Heat losses in applied smouldering systems: Sensitivity analysis via analytical modelling

Rashwan, Tarek L.; Torero, José L.; Gerhard, Jason I.

doi:10.1016/j.ijheatmasstransfer.2021.121150

Cited by 24 publications

(28 citation statements)

References 45 publications

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“…Therefore, higher temperature regions of the bed are less conductive to air flow. This effect is similar to how physically induced channelling can occur due to permeability heterogeneity (Rashwan et al, 2021c;Wang et al, 2021) and porosity variations (Dalman et al, 1986;Laguerre et al, 2006;Meier et al, 1991).…”

Section: Base Casesupporting

confidence: 66%

“…Bed temperature inhomogeneity has been investigated relative to its role in smouldering reaction dynamics. Namely, its influence on injected air flow rates ( Levin and Lutsenko, 2006 , 2008 ), non-uniform air flux ( Rashwan et al, 2021c ), pressure changes within smouldering reactors ( Zanoni et al, 2021 ) and reaction front instability ( Chen et al., 2018 ; Rabinovich et al, 2016 ). Relatedly, the results of this work provide the first investigation into how bed temperature inhomogeneities derived during the smouldering phase can have ramifications for the cooling phase.…”

Section: Resultsmentioning

confidence: 99%

“…specific surface area) of the grains was calculated as A s g = 6 ( 1 − ϕ ) / d p . Radiation heat transfer was accounted for through implementation of a radiative conductivity, which followed the Rosseland approximation ( k r a d = 16 σ d p T s 3 / 3 ) (Rashwan et al, 2021c; Zanoni et al, 2017). Heat transfer between the solid and gas phase was regulated by the solid–gas heat transfer coefficient, h s g , estimated by Zanoni et al (2017):…”

Section: Methodsmentioning

confidence: 99%

“…This equation is valid for P r = 0.72, 0.125 mm ≤ d p ≤ 2.000 mm, and 0 ≤ R e ≤ 31, which is consistent with the cases to be presented. Moreover, this h s g correlation is best suited for the low Reynolds number flows applied during STARx operation (Rashwan et al, 2021c).…”

Section: Methodsmentioning

confidence: 99%

“…Governing equations. Air flow within the porous space was modelled as an incompressible fluid (Rashwan et al, 2021c) under fully developed, laminar conditions. The air density was determined by local temperatures at each timestep by the ideal gas law (Zanoni et al, 2017).…”

Section: Model Formulationmentioning

confidence: 99%

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Understanding, controlling and optimising the cooling of waste thermal treatment beds including STARx Hottpads

et al. 2022

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STARx (Self-sustaining Treatment for Active Remediation ex situ) is a thermal treatment strategy for contaminated soils and organic wastes. Key to this technology is that organics are embedded in porous matrix beds (e.g. sand). STARx induces a self-sustaining smouldering combustion front that traverses the bed, burning away the embedded contaminants/wastes. The time and cost effectiveness of this technology is largely dictated by the time required for cooling of the hot, clean, porous matrix bed that remains after treatment. This study is the first to explore the cooling of these beds. A suite of novel simulations investigated the influence of key parameters on bed-cooling time. The results reveal that cooling time decreased nearly linearly with decreases of volume-averaged bed temperature and bed bulk density. Increased injection air fluxes led to the non-linear decrease of cooling time. Also, cooling time was negatively impacted by bed temperature inhomogeneity, which influenced preferential air flow through cooler regions of the bed, bypassing hotter regions. From these results, using lower bulk density bed materials, increased air fluxes and enhancing wall insulation to improve bed temperature homogeneity were identified as system optimisations to reduce cooling times. While the aim of this research is to improve the STARx cooling process, the results are also highly applicable to many similar engineering systems that involve hot porous bed cooling.

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