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Showing 2 results for movahedirad
Hamid Hemmati, Mansoor Shirvani, Omid Vahidi, Salman movahedirad,
Volume 17, Issue 9 (11-2017)
Abstract
In the present study direct contact heat transfer between hot water and cold air in vertical pipes with cocurrent downward flow is investigated. Experiments are performed in turbulent condition using 1, 1.5, 2 meter pipes lengths with 0.021 meter diameter. The hot water temperature was varied between 35 to 50 degrees of Celsius and the air temperature was varied between 25 to 35˚C. Air velocities were chosen to be 3, 5, 7, 9 and 11 m/s and the rates of flow rate of water was selected as 5, 8 and 10 lit/min. Two phase annular flow pattern of water and air is formed in the vertical pipe. The interface area between water and air was measured by Image Processing taken from shining laser light sheet on the transparent tubes. Over 80 percent of heat was transferred by evaporation and less than 20 percent was transferred by convection. In all three pipes, Nusselt number decreased with increase in flowrate of liquid phase. In all the verified temperatures, Nusselt number was decreasing by increasing pipe length. Experimental values for Nusselt numbers were compered to empirical values for smooth surfaces. Finally, some adjustments were suggested for Nusselt number correlation by fitting experimental data into existing correlations for pipes with smooth surface. Proposed correlations for heat transfer resulted in Nusselt number with ±15.26% average error.
S. Jamshidifard , M. Shirvani, N. Kasiri Bidhendi , S. movahedirad ,
Volume 19, Issue 5 (May 2019)
Abstract
In this paper, black powder of the separation from air flow by a helical one-channel dust concentrator have been experimentally studied and the efficiency and pressure drop have been investigated by Computational fluid dynamics (CFD) simulations in different operating conditions. Experimental set-up is a helical one-channel including 29 branches for exporting diluted stream out. It also has two suction devices at the ends of channels in order to provide testing in high inlet flow. Black powder particles with certain particle size distribution have been tested, whose average particle size has been determined 0.327 µm by DLS and SEM images processing. CFD simulation of helical one-channel dust concentrator for air-black powder separation has been done with FLUENT software. The Realizable k-ε turbulent model, as an optimal turbulence model in terms of accuracy and speed in simulation, has been used. According to evaluation of the results, the experimental results have been compared and it showed 5.2% error. To investigate the effect of operating condition, the various air flow rate and solids mass fractions were investigated and the results showed that the simulation efficiency has increased more than 4.1% by increasing 58% of the inlet volumetric flow rate. The separation efficiency had no change by increasing the solid mass fraction from 7% up to 20%.
