Entropy Generation in Laminar Forced Convective Water Flow Due to Overloading Toward the Microscale

Rastogi, Pallavi; Mahulikar, Shripad P.

doi:10.1115/1.4039608

Cited by 4 publications

(4 citation statements)

References 42 publications

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“…Rastogi and Mahulikar [13,14] implemented the theory of EG for the optimization of the MC heat sink with a laminar forced convection flow. The situation with minimum total EG rate results in the optimum channel diameter.…”

Section: Introductionmentioning

confidence: 99%

IRREVERSIBILITY ANALYSIS IN Al2O3-WATER NANOFLUID FLOW WITH VARIABLE PROPERTY

et al. 2022

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The present numerical work deals with the optimization of the micro-channel heat sink using irreversibility analysis. The nanofluid of Al2O3-water with the different nanoparticles concentration and the temperature-dependent property is chosen as a coolant. The flow is considered as fully developed, steady, and laminar in the constant cross-section of circular channels. Navier-Stokes and energy equations are solved for a single-phase flow with total mass flow rate and heat flow rate as constant. The objective functions related to the frictional and heat transfer irreversibilities are framed to assess the performance of the micro-channel heat sink. The optimum channel diameter corresponding to the optimum number of channels is determined at the lowest total irreversibility for both constant property solution and variable property solution. Designed optimum diameter is observed maximum for 2.5% Al2O3-water nanofluid with μ(T) variation followed by 1% Al2O3-water nanofluid with μ(T) variation, 2.5% Al2O3-water nanofluid with constant property solution, and 1% Al2O3-water nanofluid with constant property solution.

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Section: Introductionmentioning

confidence: 99%

IRREVERSIBILITY ANALYSIS IN Al2O3-WATER NANOFLUID FLOW WITH VARIABLE PROPERTY

et al. 2022

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“…The

{\dot{S}}_{gen}

was theoretically studied for laminar fully developed steady forced convective Hagen‐Poiseuille water flow in a circular tube, for constant heat flux Boundary Condition (

q_{w}^{^{''}}

= const. BC) . For a given rate of heat removal ( q w ) using a fixed total mass flow rate (

\overset{m}{true}

tot ) of coolant (water), Towards the microscale, number of tubes ( N ) were increased by decreasing diameter of each tube ( D N ) .…”

Section: Introductionmentioning

confidence: 99%

“…For a given rate of heat removal ( q w ) using a fixed total mass flow rate (

\overset{m}{true}

tot ) of coolant (water), Towards the microscale, number of tubes ( N ) were increased by decreasing diameter of each tube ( D N ) . At optimum D N and corresponding optimum N , sum‐total

{\dot{S}}_{gen}

(

{\dot{S}}_{gen, tot}

) was found to be the least. The

{\dot{S}}_{gen, tot}

insignificantly increased when a single circular tube was “convectively overloaded” towards the microscale by decreasing its diameter ( D ) …”

Section: Introductionmentioning

confidence: 99%

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Theoretical studies on energy degradation estimation and minimization in laminar convective flow towards the microscale

Rastogi

Mahulikar

2018

Heat Trans. Asian Res.

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The energy degraded into heat (q deg ) in laminar microconvective flow is of fundamental interest for minimizing the irreversibilities. The change in q deg for N-number of microtubes each of diameter (D N ) is studied relative to the reference tube (N = 1) of 1 mm diameter, towards the microscale. The total mass flow rate and total heat flow rate to be removed are kept fixed through all N tubes. Resultsshow that for given l, there exists an optimum D N ( = D N,opt ) and a corresponding optimum N at which, the change in sum-total q deg is minimum. As l decreases, D N,opt shifts towards the microscale. General criterion for D N,opt is analytically obtained in terms of Peclet number, Brinkman number, and dimensionless microtube length. The reported study and findings are of significance for the optimum design of microchannel heat sinks.Nomenclature:̇g en , entropy generation rate (W K −1 );̇, mass flow rate (kg s −1 ); ′′ w , wall heat flux (W cm −2 ); A cs , cross sectional flow area (m 2 ); A sur , surface area (m 2 ); C p , specific heat at constant pressure (J kg −1 K −1 ); D, tube diameter ( m); h, convective heat transfer coefficient (W m −2 K −1 ); k, thermal conductivity (W m −1 K −1 ); l, tube length (cm); N, number of microtubes (-); q deg , energy degraded (W); q w , convective heat transfer rate (W); r, radial direction (m); R, tube radius ( m); R th,conv , convective thermal resistance (K W −1 ); T, fluid temperature (K); u, axial velocity (m s −1 ); z, axial (flow) direction (m) Greek scripts: , thermal diffusivity (m 2 s −1 ); w , wall shear stress (Pa); , dynamic viscosity (Pa s); , density (kg m −3 )

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Entropy Generation and Poiseuille Number Link in Developing Isothermal Laminar Micro-Flow

Rastogi

Mahulikar

2021

Journal of Energy Resources Technology

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It is well-known that Poiseuille number (Po, hitherto viewed mainly as a Fluid Mechanics parameter) decreases along a hydrodynamically developing flow, from infinity at inlet to a fixed value downstream. This study reveals that the dimensionless entropy generation rate per unit length due to fluid friction (Sgen,fr) varies exactly the same way; hence, Po and Sgen,fr are jointly studied for their dependence. Laminar hydrodynamic development of isothermal flow of incompressible fluid (water) in a circular micro-tube (diameter, D) is examined. Results are obtained for a given flow velocity for different D and then numerical experiments are conducted for different flow velocities for the same D-values. Striking similarity in trends of Po and Sgen,fr show a unique linear relation between them for the hydrodynamically developing region. It is theoretically shown that Po is a direct measure of entropy generation due to fluid friction, which explains its numerically obtained linear relation with Sgen,fr. It is found that in hydrodynamically developing region, both Po and Sgen,fr decrease with decreasing D, which is the identified micro-effect.

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Entropy Generation in Laminar Forced Convective Water Flow Due to Overloading Toward the Microscale

Cited by 4 publications

References 42 publications

IRREVERSIBILITY ANALYSIS IN Al2O3-WATER NANOFLUID FLOW WITH VARIABLE PROPERTY

IRREVERSIBILITY ANALYSIS IN Al2O3-WATER NANOFLUID FLOW WITH VARIABLE PROPERTY

Theoretical studies on energy degradation estimation and minimization in laminar convective flow towards the microscale

Entropy Generation and Poiseuille Number Link in Developing Isothermal Laminar Micro-Flow

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