Showing 6 results for Kouhikamali
Seyed Amirreza Hosseini, Ramin Kouhikamali,
Volume 16, Issue 5 (7-2016)
Abstract
Numerical simulation of boiling has always been a challenging problem in terms of the variety and effectiveness of two-phase models. Furthermore choosing an appropriate heat and mass transfer model increases the complexity of the solution. Problem of film boiling of saturated liquid is numerically simulated in this investigation by using of VOF (volume of fluid) model together with the geo-reconstruction of interface. Three phase change models of sharp interface model, Lee model and Tanasawa model are used at the same time on a single problem in order to calculate the rate of phase change and source terms. One-dimensional Stephan benchmark is solved for verification the numerical solver. The periodic Nusselt, flow pattern, bubble form and its detachment time have been studied in mentioned various phase change models. Also empirical coefficients used in both models of Lee and Tanasawa are presented. The results of Nusselt number obtained from simulation is compared with two empirical Nusselt correlations of Berenson and Klimenko. The results show good agreement with the Klimenko’s Nusselt. The results reveal although the Lee model is dependent on empirical coefficient, it is more accurate than the two other models for prediction of film boiling on flat plate.
Tohid Khakzand, Ramin Kouhikamali, Javad Mahmoudimehr,
Volume 17, Issue 2 (3-2017)
Abstract
Spray combustion is utilized in a number of engineering applications such as energy conversion, military industrial, furance and propulsion devices. Current work focused on the effect of liquid fuel droplet diameter on the efficiency of the combustion chamber and formed emission such as NOx and CO in a two-dimensional axisymmetric combustion chamber. The discrete phase model approach employed for simulating Combustion. The gas phase is simulated using an Eulerian approach; while the droplets are treated with a Lagrangian method. The coupling between the two phases and effect of radiation is considered. The mixture-fraction/probability density function (PDF) equilibrium chemistry model is used to predict the combustion of the vaporized fuel. Also, the conservative equations of mass, momentum and energy in the turbulent flow field were solved in conjunction with the k–ε two equation turbulence model. A numerical simulation was carried out to study the influence of droplet size on the formation and emission of NOx and other contaminants. This effect was investigated under different droplet diameter and type of injection. The following conclusions be drawn: Smaller droplets produce higher NOx emission than the larger ones. Larger droplets produce higher CO than Smaller ones.
Majid Amiralipour, Ramin Kouhikamali,
Volume 18, Issue 2 (4-2018)
Abstract
Iran is located in the warm and dry region of the Middle East, where summer temperature ranges from 35 to 50 0C in the majority of the regions. Some critical factors including hot weather, population growth, and reduction in water resources as a highly impressive factor in the recent decades, all have underlined more efficient use of power plant in Iran, such that the existing power plants must function properly in simultaneous generation. Thus, the current research presents a techno-economic analysis of the function of a combined cycle unit under the condition of conversion into a water and power co-generation system. In the system, both membrane and thermal water sweetener mechanisms are used in parallel. The performance of the system in different conditions of water and power demand has been investigated. The results show that when the Thermal and Revers Osmosi are in the system alone, they can produce about 7,000 and 1,400,000 cubic meters of fresh water per day.Following the modelling of the system, the economic analysis was also performed, and Changes in the price of water sales are shown in each of the water desalination units with increased capacity. Finally, considering the average water sale price as a objective function and combined cycle efficiency as another function, two-objective optimization was performed, and the results are presented in the form of Pareto Graph, which the highest efficiency and lowest sale price are 0.454 and 1.511, respectively
H. Gholami , R. Kouhikamali , N. Sharifi,
Volume 19, Issue 2 (February 2019)
Abstract
In this study, using volume of fluid method in open source software OpenFOAM, the phenomenon of evaporation in the porous medium was analyzed. At the beginning of the solution, the system consists of a water phase and a porous copper environment. In the next steps of numerical simulation and as a result of partial evaporation of water, the vapor phase appears as the second fluid phase. Water and vapor are assumed to be incompressible and incompatible, and the phenomenon of evaporation occurs unevenly. The interface between phases is modeled by the VOF method and the Lee model has been used to mass transfer between two phases of water and vapor. For surface tension between phases, the continuous surface force (CSF) method was considered. The comparison of simulation results with experimental results showed that the combined solver of porous medium evaporation would well estimate the rate of evaporation at different sections of the channel. In addition, the results of the wall temperature indicate that the channel is divided into two zones of heating and evaporation. In the region of heating, the temperature increases linearly with the channel length to reach saturation temperature. After the point of saturation, the wall temperature first remains constant and eventually forms an oscillatory shape, in which locally there are temperature jumps. The evaporated flow rate also increases at high intensity first, but in the end regions of the porous channel, its growth rate is slow.
M. Karimi , R. Kouhikamali ,
Volume 19, Issue 3 (March 2019)
Abstract
In the present study, the performance of zigzag demister has been numerically investigated for the separation of dispersed liquid droplets from the gas flow. In general, liquid droplets are dispersed from the gas flow in contact with the vane demister and the formation of the liquid film. Depending on the energy of the droplet collision to the surface, it is likely to occur splash drop into smaller droplets, which will reduce the separation efficiency of the system. In this study, by focusing on the flow collision regime near the surface, it is attempted to investigate the effect of the flow parameters and vane geometry on the separation efficiency and the pressure drop of flow. The Euler-Lagrange is used to simulate the flow and particle motion path. In this research, an experimental model is designed and constructed. Numerical solver results are validated, using the experimental data. The result of this study shows that separation efficiency decreased with increasing gas flow velocity, such that by increasing the 2.5 times of gas velocity, the separation efficiency will lead to a 10% decrease. It was also found that increasing the diameter and increasing the droplet would increase the separation efficiency. On the other hand, choosing the geometry of vane has a significant effect on the amount of the pressure drop of the passing flow. In a way that, by increasing the 50% of the vane angle, the pressure drop will increase 5 times.
F. Hosseinnejad , R. Kouhikamali ,
Volume 20, Issue 8 (August 2020)
Abstract
In the current study, experimental and numerical methods have been used to investigate the pressure drop and the separation efficiency of wire mesh demisters in an air-water system. Using the designed and manufactured experimental model, various parameters such as air velocity, packing density, and wire diameter in plastic and metallic demisters have been studied. Numerical simulation was carried out in two-dimensional and transient form using K-epsilon (k-ε) turbulence model in commercial software ANSYS Fluent and validated against experimental results. The Eulerian-Lagrangian discrete phase model was also used to simulate the water droplet trajectory at diameters of 0.2 and 0.05mm. The numerical simulation results are sufficiently accurate compared to the experimental data. The numerical solver predicts separation efficiency with error of about 20% and pressure drop with error of less than 20% compared to experimental data. The numerical simulation results show that increasing the diameter of water droplets at higher air velocities and higher packing densities is more effective and increases the separation efficiency up to 36%. Also, increasing the packing density increases the separation efficiency for droplets with a diameter of 0.2mm and decreases the separation efficiency for droplets with a diameter of 0.05mm. The results show that the separation efficiency of plastic demister is more than the separation efficiency of metallic demister and in lower packing densities, the use of plastic demister is advisable.
