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Papers by Dr. UGANDHAR PULI

Research paper thumbnail of Analysis of Emissions in Four Stroke VCR Diesel Engine

One of the hazardous problems faced by the world is global warming. The entire world is looking t... more One of the hazardous problems faced by the world is global warming. The entire world is looking to search for the best methods to reduce global warming effect. Global warming is caused due to many reasons. Even though, there are many sources contributing the global warming, automobiles play a vital role for this. The emissions coming out from the internal combustion engine causes global warming. The present work focuses on the emissions from the 4-stroke diesel engine. The data is related to the engine emissions from VCR engine which is taken experimentally. The data of emissions such as(Hc,Nox,so2,co) hydrocarbons, nitrous oxides, sulpherdioxide and carbon monoxide and other emissions of percentage based according to the variable compression ratios. Engine emissions are measured with AVL gas analyzer. The readings of 4-stroke VCR diesel engine are taken at constant speed but varying the compression ratios and loads. The work concentrates on achieving optimized compression ratio of ...

Research paper thumbnail of Effect of Al 2 O 3 -Water Nano fluid on Bubble Size in Subcooled Flow Boiling in a Horizontal Annulus

International Journal of Materials in Engineering Applications, 2013

Research paper thumbnail of Effect of biofuels on the performance and emission characteristics of VCR engines - A review

The high energy demand in the industrial world as well as in the domestic sector and pollution pr... more The high energy demand in the industrial world as well as in the domestic sector and pollution problems caused due to the widespread use of fossil fuels make it increasingly necessary to develop the renewable energy sources with lesser environmental impact than the conventional one. This has inspired curiosity in alternative sources for petroleum based fuels. As an alternative fuels, the vegetable oils and alcohols have received great attention because these are biodegradable and renewable. This paper presents a review on the effect of biofuels on the performance, emission and combustion characteristics of VCR engines. Keywords: IC E ngines, Variable compression ratio engines (VCR) and Biofuels.

Research paper thumbnail of Investigation of Bubble Spacing in Subcooled Flow Boiling of Water in Horizontal Annulus Using High Speed Flow Visualization

Experiments have been carried out in order to study bubble spacing in subcooled flow boiling of w... more Experiments have been carried out in order to study bubble spacing in subcooled flow boiling of water in horizontal annulus at mass fluxes from 400 to 1200 kg/m2-s, heat fluxes from 0.1 to 1 MW/m2 and pressures varying from 1 to 4 bar using high speed visualization methods. Appropriate automated image processing technique was used to analyze the images obtained by high speed visualization to study bubble spacing. The parametric effect of pressure, mass flux and heat flux on bubble spacing has also been brought out. It was found that bubble spacing is significantly affected by pressure, mass flux and heat flux.

Research paper thumbnail of Flow boiling heat transfer performance of zno nanofluids

In recent years, fluids containing suspension of nanometer-sized particles (nanofluids) have been... more In recent years, fluids containing suspension of nanometer-sized particles (nanofluids) have been an active area of research due to their enhanced thermal properties over the base fluids. This makes them very attractive as heat transfer fluids in many applications. Recent studies of pool boiling heat transfer have shown that nanofluids have great potential for enhancing the heat transfer coefficients and critical heat flux. While nanofluid in pool boiling conditions has been studied broadly, data for nanofluid flow boiling which is the situation of interest for nuclear and other engineering applications are very scarce. In this study experiments were performed in subcooled flow boiling of ZnO-water nanofluids in horizontal annulus at flow rate from 0.1 to 0.175 l/s and heat fluxes from 80 to 400 kW/m 2 at 1 bar pressure and constant subcooling of 20°C. Stable aqueous ZnO nanofluids with different low particle concentrations (�0.01 vol. %) were used for determining their heat transfe...

Research paper thumbnail of An image analysis technique for determination of void fraction in subcooled flow boiling of water in horizontal annulus at high pressures

International Journal of Heat and Fluid Flow, 2012

Research paper thumbnail of WITHDRAWN: An Image Analysis Technique for Determination of Void Fraction in Subcooled Flow Boiling of Water in Horizontal Annulus at high pressures

International Journal of Heat and Fluid Flow, 2010

Research paper thumbnail of Parametric effect of pressure on bubble size distribution in subcooled flow boiling of water in a horizontal annulus

Experimental Thermal and Fluid Science, 2012

Experiments were performed in subcooled flow boiling of distilled water in horizontal annulus at ... more Experiments were performed in subcooled flow boiling of distilled water in horizontal annulus at mass fluxes from 400 to 1200 kg/m 2 s, heat fluxes from 0.1 to 1 MW/m 2 and pressures varying from 1 to 4 bar at constant subcooling of 20°C with the intention of studying parametric effect of pressure on bubble size distribution. High speed photography is used to capture bubble images and subsequently processed by National Instruments Labview IMAQ Vision building image processing software. Huge data obtained by automated image processing and analysis algorithms is presented as distribution functions without any spatial and temporal averaging. Bubble size distribution with respect to variation in pressure has been evaluated.

Research paper thumbnail of Investigation of Bubble Behavior in Sub cooled Flow Boiling of Water in Horizontal Annulus Using High Speed Flow Visualization

Experiments have been carried out to study bubble behavior in subcooled flow boiling of water in ... more Experiments have been carried out to study bubble behavior in subcooled flow boiling of water in a horizontal annulus at mass fluxes from 400 to 1200 kg/m 2-s, heat fluxes from 0.1 to 1 MW/m 2 , and pressures varying from 1 to 4 bar using high-speed visualization methods. National Instruments Labview IMAQ Vision Builder automated image-processing software was used to analyze the images obtained by high-speed visualization to obtain bubble size and bubble density. The parametric effects of pressure, mass flux, and heat flux on bubble behavior have also been brought out. Experimental results were validated by comparing with the predicted bubble sizes by using the Zeitoun and Shoukri (1996) correlation and were found to be in good agreement. It was found that bubble behavior is significantly affected by mass flux of working fluid and applied heat flux, whereas pressure of working fluid influences the bubble formation process indirectly.

Research paper thumbnail of Analysis of Emissions in Four Stroke VCR Diesel Engine

One of the hazardous problems faced by the world is global warming. The entire world is looking t... more One of the hazardous problems faced by the world is global warming. The entire world is looking to search for the best methods to reduce global warming effect. Global warming is caused due to many reasons. Even though, there are many sources contributing the global warming, automobiles play a vital role for this. The emissions coming out from the internal combustion engine causes global warming. The present work focuses on the emissions from the 4-stroke diesel engine. The data is related to the engine emissions from VCR engine which is taken experimentally. The data of emissions such as(Hc,Nox,so2,co) hydrocarbons, nitrous oxides, sulpherdioxide and carbon monoxide and other emissions of percentage based according to the variable compression ratios. Engine emissions are measured with AVL gas analyzer. The readings of 4-stroke VCR diesel engine are taken at constant speed but varying the compression ratios and loads. The work concentrates on achieving optimized compression ratio of ...

Research paper thumbnail of Effect of Al 2 O 3 -Water Nano fluid on Bubble Size in Subcooled Flow Boiling in a Horizontal Annulus

International Journal of Materials in Engineering Applications, 2013

Research paper thumbnail of Effect of biofuels on the performance and emission characteristics of VCR engines - A review

The high energy demand in the industrial world as well as in the domestic sector and pollution pr... more The high energy demand in the industrial world as well as in the domestic sector and pollution problems caused due to the widespread use of fossil fuels make it increasingly necessary to develop the renewable energy sources with lesser environmental impact than the conventional one. This has inspired curiosity in alternative sources for petroleum based fuels. As an alternative fuels, the vegetable oils and alcohols have received great attention because these are biodegradable and renewable. This paper presents a review on the effect of biofuels on the performance, emission and combustion characteristics of VCR engines. Keywords: IC E ngines, Variable compression ratio engines (VCR) and Biofuels.

Research paper thumbnail of Investigation of Bubble Spacing in Subcooled Flow Boiling of Water in Horizontal Annulus Using High Speed Flow Visualization

Experiments have been carried out in order to study bubble spacing in subcooled flow boiling of w... more Experiments have been carried out in order to study bubble spacing in subcooled flow boiling of water in horizontal annulus at mass fluxes from 400 to 1200 kg/m2-s, heat fluxes from 0.1 to 1 MW/m2 and pressures varying from 1 to 4 bar using high speed visualization methods. Appropriate automated image processing technique was used to analyze the images obtained by high speed visualization to study bubble spacing. The parametric effect of pressure, mass flux and heat flux on bubble spacing has also been brought out. It was found that bubble spacing is significantly affected by pressure, mass flux and heat flux.

Research paper thumbnail of Flow boiling heat transfer performance of zno nanofluids

In recent years, fluids containing suspension of nanometer-sized particles (nanofluids) have been... more In recent years, fluids containing suspension of nanometer-sized particles (nanofluids) have been an active area of research due to their enhanced thermal properties over the base fluids. This makes them very attractive as heat transfer fluids in many applications. Recent studies of pool boiling heat transfer have shown that nanofluids have great potential for enhancing the heat transfer coefficients and critical heat flux. While nanofluid in pool boiling conditions has been studied broadly, data for nanofluid flow boiling which is the situation of interest for nuclear and other engineering applications are very scarce. In this study experiments were performed in subcooled flow boiling of ZnO-water nanofluids in horizontal annulus at flow rate from 0.1 to 0.175 l/s and heat fluxes from 80 to 400 kW/m 2 at 1 bar pressure and constant subcooling of 20°C. Stable aqueous ZnO nanofluids with different low particle concentrations (�0.01 vol. %) were used for determining their heat transfe...

Research paper thumbnail of An image analysis technique for determination of void fraction in subcooled flow boiling of water in horizontal annulus at high pressures

International Journal of Heat and Fluid Flow, 2012

Research paper thumbnail of WITHDRAWN: An Image Analysis Technique for Determination of Void Fraction in Subcooled Flow Boiling of Water in Horizontal Annulus at high pressures

International Journal of Heat and Fluid Flow, 2010

Research paper thumbnail of Parametric effect of pressure on bubble size distribution in subcooled flow boiling of water in a horizontal annulus

Experimental Thermal and Fluid Science, 2012

Experiments were performed in subcooled flow boiling of distilled water in horizontal annulus at ... more Experiments were performed in subcooled flow boiling of distilled water in horizontal annulus at mass fluxes from 400 to 1200 kg/m 2 s, heat fluxes from 0.1 to 1 MW/m 2 and pressures varying from 1 to 4 bar at constant subcooling of 20°C with the intention of studying parametric effect of pressure on bubble size distribution. High speed photography is used to capture bubble images and subsequently processed by National Instruments Labview IMAQ Vision building image processing software. Huge data obtained by automated image processing and analysis algorithms is presented as distribution functions without any spatial and temporal averaging. Bubble size distribution with respect to variation in pressure has been evaluated.

Research paper thumbnail of Investigation of Bubble Behavior in Sub cooled Flow Boiling of Water in Horizontal Annulus Using High Speed Flow Visualization

Experiments have been carried out to study bubble behavior in subcooled flow boiling of water in ... more Experiments have been carried out to study bubble behavior in subcooled flow boiling of water in a horizontal annulus at mass fluxes from 400 to 1200 kg/m 2-s, heat fluxes from 0.1 to 1 MW/m 2 , and pressures varying from 1 to 4 bar using high-speed visualization methods. National Instruments Labview IMAQ Vision Builder automated image-processing software was used to analyze the images obtained by high-speed visualization to obtain bubble size and bubble density. The parametric effects of pressure, mass flux, and heat flux on bubble behavior have also been brought out. Experimental results were validated by comparing with the predicted bubble sizes by using the Zeitoun and Shoukri (1996) correlation and were found to be in good agreement. It was found that bubble behavior is significantly affected by mass flux of working fluid and applied heat flux, whereas pressure of working fluid influences the bubble formation process indirectly.