CYLINDRICAL OBSTACLE EFFECT ON CONVECTION INSIDE AN INCLINED ENCLOSURE FILLED WITH A NANOFLUID

This study investigated the impact of a cylindrical obstacle on convection in an inclined square cavity filled with water-Al2O3 nanofluid. Using the finite volume method, the problem was resolved by having the inner cylinder rotate adiabatically while other walls were thermally insulated. Additionally, the bottom wall was hotter than the top. The study examined the effects of cylindrical obstacle radius (0.1 ≤ R ≤ 0.2), rotation speed (-500 ≤ Ω ≤ 500), Richardson number (0.01 ≤ Ri ≤ 100), volumetric nanoparticle fraction (0.02), and Grashof number (Gr = 104 ) on heat transfer rate or Nusselt number. The results were compared with previous literature, and the influence of the cylindrical obstacle rotational speed on convection flow was evaluated. An increase in the counterclockwise angular rotating speed resulted in higher nanofluid flux. The heat transmission coefficient increased as the Richardson number decreased. The use of nanofluid in the enclosure increased the coefficient of heat flow through mixed convection. Finally, the study showed that the convection heat exchange is enhanced with the increase in the radius. Moreover, an enhancement of the Nusselt number around 46% was reported for the cylinder, under Gr=10000, ∅=0.02, =45° and Ri= 10

Theoretical study of the building principal of internal and external energy balances structures in diesel engine

Distribution knowledge of the energy introduced into the combustion chamber is of great importance in the theory of internal combustion engines. This work aims to highlight the very complex relationship, often indistinguishable between internal and external energy balances components. The scrutiny of internal balance components has permitted to trace back up to the external balance. This can be easily established on a test bench equipped for the occasion. It will assess the perfection of energy's use, the heat loss and the possibility of their reducing, the energy efficiency of exhaust gas use, the possibility and ways of engine operating parameters improving and finally it will allowing to calculate the cooling and energy recovery systems

Effects of the dimple geometry on the isothermal performance of a hydrodynamic textured tilting-pad thrust bearing

International audienceThis paper is devoted to the analysis of effects of the dimple geometry on the hydrodynamic characteristics of a tilting pad thrust bearing. In a first step a discretization of Reynolds equation has been carried out by the finite difference method. It is followed by the development and validation of a hydrodynamic model used later for the examination of the influence of different surface dimples (radial, circumferential, rectangular…) on the hydrodynamic characteristics such as maximum pressure, friction torque and power loss. This study allowed highlighting that a suitable arrangement of the dimple contact surface area and also the depth of the dimple can contribute significantly to the improvement of the hydrodynamic characteristics of the tilting-pad thrust bearing

Contribution study of the thermodynamics properties of the ammonia-water mixtures

The full thermodynamic study of the absorption refrigeration units requires the knowledge of the thermodynamic properties of the used mixture. The present work deals with the mathematical modeling of the thermodynamic properties of ammonia-water mixtures using various models. The presented model covers high vapor-liquid equilibrium pressures up to 110 [bar] and temperatures from 230 to 600 [K]. Furthermore, the calculation of the thermodynamic properties of the ammonia-water mixtures and their pure components was carried out. The obtained results were compared with results given in the literature. This shows a good concordance