Electromechanical and Systems Engineering

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Authors: Stasys Sinkunas, Jonas Gylys, Algimantas Kiela
Abstract: The purpose of the present study is to obtain a comprehension for the momentum and heat transfer developments in gravitational liquid film flow. Analytical study of stabilized heat transfer for turbulent film was performed. A calculation method of the local heat transfer coefficient for a turbulent film falling down a vertical convex surface was proposed. The dependence of heat flux variation upon the distance from the wetted surface has been established analytically. Experimental study of velocity profiles for turbulent liquid film flow in the entrance region is performed as well. Analysis of profiles allowed estimating the length of stabilization for turbulent film flow under different initial velocities.
Authors: C. Morton, S. Yarusevych, I. Carvajal-Mariscal
Abstract: Flow over a step cylinder at ReD = 2000 and D/d = 2 was investigated using a URANS-based numerical approach. The results illustrate the downstream development and interaction of wake vortices and identify streamwise vortical structures originating at the step. The observed flow development is shown to be in agreement with experimental results. Also, a comparison of the computational results and previous experimental findings is carried out for the drag coefficient and the pressure coefficient.
Authors: H. Saidani-Scott, Mike Tierney, F. Sánchez-Silva
Abstract: This paper presents experimental results following a feasibility study into the uses of textiles for water filtration and purification. This project emanated from another project called ‘Aquapol’ [1], sponsored by the EU [2], which looked at reduction of infant diseases by the use of clean filtered water. Due to the high cost and maintenance of manufactured filters used in the Aquapol project, it was decided to look at the traditional methods used locally and try and design a water filter made from simple non expensive materials. Various textile materials have been tested for water filtration particulate dealing with the simulation of traditional materials used in Africa and Asia (Like Shesh in North Africa and Sari in India). Some ‘modern’ materials (like Denim, curtain shower) have also been tested to see if their filtration capability is better or worst than the traditional ones. The results obtained showed that textiles were very efficient in reducing particles size transportation and could be used for filtering and pre-filtering. However, storage conditions and basic hygiene are still the most important factors for disease reduction
Authors: O.A. Morales-Contreras, J.G. Barbosa-Saldaña, J.A. Jiménez-Bernal, Claudia del Carmen Gutiérrez Torres
Abstract: Numerical simulation for the three-dimensional laminar flow through a forward facing step channel was simulated by Fluent 6.3 code. Four Reynolds numbers and four step lengths were analyzed. The results showed that the length of the recirculation zone upstream the step depends on Reynolds number, as well as on the step height (h), while the height of the recirculation zone extends about 70% of the step height. In addition, it was found that the velocity profile in the stream direction at the channel exit presents a fully developed profile for the axial component. Nonetheless, the profile along the transversal direction does not have a parabolic profile, even for a length of 60h
Authors: Luis A. Moreno-Pacheco, G.E. Valle-Meléndez, Claudia del Carmen Gutiérrez Torres, J.A. Jiménez-Bernal, M. Toledo-Velázquez
Abstract: A numerical simulation of a flow passing throw two NACA 0012 airfoils is presented in this paper. Aerodynamics, drag forces, and pressure drop is quantified when both profiles are axially aligned and then when one of them is vertically displaced. NUMECA code and Spalart-Allmaras turbulence model were used for this purpose. The results showed that aerodynamic losses are present in both profiles, meaning that the presence of the back profile plays an important role in the aerodynamic behavior of the frontal profile.
Authors: O. Cortés, G. Urquiza, J. Alfredo Hernández
Abstract: The present work uses the Levenberg-Marquardt Method (LMM) and a Particle Swarm Optimization (PSO) for estimating the heat generation function for a Guarded Hot-Plate Apparatus (GHPA). This device is used for thermal conductivity determination of insulating materials. The problem is one-dimensional in cylindrical coordinates. Geometries are a disc (Hot-Plate) and an annulus (Guard). A heat generation function is estimated considering one to five parameters. Capability of each method for recovering the analytical function is tested. Results are satisfactory for this kind of problem.
Authors: I. Carvajal-Mariscal, F. Sánchez-Silva, G. Polupan, J.A. Basualdo-Rojo
Abstract: Experimental research results of the operational parameter effect on Thermal Contact Resistance (TCR) in a copper-aluminum L-type finned tube are presented. The investigated operational parameters were the maximum operational temperature and the number of repeated heating-cooling cycles. The TCR was experimentally determined by measuring the total heat supply, core tube wall and inner fin surface temperatures for steady-state and natural-convection conditions. In addition, the specimen was tested through up to 200 heating-cooling cycles. The experimental results showed a TCR increase of 81% at the same time as the average temperature difference between the hot inner flow and cooling air increased from 30°C to 130°C; over the maximum operational temperature (120°C), the TCR increased faster than before; and, after the heating-cooling cycle testing the TCR presented an increase of 31% in respect with the initial value. Such findings may be useful as a reference for preliminary thermal design and as recommendations for optimal operation of heat exchangers based on copper-aluminum L-type finned tubes.

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