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free-convection
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Determine the Thickness of Boundary Layer in Free Convection on the Vertical Plate With Uniform Heat Flux
, M.Sc. Thesis Sharif University of Technology ; Shafie, Behshad (Supervisor)
Abstract
Experiments were performed to explore the free convective hat transfer characteristics of water based nanofluids. Experiments of natural convection over a vertical flat plate with constant heat flux in water-based nanofluids with Ag and TiO2 nanoparticles were performed. Velocity boundary layer measured using PIV method. Also convective heat transfer coefficient obtained using three thermometers behind the wall. Various test cases with different heat fluxes on the wall are considered. Two volumetric concentrations of Ag nanofluid, 1% and 2%, and TiO2 nanofluid, 1% and 2%, were tested in the present study. It was shown that, with increasing nanofluid concentration, velocity boundary layer...
Investigation of the effect of walkway orientation on natural ventilation
, Article Scientia Iranica ; Volume 23, Issue 2 , 2016 , Pages 678-684 ; 10263098 (ISSN) ; Forughi, A. F ; Vesali, F ; Mahmoodabadi, M. S ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
Proper orientation of walkways, based on regional winds and local shade, provides good control over walkway ventilation. The architecture of the old town of Sirjan had experimentally orientated the city's walkways in such a manner that the shadows in the walkways produced the maximum possible natural ventilation in this hot and dry town. This study has focused on the optimum design of Sirjan city considering a natural ventilation mechanism. At first, a typical walkway with certain geometric parameters is considered. Then, considering the symmetry of the shadows cast in the walkway, the natural ventilation rate is investigated at 7 different angles and at 15° intervals. The problem is modeled...
Integration of Miniature Heat Pipes into a PEM Fuel Cell for Cooling Application
, M.Sc. Thesis Sharif University of Technology ; Roshandel, Ramin (Supervisor) ; Shafii, Mohammad Behshad (Co-Advisor)
Abstract
Due to the operation of proton exchange membrane fuel cell (PEMFC), temperature will rise because of the electrochemical reactions and control of temperature is one of the most important sections that has influence on the performance of the fuel cell. In this study three alternative for cooling and controlling the temperature situation is proposed and compared. the experimental setup consists of the simulated fuel cell that produce heat just like PEMFC and number of thermosyphon miniature heat pipes for evoke the heat and three types of condenser that makes three different scenario for this cooling setup. Free convection, force convection using Fan and force convection using circulating...
Analysis of nanoparticles migration on natural convective heat transfer of nanofluids
, Article International Journal of Thermal Sciences ; Volume 68 , June , 2013 , Pages 79-93 ; 12900729 (ISSN) ; Yaghoubi, M ; Sharif University of Technology
2013
Abstract
Both experimental and numerical studies are unanimous for enhancing Nusselt number for forced convection of nanofluids with slight difference, but there is inconsistency for natural convection heat transfer of nanofluids. In this paper attempt is made to study the effects of nanoparticles migration on the natural convection behavior of nanofluids. For analysis, a mixture model is used by including important phenomena such as Brownian motion and thermophoresis effects. These two mechanisms are taken into account to compute the slip velocities between the base fluid and nanoparticles. The governing equations are solved numerically and good agreements are observed in comparison with...
Two-dimensional free convection heat transfer below a horizontal hot isothermal flat strip
, Article Journal of Heat Transfer ; Volume 137, Issue 5 , May , 2015 ; 00221481 (ISSN) ; Nouri Gheimassi, A ; Salari, A ; Behshad Shafii, M ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2015
Abstract
Convection heat transfer below a horizontal, hot, and isothermal strip of infinite length and width of 2L embedded in fluids with different Prandtl number (Pr) and Nusselt number (Nu) is analyzed with the aid of integral method. A new concept is utilized to determine the boundary layer thickness at the strip's edge, which is based on matching the flow rate of the boundary layer below the strip at its edge and the flow rate of the plume, which forms after the heated fluid detaches from the strip's edge. In addition to these novelties, a numerical model is developed to verify the analytical framework, and an excellent agreement is observed between the analytical and numerical models
Natural convection of Al2O3-water nanofluid in an inclined enclosure with the effects of slip velocity mechanisms: Brownian motion and thermophoresis phenomenon
, Article International Journal of Thermal Sciences ; Volume 105 , 2016 , Pages 137-158 ; 12900729 (ISSN) ; Mehmandoust, B ; Karimipour, A ; Pakravan, H. A ; Sharif University of Technology
Elsevier Masson SAS
Abstract
Effects of inclination angle on natural convective heat transfer and fluid flow in an enclosure filled with Al2O3-water nanofluid are studied numerically. The left and right walls of enclosure are kept in hot and cold constant temperature while the other two walls are assumed to be adiabatic. Considering Brownian motion and thermophoresis effect (two important slip velocity mechanisms) the two-phase mixture model has been employed to investigate the flow and thermal behaviors of the nanofluid. The study was performed for various inclination angles of enclosure ranging from γ = 0° to γ = 60°, volume fraction from 0% to 3%, and Rayleigh numbers varying from 105 to 107. The governing equations...