Ablation and Aero-thermodynamic Studies on Thermal Protection Systems of Sharp-Nosed Re-entry Vehicles

2006 ◽  
Vol 129 (7) ◽  
pp. 912-916 ◽  
Author(s):  
S. Rameche Candane ◽  
C. Balaji ◽  
S. P. Venkateshan
Keyword(s):  
Thermodynamic Analysis ◽  
Thermal Protection ◽  
Ablation Rate ◽  
Heat Fluxes ◽  
Zirconium Boride ◽  
Cfd Simulations ◽  
Flow And Heat Transfer ◽  
Commercial Code ◽  
Computational Fluid Dynamics Cfd ◽  
Viscous Compressible Flow

A quasi-one-dimensional ablation analysis for a sharp-nosed, reusable, re-entry vehicle that could possibly be used in an unmanned space program, has been carried out by using an in-house code. The code is based on the boundary immobilization technique and the solution has been obtained using the tri-diagonal matrix algorithm (TDMA). The heat fluxes on the spherical nose cap that are used to determine the ablation rate of a thermal coating applied over the surface of the vehicle are obtained by performing a steady state aero-thermodynamic analysis. The aero-thermodynamic analysis for the viscous, compressible flow under consideration is carried out by using FLUENT 6.2. The computational fluid dynamics (CFD) simulations are performed at three locations on the trajectory that the vehicle follows, on re-entry. These simulations yield the temperature and heat flux distributions along the surface of the vehicle and the latter are given as input to the ablation code. The shell material of the vehicle is assumed to be zirconium boride (ZrB2). The code is validated with benchmark cases and the flow and heat transfer characteristics are also discussed. In brief, the present work presents a methodology for coupling an ablation code with CFD simulations from a commercial code, to study the effect of change of the nose region on the ablation process.

Numerical Simulation of Fluid Flow and Heat Transfer Under Flow Fluctuation Condition in Horizontal Tube

2010 ◽  
Author(s):  
Yusheng Liu ◽  
Puzhen Gao ◽  
Dianchuan Xing
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Nuclear Power ◽  
Cfd Simulation ◽  
Horizontal Tube ◽  
Heat Fluxes ◽  
Practical Significance ◽  
Flow And Heat Transfer ◽  
Flow Fluctuation ◽  
Computational Fluid Dynamics Cfd

Fluctuating flow is widely presented in nuclear power plant operating procedure. When the fluctuating flow occurs in the loop, the fluid flow and heat transfer in the core will be affected, which makes the study of flow fluctuation have more practical significance. With computational fluid dynamics (CFD), characteristics of fluid flow and heat transfer are numerically simulated in a horizontal tube under periodical fluctuating flow. The influences of different factors on the fluid flow and heat transfer are analyzed. The simulation results of steady flow and heat transfer in horizontal tube agree with the traditional empirical correlations’ results, which validates the feasibility of doing this research using CFD simulation. The horizontal tube fluctuation flow and heat transfer with different flow fluctuation periods, fluctuation relative amplitudes and heat fluxes are numerically simulated. The results show that the smaller the flow fluctuation period is, the larger the flow fluctuation relative amplitude we get, and the more evident influence of flow fluctuation on fluid flow and heat transfer can be found. The larger the heat flux is, the larger amplitude of temperature fluctuation of fluid will be. What is more, there is a lag in phase between friction coefficient and velocity, which is not presented between heat transfer coefficient and velocity.

Air Flow and Heat Transfer in a Temperature-Controlled Open Top Enclosure

2012 ◽  
Author(s):  
Charlotte Barbier ◽  
Paul J. Hanson ◽  
Donald E. Todd ◽  
Damen Belcher ◽  
Eriks W. Jekabson ◽  
...  
Keyword(s):  
Wind Speed ◽  
Operating Cost ◽  
Cfd Simulations ◽  
Heating Systems ◽  
Elevated Atmospheric Co2 ◽  
Heating Efficiency ◽  
Oak Ridge ◽  
Flow And Heat Transfer ◽  
Ansys Cfx ◽  
Computational Fluid Dynamics Cfd

A large 12-meter-diameter open top enclosure (OTE) equipped with two unique belowground and above ground heating systems was built and intensively tested in Oak Ridge, TN, USA. The OTE is a prototype for use within an environmental change experiment, in which replica units will be built in Minnesota to assess the response of northern peatland ecosystems to increases in temperature and elevated atmospheric CO2. For several months, temperatures, energy, wind speed and relative humidity were monitored throughout the enclosure space to assess the enclosure performance and efficiency. In parallel, Computational Fluid Dynamics (CFD) simulations were performed with ANSYS-CFX to investigate the impacts of external wind, buoyancy, and OTE design on the temperatures achieved within the enclosure. The addition of a frustum that partially reduced the top opening was also investigated experimentally and numerically. The OTE is capable of achieving a temperature differential of at least +6°C for air using a combination of 8 electrical heaters. Differential temperatures were sustained for several months. The experimental data and the numerical results showed that the addition of a frustum dramatically decreases the operating cost of the OTE and leads to better control over the differential air temperature in the enclosure. Buoyancy forces and winds heavily impacted enclosure performance. It was also found that the heating efficiency of the OTE depends mainly on the wind speed, and that there exists a critical wind speed at which the heating efficiency is the highest.

Maximization of Solar Gains of an Air Collector by Simulations

2013 ◽  
Vol 284-287 ◽  
pp. 483-487 ◽  
Author(s):  
Ondrej Sikula ◽  
Vit Merka ◽  
Jiri Hirs ◽  
Josef Plášek
Keyword(s):  
Heat Transfer ◽  
Solar Energy ◽  
Solar Collector ◽  
Cfd Simulations ◽  
Ansys Fluent ◽  
Operation Conditions ◽  
Flow And Heat Transfer ◽  
Solar Air Collector ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

The paper deals with numerical simulations of the impact of design, shading, positioning and orientation of a solar air collector an efficiency of exploitation of solar energy. The solar collector is used to preheat of an air, which then is supplied into the building. There are various requirements for solar air collectors. We are focused on maximization of solar energy gain by optimizing geometry, orientation and positioning of a solar air collector. To achieve the desired objective was a combination of two methods used. The firs one is Computational Fluid Dynamics (CFD) simulations of flow and heat transfer by convection, conduction and radiation in software ANSYS Fluent. The second one is the numerical simulation of the annual operations of the collector in the software BSim. The result of this work is an optimal design and operation conditions of the air collector.

Energy Efficiency of an Axial Fan for Various Casing Configurations

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Alain Guedel ◽  
Mirela Robitu ◽  
Vivian Chaulet
Keyword(s):  
Energy Efficiency ◽  
Axial Fan ◽  
Cfd Simulations ◽  
Fan Performance ◽  
Commercial Code ◽  
Performance Curves ◽  
Commission Regulation ◽  
Target Energy ◽  
Parametric Studies ◽  
Computational Fluid Dynamics Cfd

The objective of this paper is to compare the measured and predicted performances of a tubeaxial fan for several casing configurations that are commonly proposed by fan manufacturers to their clients. This work is motivated by the European Commission Regulation 327/2011, which will impose target energy efficiency for fans driven by electric motors beginning 1 January 2013. The prediction is made with the computational fluid dynamics (CFD) commercial code STAR-CCM+. The agreement between the experimental and numerical results on fan performance curves is very satisfactory, which confirms that CFD simulations may advantageously replace testing in parametric studies since they predict the quantitative differences of aerodynamic performance observed experimentally between the different casing configurations quite well. Numerical simulations may, therefore, help manufacturers to improve the geometry of their fans in order to fulfill the requirements of the regulation.

scholarly journals CFD Technique to calculate tube skin peak temperatures in refinery furnaces

2011 ◽  
Vol 4 (4) ◽  
pp. 73-88
Author(s):  
Fabian A. Diaz ◽  
Jesús A. Castro
Keyword(s):  
Fluid Dynamics ◽  
Heat Fluxes ◽  
Petroleum Crude ◽  
Great Precision ◽  
Ansys Fluent ◽  
Commercial Code ◽  
Computational Fluid Dynamics Cfd ◽  
Precision And Accuracy ◽  
Skin Temperatures ◽  
Good Agreement

Tube skin peak temperature is one of the major parameters in furnaces operation since they determine the life of the tubes and the extent of an operation run. This parameter is very difficult to calculate appropriately in magnitude and location within the furnace and commercial furnace simulators usually fail in its calculation. Computational fluid dynamics (CFD) is the only technique that calculates peak skin temperatures with great precision and accuracy since radiation and convective heat fluxes can be calculated taking into account every singularity of the geometry of the furnace and the burners. In this work is developed a technique to calculate this parameter using CFD commercial code (Ansys Fluent) and an in-house furnace simulator (EcoFursim), results of the simulations are compared with data from different furnaces from Barrancabermeja refinery (Barrancabermeja, Colombia) and good agreement is observed. Refinery furnace is referred in this paper to fired heaters for non reacting heat up of hydrocarbons or petroleum crude.

scholarly journals Numerical Simulation of Internal Loop Reactor for Heavy Oil Slurry Bed Hydroprocessing

2014 ◽  
Vol 7 (1) ◽  
pp. 47-54
Author(s):  
Sun Lanyi ◽  
Wang Jian ◽  
Bai Fei ◽  
Bo Shoushi
Keyword(s):  
Flow Field ◽  
Heavy Oil ◽  
Flow Model ◽  
Scale Up ◽  
Cfd Simulations ◽  
Two Phase ◽  
Loop Reactor ◽  
Internal Loop ◽  
Commercial Code ◽  
Computational Fluid Dynamics Cfd

Computational Fluid Dynamics (CFD) simulations of internal loop reactor for heavy oil slurry bed hydroprocessing have been done in commercial code Fluent 6.3 using Euler two-phase flow model and standard k-ε turbulence model. The effects of the physical properties on the flow field in the reactor are investigated. The results show that the gas density has little effect but the liquid viscosity has a significant effect on flow field and gas hold-up. An analysis of the effect of reactor structures and scale-up on the flow field and gas hold-up are also provided, and optimal structure is obtained through simulations. The conclusions obtained in this paper have great significance for the slurry bed hydrocracking process.

Computer Simulation and Modelling of Passive Humidification Device Cavity for Intensive Care Patient Medical Applications

2014 ◽  
Author(s):  
Mahmoud Shafik ◽  
Anne Lechevretel
Keyword(s):  
Heat Transfer ◽  
Intensive Care Patient ◽  
Care Patient ◽  
Medical Applications ◽  
Cfd Simulations ◽  
Moisture Exchange ◽  
Flow And Heat Transfer ◽  
Computational Fluid Dynamics Cfd ◽  
Heat And Moisture ◽  
Exchange Properties

This paper presents the research that has been undertaken into the passive humidification device cavity airflow structures and patterns. This was aiming to improve the device airflow, Heat and Moisture Exchange (HME) materials performance, for a greater patient care. However the objectives were to assist in understanding the optimal cavity structural geometries, generating improved airflow patterns over target HME material structures and consequently leading to improved heat and moisture exchange properties. Airflow studies of the device have been undertaken using the Computational Fluid Dynamics (CFD) interface of the ANSYS. The CFD package enables analysis of fluid flow and heat transfer. This paper presents the results of the CFD simulations carried out on different passive humidification device cavity designs and materials arrangements. An optimised design leading to enhanced airflow structures and patterns, heat and moisture properties of the device is also presented in this paper.

scholarly journals Effect of Bolts on Flow and Heat Transfer in a Rotor–Stator Disk Cavity

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Sulfickerali Noor Mohamed ◽  
John W. Chew ◽  
Nicholas J. Hills
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Time Dependent ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Flow And Heat Transfer ◽  
Gap Ratio ◽  
Computational Fluid Dynamics Cfd ◽  
Dependent Flow ◽  
Insight Into

Previous studies have indicated some differences between steady computational fluid dynamics (CFD) predictions of flow in a rotor–stator disk cavity with rotating bolts compared to measurements. Recently, time-dependent CFD simulations have revealed the unsteadiness present in the flow and have given improved agreement with measurements. In this paper, unsteady Reynolds averaged Navier–Stokes (URANS) 360 deg model CFD calculations of a rotor–stator cavity with rotor bolts were performed in order to better understand the flow and heat transfer within a disk cavity previously studied experimentally by other workers. It is shown that the rotating bolts generate unsteadiness due to wake shedding which creates time-dependent flow patterns within the cavity. At low throughflow conditions, the unsteady flow significantly increases the average disk temperature. A systematic parametric study is presented giving insight into the influence of number of bolts, mass flow rate, cavity gap ratio, and the bolts-to-shroud gap ratio on the time-dependent flow within the cavity.

scholarly journals Risk Analysis of Road Tunnels: A Computational Fluid Dynamic Model for Assessing the Effects of Natural Ventilation

2020 ◽  
Vol 11 (1) ◽  
pp. 32
Author(s):  
Ciro Caliendo ◽  
Gianluca Genovese ◽  
Isidoro Russo
Keyword(s):  
Natural Ventilation ◽  
Fluid Dynamic ◽  
Movement Time ◽  
Radiant Heat ◽  
Heat Fluxes ◽  
Maximum Heat ◽  
Road Tunnels ◽  
Maximum Heat Release ◽  
Computational Fluid Dynamics Cfd ◽  
Time Required

We have developed an appropriate Computational Fluid Dynamics (CFD) model for assessing the exposure to risk of tunnel users during their evacuation process in the event of fire. The effects on escaping users, which can be caused by fire from different types of vehicles located in various longitudinal positions within a one-way tunnel with natural ventilation only and length less than 1 km are shown. Simulated fires, in terms of maximum Heat Release Rate (HRR) are: 8, 30, 50, and 100 MW for two cars, a bus, and two types of Heavy Goods Vehicles (HGVs), respectively. With reference to environmental conditions (i.e., temperatures, radiant heat fluxes, visibility distances, and CO and CO2 concentrations) along the evacuation path, the results prove that these are always within the limits acceptable for user safety. The exposure to toxic gases and heat also confirms that the tunnel users can safely evacuate. The evacuation time was found to be higher when fire was related to the bus, which is due to a major pre-movement time required for leaving the vehicle. The findings show that mechanical ventilation is not necessary in the case of the tunnel investigated. It is to be emphasized that our modeling might represent a reference in investigating the effects of natural ventilation in tunnels.

scholarly journals Using CFD to Evaluate Natural Ventilation through a 3D Parametric Modeling Approach

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2197
Author(s):  
Nayara Rodrigues Marques Sakiyama ◽  
Jurgen Frick ◽  
Timea Bejat ◽  
Harald Garrecht
Keyword(s):  
Natural Ventilation ◽  
Parametric Modeling ◽  
Cfd Simulations ◽  
3D Design ◽  
Post Process ◽  
Test House ◽  
Model Set ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up ◽  
Passive Strategy

Predicting building air change rates is a challenge for designers seeking to deal with natural ventilation, a more and more popular passive strategy. Among the methods available for this task, computational fluid dynamics (CFD) appears the most compelling, in ascending use. However, CFD simulations require a range of settings and skills that inhibit its wide application. With the primary goal of providing a pragmatic CFD application to promote wind-driven ventilation assessments at the design phase, this paper presents a study that investigates natural ventilation integrating 3D parametric modeling and CFD. From pre- to post-processing, the workflow addresses all simulation steps: geometry and weather definition, including incident wind directions, a model set up, control, results’ edition, and visualization. Both indoor air velocities and air change rates (ACH) were calculated within the procedure, which used a test house and air measurements as a reference. The study explores alternatives in the 3D design platform’s frame to display and compute ACH and parametrically generate surfaces where air velocities are computed. The paper also discusses the effectiveness of the reference building’s natural ventilation by analyzing the CFD outputs. The proposed approach assists the practical use of CFD by designers, providing detailed information about the numerical model, as well as enabling the means to generate the cases, visualize, and post-process the results.

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