Hydrodynamic and Thermal Analysis of Vertical Falling Film with Flash Evaporation
Dandotiya, Deepak
Hydrodynamic and Thermal Analysis of Vertical Falling Film with Flash Evaporation by Deepak Dandotiya - IIT Jodhpur Department of Mechanical Engineering 2019 - xvi,51p. HB
"Liquid film falling under the effect of gravity is confronted in industrial two-phase flowapplications such as distillation columns and reactors. Theoretical treatment of hydrodynamicand thermal boundary layer during vertical film flow over a flat plate is well-studied problem.All the existing studies, deal with development of these two boundary layers from the solidsurface of the flat plate. The hydrodynamic boundary layer is intuitively attached with the flatsurface, but, depending on heat transfer orientation, thermal boundary layer can develop from flatsurface as well as the free surface of the film. Thermal boundary layer developed from the freesurface is hardly studied till date. In the present work the hydrodynamic and thermal boundarylayer analysis of the vertical falling film due to heat transfer from free surface has been studied.The semi-analytical models for hydrodynamic and thermal boundary layers are postulated usingReynold’s transport theorem (RTT). For hydrodynamic analysis, the RTT form of momentum andcontinuity equation is solved analytically. The estimated velocity profile from hydrodynamicanalysis serves as the input for heat transfer analysis. Evidently one way coupling has beenused to relate hydrodynamic and thermal features. The thermal analysis requires the input fromhydrodynamic analysis, while the hydrodynamic model is a standalone scheme without anydependence on thermal field. The non-dimensional film thickness variation along the verticaldistance at different flow rate is obtained using the analytical hydrodynamic model and comparedwith the results from existing literatures. The one way coupled heat transfer analysis is performedfor two different scenarios. The first thermal problem involves convective heat loss from thefree surface. The second thermal problem describes heat transfer from the free surface due toflash evaporation. During flash evaporation, the flowing film is exposed to low ambient pressurecausing rapid evaporation from the film surface. The latent heat of evaporation is absorbed fromthe film itself, rendering rapid cooling of the film. For both thermal analyses, the thermal boundarycondition at the solid wall is considered to be adiabatic. To determine the effect of heat transferfrom the free surface due to either convection or rapid evaporation, we solved RTT form of energyequation and determined the variation of thermal boundary layer thickness, surface temperatureand vertical distance to achieve thermally fully-developed film.
"
Hydrodynamic and Thermal Analysis
MTech Theses
Department of Mechanical Engineering
621.402 / D197H
Hydrodynamic and Thermal Analysis of Vertical Falling Film with Flash Evaporation by Deepak Dandotiya - IIT Jodhpur Department of Mechanical Engineering 2019 - xvi,51p. HB
"Liquid film falling under the effect of gravity is confronted in industrial two-phase flowapplications such as distillation columns and reactors. Theoretical treatment of hydrodynamicand thermal boundary layer during vertical film flow over a flat plate is well-studied problem.All the existing studies, deal with development of these two boundary layers from the solidsurface of the flat plate. The hydrodynamic boundary layer is intuitively attached with the flatsurface, but, depending on heat transfer orientation, thermal boundary layer can develop from flatsurface as well as the free surface of the film. Thermal boundary layer developed from the freesurface is hardly studied till date. In the present work the hydrodynamic and thermal boundarylayer analysis of the vertical falling film due to heat transfer from free surface has been studied.The semi-analytical models for hydrodynamic and thermal boundary layers are postulated usingReynold’s transport theorem (RTT). For hydrodynamic analysis, the RTT form of momentum andcontinuity equation is solved analytically. The estimated velocity profile from hydrodynamicanalysis serves as the input for heat transfer analysis. Evidently one way coupling has beenused to relate hydrodynamic and thermal features. The thermal analysis requires the input fromhydrodynamic analysis, while the hydrodynamic model is a standalone scheme without anydependence on thermal field. The non-dimensional film thickness variation along the verticaldistance at different flow rate is obtained using the analytical hydrodynamic model and comparedwith the results from existing literatures. The one way coupled heat transfer analysis is performedfor two different scenarios. The first thermal problem involves convective heat loss from thefree surface. The second thermal problem describes heat transfer from the free surface due toflash evaporation. During flash evaporation, the flowing film is exposed to low ambient pressurecausing rapid evaporation from the film surface. The latent heat of evaporation is absorbed fromthe film itself, rendering rapid cooling of the film. For both thermal analyses, the thermal boundarycondition at the solid wall is considered to be adiabatic. To determine the effect of heat transferfrom the free surface due to either convection or rapid evaporation, we solved RTT form of energyequation and determined the variation of thermal boundary layer thickness, surface temperatureand vertical distance to achieve thermally fully-developed film.
"
Hydrodynamic and Thermal Analysis
MTech Theses
Department of Mechanical Engineering
621.402 / D197H