Ratnakar Kulkarni | Universiti Malaysia Pahang (UMP) (original) (raw)

Papers by Ratnakar Kulkarni

Research paper thumbnail of Investigations on Thermal Conductivity, Heat Transfer Coefficient and Viscosity of Graphite Nanoparticle Dispersed Nanofluid

Journal of Nanofluids

The thermal conductivity (k), heat transfer coefficient (HTC) and viscosity of the ethylene glyco... more The thermal conductivity (k), heat transfer coefficient (HTC) and viscosity of the ethylene glycol/water dispersed with graphite nanoparticles was studied under heating and cooling conditions for temperatures ranging from 0 C to 75 C using tubular heat exchanger system built in house. Flow rate was varied from 5 l/h to 25 l/h giving Reynolds number (Re) ranging from 50 to 750. The HTC increased with the increase of Re as well as temperature. The thermal conductivity of the nanofluid was determined at constant low Re (200) for all concentrations and temperatures used in the experiment. The concentration dependence of thermal conductivity was found to be much different than that predicted by models suggested in literature. The viscosity was measured for different concentrations of nanoparticles (0 to 0.8%) as well as temperatures 275 K to 340 K. The temperature dependence of viscosity was found to follow Arrhenius type equation = o exp E/k b T) with very little change in the activation energy from that of the base fluid. On the other hand the pre-exponential constant increased six folds with the increase in nanoparticle concentration. An empirical relation derived from Brownian motion was found between the product of viscosity and thermal conductivity (= k r • r) with respect to concentration of the nanoparticles which was found to be true for whole range of temperature and compositions studied.

Research paper thumbnail of Natural convection in enclosures with localised heating and cooling

... I take this opportunity to express my thanks with a deep sense of gratitude to my supervisor ... more ... I take this opportunity to express my thanks with a deep sense of gratitude to my supervisor Dr. Paul Cooper,- Associate Professor in the Mechanical Engineering ... Prafulla Kulkarni of Prabodh Udyog, Mr. Shrikant Gadre of Graphic Arts, Mr. Avinash ... D universal constant g/5 3 ...

Research paper thumbnail of Temperature distribution and fluid flow in an enclosure with localised heating and cooling

International Communications in Heat and Mass Transfer, 1995

Preliminary experimental results are reported for a temperature distribution inside a water fille... more Preliminary experimental results are reported for a temperature distribution inside a water filled cubicle enclosure. The enclosure is subjected to a localised heating and cooling of the same wall where a heater plate is located below the cooling window and results in a colliding boundary layer situation. The three dimensional temperature distribution and velocity distribution were measured for various values

Research paper thumbnail of Temperature distribution and fluid flow in an enclosure with localised heating and cooling

International Communications in Heat and Mass Transfer, 1995

Preliminary experimental results are reported for a temperature distribution inside a water fille... more Preliminary experimental results are reported for a temperature distribution inside a water filled cubicle enclosure. The enclosure is subjected to a localised heating and cooling of the same wall where a heater plate is located below the cooling window and results in a colliding boundary layer situation. The three dimensional temperature distribution and velocity distribution were measured for various values

Research paper thumbnail of Heat Transfer Enhancement in a Diffuser using Vortex Generators Placed on the Side Wall

The experimental investigation of heat transfer enhancement and flow analysis in a diffuser using... more The experimental investigation of heat transfer enhancement and flow analysis in a diffuser using vortex generators is carried out. Two diffuser angles are looked into. One and two vortex pairs are considered. The velocity profile at the diffuser inlet is uniform and the flow is a developing one. The vortex generators are placed on the side vertical side wall, near the diffuser inlet. It is observed that the heat transfer enhancement is more with the two pair case. The Reynolds number is in the range 2.5-3.6 5 10  . The maximum enhancement is 62% at constant Reynolds Number and 40% at constant dissipation. The diffuser efficiency is lower for the rough cases, with the two pair case yielding a lower value. The enhancement increases with the angle of attack of the vortex generator.

Research paper thumbnail of EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER PROPERTIES AND VISCOSITY OF CNT BASED NANOFLUID IN LOW TEMPERATURE CONDITIONS

Solid metallic and non-metallic materials such as copper, silver, iron, alumina, copper oxide, Si... more Solid metallic and non-metallic materials such as copper, silver, iron, alumina, copper oxide, Silicon carbide and carbon nanotubes have much higher thermal conductivities than fluids. Thermal conductivity of conventional heat transfer fluids can be improved by adding solid nanoparticles to fluids. The heat transfer enhancement of many industrial coolants by adding solid nanoparticles to liquids has attracted much attention in last few years. This work focuses on the satisfactory enhancement in heat transfer of industrial coolant by adding CNT nanoparticles (Sigma-Aldrich USA Product No. 636398). Many reports are available on studies of nanofluid at high temperature but practically none at lower temperature (below room temperature). In addition this work takes into account the change in flow properties of nanofluid due to temperature variation. Theoretical and numerical models have been proposed to predict the thermal conductivity and viscosity of nanofluid in the literature. The nanofluid heat transfer in laminar flow conditions have been explained in this study.

Research paper thumbnail of Investigations on Thermal Conductivity, Heat Transfer Coefficient and Viscosity of Graphite Nanoparticle Dispersed Nanofluid

Journal of Nanofluids

The thermal conductivity (k), heat transfer coefficient (HTC) and viscosity of the ethylene glyco... more The thermal conductivity (k), heat transfer coefficient (HTC) and viscosity of the ethylene glycol/water dispersed with graphite nanoparticles was studied under heating and cooling conditions for temperatures ranging from 0 C to 75 C using tubular heat exchanger system built in house. Flow rate was varied from 5 l/h to 25 l/h giving Reynolds number (Re) ranging from 50 to 750. The HTC increased with the increase of Re as well as temperature. The thermal conductivity of the nanofluid was determined at constant low Re (200) for all concentrations and temperatures used in the experiment. The concentration dependence of thermal conductivity was found to be much different than that predicted by models suggested in literature. The viscosity was measured for different concentrations of nanoparticles (0 to 0.8%) as well as temperatures 275 K to 340 K. The temperature dependence of viscosity was found to follow Arrhenius type equation = o exp E/k b T) with very little change in the activation energy from that of the base fluid. On the other hand the pre-exponential constant increased six folds with the increase in nanoparticle concentration. An empirical relation derived from Brownian motion was found between the product of viscosity and thermal conductivity (= k r • r) with respect to concentration of the nanoparticles which was found to be true for whole range of temperature and compositions studied.

Research paper thumbnail of Natural convection in enclosures with localised heating and cooling

... I take this opportunity to express my thanks with a deep sense of gratitude to my supervisor ... more ... I take this opportunity to express my thanks with a deep sense of gratitude to my supervisor Dr. Paul Cooper,- Associate Professor in the Mechanical Engineering ... Prafulla Kulkarni of Prabodh Udyog, Mr. Shrikant Gadre of Graphic Arts, Mr. Avinash ... D universal constant g/5 3 ...

Research paper thumbnail of Temperature distribution and fluid flow in an enclosure with localised heating and cooling

International Communications in Heat and Mass Transfer, 1995

Preliminary experimental results are reported for a temperature distribution inside a water fille... more Preliminary experimental results are reported for a temperature distribution inside a water filled cubicle enclosure. The enclosure is subjected to a localised heating and cooling of the same wall where a heater plate is located below the cooling window and results in a colliding boundary layer situation. The three dimensional temperature distribution and velocity distribution were measured for various values

Research paper thumbnail of Temperature distribution and fluid flow in an enclosure with localised heating and cooling

International Communications in Heat and Mass Transfer, 1995

Preliminary experimental results are reported for a temperature distribution inside a water fille... more Preliminary experimental results are reported for a temperature distribution inside a water filled cubicle enclosure. The enclosure is subjected to a localised heating and cooling of the same wall where a heater plate is located below the cooling window and results in a colliding boundary layer situation. The three dimensional temperature distribution and velocity distribution were measured for various values

Research paper thumbnail of Heat Transfer Enhancement in a Diffuser using Vortex Generators Placed on the Side Wall

The experimental investigation of heat transfer enhancement and flow analysis in a diffuser using... more The experimental investigation of heat transfer enhancement and flow analysis in a diffuser using vortex generators is carried out. Two diffuser angles are looked into. One and two vortex pairs are considered. The velocity profile at the diffuser inlet is uniform and the flow is a developing one. The vortex generators are placed on the side vertical side wall, near the diffuser inlet. It is observed that the heat transfer enhancement is more with the two pair case. The Reynolds number is in the range 2.5-3.6 5 10  . The maximum enhancement is 62% at constant Reynolds Number and 40% at constant dissipation. The diffuser efficiency is lower for the rough cases, with the two pair case yielding a lower value. The enhancement increases with the angle of attack of the vortex generator.

Research paper thumbnail of EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER PROPERTIES AND VISCOSITY OF CNT BASED NANOFLUID IN LOW TEMPERATURE CONDITIONS

Solid metallic and non-metallic materials such as copper, silver, iron, alumina, copper oxide, Si... more Solid metallic and non-metallic materials such as copper, silver, iron, alumina, copper oxide, Silicon carbide and carbon nanotubes have much higher thermal conductivities than fluids. Thermal conductivity of conventional heat transfer fluids can be improved by adding solid nanoparticles to fluids. The heat transfer enhancement of many industrial coolants by adding solid nanoparticles to liquids has attracted much attention in last few years. This work focuses on the satisfactory enhancement in heat transfer of industrial coolant by adding CNT nanoparticles (Sigma-Aldrich USA Product No. 636398). Many reports are available on studies of nanofluid at high temperature but practically none at lower temperature (below room temperature). In addition this work takes into account the change in flow properties of nanofluid due to temperature variation. Theoretical and numerical models have been proposed to predict the thermal conductivity and viscosity of nanofluid in the literature. The nanofluid heat transfer in laminar flow conditions have been explained in this study.