The Experts below are selected from a list of 117 Experts worldwide ranked by ideXlab platform
K. Narayan Prabhu - One of the best experts on this subject based on the ideXlab platform.
-
Wetting Kinetics and Cooling Performance of PAG Polymer Quenchants
Materials Science Forum, 2015Co-Authors: U. Vignesh Nayak, K. Narayan PrabhuAbstract:The present research work is aimed at the estimation of Quench Severity Polyalkylene Glycol (PAG) polymer Quenchants having varying concentrations. An Inconel600 probe instrumented with thermocouples was used for this purpose. The thermal history at various locations in the probe was used as an input to the inverse heat conduction model. The inverse analysis yields spatially dependent heat flux transients. The Quench Severity was assessed using the Grossmann technique. The wetting kinematics of Quenching was studied by cooling curve analysis. The Severity of Quenching as measured by the Grossmann’s technique was found to be higher for polymer Quenchants. However, the heat flux transients estimated by the inverse technique and rewetting times measured form the cooling curve analysis suggested comparable and uniform heat transfer with polymer Quenchants compared to water Quenchants.
-
Effect of thermal conductivity and viscosity on cooling performance of liquid Quench media
International Heat Treatment & Surface Engineering, 2013Co-Authors: G Ramesh, K. Narayan PrabhuAbstract:AbstractIn this present work, the effect of the thermophysical properties of Quenchants on its cooling performance was investigated. Water, brine solutions, polymer solutions and mineral oils were chosen to have Quench media with varying thermophysical properties. Cooling curve analyses were carried out by using standard ISO/DIS 9950 Quench probe. Grossmann H Quench Severity of the Quench media was determined from the relation of H and cooling rate. Cooling curve analysis results showed that the change in thermophysical properties of the Quench media had significant effect on the cooling history of the Quench probe. The viscosity of the Quenchant used for immersion Quenching is the most important factor that controls the cooling performance of the Quenchant compared to thermal conductivity of the Quench medium.
-
Effect of Boundary Heat Transfer Coefficient and Probe Section Size on Cooling Curves During Quenching
Materials Performance and Characterization, 2012Co-Authors: G Ramesh, K. Narayan PrabhuAbstract:In the present work the effect of boundary heat transfer coefficient and section size of Quench probe material on cooling curves was investigated by using finite difference heat transfer based SolidCast software. Simulations were carried out at different combinations of heat transfer coefficient and Quench probe diameter and thermal history at the geometric center of the probe was estimated to generate cooling curves. Simulation results show that both boundary heat transfer coefficient and Quench probe diameter had a significant effect on the average cooling rate. A relationship between Grossmann Quench Severity (H), thermal conductivity of material, size of the probe, and average cooling rate was established. By using this model, for a known Quench medium, probe size, and material it is possible to predict the average cooling rate of the probe. On the other-hand, for a given material and required cooling rate, cooling Severity required from the Quench media could be predicted and accordingly an appropriate Quench medium can be selected.
-
Heat Transfer during Quenching and Assessment of Quench Severity—A Review
Journal of Astm International, 2009Co-Authors: K. Narayan Prabhu, Peter FernandesAbstract:In the heat treatment of steel, Quenching is done to prevent ferrite or pearlite formation and allows formation of bainite and martensite. For a particular grade of steel, the effectiveness of Quenching depends on the cooling characteristics of the Quenching medium. The cooling rate is not a constant throughout the Quenching process; instead it varies depending upon the various stages that occur during the Quenching process. Knowledge of heat transfer during various stages of Quenching and kinetics of wetting of the Quench medium is fundamental to the understanding of the relationship between material, Quench medium, microstructure, and properties. In this paper the characteristics of various Quench media, the effect of process parameters on Quenching, mechanisms of thermal transport, methods of assessing Severity of Quenching, and techniques of estimation of heat transfer coefficients are reviewed. An attempt is also made to highlight the importance of wetting kinetics of liquid media on Quenching.
-
NanoQuenchants for Industrial Heat Treatment
Journal of Materials Engineering and Performance, 2008Co-Authors: K. Narayan Prabhu, Peter FernadesAbstract:The present work outlines the possibility of using nanofluids for industrial heat treatment. Development of nanoQuenchants having (i) high Quench Severity for enhancement of heat transfer for thick sections with low Quench sensitivity and (ii) low cooling Severity for thin sections with high Quench sensitivity would be extremely useful to the heat treating community. The temperature dependent heat transfer coefficient and the wettability of the medium are the two important parameters that can be used to characterize a nanoQuenchant to assess its suitability for industrial heat treatment.
Peter Fernandes - One of the best experts on this subject based on the ideXlab platform.
-
experimental investigation of contact angle and Quench Severity of mineral oil and palm oil blends
Journal of materials science & engineering, 2013Co-Authors: Peter Fernandes, Narayan K PrabhuAbstract:Wetting behavior and Quench Severity at the metal/Quenchant interface would be useful to the heat treating community. In the present work, wetting behavior and the heat transfer characteristics of mineral oil and palm oil with their blends was determined. The heat transfer coefficients at the metal/Quench medium interface were estimated of standard 304 stainless steel Quench probes subjected to lateral Quenching. The Quench Severity of vegetable oil is greater than conventional mineral oil with greater wettability indicated by its lower contact angles. Higher values of activation energy indicate a greater temperature dependency of contact angle relaxation. The relaxation of contact angle was sharp during the initial stages, and it became gradual as the system approached equilibrium. Blending of palm oil with mineral oil increases the spreading rate as well as the Quench Severity. This would have immense benefits from the environmental and economical point of view.
-
heat transfer during Quenching and assessment of Quench Severity a review
Journal of Astm International, 2009Co-Authors: Narayan K Prabhu, Peter FernandesAbstract:In the heat treatment of steel, Quenching is done to prevent ferrite or pearlite formation and allows formation of bainite and martensite. For a particular grade of steel, the effectiveness of Quenching depends on the cooling characteristics of the Quenching medium. The cooling rate is not a constant throughout the Quenching process; instead it varies depending upon the various stages that occur during the Quenching process. Knowledge of heat transfer during various stages of Quenching and kinetics of wetting of the Quench medium is fundamental to the understanding of the relationship between material, Quench medium, microstructure, and properties. In this paper the characteristics of various Quench media, the effect of process parameters on Quenching, mechanisms of thermal transport, methods of assessing Severity of Quenching, and techniques of estimation of heat transfer coefficients are reviewed. An attempt is also made to highlight the importance of wetting kinetics of liquid media on Quenching.
-
Heat Transfer during Quenching and Assessment of Quench Severity—A Review
Journal of Astm International, 2009Co-Authors: K. Narayan Prabhu, Peter FernandesAbstract:In the heat treatment of steel, Quenching is done to prevent ferrite or pearlite formation and allows formation of bainite and martensite. For a particular grade of steel, the effectiveness of Quenching depends on the cooling characteristics of the Quenching medium. The cooling rate is not a constant throughout the Quenching process; instead it varies depending upon the various stages that occur during the Quenching process. Knowledge of heat transfer during various stages of Quenching and kinetics of wetting of the Quench medium is fundamental to the understanding of the relationship between material, Quench medium, microstructure, and properties. In this paper the characteristics of various Quench media, the effect of process parameters on Quenching, mechanisms of thermal transport, methods of assessing Severity of Quenching, and techniques of estimation of heat transfer coefficients are reviewed. An attempt is also made to highlight the importance of wetting kinetics of liquid media on Quenching.
-
Comparative study of heat transfer and wetting behaviour of conventional and bioQuenchants for industrial heat treatment
International Journal of Heat and Mass Transfer, 2008Co-Authors: Peter Fernandes, K. Narayan PrabhuAbstract:An investigation was conducted to study the suitability of vegetable oils as bioQuenchants for industrial heat treatment. The study involved the assessment of the Severity of Quenching and wetting behaviour of conventional and vegetable oil Quench media. Quench severities of sunflower, coconut and palm oils were found to be greater than mineral oil. The Quench Severity of aqueous media is greater than oil media although their wettability is poor as indicated by their higher contact angles. A dimensionless contact angle parameter defined in this work is found to be a better parameter to compare the wetting behaviour with heat transfer.
-
Determination of Wetting Behavior, Spread Activation Energy, and Quench Severity of BioQuenchants
Metallurgical and Materials Transactions B, 2007Co-Authors: K. Narayan Prabhu, Peter FernandesAbstract:An investigation was conducted to study the suitability of vegetable oils such as sunflower, coconut, groundnut, castor, cashewnut shell (CNS), and palm oils as Quench media (bioQuenchants) for industrial heat treatment by assessing their wetting behavior and Severity of Quenching. The relaxation of contact angle was sharp during the initial stages, and it became gradual as the system approached equilibrium. The equilibrium contact angle decreased with increase in the temperature of the substrate and decrease in the viscosity of the Quench medium. A comparison of the relaxation of the contact angle at various temperatures indicated the significant difference in spreading of oils having varying viscosity. The spread activation energy was determined using the Arrhenius type of equation. Oils with higher viscosity resulted in lower cooling rates. The Quench Severity of various oil media was determined by estimating heat-transfer coefficients using the lumped capacitance method. Activation energy for spreading determined using the wetting behavior of oils at various temperatures was in good agreement with the Severity of Quenching assessed by cooling curve analysis. A high Quench Severity is associated with oils having low spread activation energy.
Narayan K Prabhu - One of the best experts on this subject based on the ideXlab platform.
-
Cooling Performance of Select Mineral Oil and Polymer Quenchants
Materials Performance and Characterization, 2014Co-Authors: Vivek Tiwary, Narayan K PrabhuAbstract:In the present investigation, Quench Severity was determined for industrial oil Quenchants and varying concentrations of PAG polymer. Viscosity, thermal conductivity, density, flash point, and fire point were measured for all Quenchants. Cooling curve parameters were determined based on cooling curve analysis ISO/DIS 9950 technique. An Inconel 600 probe was used for this purpose. Severity of Quenching was determined based on the Grossmann technique. Viscosity and thermal conductivity had a significant effect on Quench Severity. Heat flux and HTC at the metal/Quenchant interface were computed by both lumped capacitance and Inverse modeling techniques. The effect of ultrasonic and Tensi agitation on cooling curve parameters was assessed. Polymer Quenchants of lower concentrations showed marginally higher heat transfer rates compared to water particularly during unagitated condition.
-
experimental investigation of contact angle and Quench Severity of mineral oil and palm oil blends
Journal of materials science & engineering, 2013Co-Authors: Peter Fernandes, Narayan K PrabhuAbstract:Wetting behavior and Quench Severity at the metal/Quenchant interface would be useful to the heat treating community. In the present work, wetting behavior and the heat transfer characteristics of mineral oil and palm oil with their blends was determined. The heat transfer coefficients at the metal/Quench medium interface were estimated of standard 304 stainless steel Quench probes subjected to lateral Quenching. The Quench Severity of vegetable oil is greater than conventional mineral oil with greater wettability indicated by its lower contact angles. Higher values of activation energy indicate a greater temperature dependency of contact angle relaxation. The relaxation of contact angle was sharp during the initial stages, and it became gradual as the system approached equilibrium. Blending of palm oil with mineral oil increases the spreading rate as well as the Quench Severity. This would have immense benefits from the environmental and economical point of view.
-
effect of addition of aluminum nanoparticles on cooling performance and Quench Severity of water during immersion Quenching
Journal of Astm International, 2012Co-Authors: G Ramesh, Narayan K PrabhuAbstract:In the present work, the effect of the addition of aluminum nanoparticles in concentrations varying from 0.001 to 0.5 vol. % on the cooling performance and Quench Severity of water during immersion Quenching is investigated. The results of cooling curve analyses show that an increase in nanoparticle concentration increased the cooling rates at critical temperatures up to 0.05 vol. % and decreased them thereafter. The transition from the vapor blanket stage to the nucleate boiling stage was also altered by Quenching in nanofluids. A finite difference heat transfer program was employed to generate cooling curves at different values of heat transfer coefficient from thermo-physical properties of the Quench probe material. A Grossmann H Quench Severity versus cooling rate curve was established, and from this curve, the H factors of prepared nanofluids were estimated. An increase in nanoparticle concentration up to 0.05 vol. % resulted in an increase of the H value of water from 63 m−1 to 93 m−1, and any further increase in the concentration of nanoparticles resulted in a decrease in H. The results suggest both the enhancement and the deterioration of the cooling performance of water by the addition of aluminum nanoparticles.
-
heat transfer during Quenching and assessment of Quench Severity a review
Journal of Astm International, 2009Co-Authors: Narayan K Prabhu, Peter FernandesAbstract:In the heat treatment of steel, Quenching is done to prevent ferrite or pearlite formation and allows formation of bainite and martensite. For a particular grade of steel, the effectiveness of Quenching depends on the cooling characteristics of the Quenching medium. The cooling rate is not a constant throughout the Quenching process; instead it varies depending upon the various stages that occur during the Quenching process. Knowledge of heat transfer during various stages of Quenching and kinetics of wetting of the Quench medium is fundamental to the understanding of the relationship between material, Quench medium, microstructure, and properties. In this paper the characteristics of various Quench media, the effect of process parameters on Quenching, mechanisms of thermal transport, methods of assessing Severity of Quenching, and techniques of estimation of heat transfer coefficients are reviewed. An attempt is also made to highlight the importance of wetting kinetics of liquid media on Quenching.
Peter Fernades - One of the best experts on this subject based on the ideXlab platform.
-
NanoQuenchants for Industrial Heat Treatment
Journal of Materials Engineering and Performance, 2008Co-Authors: K. Narayan Prabhu, Peter FernadesAbstract:The present work outlines the possibility of using nanofluids for industrial heat treatment. Development of nanoQuenchants having (i) high Quench Severity for enhancement of heat transfer for thick sections with low Quench sensitivity and (ii) low cooling Severity for thin sections with high Quench sensitivity would be extremely useful to the heat treating community. The temperature dependent heat transfer coefficient and the wettability of the medium are the two important parameters that can be used to characterize a nanoQuenchant to assess its suitability for industrial heat treatment.
Amlan Prasad - One of the best experts on this subject based on the ideXlab platform.
-
Metal/Quenchant interfacial heat flux transients during Quenching in conventional Quench media and vegetable oils
Journal of Materials Engineering and Performance, 2003Co-Authors: K. Narayan Prabhu, Amlan PrasadAbstract:The determination of Quench Severity and the quantification of the boundary conditions at the metal/Quenchant interface would be of considerable utility to the heat treating community. In the present work, an attempt has been made to determine the Quench Severity of various Quench media, including three vegetable oils, by the Grossmann Hardenability Factor method and by estimation of heat flux transients by inverse modeling of heat conduction in 304 stainless steel Quench probes. The heat flux transient technique was found to be more accurate than the Grossmann technique in assessing the Severity of Quenching. This finding was supported by the hardness data and microstructure obtained with the Quenched steel specimens. New heat flux parameters are proposed to assess the Severity of Quenching. The boundary heat flux transients during end Quenching of AISI 1040 steel specimens were also estimated. The estimated heat flux transients could be used for modeling of heat transfer during Quenching. An attempt has also been made in the present work to assess the feasibility of three vegetable oils, namely coconut, sunflower, and groundnut oils, as Quenching media. Further investigation is required in this direction to explore the suitability of these oils for industrial heat treating applications. This application would have immense environmental and economical benefits.
