Showing 7 results for Hashemabadi
Mohammad Salimi, Seyed Mohsen Peyghambarzadeh, Seyed Hasan Hashemabadi, Alireza Chabi,
Volume 15, Issue 2 (4-2015)
Abstract
In this study, the forced convective heat transfer of pure water and alumina-water nanofluid with volume concentration of 0.5% and 1%, as a cooling fluid through a microchannel heat exchanger was experimentally investigated. This microchannel consists of 17 parallel channels with a rectangular cross section with 400 µm width, 560 µm height and 50 mm length. The experiments were performed in the range 600 to 1800 of Reynolds and constant heat flux conditions (19 W/cm2). Stability studies showed that alumina-water nanofluid at pH = 3 for 3 hours in a bath of the ultrasonic vibrating demonstrate the maximum stability. The variations of microchannel surface temperature, fluid temperature at the entrance region of the microchannel, average heat transfer coefficient of nanofluid and pure water, and their friction factor measured experimentally. Also comparison between average Nusselt number with existing heat transfer relationships was performed. The results show that heat transfer using nanofluid shows considerably increase in comparison to water. So that the maximum amount of average heat transfer coefficient for alumina-water nanofluid with 0.5% concentrations is about 32.8% and for alumina-water nanofluid with 1% concentrations about 49.7% in comparison to pure water. It was also found that the heat transfer coefficient increases with increasing Reynolds number and nanoparticle volume fraction.
Mahdi Hashemabadi, Mostafa Hadidoolabi,
Volume 15, Issue 5 (7-2015)
Abstract
In this paper, an implicit high order discretization has been developed for gridless method. In recent decade, gridless method using a distribution of points has become an important research topic in computational fluid dynamics. Gridless method usually uses the first order Taylor series for discretization of the space derivatives at any points. This paper presents an extension of high order for a central difference gridless method and investigates the results accuracy and performance of this method for solving inviscid compressible flows. Euler equations have been solved in two dimensional using second and fourth order artificial dissipation terms. These terms make a fast gridless method. The method of discretization in time, Explicit and dual-time implicit time discretization are used. In order to reduce the computational cost, local time stepping and residual smoothing techniques are utilized to speed up convergence. The capabilities and accuracy of the method are compared with finite volume method and experimental data for airfoils in transonic and supersonic flows. Results show that the second order accuracy solutions with fewer point distributions indicate higher accuracy when compared to the first order accuracy solutions in transonic and supersonic flows.
F. Asaadi, M. Eyvazi, M. Shirvani, S.h. Hashemabadi,
Volume 18, Issue 8 (12-2018)
Abstract
In this paper, the separation black powder from air flow experimentally have been studied by spiral-channels dust separator and the efficiency and pressure drop of spiral-channels dust separator has been investigated by CFD simulations in different operating conditions. Powder particles have been tested from a sample of powders of Saveh Strengthening Station, whose average particle size has been determined by DLS and SEM images processing, 0.327 micrometers. CFD simulation of spiral-channels dust separator has been done with FLUENT software. The RNG k-ε turbulent model as an optimal turbulence model has been used. The difference between the experimental and the simulation results was revealed around 16% and 7.15% for efficiency and pressure drop parameters respectively. To illustrating the effect of operating condition, the various flow rate and solids mass fraction were investigated and results showed that maximum efficiency is the highest input volumetric flow rate. Also, the results showed that this system has the efficiency of more than 80% for separating Black Powder particles and with increasing 40% of the volumetric flow rate, the separation efficiency increased up to 10%. If, by increasing the mass fraction of solids by 5 times, the efficiency increased only by 3%. The pressure drop of the separator increased up to about 50% with increasing the volumetric flow rate from 80 to 140 m3/hr.
Volume 19, Issue 3 (5-2017)
Abstract
Microwave assisted fluidized bed drying is a novel drying technique which reduces drying time and yields higher quality products. In this study the effect of this method on color changes of whole and cut hazelnut kernels was investigated. The parameters of color and resulting total color change, chroma, Hue angle and browning index were also calculated during drying in three temperatures (40, 50 and 60°C) and microwave power levels (0, 450 and 900W). Comparison was made to investigate the effect of drying condition on browning of hazelnut surface and internal cavity. The zero and first order kinetic models were also fitted to whole and cut kernel color parameters. The results showed similar behavior in color parameters of whole and cut kernels. L value and Hue angle decreased with increasing drying time, drying air temperature and microwave power but a, b, ΔE, chroma and browning index increased. L and b values of whole kernels were higher than cut kernels but the a value was lower. Zero-order model was selected as the best model for predicting a, b and ΔE while first order model best described the kinetics of color changes of L, chroma, Hue angle and browning index.
B. Sharifi, S.h. Hashemabadi,
Volume 19, Issue 6 (June 2019)
Abstract
In the present study, CFD simulation of Transit-time ultrasonic flowmeter with the PZT-5J piezoelectric sensor was modeled for light, heavy, and medium crude oil by the wave equation in the acoustic wave propagation path and finite element solving method in the unsteady state and it was implemented, using COMSOL Multiphysics 5.3 software. Different samples of light, heavy, and medium crude oil at different temperatures were modeled and simulated under constant pressure, using CFD tools. voltage and speed of sound in were calculated by the proposed model. To evaluate the accuracy of the proposed model, the simulation results were compared with the empirical data obtained from the experimental work of the researchers. The average values of the maximum voltage of signals for an ultrasonic containing light, heavy, and medium light crude oil samples are 0.9491, 1.0115, and 0.943 v, respectively. The difference between the simulation results and the experimental data for the speed of sound in the light, heavy, and medium crude oil samples was at most about 0.2336%, 0.4339%, and 0.1378%, respectively. Therefore, the high costs of designing and optimizing the transit-time ultrasonic flowmeter for crude oil can be reduced, using the proposed model.
B. Rahmati, S.h. Hashemabadi, M. Salemi Mojarrad,
Volume 20, Issue 7 (July 2020)
Abstract
The present study is a numerical model for prediction of turbine flowmeter performance, using the equation of motion based on torque balance theory. In this model, numerical simulations were carried out for a 2-inch diameter G65 and PN/ANSI 150 gas turbine flowmeter which was made by Vemmtec Company, in steady state, using Multiple Reference Frame (MRF) model and Standard k-ε turbulence model using Fluent software. In order to model torque balance equation and calculate angular velocity of rotor, a UDF (User Defined Function) code was created and was added to the software. To evaluate the model's accuracy, simulation results were compared with experimental data which was obtained from manufacturer of the meter. The difference between the simulation results and experimental data was 0.16%, approximately, which indicates the validity of the proposed model in simulating of turbine gas flowmeter performance. The results obtained from the simulation depicted that the velocity distribution asymmetry was more than 0.4Qmax at the downstream of the meter, and because this phenomenon had no negative effect on flow measurement, the suitable length for the flow development for the downstream of meter was done using simulation at least 10 times the diameter of the pipe was proposed. Therefore, using the proposed model, the capital cost of design and optimization of turbine flowmeters can be reduced.
H. Farahzadi, S.h. Hashemabadi, M. Shirvani,
Volume 20, Issue 9 (September 2020)
Abstract
Using vortex flowmeter is affordable, in addition, simple installation, high reliability, and high accuracy are some advantages of the vortex flowmeter. Vortex flowmeter works based on the vortex shedding principle, hence, the presence of particles in gas-solid flows may results in modulation in the turbulence intensity of the carrier phase and manipulate vortex shedding generated by a bluff body. In this study, the performance of the vortex flowmeter in the presence of particles with different sizes, density, solid volume fraction, and solid mass loading was studied with CFD simulation. The results indicated that the volume fraction and particles diameter are two significant parameters that affect vortex frequency. The vortex frequency is proportional to the velocity of gas flow and volume flow rate is calculated by Q= VA where V is average velocity in a pipe section with the area of A. Notwithstanding the neutral effect of microparticles on vortex frequency, moderate particles lessen the vortex frequency approximately by 20%. To coincide with the increase of solid volume fraction, the vortex frequency will descend, and in the high level of solid volume fraction, the vortex pattern goes to reach the instability. Since the size and volume fraction of the particles affects the frequency and consequently velocity, the gas flow rate measured by the vortex flowmeter is influenced by the presence of the particles. The numerical results have been validated with experimental data. The maximum relative error between the numerical simulation and the corresponding experimental data is 0.46% and 6.72 % for single-phase and gas-solid two-phase flows, respectively.
