Entropy generation of nanofluid flow with streamwise conduction in microchannels

Ting, Tiew Wei; Hung, Yew Mun; Guo, Ningqun

doi:10.1016/j.energy.2013.10.064

Cited by 41 publications

(19 citation statements)

References 39 publications

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“…Following the literature [18,37,58,59], the system has been split into contributions from Wall1, the solid porous matrix heat transfer, the fluid heat transfer, the fluid friction component and that of the mass transfer. The volumetric entropy generations for the system are expressed by the equations listed below [18,36,38].…”

Section: Entropy Generationmentioning

confidence: 99%

The effects of exothermic catalytic reactions upon combined transport of heat and mass in porous microreactors

Hunt

Karimi

Yadollahi

et al. 2019

International Journal of Heat and Mass Transfer

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Microreactors for chemical synthesis and combustion have already attracted significant attention. Exothermic catalytic activity features heavily in these devices and thus advective-diffusive transport is of key importance in their analyses. Yet, thermal modelling of the heat generated by catalytic reactions on the internal surfaces of porous microreactors has remained as an important unresolved issue. To address this, the diffusion of heat of catalytic reactions into three phases including fluid, porous solid and solid walls is investigated by extending an existing interface model of porous media under local thermal non-equilibrium. This is applied to a microchannel fully filled with a porous material, subject to a heat flux generated by a catalytic layer coated on the porous-wall boundary. The finite wall thickness and viscous dissipation of the flow kinetic energy are considered, and a twodimensional analytical model is developed, examining the combined heat and mass transfer and thermodynamic irreversibilities of the system. The analytical solution is validated against the existing theoretical studies on simpler configurations as well as a computational model of the microreactor in the limit of very large porosity. In keeping with the recent findings, the wall thickness is shown to strongly influence the heat and mass transport within the system. This remains unchanged when the symmetricity of the microchannel is broken through placing walls of unequal thicknesses, while deviation from local thermal equilibrium is significantly intensified in this case. Importantly, the Nusselt number is shown to have a singular point, which remains fixed under various conditions. NomenclatureInterfacial area per unit volume of porous media, (m -1 ) Prandtl number Biot number Wall heat flux ratio ′ Modified Brinkman number ′′ Total catalytic heat flux (W m -2 ) Mass species concentration (kg m -3 ) 1 ′′ Lower wall heat flux (W m -2 ) 0 Inlet concentration (kg m -3 ) 2 ′′ Upper wall heat flux (W m -2 ) Specific heat capacity (J K -1 kg -1 ) Reynolds number Mass diffusion coefficient (m 2 s -1 ) Specific gas constant (J K -1 kg -1 ) Darcy number Shape factor of the porous medium Coefficient of thermal mass diffusion (m K -1 kg -1 s -1 ) ̇′ ′′ Volumetric entropy generation due to mass diffusion (W K -1 m -3 ) ℎ 1 Half-thickness of the microchannel to lower wall (m) ′ ′′ Volumetric entropy generation due to fluid friction (W K -1 m -3 ) ℎ 2 Half-thickness of the microchannel to upper wall (m) ̇′ ′′ Volumetric entropy generation in the fluid (W K -1 m -3 ) ℎ 3 Half-height of microchannel (m) ′ ′′ Volumetric entropy generation in the porous solid (W K -1 m -3 ) ℎ Interstitial heat transfer coefficient (W K -1 m -2 ) ̇1 ′′′ Volumetric entropy generation rate from lower wall (W K -1 m -3 )

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Section: Entropy Generationmentioning

confidence: 99%

The effects of exothermic catalytic reactions upon combined transport of heat and mass in porous microreactors

Hunt

Karimi

Yadollahi

et al. 2019

International Journal of Heat and Mass Transfer

View full text Add to dashboard Cite

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“…Additionally, neglecting viscous heating effects would give incorrect predictions. Ting et al [143] investigated the effects of streamwise conduction on the thermal performance of nanofluid flow in MCHS's under exponentially decaying wall heat flux. The Peclet number was found to strongly affect the temperature distribution when the streamwise conduction is incorporated.…”

Section: Nanofluids For Microsystem Coolingmentioning

confidence: 99%

Mathematical Modeling and Computer Simulations of Nanofluid Flow with Applications to Cooling and Lubrication

Kleinstreuer

2016

Fluids

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There is a growing range of applications of nanoparticle-suspension flows with or without heat transfer. Examples include enhanced cooling of microsystems with low volume-fractions of nanoparticles in liquids, improved tribological performance with lubricants seeded with nanoparticles, optimal nanodrug delivery in the pulmonary as well as the vascular systems to combat cancer, and spray-coating using plasma-jets with seeded nanoparticles. In order to implement theories that explain experimental evidence of nanoparticle-fluid dynamics and predict numerically optimum system performance, a description of the basic math modeling and computer simulation aspects is necessary. Thus, in this review article, the focus is on the fundamental understanding of the physics of nanofluid flow and heat transfer with summaries of microchannel-flow applications related to cooling and lubrication.

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“…In this analysis, copper and alumina were used as nanoparticles, and water and ethylene glycol were used as base fluids. Another entropy generation analysis of nanofluid flow within circular microchannels was conducted by Ting et al [24]. Khorasanizadeh et al [25] solved energy and momentum equations within a lid-driven cavity.…”

Section: Introductionmentioning

confidence: 99%

Temperature and Entropy Generation Analyses Between and Inside Rotating Cylinders Using Copper–Water Nanofluid

Torabi

Zhang

Mahmud

2015

Journal of Heat Transfer

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Entropy generation is squarely linked with irreversibility, and consequently with exergy destruction within a thermal system. This study concerns with the temperature distribution, and local and volumetric averaged entropy generation rates within a cylindrical system with two solid co-rotating inner and outer parts and the middle nanofluid flow part. Temperature-dependent thermal conductivities for solid materials are included within the modeling. To obtain the temperature formula within all three sections, a combined analytical-numerical solution technique is applied. An exact analytical solution is also obtained, when constant thermal conductivities for solid materials are assumed. The resultant data from the analytical-numerical solution technique is verified against the investigated exact solution. Thereafter, the velocity and temperature fields from the combined analytical-numerical solution technique are incorporated into the entropy generation formulations to obtain the local and volumetric averaged entropy generation rates. Using abovementioned procedure, the effects of thermophysical parameters such as nanoparticles volume concentration, Brinkman number, thermal conductivity parameter ratios, outer temperature boundary condition, internal heat generation rates and velocity ratios on the temperature field, and entropy generation rates are investigated.

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Entropy generation of nanofluid flow with streamwise conduction in microchannels

Cited by 41 publications

References 39 publications

The effects of exothermic catalytic reactions upon combined transport of heat and mass in porous microreactors

The effects of exothermic catalytic reactions upon combined transport of heat and mass in porous microreactors

Mathematical Modeling and Computer Simulations of Nanofluid Flow with Applications to Cooling and Lubrication

Temperature and Entropy Generation Analyses Between and Inside Rotating Cylinders Using Copper–Water Nanofluid

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