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Heat Transfer and Entropy Generation in a Porous Square Enclosure in Presence of an Adiabatic Block

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Abstract

The present work investigates the thermal aspects of a differentially heated porous square enclosure in the presence of an adiabatic block of different block sizes utilizing Darcy–Rayleigh number in the range of 1–10,000 with Darcy number \(10^{-2}\)\(10^{-6}\). Heatlines and Nusselt number, streamlines, and entropy generation are used for the analysis of heat transfer, flow circulation, and irreversibility production in the enclosure. The study reveals that the presence of an adiabatic block affects the heat transfer process severely, and three different zones of heat transfer are identified. These are namely the zone of heat transfer augmentation, the zone of heat transfer augmentation along with entropy generation reduction, and the zone of both heat transfer and entropy generation reduction. It is also found that the presence of an adiabatic block can enhance heat transfer up to a certain critical block size; thereafter, further increasing in block size reduces the heat transfer rate. An optimal block size where the heat transfer enhancement is maximum is observed to be smaller than the critical block size. The study demonstrates the analyses of heat transfer and entropy generation for a better thermal design of a system. This study is also extended for higher Prandtl number fluids.

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Abbreviations

Be :

Bejan number

\(C_P \) :

Specific heat (J/kg K)

Da :

Darcy number

Ec :

Eckert number

EG:

Ethylene glycol

EO:

Unused engine oil

\(F_C\) :

Forchheimer coefficient

g :

Acceleration due to gravity (\(\hbox {m\,s}^{-2 }\))

k :

Thermal conductivity (\(\hbox {W\,m}^{-1}\,\hbox {K}^{-1 }\))

K :

Permeability (\(\hbox {m}^{2 }\))

L :

Length scale (m)

NS :

Dimensionless entropy generation

Nu :

Nusselt number

p :

Pressure, Pa

P :

Dimensionless pressure

\(q_\mathrm{in}\) :

Dimensionless heat input

\(q_\mathrm{out}\) :

Dimensionless heat going out

Pr :

Prandtl number

\(R_k\) :

Thermal diffusivity ratio

Ra :

Fluid Rayleigh number

\({Ra}_{{m}}\) :

Darcy–Rayleigh number

T :

Temperature (K)

\(T_C\) :

Cold wall temperature (K)

\(T_H\) :

Hot wall temperature (K)

\(T^{*}\) :

Dimensionless reference temperature

UV :

Dimensionless velocities

xy :

Cartesian coordinates (m)

uv :

Velocity (\(\hbox {m\,s}^{-1}\))

XY :

Dimensionless Cartesian coordinates

\(\alpha \) :

Thermal diffusivity (\(\hbox {m}^{2}\,\hbox {s}^{-1}\))

\(\beta \) :

Thermal expansion coefficient (\(\hbox {K}^{-1}\))

\(|\psi |\) :

Dimensionless absolute streamfunction

\(\theta \) :

Dimensionless temperature

\(\phi \) :

Dimensionless block area

\(\Delta T\) :

\(T_H -T_C\)

\(\nu \) :

Kinematic viscosity (\(\hbox {m}^{2}\,\hbox {s}^{-1}\))

\(\rho \) :

Fluid density (\(\hbox {kg/m}^{3}\))

\(\varPi \) :

Dimensionless heatfunction

\(\eta \) :

Heat transfer parameter

\(\zeta \) :

Entropy generation parameter

\(\varepsilon \) :

Porosity

avg:

Average value

cond :

Conduction

c :

Critical

f :

Fluid

loc :

Local

max :

Maximum value

o :

Optimal

s :

Porous media

tot:

Total

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Acknowledgments

Authors would like to thank anonymous reviewers for their critical comments and valuable suggestions, which have improved the quality of this manuscript.

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Correspondence to Pallab Sinha Mahapatra.

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Datta, P., Mahapatra, P.S., Ghosh, K. et al. Heat Transfer and Entropy Generation in a Porous Square Enclosure in Presence of an Adiabatic Block. Transp Porous Med 111, 305–329 (2016). https://doi.org/10.1007/s11242-015-0595-5

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