Τμήμα Μηχανολόγων και Αεροναυπηγών Μηχαν. (Δημοσ. Π.Π. σε συνέδρια)
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- ItemOpen AccessTechnical control of reliability of vehicles(ASME, )The object of this paper is the evaluation of the reliability of vehicles based on a results’ analysis of the technical control procedure between 1987 and 2000 in the Vehicles’ Technical Inspection Center (KTEO) of Patras. First, we present a short reference on the legislation concerning the technical inspection of Vehicles in Greece. Second, we analyze statistically the results of the technical control of reliability of all kind of vehicles, which have been inspected by KTEO of Patras. The aim was to determine the chronological evolution of the percentage of the inspected vehicles with serious technical problems. We also examine the frequency of appearance of serious reliability problems in every inspected system of the vehicle in order to predict the systems with the most reliability problems. In the end we present the findings of the statistical analysis along with some thoughts about the improvement of the technical inspection procedure of vehicles in cooperation with the University of Patras.
- ItemOpen AccessAn experimental study on convective drying of quince(2013-08-06)A laboratory convective drying unit (LCDU) has been designed, constructed and equipped with an integrated measurement and control instrumentation, in order to evaluate the essential drying characteristics of various horticultural and agricultural products. The current paper presents experimental results from tests with quince slices. Drying kinetics was investigated as a function of drying conditions. Experiments were conducted at air flow temperatures of 40, 50 and 60oC and average velocities of 1, 2 and 3 m/s. Temperature changes of the drying quince samples, the relative humidity and the temperature of the drying air were measured during the drying processes and finally the moisture ratio (MR) was calculated. The experimental MR data were fitted with three mathematical models available in the literature and a good agreement was observed. In the ranges measured, Fick’s 2nd law of diffusion was used to fit the experimental data for the determination of the effective moisture diffusivity. The activation energy was determined, assuming an Arrhenius type temperature relationship with moisture diffusivity.
- ItemOpen AccessAirflow patterns in a laboratory batch-type, tray air dryer(2013-07-30)The batch-type dryer is one of the most popular equipment for fruit drying. However, the optimization of the air distribution inside the drying chamber remains a very important issue, due to its strong impact on efficient drying and uniformity of moisture content of products. A new scale laboratory batch-type, tray air dryer has been designed, constructed and evaluated for drying several horticultural and agricultural products. The flow field inside the dryer is studied through computational fluid dynamics (CFD). A three-dimensional model for laboratory dryer has been created and the steady state incompressible, Reynolds-Averaged Navier-Stokes (RANS) equations that formulate the flow problem are solved, incorporating standard and RNG k-ε turbulence models. The simulations are conducted for testing chamber average velocity of 2,9 m/s at ambient temperature. The CFD models are evaluated by comparing airflow patterns and velocity distributions to measured data. Numerical simulations and measurements convince that the new scale laboratory batch-type dryer is able to produce a sufficiently uniform air distribution throughout the testing chamber of the dryer.
- ItemOpen AccessUse of virtual instrumentation and computational fluid dynamics in an undergraduate research project(2013-07-30)The current paper demonstrates how to introduce a combination of CFD (Computational Fluid Dynamics) and virtual instrumentation to undergraduates in a research setting in the framework of a fluid mechanics course. A laboratory research project has been developed to enable students to compare and analyze pressure and velocity measurements obtained experimentally in a “Venturi tube” setup to those generated using a commercial CFD software package. An old but proven laboratory setup has been retrofitted with computer data acquisition system and custom written software has been developed to suit the experimental module. Pressure measurements received along the tube for five Reynolds numbers are directly compared with corresponding predictions using CFD code and all are contrasted with the 1-d inviscid flow solution. It is shown that, although undergraduate students may have limited knowledge in the underlying theories and equations used by CFD codes to solve flow problems, they are capable of using the code in solving classical and more complex problems with supervision by a faculty member. The developed project provides a cost-effective means for laboratory improvement in addition to educational benefits derived by the students since they have the opportunity to explore first-hand the various capabilities of CFD as an analysis tool and additionally to familiarize using modern measurements techniques such as pressure and temperature transmitters, experimental data acquisition and processing.
- ItemOpen AccessIndustrial drying of wooden pallets - CFD analysis of air flow(2013-07-30)This paper presents the results of the airflow 2D numerical simulation inside an industrial unit designed for drying of wooden pallets. The airflow field profile was examined in different operation conditions by plotting velocity vector distribution, path lines and pressure contours for both loaded with the wooden pallets and unloaded drying room. The analysis of the obtained results shows the presence of stagnation zones between and above the pallet columns and recirculation regions in different zones of the drying room. Further work will focus on validation of the predicted CFD results by means of local measurements that will be taken on a full scale dryer.