Fethi Kamışlı

Free coating of a non-Newtonian liquid onto walls of a vertical and inclined tube

Abstract The one-dimensional approximate equations governing flow in a free coating and a gas-assisted displacement of liquid in a vertical or inclined tube is derived using asymptotic techniques. These techniques are employed to place the free coating flow and mass conservation equations, utilized in previous studies, on a firmer theoretical ground. The derived one-dimensional flow equation for the motion of a long bubble rising steadily in a vertical or inclined tube filled with a power-law fluid is found to be identical to that of Gutfinger and Tallmadge [AIChE 11 (1965) 403] for a free coating on a flat plate withdrawn vertically from the liquid reservoir. The theoretical analysis indicated that the residual liquid film thickness increases with decreasing power-law index. This trend is similar to that observed experimentally by Huzyak and Koelling [J. Non-Newt. Fluid Mech. 175 (1997) 73] for Boger fluids. The prediction of the liquid film thickness from this analysis qualitatively agrees with the experimental results of Huzyak and Koelling [J. Non-Newt. Fluid Mech. 175 (1997) 73].

Flow of a long bubble in a square capillary

Abstract The fraction of a Newtonian liquid deposited on the walls of a square capillary as a function of capillary number is theoretically determined by solving the differential equation that governs the motion of a quasi three-dimensional flow. A theoretical analysis of the equation of continuity and motion is formulated in terms of the stream function and thereby a fourth-order differential equation is obtained by eliminating the pressure. This equation is solved analytically to obtain an eigenfunction solution for θ → π /2, where θ is the angle between the normal of the gas–liquid interface and the axial direction. The relationship between the Ca , λ a , λ b and kd with respect to the amount of liquid deposited on the walls of the square channel is obtained implicitly. The fractional coverage of a Newtonian fluid on the walls of the capillary computed from this analysis is compared with that of the experimental data. It was observed that the deviation between the theoretical analysis and the experimental study occurs at the entire range of capillary number. The solution is valid for an interface that is almost parallel to the walls of the square channel.

Experimental Study of Thin Layer Drying Behavior of a Fish

This study covers the drying behavior of rainbow trout (Oncorhynchus mykiss) in a square cross-sectioned dryer. For this, approximately 200 g fish was used to dry at different air inlet velocities like 0.5, 1.5, and 2.5 m/s for the constant air inlet temperature at 46 °C in ranges of 28–43 % of relative humidity. In the experiments, interior temperature values and moisture loses of fish were measured as a function of the drying time. It is seen that the moisture content of the fish has decreased with time and drying procedure for inlet air velocity to be effective. And it is suggested that the fish samples should be dried as single layer at 46 ± 0.1 °C and velocity of 2.5 ms−1 for optimal boundary conductions.