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Distribution of the local heat transfer coefficient in the agitated vessel equipped with turbine impellers

Broniarz-Press L., Różańska S.

Polish Journal of Chemical Technology

2006

Vol. 8, nr 4

27-30

The results of experimental studies on the distribution of a local heat transfer coefficient on the vertical wall of the agitated vessel have been presented. Four various type turbine impellers were used (Rushton turbine, paddle with 6 pitched blade of the angles of beta = 45, 90 and 135°). The experiments were carried out for the Newtonian and shear-thinning fluids without yield stress (Na-CMC and guar gum).The potassium ferri-and ferrocyanide solutions with the sodium hydroxide and potassium sulphate as the supporting electrolytes have been used as the Newtonian model solutions. For the shear-thinning media the formula of the Reynolds number proposed by Metzner and Otto Re(MO), has been applied. The results of the experimental studies in the graphical form have been presented. The common relationships for the Newtonian and non-Newtonian fluids have been obtained.

Experimental investigation of a liquid film formed by impingement of an axisymmetric jet on a flat heated surface

Bykuć S.

Turbulence : international journal

2005

Vol. 11

235-237

The aim of the present work was to study experimentally hydrodynamic and heat transfer characteristics of the flow of a liquid film over a surface. A round jet of water impinging vertically on a horizontal plane forms a thin film flowing radially until the sudden increase of depth occurs (hydraulic jump). During the experiment, the temperature of the solid surface and liquid film thickness in the suhcritical region (downstream of the hydraulic jump) and supercritical region (upstream of the hydraulic jump) were measured. Radial film thickness and Nusselt number distributions were achieved. Experiments were performed for a range of flow rates between 0.3 and 0.8 I/min. The liquid film thickness upstream of the hydraulic jump was an order of magnitude smaller than that of the subcritical region. With the growth of the flow rate, the radius of the hydraulic jump and film thickness after the jump, increased. It was found that the local Nusselt number reached maximum near the stagnation region and decreases gradually with radius as the flow moves downstream with the biggest drop corresponding to the location of hydraulic jump. Downstream of the jump, Nu was approximately uniform. Higher Nusselt numbers were reached for higher flow rates. These differences for various flow rates were much bigger in the supercritical region than that in the subcritical one.