International Journal of Energy

ISSN: 1998-4316
Volume 14, 2020

Notice: As of 2014 and for the forthcoming years, the publication frequency/periodicity of NAUN Journals is adapted to the 'continuously updated' model. What this means is that instead of being separated into issues, new papers will be added on a continuous basis, allowing a more regular flow and shorter publication times. The papers will appear in reverse order, therefore the most recent one will be on top.

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Volume 14, 2020

Title of the Paper: Numerical Analysis of MHD Stagnation Point Flow Towards a Radially Stretching Convectively Heated Disk


Authors: Stanford Shateyi, Daniel Makinde

Pages: 53-58

Abstract: The steady stagnation point flow and heat transferof an electrically conducting incompressible viscous fluid isextended to the case where the disk surface is convectivelyheated and radially stretching. The fluid is subjected to anexternal uniform magnetic field perpendicular to the planeof the disk. The governing momentum and energy balanceequations give rise to non-linear boundary value problem.Using a spectral relaxation method with a Chebyshev spectralcollocation method, the numerical solutions are obtained overthe entire range of the physical parameters. Emphasis hasbeen laid to study the effects of viscous dissipation and Jouleheating on the thermal boundary layer. Pertinent results on theeffects of various thermophysical parameters on the velocityand temperature fields as well as local skin friction and localNusselt number are discussed in detail and shown graphicallyand/or in tabular form.

Title of the Paper: A Numerical Study of Crown Forest Fires Behaviour


Authors: Valeriy Perminov

Pages: 47-52

Abstract: The theoretical investigation of the problems oflarge forest fires initiation and spread was carried out in thispaper. Mathematical model of forest fire was based on ananalysis of experimental data and using concept and methodsfrom reactive media mechanics. The research was based onnumerical solution of three dimensional Reynolds equations. Theboundary-value problem is solved numerically using the methodof splitting according to physical processes. A discrete analoguefor the system of equations was obtained by means of the controlvolume method. The developed numerical model of forest fireinitiation and spreading would make it possible to obtain adetailed picture of the variation in the velocity, temperature andchemical species concentration fields with time. The results ofcalculation give an opportunity to describe conditions of crownforest fires initiation and spread at different properties of forestsand meteorological conditions. Forest fires contours and theirsizes depend on crown properties: bulk density, moisture contentof forest fuel, distribution of combustion sources and etc.

Title of the Paper: Numerical Study of Three-Dimensional Natural Convection in a Differentially Heated Cubical Enclosure


Authors: H. S. Lee, J. H. Jung, H. S. Yoon

Pages: 42-46

Abstract: A high-resolution, finite difference numerical studyis reported on three-dimensional steady-state natural convectionof air, for two Rayleigh numbers, in a cubical enclosure, which isheated differentially at one side walls. The temperature of thewall is TC except for the right vertical wall, in which is TH.Thedetails of the three-dimensional flow and thermal characteristicsare described.

Title of the Paper: Using Latent Energy of Water-ice Phase Change to Reduce Energy Losses in Buildings in Cold Climate


Authors: Gatis ┼Żogla, Andra Blumberga, Kristaps Kašs

Pages: 34-41

Abstract: Energy efficiency in buildings is a very important challenge that has to be faced in order to achieve the aims set by the new EU directive on Building energy efficiency encouraging nearly zero energy buildings. Unfortunately in countries with cold climate it is very hard to achieve this goal. The thickness of insulation needed to reach low energy consumption in cold climate is very big and in many cases it is not economically feasible. There is a need for new solutions for increasing building energy efficiency. In this paper a new solution for increasing building energy efficiency is proposed. It is proposed to use the latent energy of water-ice phase change to reduce heat conduction losses through building envelope. The latent energy is recovered by using low potential heat source. In this paper the validity of the proposed new solution is tested on a one dimensional scale – homogeneous infinite wall. The presented methodology is chosen to calculate systems operational efficiency throughout the whole year.

Title of the Paper: Analysis of Two Colliding Thin Spherical Shells


Authors: Yury Rossikhin, Vyacheslav Shamarin, Marina Shitikova

Pages: 29-33

Abstract: In the present paper, the collision of two elastic spherical shells is investigated using the wave theory of impact. The model developed here suggests that after the moment of impact quasi-longitudinal and quasi-transverse shock waves are generated, which then propagate along the spherical shells. The solution behind the wave fronts is constructed with the help of the theory of discontinuities. Since the local bearing of the materials of the colliding elastic shells is taken into account, then the solution in the contact domain is found via the Hertz contact theory.

Title of the Paper: A New Failure Criterion for Woven-roving GFRE Thick Tube Subjected to Combined Fatigue Bending Moments and Internal hydrostatic Pressure


Authors: M. N. Abouelwafa, Hassan El-Gamal, Yasser S. M, Wael A. Al-Tabey

Pages: 21-28

Abstract: Choosing the suitable failure criterion represents the main target for many researchers working with materials, and it represents the first step for new materials before being used in the field. Considering composite materials, specifically, makes it more challenging, because of their very special behavior and characteristics. Besides, it must be noted that, the suitability of a certain criterion differs greatly according to the tested material, and its stress state. Thick-walled tubular specimens, made from wovenroving Glass Fiber- Reinforced Epoxy (GFRE) with two fiber orientations, [0o ,90o ]3s and [±45o ]3s, and two manufacture methods M1 and M2 to prepare the test specimens, were tested under combined fatigue bending and Internal hydrostatic Pressure at different pressure ratios (Pr), PPrr= 00, 00.2222, 00.55, 00.7777 (i.e. pressures amounting to 0%, 25%, 50% and 75% of the burst pressure). The [0o ,90o ]3s specimens were found to have higher bending strength than the [±45o ]3s specimens, at all pressure ratios; This is due to the fiber orientation [0,90°]3s has a minimum value of stress component σ6 which equal to zero. For both fiber orientations [0o ,90o ]3s and [±45o ]3s and both manufacture methods M1 and M2, were found none of the available criteria succeeded in predicting failure for the studied case, this due to the effect of hoop stress on values of amplitude component and the corresponding fatigue strength; consequently. A new modifying term was introduced that made Norris-Distortional, Tsai-Hahn, and Tsai-Hill criteria suitable for this studied case, resulting in a new criterion

Title of the Paper: Laminar MHD Mixed Convection Flow of Newtonian Fluid between Vertical Parallel Plates Channel


Authors: Ebrahim Salehi, Rasul alizadeh, Alireza Darvish

Pages: 16-20

Abstract: This study investigates MHD mixed convection flow in a two parallel-plates vertical channel with reference to laminar, thermal and hydrodynamical developing flow of Newtonian fluid. The boundaries are considered to be isothermal with equal temperatures. The governing equations are solved numerically. Also, their dependence upon certain material parameters have been studied. Velocity, temperature, pressure gradient and Nusselt number profiles have also been presented

Title of the Paper: The Study of the Mixing Layer Particles Distribution in Dependence on the Convective Mach Numbers


Authors: Altyn Makasheva, Altynshash Naimanova

Pages: 7-15

Abstract: The numerical studies of the quasi twodimensional supersonic turbulent gas-particle mixing layer are performed using the 2D-DNS (Direct Numerical Simulations). The system of Navier-Stokes equations of a multi-species flow is solved using the ENO scheme of a third-order accuracy. The dispersion of the particles is simulated by the Lagrangian method following their trajectories in the mixing layer. The study focuses on the roles of the large-scale vortex structures in a particle dispersion dependence on the Stokes numbers and convective Mach numbers.

Title of the Paper: Application of Solar Organic Rankine System for Energy Generation in Buildings: the Case of Athens


Authors: G.K. Alexis, E.I. Sfinias

Pages: 1-6

Abstract: This paper describes the performance of an ORC system driven by solar energy and R134a as working fluid. The system is predicted along the twelve months of the year. The operation of the system and the related thermodynamics are simulated by suitable computer codes and the required local climate data are determined by statistical processing over a considerable number of years. It’s found that the solar to electricity efficiency of this SORC system varies from 0.049 to 0.058 while the ambient temperature varies from 11.3oC to 29.2oC and the total solar irradiance varies from 443 W/m2 to 679 W/m2. The system’s arrangement comprises a solar thermal array which is coupled with an organic Rankine engine. The mean annual overall efficiency of the SORC system is estimated at 0.055 while the thermodynamic efficiency of Rankine is calculated at 0.107. The obvious advantage of this arrangement is that electricity can be produced in buildings by using the existing common solar thermals installed. Easy–to–find machinery is employed in order to attain a simple and practical small–scale organic Rankine cycle arrangement coupled with common solar thermals used widely in Greek buildings for DHW production and space heating assistance.