Nanoliquid film flow due to a moving substrate and heat transfer

Thin films and coatings which have a high demand in a variety of industries—such as manufacturing, optics, and photonics—need regular improvement to sustain industrial productivity. Thus, the present work examined the problem of the Carreau thin film flow and heat transfer with the influence of thermocapillarity over an unsteady stretching sheet, numerically. The sheet is permeable, and there is an injection effect at the surface of the stretching sheet. The similarity transformation reduced the partial differential equations into a system of ordinary differential equations which is then solved numerically by the MATLAB boundary value problem solver bvp4c. The more substantial effect of injection was found to be the reduction of the film thickness at the free surface and development of a better rate of convective heat transfer. However, the increment in the thermocapillarity number thickens the film, reduces the drag force, and weakens the rate of heat transfer past the stretching sheet. The triple solutions are identified when the governing parameters vary, but two of the solutions gave negative film thickness. Detecting solutions with the most negative film thickness is essential because it implies the interruption in the laminar flow over the stretching sheet, which then affects the thin film growing process.

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Thin film flow of a second grade fluid in a porous medium past a stretching sheet with heat transfer

Alexandria Engineering Journal ◽

10.1016/j.aej.2017.01.036 ◽

2018 ◽

Vol 57 (2) ◽

pp. 1019-1031 ◽

Cited By ~ 45

Author(s):

Noor Saeed Khan ◽

Saeed Islam ◽

Taza Gul ◽

Ilyas Khan ◽

Waris Khan ◽

...

Keyword(s):

Thin Film ◽

Heat Transfer ◽

Porous Medium ◽

Stretching Sheet ◽

Film Flow ◽

Second Grade ◽

Thin Film Flow ◽

Second Grade Fluid ◽

Grade Fluid

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Theoretical and Experimental Analysis of Turbulent Liquid Film Flowing down a Vertical Surface

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.15.3 ◽

2009 ◽

Vol 15 ◽

pp. 3-8

Author(s):

Stasys Sinkunas ◽

Jonas Gylys ◽

Algimantas Kiela

Keyword(s):

Heat Transfer ◽

Liquid Film ◽

Analytical Study ◽

Film Flow ◽

Convex Surface ◽

Local Heat Transfer ◽

Local Heat ◽

Vertical Surface ◽

Momentum And Heat Transfer ◽

Liquid Film Flow

The purpose of the present study is to obtain a comprehension for the momentum and heat transfer developments in gravitational liquid film flow. Analytical study of stabilized heat transfer for turbulent film was performed. A calculation method of the local heat transfer coefficient for a turbulent film falling down a vertical convex surface was proposed. The dependence of heat flux variation upon the distance from the wetted surface has been established analytically. Experimental study of velocity profiles for turbulent liquid film flow in the entrance region is performed as well. Analysis of profiles allowed estimating the length of stabilization for turbulent film flow under different initial velocities.

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Wettability Effects on Falling Film Flow and Heat Transfer Over Horizontal Tubes in Jet Flow Mode

Journal of Heat Transfer ◽

10.1115/1.4048088 ◽

2020 ◽

Vol 142 (12) ◽

Author(s):

Avijit Karmakar ◽

Sumanta Acharya

Keyword(s):

Heat Transfer ◽

Contact Angle ◽

Nusselt Number ◽

Film Flow ◽

Jet Flow ◽

Equilibrium Contact Angle ◽

Flow Mode ◽

Falling Film ◽

Tube Surface ◽

Horizontal Tubes

Abstract The performance of a falling-film heat exchanger is strongly linked to the surface characteristics and the heat transfer processes that take place over the tubes. The primary aim of this numerical study is to characterize the influence of surface wettability on the film flow behavior and its associated surface heat transfer in the jet-flow mode. Volume of fluid (VOF) based simulations are carried out for horizontal tubes with different surface wettabilities. The wettability of the tube surfaces is represented using the Kistler's dynamic contact angle model. Surface wettability effects ranging from superhydrophilic to superhydrophobic are studied by varying the equilibrium contact angle from 2 deg to 175 deg. Two different liquid mass flow rates of 0.06 and 0.18 kg/m-s corresponding to the inline and staggered jet flow modes are studied. Results are presented in terms of the liquid film thickness, the contact areas between the different phases (solid–liquid and liquid–air), and the heat transfer coefficient or Nusselt number. The resistance imposed by the increasing contact angles inhibits the extent of the liquid spreading over the tube surface, and this, in turn, influences the liquid film thickness, and the wetted area of the tube surface. A significant decrement in the heat transfer rate from the tube surfaces was observed as the equilibrium contact angle increased from 2 deg to 175 deg. The local distributions of the Nusselt number over the tube surface are strongly influenced by the flow recirculation in the liquid bulk.

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