Experimental study of local thermal non-equilibrium phenomena during phase change in porous media

Nnanna, A. G. Agwu; Haji‐Sheikh, A.; Harris, Kendall T.

doi:10.1016/j.ijheatmasstransfer.2004.04.029

Cited by 32 publications

(10 citation statements)

References 16 publications

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“…This is a unified model trying to incorporate many different situations of heat transport at different scales by grasping the common feature. From our perspective, the DPL model usually captures well the behavior of heat transport mediated by two (or multi-) carriers (or media), such as the electron-phonon interactions in the laser-heating process in metal [90], superfluid and normal components induced heat wave propagation in superfluid liquid helium [90], multi-phase induced nonhomogeneous heating response in porous media [91] and amorphous media [92]. Another characteristic of DPL model is that the two phase lags have usually to be determined by adjusting to the experimental data of thermal response.…”

Section: Macroscopic Methodsmentioning

confidence: 99%

Phonon hydrodynamics and its applications in nanoscale heat transport

2015

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Section: Macroscopic Methodsmentioning

confidence: 99%

Phonon hydrodynamics and its applications in nanoscale heat transport

2015

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“…More detailed work, both analytical and experimental, has been furnished to introduce porosity in describing the lagging response in porous media (Amiri and Vafai, 1998;Minkowycz et al, 1999;Agwu Nnanna et al, 2004). They treat the solid and gaseous phases as two distinct energy carriers, in ways parallel to phonons and electrons in metals to draw the analogy.…”

Section: þmentioning

confidence: 99%

“…They treat the solid and gaseous phases as two distinct energy carriers, in ways parallel to phonons and electrons in metals to draw the analogy. For PCMsaturated porous media, Agwu Nnanna et al (2004), their values are τ T = 64.9 s and τ q = 59 s. As compared to the value of τ T , the values of τ q cover a much wider range due to its strong dependence on the interfacial heat transport across the solid-fluid/air interface, and hence the thermal contact resistance. The coupling factor G, in particular, is weighted by the volumetric porosity and is a fraction of the quantity (h/r h ), with h being the interstitial heat transfer coefficient at the solid/gas interface and r h the volume-to-surface-area ratio of the pore, called hydraulic radius.…”

Section: þmentioning

confidence: 99%

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Nonhomogeneous Lagging Response in Porous Media

Tzou¹

2014

Macro‐ to Microscale Heat Transfer

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Heat transport in discrete media could display a different type of lagging due to the finite times required for the solid and gaseous phases to reach thermal equilibrium and the wavy conducting path that energy carriers have to follow along the solid phase. The microscopic two-step model is extended in this chapter to describe thermal lagging in sands, due to its easy access for reproducing the results, with emphasis on identifying the microstructural parameters dominating the delayed response between the heat flux vector and the temperature gradient. The dual-phase-lag model is compared with the experimental results to reveal the nonhomogeneous variation of the phase lags from near to far fields of the heater. For medium-sized blasting sand, both phase lags are of the order of seconds. In transition from the near (discrete) to the far (continuum) field, the lagging response displays a vivid pattern of precedence switch, from the gradient-to the flux-precedence type of heat flow, resulting from the accumulated effect of thermal lagging in the gradually expanded sample size.From the experimental results described in Chapters 4 and 5, it is clear that the success of the dual-phase-lag model lies in its unique way of describing the microscale interaction effect in space by the resulting delayed response in time. For heat propagation in superfluid liquid helium, Chapter 4, the time delay between the heat flux vector and the temperature gradient is caused by the finite time required for activating the molecules at a low temperature to an energy level appropriate for efficient heat conduction. For the short-pulse laser heating on metal films discussed in Chapter 5, alternately, the delayed response in metals is caused by the finite time required for the energy exchange between phonons and electrons. The physical mechanisms are different, but the philosophy of trading the microstructural interaction effect in space with the fast-transient effect in time is the same.This chapter generalizes the phonon-electron interaction (microscopic two-step) model to account for the lagging response caused by the energy exchange between different types of substances in the conductor. In ways parallel to the energy exchange between phonons and electrons, which are equivalent to two different substances in general, energy exchange between interstitial gas (gaseous phase) and medium-sized blasting sand (solid phase) are examined to extract the lagging behavior. Sand beds are used due to their easy access and

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“…The area of local thermal non-equilibrium is proportionally increase with the increase of all parameters except modified Rayleigh number. Nanna et al [5] did a practical investigation to study the thermal non-equilibrium in porous medium saturated with a fluid subjected to phase change effect. Their model was insulated box made from insulated material called (Plexiglas) and filled with glass balls of (3mm) diameter immersed in (Tetracosane).…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Heat Transfer by Natural Convection of Porous Layer Using Non-Equilibrium Model

Radhi¹,

Dawood²

2012

(AREJ)

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This numerical study documents the phenomena of heat transfer by natural convection in thermally non-equilibrium porous cavity for Darcy flow model. The cavity is heated from below at constant temperature   h T with keeping the upper plate isothermal   c T. The side walls were assumed to be thermally insulated. Finite difference 100 1. 0   r K. The non-equilibrium is found to be affected by scaled heat transfer coefficient more than being affected by the thermal conductivity ratio. So It had been noticed that all Nusselt numbers are affected by the thermal conductivity ratio, while the effect of scaled heat transfer coefficient was confined to a solid phase Nusselt number.

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Experimental study of local thermal non-equilibrium phenomena during phase change in porous media

Cited by 32 publications

References 16 publications

Phonon hydrodynamics and its applications in nanoscale heat transport

Phonon hydrodynamics and its applications in nanoscale heat transport

Nonhomogeneous Lagging Response in Porous Media

Numerical Study of Heat Transfer by Natural Convection of Porous Layer Using Non-Equilibrium Model

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