Showing 4 results for Abbasian Arani
Ali Akbar Abbasian Arani, Narges Hatami Nesar, Mohammad Rezaee,
Volume 14, Issue 6 (9-2014)
Abstract
In this work, mixed convection of Cu-water nanofluid in a trapezoidal enclosure with heat source on lateral walls has been numerically investigated. Vertical walls of the enclosure are kept at constant temperatures of Th and Tc, while horizontal walls are insulated. The mixed convection flow has been generated by passing the fluid through the enclosure and natural convection has been, also, investigated by holding the left wall at a temperature higher than the right wall. In order to examine the effect of the ports position, two cases were considered. Comparison between the results indicates that the rate of heat transfer is higher when the inlet port is near the cold wall than the hot wall. The results have been presented for various volume fractions, Richardson and Reynolds numbers. It was observed that for the considered Reynolds numbers and Richardson number, at a given Reynolds number and solid volume fraction, the Nusselt number increases with increasing the Richardson number. Moreover, at a given Richardson number and solid volume fraction, increasing the Reynolds number results in an increase in the Nusselt number. For the higher Richardson and Reynolds numbers, the nanofluid has more effect on the increase of the heat transfer performance.
M. Rashidinejad , R. Maddahian, A.a. Abbasian Arani,
Volume 20, Issue 4 (April 2020)
Abstract
The closed-circuit cooling tower is described as the combination of both wet and dry cooling towers that hot water passes through the bundle of tubes as in the dry cooling towers and surrounding air passes around them in a forced or natural regimes. Thus, secondary water circulates as an open cycle and is sprayed on the bundle of tubes to preserve the tower cooling process. In the present research, the operation of a model of the closed-circuit wet cooling tower has been investigated numerically and experimentally. The effects of environmental condition on process water temperature, sprayed water temperature and air temperature have been evaluated, and the mass and heat transfer coefficients on the surface of hot water tubes have been calculated. According to these results, surrounding air temperature and humidity increasing decreases the tube outer surface mass and heat transfer coefficients. The mass and heat transfer coefficients rates are decreased by about 3% and 4% between the 278 and 288 K and are 6% and 7% between the 288 and 298 K inlet air temperature, respectively. The mass and heat transfer coefficients are both 18% for air inlet temperature between the 298 and 308 K. After 308 K these values are 4%. The decreasing rate of heat and mass transfer coefficient with increasing relative humidity from 10% to 20% is very low and from 20% to 40% is almost constant, and from 40% to 50% a 16% decrease in heat and mass transfer coefficients is observed.
Reza Maddahian, Ali Akbar Abbasian Arani, Mohsen Rashidinejad,
Volume 20, Issue 11 (October 2020)
Abstract
The main disadvantage of natural draft dry cooling towers is the influence of atmospheric conditions as ambient temperature and wind speed on the thermal performance. Wind disrupts the natural flow of air inside the tower creating vortices at the back and inside the tower that disrupts the air flow structure. When the wind blows, increasing the velocity of inlet air through the front louvers causes the air to pass through the behind louvers rather than outlet opening. The negative effect of this phenomenon reduces the cooling performance and consequently reduces the turbine production power in power plants. A good solution to this problem is to adjust the Louvers angle correctly. Therefore, in the present study, the thermal performance of the dry cooling tower was evaluated under the conditions of opening and closing the front louvers and changing their angle. In this regard, a natural draft dry cooling tower unit with the dimensions of the cooling tower located in combined cycle power plant was simulated in 3D using fluent software and the numerical results with the experimental data have been validated. The Realizable k-ε turbulent model is used to model the turbulent flow and the performance of the tower has been studied in three modes, including no wind, with the wind and the fully open louvers and with the wind and the semi-open louvers. According to the results, by partially removing the louvers to 60°, the heat transfer can be increased to 16% and the mass flow rate to 15%.
Mehrdad Kiani, Ali Akbar Abbasian Arani, Ehsan Houshfar, Mehdi Ashjaee,
Volume 24, Issue 3 (March 2024)
Abstract
The great attention and interest of researchers to use ammonia in combustion systems as a carbon-free fuel for gas turbines, as well as the existence of developed infrastructure for its production, show the importance of present fuel and this issue. In addition, one of the best candidates for storing renewable energies on large scales or transporting them for long distances is doubtlessly Ammonia (NH3). In gas turbines and boilers, adding landfill gas improve NH3 reactivity effectively. The present effort studies NH3/landfill mixtures’ laminar flame propagation from 1 to 10 atm in an 11-liter constant volume combustion chamber using experimental approaches such as Mach-Zehnder and Schlieren interferometry method. The numerical study was performed using the Ansys Chemkin-Pro package via San Diego, Okafor, and GRI-Mech 3.0 mechanisms which can provide very accurate predictions for laminar burning velocities. The results indicated that the most considerable influence on increasing laminar burning velocities could be attributed to Ammonia concentration in the mixture. The experiments also showed that laminar burning velocity is reduced when the pressure is increased.
