Performance optimization of thin fire blankets by varying their radiative properties

2021 ◽  
pp. 073490412110503
Author(s):  
Kevin M Brent ◽  
James S T’ien
Keyword(s):  
Heat Flux ◽  
Performance Optimization ◽  
Radiative Properties ◽  
Total Heat Flux ◽  
Multi Objective Optimization ◽  
Optimization Scheme ◽  
Pure Radiation ◽  
Optimization Study ◽  
Blocking Mechanisms ◽  
Optimization Schemes

In using thin fire blankets to protect structures in wildfires, heat rejections by radiation (reflection and emission) are essential for good performance. By varying the radiative properties of the front and back surfaces of the blankets, this article offers an optimization study of several scenarios of incident heat flux including pure convection, pure radiation, and combinations of the two. Two types of blanket heat-blocking efficiencies are studied in the optimization scheme. An overall efficiency is defined as the amount of incident heat blocked to the total amount of incident heat in specified wildfire scenarios. An instantaneous heat-blocking efficiency is defined as the instantaneous heat flux blocked to the instantaneous incident total heat flux which provides good understanding of the physics of heat-blocking mechanisms of fire blanket under quasi-steady conditions. In addition to maximizing these heat-blocking efficiencies, there are other optimization objectives, including the minimization of the blanket backside temperature. A genetic algorithm is used for the multi-objective optimization schemes. For the transient heat incidence, the optimization for the entire time sequence is performed with the possibility of a change of blanket radiative properties during the fire sequence, accounting for changes to the fire-facing surface caused by the incident heat.

Use Multi-Objective Optimization for Designing Cloaks With Acoustic and Elastic Materials

2012 ◽  
Author(s):  
Chunyan Bao ◽  
Liang-Wu Cai
Keyword(s):  
Optimization Approach ◽  
Multi Objective Optimization ◽  
Frequency Range ◽  
Elastic Materials ◽  
Optimization Scheme ◽  
Multi Objective ◽  
Wide Range ◽  
Optimization Schemes ◽  
Elastic Layers

The various optimization schemes have been recently shown to be a capable tool for designing acoustic cloaks based on Cummer-Schurig prescription without requiring material singularity. However, when using an optimization scheme to optimize a cloak at one specified frequency, sometimes it is observed that the cloaking effect deteriorate at other frequencies. This paper explores the use of multi-objective optimization approach such that the cloaking performance is maintained over a wide range of frequencies. Two examples are presented. The first cloak is comprised of all aocustic layers, and the second cloak is comprised of a mixture of acoustic and elastic layers. The results show the effectiveness of the multi-objective optimization approach on maintaining cloaking performance over a specified frequency range.

Analysis of Radiative Heat Flux for Nozzle Flow

2011 ◽  
Vol 110-116 ◽  
pp. 3025-3030
Author(s):  
Sung Nam Lee ◽  
Seung Wook Baek
Keyword(s):  
Heat Flux ◽  
Radiative Heat ◽  
Narrow Band ◽  
Radiative Properties ◽  
Radiative Heat Flux ◽  
Computational Time ◽  
Weighted Sum ◽  
Total Heat Flux ◽  
Volume Method ◽  
Inside Wall

— A finite volume method with non-gray gas model is applied to investigate radiative heat flux on the inside wall of nozzle. The radiative properties of non-gray gas are predicted by using weighted sum of gray gases model (WSGGM). Again, 4 gray gases and narrow band based WSGGM is used to predict total heat flux and spectral intensity on the nozzle wall. Finally, the hybrid use of 4 gray gases and narrow band based model is applied to reduce computational time preserving accuracy.

scholarly journals A spam filtering multi-objective optimization study covering parsimony maximization and three-way classification

2016 ◽  
Vol 48 ◽  
pp. 111-123 ◽  
Author(s):  
Vitor Basto-Fernandes ◽  
Iryna Yevseyeva ◽  
José R. Méndez ◽  
Jiaqi Zhao ◽  
Florentino Fdez-Riverola ◽  
...  
Keyword(s):  
Spam Filtering ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Optimization Study

scholarly journals Projected Changes in Soil Temperature and Surface Energy Budget Components over the Alps and Northern Italy

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 954 ◽  
Author(s):  
Claudio Cassardo ◽  
Seon Park ◽  
Sungmin O ◽  
Marco Galli
Keyword(s):  
Heat Flux ◽  
Surface Energy ◽  
Soil Temperature ◽  
Energy Budget ◽  
Regional Climate ◽  
Northern Italy ◽  
Surface Energy Budget ◽  
Future Climate ◽  
Radiative Properties ◽  
The Alps

This study investigates the potential changes in surface energy budget components under certain future climate conditions over the Alps and Northern Italy. The regional climate scenarios are obtained though the Regional Climate Model version 3 (RegCM3) runs, based on a reference climate (1961–1990) and the future climate (2071–2100) via the A2 and B2 scenarios. The energy budget components are calculated by employing the University of Torino model of land Processes Interaction with Atmosphere (UTOPIA), and using the RegCM3 outputs as input data. Our results depict a significant change in the energy budget components during springtime over high-mountain areas, whereas the most relevant difference over the plain areas is the increase in latent heat flux and hence, evapotranspiration during summertime. The precedence of snow-melting season over the Alps is evidenced by the earlier increase in sensible heat flux. The annual mean number of warm and cold days is evaluated by analyzing the top-layer soil temperature and shows a large increment (slight reduction) of warm (cold) days. These changes at the end of this century could influence the regional radiative properties and energy cycles and thus, exert significant impacts on human life and general infrastructures.

Aero-Thermal Investigation of Tip Leakage Flow in a Film Cooled Industrial Turbine Rotor

2008 ◽  
Author(s):  
S. K. Krishnababu ◽  
H. P. Hodson ◽  
G. D. Booth ◽  
G. D. Lock ◽  
W. N. Dawes
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flow ◽  
Turbine Rotor ◽  
Total Heat ◽  
Leakage Flow ◽  
Total Heat Flux ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Flow And Heat Transfer

A numerical investigation of the flow and heat transfer characteristics of tip leakage in a typical film cooled industrial gas turbine rotor is presented in this paper. The computations were performed on a rotating domain of a single blade with a clearance gap of 1.28% chord in an engine environment. This standard blade featured two coolant and two dust holes, in a cavity-type tip with a central rib. The computations were performed using CFX 5.6, which was validated for similar flow situations by Krishnababu et al., [18]. These predictions were further verified by comparing the flow and heat transfer characteristics computed in the absence of coolant ejection with computations previously performed in the company (SIEMENS) using standard in-house codes. Turbulence was modelled using the SST k-ω turbulence model. The comparison of calculations performed with and without coolant ejection has shown that the coolant flow partially blocks the tip gap, resulting in a reduction of the amount of mainstream leakage flow. The calculations identified that the main detrimental heat transfer issues were caused by impingement of the hot leakage flow onto the tip. Hence three different modifications (referred as Cases 1 to 3) were made to the standard blade tip in an attempt to reduce the tip gap exit mass flow and the associated impingement heat transfer. The improvements and limitations of the modified geometries, in terms of tip gap exit mass flow, total area of the tip affected by the hot flow and the total heat flux to the tip, are discussed. The main feature of the Case 1 geometry is the removal of the rib and this modification was found to effectively reduce both the total area affected by the hot leakage flow and total heat flux to the tip while maintaining the same leakage mass flow as the standard blade. Case 2 featured a rearrangement of the dust holes in the tip which, in terms of aero-thermal-dynamics, proved to be marginally inferior to Case 1. Case 3, which essentially created a suction-side squealer geometry, was found to be inferior even to the standard cavity tip blade. It was also found that the hot spots which occur in the leading edge region of the standard tip and all modifications contributed significantly to the area affected by the hot tip leakage flow and the total heat flux.

scholarly journals Round robin study of total heat flux gauge calibration at fire laboratories

2004 ◽  
Author(s):  
William M Pitts ◽  
Annageri V Murthy ◽  
John L deRis ◽  
Jean-Remy R Filtz ◽  
Kjell Nygard ◽  
...  
Keyword(s):  
Heat Flux ◽  
Round Robin ◽  
Total Heat ◽  
Total Heat Flux

Spectral Radiative Heat Transfer Analysis of the Planar SOFC

2004 ◽  
Author(s):  
David L. Damm ◽  
Andrei G. Fedorov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Solid Oxide ◽  
Radiative Properties ◽  
Radiative Heat Flux ◽  
Oxide Fuel

Thermo-mechanical failure of components in planar-type solid oxide fuel cells (SOFCs) depends strongly on the local temperature gradients at the interfaces of different materials. Therefore, it is of paramount importance to accurately predict the temperature fields within the stack, especially near the interfaces. Because of elevated operating temperatures (of the order of 1000 K or even higher), radiation heat transfer could become a dominant mode of heat transfer in the SOFCs. In this study, we extend our recent work on radiative effects in solid oxide fuel cells (Journal of Power Sources, Vol. 124, No. 2, pp. 453–458) by accounting for the spectral dependence of the radiative properties of the electrolyte material. The measurements of spectral radiative properties of the polycrystalline yttria-stabilized zirconia (YSZ) electrolyte we performed indicate that an optically thin approximation can be used for treatment of radiative heat transfer. To this end, the Schuster-Schwartzchild two-flux approximation is used to solve the radiative transfer equation (RTE) for the spectral radiative heat flux, which is then integrated over the entire spectrum using an N-band approximation to obtain the total heat flux due to thermal radiation. The divergence of the total radiative heat flux is then incorporated as a heat sink into a 3-D thermo-fluid model of a SOFC through the user-defined function utility in the commercial FLUENT CFD software. The results of sample calculations are reported and compared against the baseline cases when no radiation effects are included and when the spectrally gray approximation is used for treatment of radiative heat transfer.

Session and Network Support for Autonomous Context-Aware Multiparty Communications in Heterogeneous Mobile Systems

2010 ◽  
Vol 1 (4) ◽  
pp. 1-24 ◽  
Author(s):  
Josephina Antoniou ◽  
Christophoros Christophorou ◽  
Augusto Neto ◽  
Susana Sargento ◽  
Filipe Pinto ◽  
...  
Keyword(s):  
Mobile Devices ◽  
Performance Optimization ◽  
Network Performance ◽  
Future Internet ◽  
Mobile Systems ◽  
Context Aware ◽  
Network Support ◽  
Different Types ◽  
Optimization Schemes ◽  
Service Groups

The increase of networking complexity requires the design of new performance optimization schemes for delivering different types of sessions to users under different conditions. In this regard, special attention is given to multi-homed environments, where mobile devices cross areas with overlapping access technologies (Wi-Fi, 3G, WiMax). In such a scenario, efficient multiparty delivery depends upon the grouping operation, which must be done based on several parameters. In this paper, the authors propose context-aware sub-grouping of content-based service groups so that the same service session can be delivered using different codings of the same content, adapting to current network, users, session, and environment context. The context-aware information is used to improve the sub-grouping process. This paper aims to describe these sub-grouping techniques, and in particular how they improve network performance and user experience in the future Internet by focusing on the improved network-level and session-level mechanisms.

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