Numerical Study of Fluid Flow and Heat Transfer In Reticulated Porous Media
Date
2023
Authors
Rambabu, Siddam
Journal Title
Journal ISSN
Volume Title
Publisher
National Institute Of Technology Karnataka Surathkal
Abstract
The transport of heat and mass in porous media have a significant influence on a
wide range of engineering applications such as solar reactors, building thermal insulation,
packed cryogenic microsphere insulation, combustors, chemical and biological
reactors, etc. The reticulated porous media are heterogeneous systems consisting of
several interconnected solid phases with continuous void/fluid space. It is well acknowledged
that more efficient heat transfer technologies and novel materials are required
to improve performance of energy and heat transfer devices while maintaining
tolerable levels of power consumption, size, and cost. Reticulated porous structures are
excellent candidates for enhancing the thermal efficiency of heat transfer devices while
simultaneously enabling the use of smaller and lighter equipment. The present research
work involved in studying the fluid flow, heat and mass transfer in open-cell reticulated
porous structures with help of Direct Pore Level Simulations (DPLS). The reticulated
porous structures are modelled based on the theoretical Kelvin model. The geometry of
these structures are generated with the help of in-house code and visualisation tool kit
(VTK) libraries. The ideal and randomized Kelvin structures are generated for different
PPI & porosities. By varying the geometrical parameters, the influence of geometries
on pressure drop, dispersion, and heat transfer between the flowing fluid and solid phase
of open-cell foams are investigated. For this reason, the mass, momentum and energy
equations in reticulated structures are solved using the standard CFD-FVM approach.
The simulation results are used to acquire the pressure drop across the structures.
The pressure drop variation with respect to pore density, porosity, specific surface area,
and randomization are analyzed. The fluid transport properties such as permeability
and drag coefficient are calculated for various porous structures and a pressure drop
iii
correlation with new values of viscous and inertial coefficients is proposed. Along with
the fluid flow, the dispersion of a tracer is traced across the structures and analysed in
terms of the effective diffusivity coefficient. Then the influence of dispersion on mass
transfer is characterized by estimating the longitudinal dispersion coefficient. The effect
of tortuosity on dispersion is also studied. The characteristic length dependent correlation
is proposed in terms of strut diameter and flow tortuosity to relate the longitudinal
Peclet number as a function of molecular Peclet number. Subsequent simulations are
performed to evaluate the forced convective heat transfer coefficient for different fluids
of Prandtl numbers (air, water & seawater). Based on the simulation outcomes, two
new correlations are proposed to calculate the heat transfer coefficients in the reticulated
porous structures. The proposed correlation is validated by comparing it with numerical
and experimental data of real reticulated porous structures available in the literature.
Description
Keywords
Open-cell foams, Kelvin cell model, Randomization, Direct pore level simulation