The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
I. Mudawar - One of the best experts on this subject based on the ideXlab platform.
-
Film and transition boiling correlations for quenching of Hot Surfaces with water sprays
Journal of Heat Treating, 1992Co-Authors: W. P. Klinzing, J. C. Rozzi, I. MudawarAbstract:Using a miniature gold plated copper disk as target, quenching experiments were performed with water sprays to correlate heat flux q′’ to surface-to-fluid temperature difference A T , and the local values for the spray hydrodynamic parameters of volumetric flux Q′’ , mean drop velocity U _ m and Sauter mean drop diameter d _ 32 over a wide range of operating conditions ( Q′’ = 0.58 x 10^−3−9.96 x 10^−3 m^3 sec^−1/m^2, U _ m = 10.1-29.9 m/sec, d _ 32 = 0.137-1.350 mm), and surface temperatures up to 520° C. Drop diameter was found to have a weak effect on heat transfer in film boiling for all the conditions tested. Two distinct spray cooling regimes were identified, allowing the classification of sprays with respect to volumetric flux, low flux sprays for Q″< 3.5 x 10^−3 m^3 sec^−1/m^2, and high flux sprays for Q″ > 3.5 x 10^−3 m^3 sec^−1/m^2. While Q″ had a significant influence on film boiling in both regimes, drop velocity was important only for the high flux sprays. A spray quenching test bed was also constructed to simulate, under controlled laboratory conditions, spray quenching of alloys in an industrial environment. The test bed was used to generate temperature-time records for a rectangular aluminum plate during spray quenching. Using the software package ANSYS, the measured temperature response was successfully simulated by utilizing the newly developed boiling correlations in defining boundary conditions for the quenched surface after accounting for spatial variations in the hydrodynamic parameters within the spray field. The effectiveness of this numerical technique for the tested configuration is proof that it may be possible to predict the temperature-time history for quenched parts with complicated shapes provided the spatial distributions of the hydrodynamic parameters are well mapped or predetermined.
-
film and transition boiling correlations for quenching of Hot Surfaces with water sprays
Journal of Heat Treating, 1992Co-Authors: W. P. Klinzing, J. C. Rozzi, I. MudawarAbstract:Using a miniature gold plated copper disk as target, quenching experiments were performed with water sprays to correlate heat fluxq′’ to surface-to-fluid temperature difference AT, and the local values for the spray hydrodynamic parameters of volumetric fluxQ′’, mean drop velocityUm and Sauter mean drop diameterd32 over a wide range of operating conditions (Q′’ = 0.58 x 10−3−9.96 x 10−3 m3 sec−1/m2,Um = 10.1-29.9 m/sec,d32 = 0.137-1.350 mm), and surface temperatures up to 520° C. Drop diameter was found to have a weak effect on heat transfer in film boiling for all the conditions tested. Two distinct spray cooling regimes were identified, allowing the classification of sprays with respect to volumetric flux, low flux sprays forQ″ 3.5 x 10−3 m3 sec−1/m2. WhileQ″ had a significant influence on film boiling in both regimes, drop velocity was important only for the high flux sprays. A spray quenching test bed was also constructed to simulate, under controlled laboratory conditions, spray quenching of alloys in an industrial environment. The test bed was used to generate temperature-time records for a rectangular aluminum plate during spray quenching. Using the software package ANSYS, the measured temperature response was successfully simulated by utilizing the newly developed boiling correlations in defining boundary conditions for the quenched surface after accounting for spatial variations in the hydrodynamic parameters within the spray field. The effectiveness of this numerical technique for the tested configuration is proof that it may be possible to predict the temperature-time history for quenched parts with complicated shapes provided the spatial distributions of the hydrodynamic parameters are well mapped or predetermined.
W. P. Klinzing - One of the best experts on this subject based on the ideXlab platform.
-
Film and transition boiling correlations for quenching of Hot Surfaces with water sprays
Journal of Heat Treating, 1992Co-Authors: W. P. Klinzing, J. C. Rozzi, I. MudawarAbstract:Using a miniature gold plated copper disk as target, quenching experiments were performed with water sprays to correlate heat flux q′’ to surface-to-fluid temperature difference A T , and the local values for the spray hydrodynamic parameters of volumetric flux Q′’ , mean drop velocity U _ m and Sauter mean drop diameter d _ 32 over a wide range of operating conditions ( Q′’ = 0.58 x 10^−3−9.96 x 10^−3 m^3 sec^−1/m^2, U _ m = 10.1-29.9 m/sec, d _ 32 = 0.137-1.350 mm), and surface temperatures up to 520° C. Drop diameter was found to have a weak effect on heat transfer in film boiling for all the conditions tested. Two distinct spray cooling regimes were identified, allowing the classification of sprays with respect to volumetric flux, low flux sprays for Q″< 3.5 x 10^−3 m^3 sec^−1/m^2, and high flux sprays for Q″ > 3.5 x 10^−3 m^3 sec^−1/m^2. While Q″ had a significant influence on film boiling in both regimes, drop velocity was important only for the high flux sprays. A spray quenching test bed was also constructed to simulate, under controlled laboratory conditions, spray quenching of alloys in an industrial environment. The test bed was used to generate temperature-time records for a rectangular aluminum plate during spray quenching. Using the software package ANSYS, the measured temperature response was successfully simulated by utilizing the newly developed boiling correlations in defining boundary conditions for the quenched surface after accounting for spatial variations in the hydrodynamic parameters within the spray field. The effectiveness of this numerical technique for the tested configuration is proof that it may be possible to predict the temperature-time history for quenched parts with complicated shapes provided the spatial distributions of the hydrodynamic parameters are well mapped or predetermined.
-
film and transition boiling correlations for quenching of Hot Surfaces with water sprays
Journal of Heat Treating, 1992Co-Authors: W. P. Klinzing, J. C. Rozzi, I. MudawarAbstract:Using a miniature gold plated copper disk as target, quenching experiments were performed with water sprays to correlate heat fluxq′’ to surface-to-fluid temperature difference AT, and the local values for the spray hydrodynamic parameters of volumetric fluxQ′’, mean drop velocityUm and Sauter mean drop diameterd32 over a wide range of operating conditions (Q′’ = 0.58 x 10−3−9.96 x 10−3 m3 sec−1/m2,Um = 10.1-29.9 m/sec,d32 = 0.137-1.350 mm), and surface temperatures up to 520° C. Drop diameter was found to have a weak effect on heat transfer in film boiling for all the conditions tested. Two distinct spray cooling regimes were identified, allowing the classification of sprays with respect to volumetric flux, low flux sprays forQ″ 3.5 x 10−3 m3 sec−1/m2. WhileQ″ had a significant influence on film boiling in both regimes, drop velocity was important only for the high flux sprays. A spray quenching test bed was also constructed to simulate, under controlled laboratory conditions, spray quenching of alloys in an industrial environment. The test bed was used to generate temperature-time records for a rectangular aluminum plate during spray quenching. Using the software package ANSYS, the measured temperature response was successfully simulated by utilizing the newly developed boiling correlations in defining boundary conditions for the quenched surface after accounting for spatial variations in the hydrodynamic parameters within the spray field. The effectiveness of this numerical technique for the tested configuration is proof that it may be possible to predict the temperature-time history for quenched parts with complicated shapes provided the spatial distributions of the hydrodynamic parameters are well mapped or predetermined.
David F Fletcher - One of the best experts on this subject based on the ideXlab platform.
-
a hydrodynamic and thermodynamic simulation of droplet impacts on Hot Surfaces part i theoretical model
International Journal of Heat and Mass Transfer, 2001Co-Authors: Dalton J E Harvie, David F FletcherAbstract:Abstract A model is presented to simulate the behaviour of an axisymmetric volatile liquid droplet impacting on a Hot solid surface in the film boiling region. A volume of fluid (VOF) algorithm is used to model the gross deformation of the droplet. This algorithm is coupled to a separate one-dimensional algorithm used to model fluid flow within the viscous vapour layer existing between the droplet and solid surface. Heat transfer within the solid, liquid and vapour phases is solved, and a kinetic theory treatment is used to calculate conditions existing at the non-equilibrium interfaces of the vapour layer.
-
a hydrodynamic and thermodynamic simulation of droplet impacts on Hot Surfaces part ii validation and applications
International Journal of Heat and Mass Transfer, 2001Co-Authors: Dalton J E Harvie, David F FletcherAbstract:Abstract A model was previously presented to simulate the behaviour of an axisymmetric droplet impacting on a Hot solid surface in the film boiling region (D.J.E. Harvie, D.F. Fletcher, International Journal of Heat and Mass Transfer 44 (2001) 2633–2642). In this paper comparisons against experimental water and n-heptane droplet impacts are made which validate the hydrodynamic and thermodynamic predictive capabilities of the model. Specifically, it is shown that the hydrodynamic behaviour of impacting droplets is predicted accurately below a Weber number of approximately 30, while above this level, at least the initial hydrodynamical aspects of an impact can be predicted. The model is found to reproduce the thermodynamic behaviour of actual droplet impacts when no contact between the solid and liquid phases occurs.
J. C. Rozzi - One of the best experts on this subject based on the ideXlab platform.
-
Film and transition boiling correlations for quenching of Hot Surfaces with water sprays
Journal of Heat Treating, 1992Co-Authors: W. P. Klinzing, J. C. Rozzi, I. MudawarAbstract:Using a miniature gold plated copper disk as target, quenching experiments were performed with water sprays to correlate heat flux q′’ to surface-to-fluid temperature difference A T , and the local values for the spray hydrodynamic parameters of volumetric flux Q′’ , mean drop velocity U _ m and Sauter mean drop diameter d _ 32 over a wide range of operating conditions ( Q′’ = 0.58 x 10^−3−9.96 x 10^−3 m^3 sec^−1/m^2, U _ m = 10.1-29.9 m/sec, d _ 32 = 0.137-1.350 mm), and surface temperatures up to 520° C. Drop diameter was found to have a weak effect on heat transfer in film boiling for all the conditions tested. Two distinct spray cooling regimes were identified, allowing the classification of sprays with respect to volumetric flux, low flux sprays for Q″< 3.5 x 10^−3 m^3 sec^−1/m^2, and high flux sprays for Q″ > 3.5 x 10^−3 m^3 sec^−1/m^2. While Q″ had a significant influence on film boiling in both regimes, drop velocity was important only for the high flux sprays. A spray quenching test bed was also constructed to simulate, under controlled laboratory conditions, spray quenching of alloys in an industrial environment. The test bed was used to generate temperature-time records for a rectangular aluminum plate during spray quenching. Using the software package ANSYS, the measured temperature response was successfully simulated by utilizing the newly developed boiling correlations in defining boundary conditions for the quenched surface after accounting for spatial variations in the hydrodynamic parameters within the spray field. The effectiveness of this numerical technique for the tested configuration is proof that it may be possible to predict the temperature-time history for quenched parts with complicated shapes provided the spatial distributions of the hydrodynamic parameters are well mapped or predetermined.
-
film and transition boiling correlations for quenching of Hot Surfaces with water sprays
Journal of Heat Treating, 1992Co-Authors: W. P. Klinzing, J. C. Rozzi, I. MudawarAbstract:Using a miniature gold plated copper disk as target, quenching experiments were performed with water sprays to correlate heat fluxq′’ to surface-to-fluid temperature difference AT, and the local values for the spray hydrodynamic parameters of volumetric fluxQ′’, mean drop velocityUm and Sauter mean drop diameterd32 over a wide range of operating conditions (Q′’ = 0.58 x 10−3−9.96 x 10−3 m3 sec−1/m2,Um = 10.1-29.9 m/sec,d32 = 0.137-1.350 mm), and surface temperatures up to 520° C. Drop diameter was found to have a weak effect on heat transfer in film boiling for all the conditions tested. Two distinct spray cooling regimes were identified, allowing the classification of sprays with respect to volumetric flux, low flux sprays forQ″ 3.5 x 10−3 m3 sec−1/m2. WhileQ″ had a significant influence on film boiling in both regimes, drop velocity was important only for the high flux sprays. A spray quenching test bed was also constructed to simulate, under controlled laboratory conditions, spray quenching of alloys in an industrial environment. The test bed was used to generate temperature-time records for a rectangular aluminum plate during spray quenching. Using the software package ANSYS, the measured temperature response was successfully simulated by utilizing the newly developed boiling correlations in defining boundary conditions for the quenched surface after accounting for spatial variations in the hydrodynamic parameters within the spray field. The effectiveness of this numerical technique for the tested configuration is proof that it may be possible to predict the temperature-time history for quenched parts with complicated shapes provided the spatial distributions of the hydrodynamic parameters are well mapped or predetermined.
Yuichi Mitsutake - One of the best experts on this subject based on the ideXlab platform.
-
homogeneous nucleation boiling during jet impingement quench of Hot Surfaces above thermodynamic limiting temperature
International Journal of Heat and Mass Transfer, 2011Co-Authors: Mohammad Nasim Hasan, Masanori Monde, Yuichi MitsutakeAbstract:Abstract What happens in the early stages of jet impingement quenching, when the surface temperature remains well above the thermodynamic limiting temperature for stable solid–liquid contact, is not clearly understood yet. The footage of the boiling and flow phenomena of this period of quenching reveals that the jet impacts on the surface due to hydrodynamic force and immediately splashes away violently, because of explosive boiling or boiling explosion that leaves the surface dry again. It is speculated that, a repetition of wetting and drying of the surface continues until the surface is cooled enough down to allow stable solid–liquid contact. However, neither high speed visual observation nor temperature measurement can help us to find out any concrete and quantitative explanation of the above mentioned wetting and drying phenomena of the surface as it takes place within a very short time. In the present study, we focused on the event of explosive boiling due to homogeneous nucleation that occurs when a liquid jet comes in contact with a very Hot surface during jet impingement quenching. Assuming the liquid jet as 1-D semi-infinite solid during its brief contact with the solid, the authors proposed a model based on the concept of 1-D semi-infinite heat conduction and that of molecular theory of homogeneous nucleation boiling. In this model, a characteristic liquid cluster at the boundary is considered and the corresponding energy balance is obtained by accounting two parallel competing processes that take place inside the cluster, namely, transient external heat deposition and internal heat consumption due to bubble nucleation and associated growth. Results obtained are presented in terms of the liquid temperature escalation within the cluster, the limit of maximum attainable liquid temperature and the time necessary to reach the temperature limit at the boiling explosion. From the present model, the temperature at which homogeneous nucleate boiling takes place during quenching of carbon steel with water (20 °C) at atmospheric pressure can be obtained to be higher than 335 °C which might be regarded as the lower limit of surface temperature for homogeneous nucleate boiling. This lower limit of surface temperature for homogeneous nucleate boiling depends on the ratio of thermo-physical properties of the solid and the liquid, namely, β = ( ρ c λ ) s / ( ρ c λ ) l . As the precontact temperatures of the Hot surface increases above the lower limit, the interface temperature between the solid and the liquid increases and the time at which homogeneous nucleation boiling appears is greatly shortened.
-
jet impingement quenching phenomena for Hot Surfaces well above the limiting temperature for solid liquid contact
International Journal of Heat and Mass Transfer, 2008Co-Authors: M A Islam, Masanori Monde, Peter Woodfield, Yuichi MitsutakeAbstract:Abstract Experiments were conducted to understand the phenomena that happen just after a subcooled free-surface circular water jet impinges on a high temperature surface. A 2 mm-water-jet of 5–80 K subcooling and 3–15 m/s velocity was impinged on the flat surface of a cylindrical steel/brass block that was preheated to 500–600 °C. The transient temperature data were recorded and used to predict the surface temperature by an inverse heat conduction technique. A high-speed video camera was also employed to capture the flow condition. It is found that for a certain period of time the surface temperature remains well above the thermodynamic limiting temperature that allows stable solid–liquid contact. What happens during this period and what makes the surface temperature drop to the limiting temperature are important questions whose possible answers are given in this article. The cooling curves at the center of the impinging surface for different experimental conditions are also explained in relation with the limiting temperature and three characteristic regions having different types of flow patterns are identified.