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1

A comparative study for double pass solar air collector utilizing medial glass panel

Salih Hussein M.

Archive of Mechanical Engineering

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2022

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LXIX, nr 4

729--747

EN

A numerical investigation of thermal prediction of double-pass solar air heater of-counter flow is developed in the present study. The main idea of the current study is that the collector consists of two layers of glass so that the middle layer is glass instead of the usual metal plate. The performance of double-pass solar air heater is studied for a wide range of solar radiation intensities (600, 750 and 900 W/m 2). A FORTRAN-90 program is built to simulate the mathematical model of double-pass solar air heater based on solving steady state two-dimensional Navier-Stokes equations and energy equation based on finite volume method. Turbulence effect is simulated by two equations k-ε module. The results are compared with the results of a previous experimental study and a good agreement was found. From compression calculating efficiency of the present and traditional collector for each solar intensity, it was found that the efficiency of the current collector is higher than that of the traditional one, where the efficiency of the current collector at the solar intensity of (600, 750 and 900) W/m 2 are (0.529, 0.514 and 0.503), respectively, while those of the traditional collector (0.508, 0.492 and 0.481), respectively. In addition to this, the effect of the mass flow rate on the temperature difference of the current proposed collector was studied. Three values of the mass flow rate were studied (0.009,0.018, and 0.027) kg/s at solar intensity of 750 W/m 2. From this it was found that the temperature difference decreases with increasing mass flow rate. Accordingly, the efficiency decreases

2

Simulation and analysis of a turbulent flow around a three-dimensional obstacle

Benahmed Lamia, Aliane Khaled

Acta Mechanica et Automatica

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2019

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Vol. 13, no. 3

173--180

EN

The study of flow around obstacles is devised into three different positions: above the obstacle, upstream of the obstacle, and downstream of the latter. The behaviour of the fluid downstream of the obstacle is less known, and the physical and numerical modelling is being given the existence of recirculation zones with their complex behaviour. The purpose of the work presented below is to study the influence of the inclined form of the two upper peaks of a rectangular cube. A three-dimensional study was carried out using the ANSYS CFX calculation code. Turbulence models have been used to study the flow characteristics around the inclined obstacle. The timeaveraged results of contours of velocity vectors , cross-stream and stream wise velocity and streamlines were obtained by using K-ω shear -stress transport (SST), RANG K-ε and K-ε to model the turbulence, and the governing equations were solved using the finite volume method. The turbulence model K-ω SST has presented the best prediction of the flow characteristics for the obstacle among the investigated turbulence models in this work.

3

Numerical heat transfer in a rectangular channel with mounted obstacle

Gareh S.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 19, iss. 2

111--119

EN

The fully-incompressible, viscous and stationary Navier–Stokes equations are solved for the laminar flow over an obstacle placed on the lower of a channel. The Reynolds number is varied from 100 to 400. In all cases studied the flow field proves to be steady. Several distinct flow features are identified: a horseshoe vortex system, inward bending flow at the side walls of the obstacle, a horizontal vortex at the downstream lower-half of the obstacle and a downstream wake containing two counter-rotating vortices. The shape and size of these flow features are mainly dominated by the Reynolds number. For higher Reynolds numbers, both the horseshoe vortex and the wake region extend over a significantly larger area. The correlation of the position of the separation and attachment point with the Reynolds number has been calculated. A detailed analysis is carried out to investigate flow pattern and Nusselt number.

4

Application of Overlapping Mesh in Numerical Hydrodynamics

Panahi R., Shafieefar M.

Polish Maritime Research

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2009

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nr 2

24-33

EN

A Finite Volume (FV) algorithm is presented to investigate two-dimensional hydrodynamic problems including viscous free surface flow interaction with free rigid bodies in the case of large and/or relative motions. Two-phase flow with complex deformations at the interface is simulated using a fractional stepvolume of fluid algorithm while it is also capable of representing a high quality wave tank, according to implemented temporal discretisation. Rigid body motions are also captured using two overset meshes. Flow variables are transferred using a simple fully implicit non-conservative interpolation scheme which maintains the second-order accuracy of implemented spatial discretisation. A code is developed and an appropriate set of problems are investigated. Results show a good potential to develop a virtual hydrodynamics laboratory.

5

Transformation kinetic for instantaneous nucleation in the finite volume - application of statistical theory of shielding

Burbelko A. A.

Archives of Metallurgy and Materials

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2009

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Vol. 54, iss. 2

358-367

EN

The framework of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory is applied usually for the study of transition kinetics when the processes are ruled by nucleation and growth. This theory accurately describes only the transitions with the identical convex shape of new nuclei with the identical growth velocity distribution at an interface of the growing grains. The infinite initial volume of the mother phase is one of the indispensable conditions for the above theory. The proposed earlier extension of KJMA theory (statistical theory of the shielding growth) enlarges the scope of its application and eliminates the above limitation. The model of the transformation kinetics in the space of finite volume has been analyzed and discussed.

PL

W badaniach kinetyki procesów kontrolowanych zarodkowaniem i wzrostem skutecznie wykorzystuje się statystyczną teorię krystalizacji, podwaliny której zostały założone przez Kołmogorova, Jonhsona, Mehla i Avramiego (teoria KJMA). Powyższa teoria opisuje badane zjawiska precyzyjnie w przypadku, gdy wszystkie nowopowstające obiekty mają identyczny rozkład prędkości wzrostu na powierzchni (podobny kształt geometryczny), są wypukłe, a w przypadku anizotropii kształtu są identycznie zorientowane w przestrzeni. Jednym z założeń powyższej teorii jest nieskonczona objetość zanikającego materiału. Zaproponowane wczesniej rozszerzenie teorii KJMA (statystyczna teoria ekranowanego wzrostu) zwiększa zakres zastosowania klasycznych równań, pokonując niektóre ograniczenia. W artykule przedstawiono badania kinetyki wzrostu ziaren nowej fazy w przypadku małej objętosci fazy macierzystej.