Showing 7 results for Jahanshahi Javaran
Behnam Khalili, Mohammad Rahnama, Saeed Jafari, Ebrahim Jahanshahi Javaran,
Volume 16, Issue 9 (11-2016)
Abstract
Investigation of fluid-solid interaction has been studied as an introduction to simulate a wide range of engineering problems such as fluidized beds, sediment transportation and catalyst inks in fuel cells. An efficient method for performing such simulations is a combination of Lattice Boltzmann method (LBM) and Smoothed Profile Method (SPM). In addition, the operations in the SPM are local; it can be easily programmed for parallel processing. In this approach, the flow is computed on fixed Eulerian grids which are also used for the particles. Owing to the use of the same grids for simulation of fluid flow and particles, this method is highly efficient for purpose of parallel processing by means of GPU. In this study, a combination of Lattice Boltzmann method (LBM) and Smoothed Profile method has been implemented in parallel processing on GPU. For validation purpose, the fluid flow within a channel was investigated. Results suggest that computational time can be reduced up to 80 times by means of GPU.Then, drag force exerted on a sphere in fluid flow and the sedimentation of one sphere in a quiescent fluid were studied. Results show that performance of GPU can be increased up to 6.5 million fluid nods per second by using this method.
Seyed Kazem Mousavi, Seyed Mohammad Hojjat Mohammadi, Ebrahim Jahanshahi Javaranehran, Mehran Ameri,
Volume 16, Issue 13 (Conference Special Issue 2017)
Abstract
Hoda Shabani Nejad, Seyed Abdolreza Gandjalikhan Nassab, Ebrahim Jahanshahi Javaran,
Volume 17, Issue 12 (2-2018)
Abstract
In the present study, combustion phenomenon and heat transfer in a 3-D rectangular porous radiant burner (PRB) are numerically studied. Methane- air mixture with detailed chemical kinetics is considered to model the combustion process inside the porous matrix. Assuming the non-local thermal equilibrium between solid and gas phases, separate energy equations are considered for two phases. Porous medium is assumed as a gray medium that can absorb, scatter, and emit thermal radiation, where the gas phase is considered to be transparent. The governing equations including gas and porous energy equations, the chemical species transport equation and the radiative transfer equation are simultaneously and numerically solved. Discrete ordinates method is used to solve the radiative transfer equation in order to calculate the radiative term in the solid energy equation. The simulation results include temperature fields for the gas and solid phase, species mass fraction distributions, and radiative heat flux profiles along the burner. Finally, the effect of different parameters such as optical thickness, scattering albedo, excess air ratio (EAR) and porosity on the performance of burner are explored.
Seyed Amir Hosseini Moghaddam, Masoud Iranmanesh, Ebrahim Jahanshahi Javaran, Abed Zadehgol,
Volume 18, Issue 8 (12-2018)
Abstract
In this research work, using the recently introduced entropic constant speed kinetic model and employing the Pseudo-Potential model of Shan and Chen (SC), two phase flow of incompressible and immiscible fluids through porous media is studied. Applications of the entropic kinetic models in simulating multi-phase and multi-component flows have been thoroughly investigated, during the past decade. Lack of an entropy function, in a kinetics based model, implies that the existence of a unique equilibrium state, under all flow conditions and for all positions and times, cannot be guaranteed by the model. Hence, simulation of two multi-phase flows with high density ratios, using the conventional kinetic models (which do not satisfy the second law of thermodynamics) may not yield proper results, due to numerical instabilities. In this research, performing numerical simulations, the accuracy and stability of the recently introduced constant speed kinetic model and the conventional lattice Boltzmann models have been compared with each other. The present simulations include the verification of the Laplace Law and the contact angles and two phase flow through simple channels. In addition to the above, two phase flow in porous media has been simulated and the relative permeability vs wettability has been reported. The obtained results are in excellent agreement with previous results reported by others researchers.
N. Sahraiyan, S.m.h. Mohammadi, E. Jahanshahi Javaran,
Volume 20, Issue 2 (February 2020)
Abstract
The application of solar energy for space cooling has been increasingly considered in Iran and other countries in the last two decades. In this study, two different configurations of a solar assisted refrigeration system have been studied. The first system is the combination of a lithium bromide vapor absorption refrigeration system and flat plate collectors. The other system is consisted of a compression refrigeration system and thermal photovoltaic panels. For this purpose, 32% of the roof area of the building has been covered with 105 flat plate collectors, each with a total area of 1.591 m2, or 288 photovoltaic panels each with an area of 0.556 m2. Both systems have been compared in terms of energy, exergy, and economic viewpoints. This comparison has been conducted for providing the 70 kW cooling capacity system required for an office building with an area of 500 m2. The results of this study showed that at an evaporator temperature of 5°C and the ambient temperature of 27°C, the coefficient of performance of the compression chiller is 3.5 and the absorption chiller is 0.71. Also, the total energy efficiency and the total exergy efficiency in the compression chiller system combined with thermal photovoltaic panels are 7.43% and 8.25% respectively. Those two parameters for the absorption chiller combined with flat plate collectors are 9.16% and 6.66%, respectively. In the economic analysis, the annual life cycle cost for the compression chiller system combined with thermal photovoltaic collectors is 9710 $ and this cost for the absorption chiller system combined with flat plate collectors is estimated 7649 $.
R. Safa , A. Soltani Goharrizi , S. Jafari , E. Jahanshahi Javaran,
Volume 20, Issue 3 (March 2020)
Abstract
In the present study, the combination of concentration lattice Boltzmann method with a smoothed profile method was used to simulate the dissolution of solid circular particles between parallel plates that are moving in opposite directions. The hydrodynamic simulation was performed based on the single relaxation time lattice Boltzmann method and the convection-diffusion equation was used to determine the concentration of the solute in the liquid phase. Additionally, the smoothed profile method was used to calculate the no-slip boundary condition at the liquid-solid interface and concentration forces. To evaluate the accuracy of the proposed model, the simulation results were compared with the empirical data in the literature. The difference between the simulation results and the empirical data for the Sherwood number at different Peclet numbers was less than 2%. The results show that the smallest dissolution time in systems with different volume fractions is in a system with the least volume fraction. As the volume fraction increases, the solid-liquid mass transfer driving force is decreased in the system. The simulation results showed that by increasing the Reynolds number from 0.05 to 0.38, the time required to reach the normalized volume fraction to 0.05 of its initial value reduced from 0.36 s to 0.17 s. Also, by increasing the Peclet number from 5.5 to 115, the Sherwood number increased from 1.74 to 4.06. In addition, the increase in the Schmidt number in the system leads to a slower dissolution time. Finally, the polydispersity in the system was studied.
S. Amiri Dogahe, E. Jahanshahi Javaran, M. Abdolzadeh Dashtkhaki, S. Sadeghi,
Volume 20, Issue 6 (June 2020)
Abstract
In this study, techno-economic comparison of monocrystalline and concentrating photovoltaic power plants for the selected cities of Kerman province was carried out. After modeling the implied photovoltaic systems and validating the modeling results of the monocrystslline photovoltaic system with the measured data of an installed 5kW monocrystalline photovoltaic power plant at the Graduate University of Advanced Technology, daily and yearly electrical energies production analysis for both plants was presented. Then, the electrical efficiency and the performance factors, including capacity factor, final yield, reference yield and the performance ratio were determined. The economic analysis results showed that the northern cities of Kerman province had more favorable economic indicators, so internal rate of return, balanced cost of electricity, net present value, and benefit-cost ratio for the monocrystal photovoltaic plant were 21-22.1%, 13.3-13.9 dollars per kilowatt, 2-4.2 thousand dollars, and 1.04-1.09, respectively and for the concentrating photovoltaic plant were 24.9-28.6%, 8.8-10.2 dollars per kilowatt, 17.1-30.5 thousand dollars, and 1.24-1.43, respectively. Finally, a comprehensive comparison was made between the conventional PV systems and the CPV system for two scenarios: the same capital investment cost and the same nominal installed power. Results showed that at both scenarios, the concentrating photovoltaic is superior to the monocrystalline PV plant, in a way that Kerman and Jiroft cities, as the best cities, had the net present value of 30.5 thousand dollars and 21 thousand dollars, respectively.
