Evaporation and Heating With Turbulent Falling Liquid Films

Heat transfer to a power law non-Newtonian falling liquid film

“…1 The subject of fluid flow in annuli with blowing and suction at the walls has received attention recently because of applications of the concentric annular heat pipe. 2 ' 3 The numerical solutions by Faghri 1 were obtained using finite difference methods for thermally and hydrodynamically developing laminar flow in annular passages with blowing and suction at the walls. In the present study, the thermal-entry-length heat transfer characteristics of annuli with blowing at the walls have been approximated by using the fully developed axial and radial velocity profiles that were obtained analytically and used in a simple numerical scheme to solve the energy equation.…”

Modelling of multiple‐effect falling‐film evaporators

“…(1) On the contrary, this trend was experimentally confirmed only for Re less than a critical value ranging from 1600 to 3200, and better correlated by means of the following empirical expression by Chung & Seban (1971): (2) A complete description of the phenomenon under study might be carried out by describing the hydrodynamic and thermal behaviour of the film by means of combined laminar and turbulent mechanisms, although suitable expressions for eddy diffusivity of momentum and heat are not yet available (Dukler, 1959;Seban & Faghri, 1976;Brumfield & Theofanous, 1976;Narayanamurthy & Sarma, 1977). From the chemical engineering point of view a rational design of FFEs might even be carried out by using a simple, but reliable correlation of H+ under turbulent flow conditions, since the wave structure of the turbulent film involves a reduction of the average film thickness, thus increasing H+ and reducing the heat transfer surface.…”

“…Recently, many rigorous mathematical models were proposed to optimize the evaporation process in general (Holland, 1975;Stewart & Beveridge, 1977) or in the sugar industry (Radovik et al, 1979).…”

Computational modeling of turbulent evaporating falling films

“…But eddy diffusivity profiles commonly utilized with internal or external flows single-phase flows [24,25] lack the ability to account for the dampening influence of surface tension on turbulence eddies near a liquid-vapor interface. Mills and Chung [26], Seban and Faghri [27], Hubbard et al [28], and Mudawar and El-Masri [29] recommended different formulations to account for the dampening of eddy diffusivity near the interface. Mudawar and El-Masri developed a single continuous eddy diffusivity profile incorporating the Van Driest model near the wall, an experimental profile derived from open channel flow data for the bulk region of the film, and a dampening multiplier for the interface region.…”