Key words: Solar energy, Absorption refrigeration, Ammonia-water, Simulation, COP.

Abstract: A steady state computer simulation model has been developed to predict the performance of an absorption refrigeration system using NH3-H2O as a working pair and driven by solar energy. It satisfies the air-conditioning supplies of a classroom. The absorption system includes an absorber, a generator, a condenser, an evaporator and a liquid heat exchanger. It uses a solar collector to achieve the thermal necessities of the vapor generator. The model is based on detailed mass and energy balances and heat and mass transfer relationships. The effects of the coefficient of performance and effectiveness of heat exchangers on the key operational parameters are investigated. To eliminate the numerical errors, thermodynamic properties of the working pair are taken from the EES software. The results show that the COP of the system can reach a value greater than 0.4. The effectiveness increase leads to an increase in COP of about 55%.

Key words: hydrodynamic, thermal, disc brake.

Abstract: Optimization ventilated disc brake requires a thorough knowledge of the hydrodynamics of the air flow through the ventilation ducts of the disk to determine the design to facilitate the evacuation of heat by friction pads engaging the disc. In this work we present the results of numerical simulation giving behaviors coupled hydrodynamic and thermal cooling air on the one hand, and the thermal behavior of unsteady ventilated disc, on the other hand.

Key words: Modeling, microchannel, fluid flow, heat transfer, ac electric field.

Abstract: In the last decade, microfluidics has flourished for their required in several sectors. The applications areas involved are huge, from the world of transport to the nuclear engineering, aerospace, engineering wind, and from biomechanics to the micro-electronics (e.g. cooling integrated circuits). In this paper, we present a numerical investigation of electrothermal fluid flow through a microchannel. The main purpose of this study is to investigate the flow instability induced by the electrothermal forces. The mathematical model includes the Navier-Stokes equation coupled with Maxwell and the balance energy equations. The equation system obtained is solved using the finite element method (FEM). The model provides insight and understanding of many physical and dynamic properties of flow. The numerical results show that the flow becomes highly unstable when the potential difference is great inducing the appearance of large swirls localized at the electrodes. Specifically, numerical calculations of voltage influence on the temperature and velocity of fluid flow fields are presented. Numerical suggest that 40 V applied to electrodes can increase maximum velocity by a factor of 600 compared to the inlet velocity. A slight increase in temperature (300 to 318 for Vrms = 40 V) was achieved.

Key words: Elasto-plasticity, numerical analysis, EFGM, MLS, transformation method.

Abstract: In this paper, we present a theoretical and numerical analysis of elasto-plastic problems based on the element-free Galerkin method (EFGM) and the numerical analysis. The study has been examined in planar stress analysis around the tip of a crack and in its opening mode of loading. In the EFGM, the implementation of the Moving Least Squares (MLS) approximation is used to obtain the approximation function and the transformation method is proposed to impose the essential boundary conditions. The discritized variational formulation for elasto-plastic materials obeying to the von Mises criterion is presented. To examine the validity of this technique, stress fields in a plate with a crack have been calculated.

Key words: Air conditioning; desalination; design; desiccant wheel; modelling; simulation; experimental investigation.

Abstract: In this research, a presentation of a new solar unit for air conditioning and desalination is presented firstly. Secondly, a dynamic modelling study of the desiccant wheel is developed. After that, a simulation study and an experimental investigation of the behaviour of desiccant wheel are developed. Concerning the modelling study, mathematical equations are based mainly on thermal and mass balances. Concerning the simulation study, a finite differences method is applied to the partial differential equations. The experimental investigation is done in the chamber of commerce in Freiburg-Germany. Indeed, the variations of calculated and measured temperatures and specific humidity of dehumidified and rejected air are presented. Finally, this study shows that good agreement is found when comparing the model predictions with experimental data under the considered range of operating conditions.