreement

Computational Fluid Dynamics (CFD) simulations are becoming increasingly important to enhancing the understanding of rotor aerodynamics and improving blade design for wind turbines. The present study addresses the effect of turbulence treatment on the CFD-based performance assessment of wind turbines by successively increasing the modeling depth. A process for 2D and 3D CFD simulations is described, which is based on the geometry of the NREL 5MW reference wind turbine. It is shown that the main differences between fully turbulent computations and transition model simulations with and without additional curvature correction model occur in the inner blade region, and increase in 3D flow regimes. Literature and the findings of the present study lead to the conclusion that simulations with the transition model in conjunction with the curvature correction model should be preferred. The resulting power output of this setup is also in good agreement with the Blade Element Momentum (BEM) calculation.

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