[en] At high temperature, the circulation of fluid in heat exchangers provides a tendency for fouling accumulation to take place on the internal surface of tubes. This paper shows an experimental process of thermophysical properties estimation of the fouling deposited on internal surface of a heat exchanger tube using genetic algorithms (GAs). The genetic algorithm is used to minimize an objective function containing calculated and measured temperatures. The experimental bench using a photothermal method with a finite width pulse heat excitation is used and the estimated parameters are obtained with high accuracy

[en] This book contains the short papers from the International Symposium on Convective heat and Mass Transfer in sustainable Energy ( Conv-09), organized on behalf of the International Centre for Heat and Mass Transfer, it was held on April 26- 1st May, In Hammamet, Tunisia. The objective of this conference is to bring together researchers in a forum to exchange innovative ideas, methods and results, and visions of the future related to the general theme of convective heat and mass transfer

[en] This paper presents the results of an experimental study related to characterisation of a mini channel heat exchanger. Such heat exchanger may be used in water cooling of electronic components. The results obtained show the efficiency of this exchanger even with very low water flow rates. Indeed, in spite of the importance of the extracted heat fluxes which can reach about 50Kw/m², the temperature of the cooled Aluminium bloc remained always lower than the tolerated threshold of 80 degree in electronic cooling. Moreover, several thermal characteristics such as equivalent thermal resistance of the exchanger, the average internal convective heat transfer coefficient and the increase in the temperature of the cooling water have been measured. The results presented have been obtained with in ^quinconce^rectangular mini-channel heat exchanger, with a hydraulic diameter D_h = 2mm. NOMENCLATURE h D Hydraulic diameter (mm). int

[en] The influence of an external magnetic field on transient thermal and viscous irreversibilities in Poiseuille-Benard channel for the laminar flow of an incompressible electrically conducting fluid is numerically investigated by solving the mass, momentum and energy conservation equations. Numerical simulation was performed for Reynolds number (Re) equal to 10 and an irreversibility distribution ratio φ equal to 0.1. The Stuart number (N) that describes the magnetic field effect, ranges between 0 and 10. Rayleigh and Prandtl numbers are fixed respectively at 104 and 0.71

[en] The investigation purpose an experimental study of the natural convection flow. This study simulates the fires evolving in a free and unlimited environment then in interaction with their material surrounding. The fires met such as in the forests in the oil fields and in the tower blocks create a thermal plume which extends in space. The pollutants transported by the fires flows threaten the inhabitants health and cause a natural imbalance of the environment. In reality the thermal plume generated by these fires undergone the influence of the neighbouring walls. Indeed, the walls which surround it are heated by thermal radiation thus creating a thermosyphon flow which interacts with the plume. According to former work, the researchers [16, 20] noticed that the fires can be simulated by a hot source heated by Joule effect. For that, we studied the thermal plume flow generated by a hot rectangular source placed in a free then in a semi-confined environment. To better understand the development mechanisms of the free fire flow and in interaction with surrounding, we simulated these phenomena at the laboratory. In a first time we studied a thermal plume generated by a rectangular source heated uniformly by Joule effect. In a second time the same source is placed at the entry of a vertical canal which its the two Duralumin walls are heated at a constant temperature. The visualization by laser plane enables us to follow the vertical evolution of the flow for two studied configurations. Using hot wire anemometry, we explored the thermal and dynamic field of the flow. In order to better describe the fine structure of the flow, we analyzed the spectra of temperature fluctuations

[en] This study investigates the effects of the flooding of the gas diffusion layer (GDL), as a result of liquid water accumulation, on the performance of a proton exchange membrane fuel cell (PEMFC). The transient profiles of the current generated by the cell are obtained using the numerical resolution of the transport equation for the oxygen molar concentration in the unsteady state. The dynamics of the system are captured through the reduction of the effective porosity of the GDL by the liquid water which accumulates in the void space of the GDL. The effects of the GDL porosity, GDL thickness and mass transfer at the GDL-gas channel interface on the evolution with time of the averaged current density are reported. The effects of the current collector rib on the evolution of the molar concentration of oxygen are also examined in detail

[en] This paper deals with the interaction of twin inclined jets in crossflow. The consideration of this particular configuration is of great interest due to its wide presence in various domains and applications and to its dependence in many parameters. These parameters may be geometric like the jets height, the jet nozzles separating distance, the jet nozzles, exit section, etc... It may also be based upon one of the reigning features like the velocity ratio, the temperature gradient, etc...The gradient between the jets and the crossflow temperatures is precisely the parameter we intend to handle in the present work due to its great relevance in several environmental concerns and in technical constraints as well. The evaluation of this parameter will be carried out numerically on the temperature distribution itself. This evaluation is likely to give a thorough idea about the cooling/heating process resulted from the jets interaction with the oncoming crossflow. Such an understanding is likely to give viable solutions to problems raised by this configuration like the acid rain engendered by too hot fumes or the deterioration of the combustors walls by too high temperature jets, etc...The numerically simulated model is based on the resolution of the Navier-Stokes equations by means of the finite volume method and the RSM second order turbulent model and is validated by confrontation to experimental data depicted on the same geometric replica

[en] This paper numerically investigates the effect of an externally evanescent magnetic field on flow patterns and heat transfer of fluid in a square cavity. The horizontal walls of the enclosure are assumed to be insulated while the vertical walls are kept isothermal. A control volume finite element method is used to solve the conservation equations at Prandtl number of 0.71. The effect of constant Hartman number on Nusselt number was studied. Validation tests with existing data demonstrate the aptitude of the present method to produce accurate results. The effects of magnetic field inclination angle from 0 degree to 90 degree on streamlines distributions are shown for different values of Hartman number. For Grashof number equal to 10⁵, the values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of Nusselt number in natural convection. The Nusselt number was calculated for different values of the inverse relaxation time varying from 0 to + ∞. The magnitude and the number of oscillations of the Nusselt number were observed. It has been found that no oscillation was seen at relaxation time equal to 20

[en] We numerically study the effect of an externally-evanescent magnetic field on total entropy generation in conducting and non-reactive fluid enclosed in a square cavity. The horizontal walls of the enclosure are assumed to be insulated while the vertical walls are kept isothermal. A control volume finite element method is used to solve the conservation equations at Prandtl number of 0.71. The values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of entropy generation in natural convection. The total entropy generation was calculated for fixed value of irreversibility distribution ratio, different relaxation time varying from 0 to 1/5 and Grashof number equal to 10⁵

[en] Synthetic jet actuators show good promise as an enabling technology for innovative boundary layer flow control applied to external surfaces, like airplane wings, and to internal flows, like those occurring in a curved engine inlet. The appealing characteristics of a synthetic jet are zero-net-mass flux operation and an efficient control effect that takes advantages of unsteady fluid phenomena. The formation of a synthetic jet in a quiescent external air flow is only beginning to be understood and a rational understanding of these devices is necessary before they can be applied to the control of flows outside of the laboratory. The synthetic jet flow generated by a planar orifice is investigated here using computational approach. Computations of the 2D synthetic jet are performed with unsteady RANS modeled with the Realizable κ - ε turbulence model available in FLUENT environment. In this present work, the ability of the first order turbulence model, employed in our computations, to model the formation of the counter-rotating-vortex pair (CVP) that appears in the flow-field was investigated. Computational results were in good agreement with experimental measurements. The effectiveness of such control actuator was tested on separated boundary layer. Preliminary investigation were presented and discussed