scholarly journals Thermal and hydrodynamic characteristics of forced and mixed convection flow through vertical rectangular channels

2008 ◽  
Vol 12 (2) ◽  
pp. 103-117
Author(s):  
Abdalla Hanafi ◽  
Safaa Mahmoud ◽  
Hesham Elbakhshawangy
Keyword(s):  
Nusselt Number ◽  
Mixed Convection ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Convection Flow ◽  
Temperature Profiles ◽  
Mixed Convection Flow ◽  
Downward Flow ◽  
Flow Through ◽  
Flow Directions

This paper presents experimental and numerical studies for the case of turbulent forced and mixed convection flow of water through narrow vertical rectangular channel. The channel is composed of two parallel plates which are heated at a uniform heat flux, whereas, the other two sides of the channel are thermally insulated. The plates are of 64 mm in width, 800 mm in height, and separated from each other at a narrow gap of 2.7 mm. The Nusselt number distribution along the flow direction normalized by the Nusselt number for the case of turbulent forced convection flow is obtained experimentally with a comparison with the numerical results obtained from a commercial computer code. The quantitative determination of the nor- malized Nusselt number with respect to the dimension-less number Z = (Gr/Re21/8Pr0.5) is presented with a comparison with previous experimental results. Qualitative results are presented for the normalized temperature and velocity profiles in the transverse direction with a comparison between the forced and mixed convection flow for both the cases of upward and downward flow directions. The effect of the axial locations and the parameter Gr/Re on the variation of the normalized temperature profiles in the transverse direction for both the regions of forced and mixed convection and for both of the upward and downward flow directions are obtained. The normalized velocity profiles in the transverse directions are also determined at different inlet velocity and heat fluxes for the previous cases. It is found that the normalized Nusselt number is greater than one in the mixed convection region for both the cases of upward and downward flow and correlated well with the dimension-less parameter Z for both of the forced and mixed convection regions. The temperature profiles increase with increasing the axial location along the flow direction or the parameter Gr/Re for both of the forced and mixed convection regions, but this increase is more pronounced in the case of the mixed convection flow. For the forced convection region, the velocity profile depends only on Re with no difference between the upward and downward flow directions. Whereas, for the case of mixed convection flow, the velocity profile depends on the parameter Gr/Re with a main difference between upward and downward flow. These results are of great importance for any research reactor using plate type fuel elements or for any engineering application in which mixed convection flow through rectangular channel is encountered. .

Effect of Nanofluid on Heat Transfer Enhancement for Mixed Convection Flow Over a Corrugated Surface

2020 ◽  
Vol 45 (4) ◽  
pp. 373-383
Author(s):  
Nepal Chandra Roy ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Local Nusselt Number ◽  
Richardson Number ◽  
Thermal Boundary Layer ◽  
Volume Fraction ◽  
Convection Flow ◽  
Mixed Convection Flow

AbstractA mathematical model for mixed convection flow of a nanofluid along a vertical wavy surface has been studied. Numerical results reveal the effects of the volume fraction of nanoparticles, the axial distribution, the Richardson number, and the amplitude/wavelength ratio on the heat transfer of Al2O3-water nanofluid. By increasing the volume fraction of nanoparticles, the local Nusselt number and the thermal boundary layer increases significantly. In case of \mathrm{Ri}=1.0, the inclusion of 2 % and 5 % nanoparticles in the pure fluid augments the local Nusselt number, measured at the axial position 6.0, by 6.6 % and 16.3 % for a flat plate and by 5.9 % and 14.5 %, and 5.4 % and 13.3 % for the wavy surfaces with an amplitude/wavelength ratio of 0.1 and 0.2, respectively. However, when the Richardson number is increased, the local Nusselt number is found to increase but the thermal boundary layer decreases. For small values of the amplitude/wavelength ratio, the two harmonics pattern of the energy field cannot be detected by the local Nusselt number curve, however the isotherms clearly demonstrate this characteristic. The pressure leads to the first harmonic, and the buoyancy, diffusion, and inertia forces produce the second harmonic.

scholarly journals MHD Mixed Convection Micropolar Fluid Flow through a Rectangular Duct

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Mekonnen Shiferaw Ayano ◽  
Stephen T. Sikwila ◽  
Stanford Shateyi
Keyword(s):  
Magnetic Field ◽  
Differential Equations ◽  
Mixed Convection ◽  
Applied Magnetic Field ◽  
Flow Reversal ◽  
Convection Flow ◽  
Temperature Profiles ◽  
Rectangular Duct ◽  
Micropolar Fluid Flow ◽  
Flow Through

Mixed convection flow through a rectangular duct with at least one of the sides of the walls of the rectangle being isothermal under the influence of transversely applied magnetic field has been analyzed numerically in this study. The governing differential equations of the problem have been transformed into a system of nondimensional differential equations and then solved numerically. The dimensionless velocity, microrotation components, and temperature profiles are displayed graphically showing the effects of various values of the parameters present in the problem. The results showed that the flow field is notably influenced by the considered parameters. It is found that increasing the aspect ratio increases flow reversal, commencement of the flow reversal is observed after some critical value, and the applied magnetic field increases the flow reversal in addition to flow retardation. The microrotation components flow in opposite direction; also it is found that one component of the microrotation will show no rotational effect around the center of the duct.

Effects of Magnetic Field on an Unsteady Mixed Convection Flow of Nanofluids Containing Spherical and Cylindrical Nanoparticles

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Kalidas Das ◽  
Pinaki Ranjan Duari ◽  
Prabir Kumar Kundu
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Mixed Convection ◽  
Time Dependent ◽  
Convection Flow ◽  
Temperature Profiles ◽  
Mixed Convection Flow ◽  
Shooting Technique ◽  
Similarity Transformations ◽  
Unsteady Mixed Convection

The present article gives a ray of light on the effects of magnetic field on an unsteady mixed convection flow of nanofluids containing nanoparticles which are spherical and cylindrical in nature. The unsteadiness in the flow is mainly caused by time dependent stretching velocity and temperature of the sheet at the surface. The governing transportation equations are first transformed into ordinary differential equations by using similarity transformations and then solved by employing Runga–Kutta–Frelberg method with shooting technique. The influence of various parameters on velocity and temperature profiles as well as wall shear stress and the rate of mass transfer are discussed through graphs and tables. The results for regular fluid (water) from the study are in excellent agreement with the results reported in the literature.

scholarly journals Influence of differently shaped copper nanoparticles in mixed convection flow through a curved wavy channel

2021 ◽  
Vol 60 (3) ◽  
pp. 3305-3314
Author(s):  
Muhammad Qasim ◽  
Muhammad Usman Ashraf ◽  
Dianchen Lu ◽  
Abid Hussanan
Keyword(s):  
Mixed Convection ◽  
Copper Nanoparticles ◽  
Convection Flow ◽  
Mixed Convection Flow ◽  
Wavy Channel ◽  
Flow Through

Improvement of Correlative Approaches for Mixed Convective Flow Through a Horizontal Vent

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Kevin Varrall ◽  
Hugues Pretrel ◽  
Samuel Vaux ◽  
Olivier Vauquelin
Keyword(s):  
Mixed Convection ◽  
Literature Survey ◽  
Convection Flow ◽  
Safety Engineering ◽  
Mixed Convection Flow ◽  
Flow Rates ◽  
Laboratory Facility ◽  
Flow Through ◽  
Mixed Convective Flow ◽  
Horizontal Vent

This study deals with the mixed convection flow through a shallow horizontal vent linking two compartments (one over the other). Depending on the temperature difference of gas as well as the ventilation flow rate between the two compartments, the flow through the vent can be bi- or uni-directional. A literature survey highlights that three correlations are used in safety engineering to calculate these upward and downward mixed convection flow rates. Unfortunately, for the same conditions, these correlations give very different results and, to date, there is no common agreement in the scientific community to identify quantitatively the most accurate model. This study proposes a new assessment of these correlations based on new experimental data obtained from the laboratory facility as well from the industrial apparatus. In addition, an improvement of the best model is proposed which better reproduced the experimental results.

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