scholarly journals Tomography-Based Heat and Mass Transfer Characterization of Reticulate Porous Ceramics for High-Temperature Processing

2009 ◽  
Author(s):  
Sophia Haussener ◽  
Patrick Coray ◽  
Wojciech Lipin´ski ◽  
Peter Wyss ◽  
Aldo Steinfeld
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Diffusion Tensor ◽  
Porous Ceramics ◽  
Interfacial Heat Transfer Coefficient ◽  
Flow Characterization ◽  
Scattering Phase Function

Reticulate porous ceramics employed in high-temperature processes are characterized for heat and mass transfer. The exact 3D digital geometry of their complex porous structure is obtained by computer tomography and used in direct pore-level simulations to numerically calculate their effective transport properties. Two-point correlation functions and mathematical morphology operations are applied for the geometrical characterization that includes the determination of porosity, specific surface area, representative elementary volume edge size, and mean pore size. Finite volume techniques are applied for conductive/convective heat transfer and flow characterization that includes the determination of the thermal conductivity, interfacial heat transfer coefficient, permeability, Dupuit-Forchheimer coefficient, residence time, tortuosity, and diffusion tensor. Collision-based Monte Carlo method is applied for the radiative heat transfer characterization that includes the determination of the extinction coefficient and scattering phase function.

scholarly journals Tomography-Based Heat and Mass Transfer Characterization of Reticulate Porous Ceramics for High-Temperature Processing

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Sophia Haussener ◽  
Patrick Coray ◽  
Wojciech Lipiński ◽  
Peter Wyss ◽  
Aldo Steinfeld
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Diffusion Tensor ◽  
Porous Ceramics ◽  
Interfacial Heat Transfer Coefficient ◽  
Flow Characterization ◽  
Scattering Phase Function

Reticulate porous ceramics employed in high-temperature processes are characterized for heat and mass transfer. The exact 3D digital geometry of their complex porous structure is obtained by computer tomography and used in direct pore-level simulations to numerically calculate their effective transport properties. Two-point correlation functions and mathematical morphology operations are applied for the geometrical characterization that includes the determination of porosity, specific surface area, representative elementary volume edge size, and mean pore size. Finite volume techniques are applied for conductive/convective heat transfer and flow characterization, which includes the determination of the thermal conductivity, interfacial heat transfer coefficient, permeability, Dupuit–Forchheimer coefficient, residence time, tortuosity, and diffusion tensor. Collision-based Monte Carlo method is applied for the radiative heat transfer characterization, which includes the determination of the extinction coefficient and scattering phase function.

Droplet Evaporation in High Temperature Environments

1981 ◽  
Vol 103 (1) ◽  
pp. 86-91 ◽  
Author(s):  
G. M. Harpole
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Stagnation Point ◽  
Convective Heat ◽  
Temperature Effects ◽  
Simple Correlation ◽  
Fluid Properties ◽  
Pure Steam

Axisymmetric-stagnation-point convective heat and mass transfer solutions are presented for water evaporating into dry air and into pure steam for free stream temperatures from 373K to 1450K and radiative to convective heat flux ratios from 0 to 2. Effects of (1) blowing (evaporation), (2) variable fluid properties, (3) interdiffusion (binary diffusion with nonequal heat capacities), and (4) radiation are all included. A simple correlation which fits these stagnation point solutions within 3 percent is presented. Whole droplet heat transfer is shown to behave much like stagnation-point heat transfer when the Reynolds number is on the order of 100. Blowing and other high temperature effects on whole droplet heat and mass transfer can be estimated with stagnation point solutions. The ratio of stagnation point solutions with and without high temperature effects should multiply no-blowing constant-fluid-properties whole-droplet heat transfer correlations as a correction factor. Such a corrected whole-droplet correlation compares favorably with experimental data in the literature.

scholarly journals Characteristics of supercritical heat transfer during filmboiling of nanofluids on a vertical heated wall

2018 ◽  
pp. 29-35
Author(s):  
А. Avramenko ◽  
M. Kovetskaya ◽  
A. Tyrinov ◽  
Yu. Kovetska
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mathematical Model ◽  
Mass Transfer ◽  
Heat Flux ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Heated Surface ◽  
Heated Wall ◽  
Film Boiling

Nanofluid using for intensification of heat transfer during boiling are analyzed. The using boiling nanofluids for cooling high-temperature surfaces allows significantly intensify heat transfer process by increasing the heat transfer coefficient of a nanofluid in comparison with a pure liquid. The properties of nanoparticles, their concentration in the liquid, the underheating of the liquid to the saturation temperature have significant effect on the rate of heat transfer during boiling of the nanofluid. Increasing critical heat flux during boiling of nanofluids is associated with the formation of deposition layer of nanoparticles on heated surface, which contributes changing in the microcharacteristics of heat exchange surface. An increase in the critical heat flux during boiling of nanofluids is associated with the formation of a layer of deposition of nanoparticles on the surface, which contributes to a change in the microcharacteristics of the heat transfer of the surface. Mathematical model and results of calculation of film boiling characteristics of nanofluid on vertical heated wall are presented. It is shown that the greatest influence on the processes of heat and mass transfer during film boiling of the nanofluid is exerted by wall overheating, the ratio of temperature and Brownian diffusion and the concentration of nanoparticles in the liquid. The mathematical model does not take into account the effect changing structure of the heated surface on heat transfer processes but it allows to evaluate the effect of various thermophysical parameters on intensity of deposition of nanoparticles on heated wall. The obtained results allow to evaluate the effect of nanofluid physical properties on heat and mass transfer at cooling of high-temperature surfaces. The using nanofluids as cooling liquids for heat transfer equipment in the regime of supercritical heat transfer promotes an increase in heat transfer and accelerates the cooling process of high-temperature surfaces. Because of low thermal conductivity of vapor in comparison with the thermal conductivity of the liquid, an increase in the concentration of nanoparticles in the vapor contributes to greater growth in heat transfer in the case of supercritical heat transfer.

scholarly journals Impact of Binary Chemical Reaction and Activation Energy on Heat and Mass Transfer of Marangoni Driven Boundary Layer Flow of a Non-Newtonian Nanofluid

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 702
Author(s):  
Ramanahalli Jayadevamurthy Punith Gowda ◽  
Rangaswamy Naveen Kumar ◽  
Anigere Marikempaiah Jyothi ◽  
Ballajja Chandrappa Prasannakumara ◽  
Ioannis E. Sarris
Keyword(s):  
Heat Transfer ◽  
Activation Energy ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Velocity Gradient ◽  
Boundary Layer Flow ◽  
Biological Fluids ◽  
Porosity Parameter ◽  
Layer Flow

The flow and heat transfer of non-Newtonian nanofluids has an extensive range of applications in oceanography, the cooling of metallic plates, melt-spinning, the movement of biological fluids, heat exchangers technology, coating and suspensions. In view of these applications, we studied the steady Marangoni driven boundary layer flow, heat and mass transfer characteristics of a nanofluid. A non-Newtonian second-grade liquid model is used to deliberate the effect of activation energy on the chemically reactive non-Newtonian nanofluid. By applying suitable similarity transformations, the system of governing equations is transformed into a set of ordinary differential equations. These reduced equations are tackled numerically using the Runge–Kutta–Fehlberg fourth-fifth order (RKF-45) method. The velocity, concentration, thermal fields and rate of heat transfer are explored for the embedded non-dimensional parameters graphically. Our results revealed that the escalating values of the Marangoni number improve the velocity gradient and reduce the heat transfer. As the values of the porosity parameter increase, the velocity gradient is reduced and the heat transfer is improved. Finally, the Nusselt number is found to decline as the porosity parameter increases.

Sign in / Sign up

Export Citation Format

Share Document