scholarly journals Pennes’ bioheat equation vs. porous media approach in computer modeling of radiofrequency tumor ablation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Claudio Tucci ◽  
Macarena Trujillo ◽  
Enrique Berjano ◽  
Marcello Iasiello ◽  
Assunta Andreozzi ◽  
...  
Keyword(s):  
Porous Media ◽  
Experimental Studies ◽  
Local Thermal Equilibrium ◽  
Comsol Multiphysics ◽  
Bioheat Equation ◽  
Governing Equations ◽  
Two Phase ◽  
Patient Profiles ◽  
Phase Water

AbstractThe objective of this study was to compare three different heat transfer models for radiofrequency ablation of in vivo liver tissue using a cooled electrode and three different voltage levels. The comparison was between the simplest but less realistic Pennes’ equation and two porous media-based models, i.e. the Local Thermal Non-Equilibrium (LTNE) equations and Local Thermal Equilibrium (LTE) equation, both modified to take into account two-phase water vaporization (tissue and blood). Different blood volume fractions in liver were considered and the blood velocity was modeled to simulate a vascular network. Governing equations with the appropriate boundary conditions were solved with Comsol Multiphysics finite-element code. The results in terms of coagulation transverse diameters and temperature distributions at the end of the application showed significant differences, especially between Pennes and the modified LTNE and LTE models. The new modified porous media-based models covered the ranges found in the few in vivo experimental studies in the literature and they were closer to the published results with similar in vivo protocol. The outcomes highlight the importance of considering the three models in the future in order to improve thermal ablation protocols and devices and adapt the model to different organs and patient profiles.

Experimental Investigation of a Two-Phase Drainage Process in Porous Media

2013 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Yap Yit Fatt ◽  
Jake Joong Hoon Song ◽  
John Chai ◽  
Francisco Vargas
Keyword(s):  
Porous Media ◽  
Volume Fraction ◽  
Porous Matrix ◽  
Working Fluid ◽  
Two Phase ◽  
Constant Flow Rate ◽  
Porous Media Model ◽  
Mini Channels ◽  
Phase Water ◽  
Bottom Injection

This paper presents an experimental study of two phase water-oil displacement in transparent porous media model made of mini-channels. The working fluid (water or/and oil) was injected into the porous matrix using a syringe pump with a constant flow rate. The influence of gravity and flow rates were studied. The volume fraction was defined and measured during the drainage. Two different experimental configurations, namely vertical and horizontal mini-channel were studied. For the vertical mini-channel, two injections, namely gravity-assisted (top-to-bottom) injection and anti-gravity (bottom-to-top) injection were performed. Experiments using horizontal mini-channel were also performed with the inlet and outlet placed on the same horizontal plane. It was observed that the gravity has significant effect in case of gravity-assisted injection and did not influence the anti-gravity injection or the horizontal injection setups.

scholarly journals Measurement of Interfacial Area Production and Permeability Within Porous Media

2010 ◽  
Author(s):  
Dustin Crandall ◽  
Goodarz Ahmadi ◽  
Duane Smith
Keyword(s):  
Porous Media ◽  
Two Phase Flow ◽  
Experimental Studies ◽  
Interfacial Area ◽  
Flow Cell ◽  
Flow In Porous Media ◽  
Additional Parameter ◽  
Phase Flow ◽  
Dynamic Parameters ◽  
Two Phase

An understanding of the pore-level interactions that affect multi-phase flow in porous media is important in many subsurface engineering applications, including enhanced oil recovery, remediation of dense non-aqueous liquid contaminated sites, and geologic CO2 sequestration. Standard models of two-phase flow in porous media have been shown to have several shortcomings, which might partially be overcome using a recently developed model based on thermodynamic principles that includes interfacial area as an additional parameter. A few static experimental studies have been previously performed, which allowed the determination of static parameters of the model, but no information exists concerning the interfacial area dynamic parameters. A new experimental porous flow cell that was constructed using stereolithography for two-phase gas-liquid flow studies was used in conjunction with an in-house analysis code to provide information on dynamic evolution of both fluid phases and gas-liquid interfaces. In this paper, we give a brief introduction to the new generalized model of two-phase flow model and describe how the stereolithography flow cell experimental setup was used to obtain the dynamic parameters for the interfacial area numerical model. In particular, the methods used to determine the interfacial area permeability and production terms are shown.

Modeling of Effective Stagnant Thermal Conductivity of Porous Media

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Yasuyuki Takatsu ◽  
Takashi Masuoka ◽  
Takahiro Nomura ◽  
Yuji Yamada
Keyword(s):  
Thermal Conductivity ◽  
Porous Media ◽  
Heat Conduction ◽  
Local Thermal Equilibrium ◽  
Two Phase ◽  
Spatially Periodic ◽  
Phase Systems ◽  
Multi Phase ◽  
Theory And Experiments ◽  
Good Agreement

Based on one-dimensional analysis of heat conduction, a general formula for the effective stagnant thermal conductivity of spatially periodic porous media is derived without assuming local thermal equilibrium. Furthermore, we discuss the contribution of the contact area between particles to the effective stagnant thermal conductivity in detail, and the modification of the formula is proposed to predict the actual effective stagnant thermal conductivity for the porous media. The present results are in good agreement with experimental results of Nozad et al. (1985, “Heat Conduction in Multi-Phase Systems I: Theory and Experiments for Two-Phase Systems,” Chem. Eng. Sci., 40(5), pp. 843–855) for a packed-sphere bed.

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