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The heat transfer coefficient during the pool boiling on the outside of a horizontal tube can be predicted by correlations. Our choice was based on ten correlations known from the literature. The experimental data were recovered from the recent work, for different fluids used. An evaluation was made of agreement between each of the correlations and the experimental data. The results of the present study firstly showed a good reliability for the correlations of Labuntsov [10], Stephan and Abdeslam [11] with deviations of 20% and 27%, respectively. Also, the results revealed acceptable agreements for the correlations of Kruzhlin [6], Mc Nelly [7] and Touhami [15] with deviations of 26%, 29% and 29% respectively. The remaining correlations showed very high deviations from the experimental data. Finally, improvements have been made in the correlations of Shekriladze [12] and Mostinski [9], and a new correlation was proposed giving convincing results.

A numerical study is carried out to test the effect of tube shape on heat transfer and fluid flow in a finned tube heat exchanger. The effects of different shapes (circular, flat, elliptical and oval in both orientations: left and right) are analyzed. The simulations are carried out for two-dimensional and external flow of an incompressible fluid with Reynolds numbers varying between 3000 and 20000. The results obtained indicate that the shape of the tube directly affects the thermal and dynamic behaviors of a fin and tube heat exchanger. Where the circular tube ensures higher heat transfer coefficient of about 18% than the flat tube, and it generate a moderate pressure drop of about 10% in the same conditions. Also, some reliable empirical correlations are proposed to predict the Nusselt number and the friction factor.

The present paper is an investigation of the cooling of hot shear thinning fluids flowing through cylindrical pipes. The study is achieved via numerical simulations with the help of the computer code CFX, which is based on the finite volume method to solve the governing equations. The efficiency of two techniques for achieving the cooling process is investigated, namely: the counter flow and the baffling techniques. In the first part and for the first strategy, the hot fluids are cooled by an external turbulent counter flow of a Newtonian liquid. In the second part and in an attempt to enhance the energy efficiency of the heat exchanger system, semi-circular baffles are inserted. We note that two strategies are used in combination in the second part of study. Effects of the flow rates and the pitch ratio of the inserted baffles on the flow and thermal fields are explored. The obtained results show a great enhancement of heat transfer rates when using both strategies in combination.

In this paper, the data assembled concerning the agitation of a Newtonian fluid in a cylindrical vessel is disclosed. The stirred vessel is not provided with baffles and has a flat-bottom. The data presents some information on the characteristics of two impellers: a six-blade Rushton turbine and a six-blade paddle impeller. The flow patterns generated by both impellers are depicted and compared. Also, the power required when changing the impeller rotational speed is given. The data summarized here via three-dimensional calculations of velocities and viscous dissipation in the whole volume of the tank provides additional knowledge for the best choice of impellers for each industrial process. Keywords: Stirred tank, Rushton turbine, Paddle impeller, Power input, Flow patterns

In this article, the data assembled regarding the mixing of Newtonian and shear thinning fluids by screw impellers in a cylindrical tank is disclosed. The data summarizing some information on the efficiency of such impellers are obtained via 3D calculations of velocities and viscous dissipation in the whole vessel volume. The data presented herein may be useful for those who want to outline the mixing characteristics in terms of fluid circulation and power consumption for this kind of impellers, therefore, avoiding a great effort for achieving a high number of experiments. Keyword: Mixing, Helical screw agitator, Power consumption, Fluid circulation, Cylindrical tanks

The energy efficiency of a deep hollow blade disk turbine in unbaffled mixing vessel is determined in this article via numerical simulations. The vessel is filled with xanthan gum solutions, which have a shear thinning behavior with yield stress (viscoplastic). The Herschel-Bulkley law is used to model the fluid behavior. Three-dimensional calculations are achieved by the computer tool CFX (version 16.0), and the computational domain is meshed using the software ICEM CFD (version 16.0). Mixing is achieved at low impeller rotational speeds which correspond to the laminar and transitional flow regimes. Our main purpose is to explore the effect of blade size (width and height), Reynolds number, and fluid properties on the mixing efficiency of deep hollow bladed impellers. A validation test of our predicted results with experimental data of a previous study was done, and it has shown a good agreement.

The present paper deals with the mixing of a highly viscous fluid by close-clearance impellers in cylindrical vessels. The study is performed via numerical simulations. Calculations are achieved by the discretization of continuity and momentum equations with the finite volume method. The effect of blade diameter and its shape on the well-stirred region size and the power consumption is investigated. For highly viscous fluids, the obtained results suggest the use of impellers rotating at low Reynolds number, and having a blade with the same shape of the tank to ensure mixing near the vessel base. A comparison is made between the performance of a simple helical ribbon (HR), a simple small screw (SS), helical ribbon-small screw (HR-SS) and a large screw (LS) impeller. The predicted results allow the following classification of impellers studied, based on less power requirements and small size of well-agitated region: SS < HR < HR-SS < LS.