Heat transfer in a falling laminar liquid film with in-depth radiation absorption

Abstract

A heat transfer problem involving a steady-state falling liquid film along a vertical wall with an imposed constant heat flux on the liquid film surface and an in-depth thermal radiation absorption in the film layer is analyzed. The liquid film is assumed to be normal to the incident radiative heat flux, and the heat flux is assumed to be parallel and unidirectional. Nondimensionalized governing equations are formulated and solved numerically. Sample calculations are provided. The effects of pertinent dimensionless parameters on the heat transfer process are demonstrated. The calculated results reveal that the in-depth thermal radiation absorption would play a key role in the heat transfer in the liquid film.

Effect of evaporation rate for the heat and mass transfer of the laminar liquid falling film in still air

“…According to the above assumptions and Figure 1, the Navier-Stokes equations describing the laminar falling film can be reduced to (Nusselt, 1916;Yang and Yuen, 2018):…”

“…Combining Eqs 1-3, the velocity u(y), thickness Δ, mass flow rate Γ, and mean velocity u m of the liquid falling film can be induced as follows (Nusselt, 1916;Yang and Yuen, 2018):…”

“…Vertical falling film heat dissipation refers to the process in which the film flows from top to bottom under the action of gravity, viscous shear, and wall adhesion, and the heat is transferred from the wall to the film and accompanied by evaporation. It is widely used as an enhanced cooling method in the fields of chemical process, nuclear reactor safety, and fire protection engineering (Yang and Yuen, 2018;Turkyilmazoglu, 2021;Choi and Cho, 2022). In particular, the mixed ferromagnetic nanofluid film and microchannel fluid film show a good application prospect for heat transfer (Tlili et al, 2020;Tlili et al, 2022).…”