Parametric optimization of a coiled agitated vessel with TiO2/water nanofluid

An effective procedure of response surface methodology (RSM) has been successfully developed for a coiled agitated vessel by finding the optimal values of working parameters to achieve the high heat transfer performance. Studies have been performed for two types of agitators, propeller and disk turbine respectively. TiO2/water nanofluid has been used as agitated medium. Various operating parameters, such as impeller speed (100–700 rpm for propeller and 100–300 rpm for disk turbine), TiO2/water nanofluid concentration (0–0.3 vol%), heat input (400–2200 W) to the agitated medium were explored by experiment. Experiments were performed at desired set of working conditions suggested by a standard RSM design called a Box-Behnken Design. Nusselt number was considered as performance parameter. The results identify the significant influence factors to achieve high coefficient of heat transfer. A set of 690 rpm, 0.28 vol%, 1480 W for propeller and 220 rpm, 0.15 vol%, 1330 W for disk turbine have been suggested by the model for achieving improved heat transfer performances. The obtained optimal working parameters have been predicted and verified by conducting validation experiments. A good agreement of discrepancy ±4% have been obtained between experimental and predicted values.

Effect of Impeller Design on Power Characteristics and Newtonian Fluids Mixing Efficiency in a Mechanically Agitated Vessel at Low Reynolds Numbers

The mixing process is a widespread phenomenon, which plays an essential role among a large number of industrial processes. The effectiveness of mixing depends on the state of mixed phases, temperature, viscosity and density of liquids, mutual solubility of mixed fluids, type of stirrer, and, what is the most critical property, the shape of the impeller. In the present research, the objective was to investigate the Newtonian fluids flow motion as well as all essential parameters for the mechanically agitated vessel with a new impeller type. The velocity field, the power number, and the pumping capacity values were determined using computer simulation and experimental measurements. The basis for the assessment of the intensity degree and the efficiency of mixing had to do with the analysis of the distribution of velocity vectors and the power number. An experimental and numerical study was carried out for various stirred process parameters and for fluids whose viscosity ranged from low to very high in order to determine optimal conditions for the mixing process.

Experimental studies of helical coils in laminar regime for mechanically agitated vessel

The aim of this experimental study is to determine the heat transfer coefficients in laminar regime of mechanically agitated vessel for Newtonian (water) and non-Newtonian fluids, i.e. CMC (carboxy methyl cellulose) solutions in mechanically agitated vessel. It is found that Dean number and Prandtl number play an important role with Nusselt number while determining heat transfer coefficients. Modified Wilson plot is used to find heat transfer. The effect of friction factor on Reynolds number is also studied. The laminar flow heat transfer results have been successfully correlated in the following form with 15% standard deviation and this equation is suitable for the correlation for both Newtonian and non-Newtonian fluids to find heat transfer coefficients in helical coils in mechanically agitated stirred vessel.

Effect of impeller diameter on Nusselt number in mechanically agitated vessel

Purpose The purpose of the study is to developed the effect of Nusselt number on impeller diameter in agitated vessel, which is beneficial to find out the heat transfer coefficient in the process industry. A comparison has been done between the experimental and calculated Nusselt numbers with standard deviation found to be 8.03 per cent. Design/methodology/approach For studying the effect of impeller diameter on Nusselt Number, the heat transfer measurements were made with three different impellers of diameter. Although the diameter of impeller, Da shows its effect in Reynolds number, an attempt has been made to find the relationship between the impeller diameter and Nusselt number. A correlation between (NNuj/N″Pra1/3 N″Rea2/3) vs Da/DT and (NNuoc/N″Pra1/3 N″Rea2/3) vs Da/Dc in which data of three fluids [1, 2 and 4 per cent carboxy methyl cellulose solution of A type (CMC-A) solutions] have been plotted. Findings The heat transfer data for agitated Newtonian and non-Newtonian fluids have been successfully correlated by using the viscosity of the fluid evaluated at the impeller tip assuming a cylinder of diameter equal to that of impeller rotating in an infinite fluid. Data of 1, 2 and 4 per cent CMC-A, for three impeller diameters, have been correlated by equations. Using the above concepts of Reynolds and Prandtl numbers, Nusselt Numbers and Da/DT, it is also possible to correlate the available published data for other non-Newtonian fluids obtained with different impeller geometries. Originality/value A set up was made for studying the effect of impeller diameter, the heat transfer measurements were made with three impellers of diameter 7.5, 12.7 and 18.35 cm respectively. Although the diameter of impeller, Da shows its effect is Reynolds number, an attempt has been made to find the effect of Da/DT ratio on Nusselt number.