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Enhancement Of Performance Parameters Of Transformer Using Nanofluids, Innovative Research Publications Irp India, Raja Sekhar Dondapati, Vishnu Saini, Niraj Kishore, Vicky V Jun 2015

Enhancement Of Performance Parameters Of Transformer Using Nanofluids, Innovative Research Publications Irp India, Raja Sekhar Dondapati, Vishnu Saini, Niraj Kishore, Vicky V

Innovative Research Publications IRP India

Transformer is a soul of both transmission and distribution systems. It performs low voltage to high voltage conversion in transmission lines and similarly high voltage to low voltage conversion in distribution lines. The operation of transformer is decided by the cooling provided to the system. The efficient cooling method is achieved by the use of forced (or) natural oil cooling medium. The oils used for the purpose of coolants are the hydrocarbons of paraffin (or) naphtha based petroleum products. The oil is used as coolant is made from highly refined mineral oil and it has high dielectric strength. During the ...


Experimental And Numerical Investigation Of Heat Transfer In Cnt Nanofluids May 2015

Experimental And Numerical Investigation Of Heat Transfer In Cnt Nanofluids

Faculty of Engineering University of Malaya

Nanofluids with their enhanced thermal conductivity are believed to be a promising coolant in heat transfer applications. In this study, carbon nanotube (CNT) nanofluids of 0.01wt%, stabilised by 1.0wt% gum arabic were used as a cooling liquid in a concentric tube laminar flow heat exchanger. The flow rate of cold fluid varied from 10 to 50g/s. Both experimental and numerical simulations were carried out to determine the heat transfer enhancement using CNT nanofluids. Computational fluid dynamics (CFD) simulations were carried out using Fluent v 6.3 by assuming single-phase approximation. Thermal conductivity, density and rheology of the ...


Performance Dependence Of Thermosyphon On The Functionalization Approaches: An Experimental Study On Thermo-Physical Properties Of Graphene Nanoplatelet-Based Water Nanofluids Mar 2015

Performance Dependence Of Thermosyphon On The Functionalization Approaches: An Experimental Study On Thermo-Physical Properties Of Graphene Nanoplatelet-Based Water Nanofluids

Faculty of Engineering University of Malaya

Graphene Nanoplatelets (GNP) were stably dispersed in aqueous media by covalent and non-covalent functionalization. Covalent functionalization was performed by a rapid microwave-assisted approach. Surface functionality groups and morphology of acid-treated GNP were analyzed by Fourier transform infrared spectroscopy and transmission electron microscopy. The GNP-based water nanofluids were then prepared with different concentrations of GNP to evaluate the thermo-physical and rheological properties. It was found that the rheological and thermo-physical properties of all treated samples were significantly enhanced compared to the pure water. The amount of enhancement also increased as the weight concentration increased. Thermo-physical results also confirmed that the thermal ...


Heat Transfer Coefficient Of Flowing Wood Pulp Fibre Suspensions To Monitor Fibre And Paper Quality Mar 2015

Heat Transfer Coefficient Of Flowing Wood Pulp Fibre Suspensions To Monitor Fibre And Paper Quality

Faculty of Engineering University of Malaya

Heat transfer measurements were obtained for a range of suspensions of wood pulp fibre flowing through a pipeline. Data were generated over a selected range of flow rates and temperatures from a specially built flow loop. It was found that the magnitude of the heat transfer coefficient was above water at equivalent experimental conditions at very low fibre concentrations, but progressively decreased until it was below water at slightly higher concentrations. It was found that the heat transfer was affected by varying fibre properties, such as fibre length, fibre flexibility, fibre chemical and mechanical treatment, the variation of fibres from ...


Integral-Balance Solution To The Stokes’ First Problem Of A Viscoelastic Generalized Second Grade Fluid, Jordan Hristov Jun 2012

Integral-Balance Solution To The Stokes’ First Problem Of A Viscoelastic Generalized Second Grade Fluid, Jordan Hristov

Jordan Hristov

Integral balance solution employing entire domain approximation and the penetration dept concept to the Stokes’ first problem of a viscoelastic generalized second grade fluid has been developed. The solution has been performed by a parabolic profile with an unspecified exponent allowing optimization through minimization of the norm over the domain of the penetration depth. The closed form solution explicitly defines two dimensionless similarity variables and , responsible for the viscous and the elastic responses of the fluid to the step jump at the boundary. The solution was developed with three forms of the governing equation through its two dimensional forms (the ...


Thermal Impedance At The Interface Of Contacting Bodies: 1-D Example Solved By Semi-Derivatives, Jordan Hristov Jun 2012

Thermal Impedance At The Interface Of Contacting Bodies: 1-D Example Solved By Semi-Derivatives, Jordan Hristov

Jordan Hristov

Simple 1-D semi-infinite heat conduction problems enable to demonstrate the potential of the fractional calculus in determination of transient thermal impedances of two bodies with different initial temperatures contacting at the interface ( ) at . The approach is purely analytic and uses only semi-derivatives (half-time) and semi-integrals in the Riemann-Liouville sense. The example solved clearly reveals that the fractional calculus is more effective in calculation the thermal resistances than the entire domain solutions


Transient Flow Of A Generalized Second Grade Fluid Due To A Constant Surface Shear Stress: An Approximate Integral-Balance Solution, Jordan Hristov Dec 2011

Transient Flow Of A Generalized Second Grade Fluid Due To A Constant Surface Shear Stress: An Approximate Integral-Balance Solution, Jordan Hristov

Jordan Hristov

Integral balance solution to start-up problem of a second grade viscoelastic fluid caused by a constant surface stress at the surface has been developed by an entire-domain parabolic profile with an unspecified exponent. The closed form solution explicitly defines two dimensionless similarity variables ξ = y ν t and 2 D0 p t= χ = ν β , responsible for the viscous and the elastic responses of the fluid to the step jump at the boundary. Numerical simulations demonstrating the effect of the various operating parameter and fluid properties on the developed flow filed, as well comparison with the existing exact solutions have ...


Transferts De Chaleur Dans Un Réacteur Thermochimique Solaire Muni D’Un Récepteur Volumique Poreux, Hernando Romero Paredes Rubio May 2011

Transferts De Chaleur Dans Un Réacteur Thermochimique Solaire Muni D’Un Récepteur Volumique Poreux, Hernando Romero Paredes Rubio

Hernando Romero Paredes Rubio

Un réacteur thermochimique solaire de 1 kW muni d’une structure céramique poreuse en céramique est modélisé pour simuler les transferts thermiques a l’intérieur du récepteur volumétrique. Le modèle développé a été utilisé pour prévoir le comportement thermique du réacteur en fonction des différentes conditions opératoires qui concernent le débit de gaz inerte, le flux solaire incident, la porosité, la longueur du récepteur, et la prise en compte de réactions chimiques. Les résultats montrent que la température maximale est de 1850K pour une concentration solaire de 1000 soleils. La température diminue de manière significative lorsque le débit de gaz ...


The Analysis Of Heat Transfer In A Gas-Gas Heat Exchanger Operated Under A Heat-Recirculating Mode, Mariusz Salaniec, Wojciech M. Budzianowski Jan 2011

The Analysis Of Heat Transfer In A Gas-Gas Heat Exchanger Operated Under A Heat-Recirculating Mode, Mariusz Salaniec, Wojciech M. Budzianowski

Wojciech Budzianowski

The present paper presents the analysis of heat transfer in a gas-gas heat exchanger operated in a heat-recirculating mode.


Can Segmented Flow Enhance Heat Transfer In Microchannel Heat Sinks?, Amy Rachel Betz, Daniel Attinger Sep 2010

Can Segmented Flow Enhance Heat Transfer In Microchannel Heat Sinks?, Amy Rachel Betz, Daniel Attinger

Daniel Attinger

Liquid cooling is an efficient way to remove heat fluxes with magnitudes up to 10,000 W/cm2. One limitation of current single-phase microchannel heat sinks is the relatively low Nusselt number, due to laminar flow. In this work, we experimentally investigate how to enhance the Nusselt number with the introduction of segmented flow. The segmented flow pattern was created by the periodic injection of air bubbles through a T-junction into water-filled channels. We designed a polycarbonate heat sink consisting of an array of seven parallel microchannels each with a square cross-section 500 μm wide. We show that segmented flow ...


Unsteady Nanoscale Thermal Transport Across A Solid-Fluid Interface, Ganesh Balasubramanian, Soumik Banerjee, Ishwar K. Puri Sep 2008

Unsteady Nanoscale Thermal Transport Across A Solid-Fluid Interface, Ganesh Balasubramanian, Soumik Banerjee, Ishwar K. Puri

Ganesh Balasubramanian

We simulate unsteady nanoscale thermal transport at a solid-fluidinterface by placing cooler liquid-vapor Ar mixtures adjacent to warmer Fe walls. The equilibration of the system towards a uniform overall temperature is investigated using nonequilibrium molecular dynamics simulations from which the heat flux is also determined explicitly. The Ar–Fe intermolecular interactions induce the migration of fluid atoms into quasicrystallineinterfacial layers adjacent to the walls, creating vacancies at the migration sites. This induces temperature discontinuities between the solidlikeinterfaces and their neighboring fluid molecules. The interfacial temperature difference and thus the heat flux decrease as the system equilibrates over time. The averaged ...


Unsteady Effects On Trailing Edge Cooling, G. Medic, Paul A. Durbin Apr 2005

Unsteady Effects On Trailing Edge Cooling, G. Medic, Paul A. Durbin

Paul A. Durbin

It is shown how natural and forced unsteadiness play a major role in turbine blade trailing edge cooling flows. Reynolds averaged simulations are presented for a surface jet in coflow, resembling the geometry of the pressure side breakout on a turbine blade. Steady computations show very effective cooling; however when natural-or even moreso, forced-unsteadiness is allowed, the adiabatic effectiveness decreases substantially. Streamwise vortices in the mean flow are found to be the cause of the increased heat transfer.


Toward Improved Film Cooling Prediction, G. Medic, Paul A. Durbin Apr 2002

Toward Improved Film Cooling Prediction, G. Medic, Paul A. Durbin

Paul A. Durbin

Computations of flow and heat transfer for a film-cooled high pressure gas turbine rotor blade geometry are presented with an assessment of several turbulence models. Details of flow and temperature field predictions in the vicinity of cooling holes are examined. It is demonstrated that good predictions can be obtained when spurious turbulence energy production by the turbulence model is prevented.


Toward Improved Prediction Of Heat Transfer On Turbine Blades, G. Medic, Paul A. Durbin Apr 2002

Toward Improved Prediction Of Heat Transfer On Turbine Blades, G. Medic, Paul A. Durbin

Paul A. Durbin

Reynolds averaged computations of turbulent flow in a transonic turbine passage are presented to illustrate a manner in which widely used turbulence models sometimes provide poor heat transfer predictions. It is shown that simple, physically and mathematically based constraints can substantially improve those predictions.


Laminar Natural Convection In A Discretely Heated Cavity: I—Assessment Of Three-Dimensional Effects, Theodore J. Heindel, S. Ramadhyani, F. P. Incropera Nov 1995

Laminar Natural Convection In A Discretely Heated Cavity: I—Assessment Of Three-Dimensional Effects, Theodore J. Heindel, S. Ramadhyani, F. P. Incropera

Theodore J. Heindel

Two and three-dimensional calculations have been performed for laminar natural convection induced by a 3 × 3 array of discrete heat sources flush-mounted to one vertical wall of a rectangular cavity whose opposite wall was isothermally cooled. Edge effects predicted by the three-dimensional model yielded local and average Nusselt numbers that exceeded those obtained from the two-dimensional model, as well as average surface temperatures that were smaller than the two-dimensional predictions. For heater aspect ratios Ahtr ≲ 3, average Nusselt numbers increased with decreasing Ahtr . However, for Ahtr ≳ 3, the two and three-dimensional predictions were within 5 percent of each other and ...


Laminar Natural Convection In A Discretely Heated Cavity: Ii—Comparisons Of Experimental And Theoretical Results, Theodore J. Heindel, F. P. Incropera, S. Ramadhyani Nov 1995

Laminar Natural Convection In A Discretely Heated Cavity: Ii—Comparisons Of Experimental And Theoretical Results, Theodore J. Heindel, F. P. Incropera, S. Ramadhyani

Theodore J. Heindel

Three-dimensional numerical predictions and experimental data have been obtained for natural convection from a 3 × 3 array of discrete heat sources flush-mounted on one vertical wall of a rectangular cavity and cooled by the opposing wall. Predictions performed in a companion paper (Heindel et al., 1995a) revealed that three-dimensional edge effects are significant and that, with increasing Rayleigh number, flow and heat transfer become more uniform across each heater face. The three-dimensional predictions are in excellent agreement with the data of this study, whereas a two-dimensional model of the experimental geometry underpredicts average heat transfer by as much as 20 ...


Liquid Immersion Cooling Of A Longitudinal Array Of Discrete Heat Sources In Protruding Substrates: I—Single-Phase Convection, Theodore J. Heindel, F. P. Incropera, S. Ramadhyani Mar 1992

Liquid Immersion Cooling Of A Longitudinal Array Of Discrete Heat Sources In Protruding Substrates: I—Single-Phase Convection, Theodore J. Heindel, F. P. Incropera, S. Ramadhyani

Theodore J. Heindel

Experiments have been performed using water and FC-77 to investigate heat transfer from an in-line 1 x 10 array of discrete heat sources, flush mounted to protruding substrates located on the bottom wall of a horizontal flow channel. The data encompass flow regimes ranging from mixed convection to laminar and turbulent forced convection. Buoyancy-induced secondary flows enhanced heat transfer at downstream heater locations and provided heat transfer coefficients comparable to upstream values. Upstream heating extended enhancement on the downstream heaters to larger Reynolds numbers. Higher Prandtl number fluids also extended heat transfer enhancement to larger Reynolds numbers, while a reduction ...