scholarly journals Nanoparticle shape effect on the natural convection heat transfer of hybrid nanofluid inside a U-shaped enclosure

2021 ◽  
pp. 139-139
Author(s):  
Muhammad Asmadi ◽  
Zailan Siri ◽  
Ruhaila Kasmani ◽  
Habibis Saleh
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Hybrid Nanofluid ◽  
Shape Effect ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Triangular Finite Element ◽  
Nanoparticle Shape ◽  
Nusselt Numbers

The effect of nanoparticle shape on the natural convection heat transfer of Cu-Al2O3/water hybrid nanofluid inside a U-shaped enclosure is presented in this paper. The governing equations are transformed into the dimensionless form using dimensionless variables. A three-node triangular finite element method is used with the Newton-Raphson method to solve the problem numerically. The streamlines and isotherms as well as the local and average Nusselt numbers are presented for the fluid flow with Rayleigh number of 104 to 106.It is found that blade nanoparticle shape produces the highest heat transfer rate while sphere is the lowest.

Natural Convection Heat Transfer From Horizontal Rectangular Ducts

2006 ◽  
Vol 129 (9) ◽  
pp. 1195-1202 ◽  
Author(s):  
Mohamed E. Ali
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Rayleigh Numbers

Experimental investigations have been reported on steady state natural convection from the outer surface of horizontal ducts in air. Five ducts have been used with aspect ratios (Γ=duct height/duct width) of 2, 1, and 0.5. The ducts are heated using internal constant heat flux heating elements. The temperatures along the surface and peripheral directions of the duct wall are measured. Longitudinal (circumference averaged) heat transfer coefficients along the side of each duct are obtained for laminar and transition regimes of natural convection heat transfer. Total overall averaged heat transfer coefficients are also obtained. Longitudinal (circumference averaged) Nusselt numbers are evaluated and correlated using the modified Rayleigh numbers for transition regime using the axial distance as a characteristic length. Furthermore, total overall averaged Nusselt numbers are correlated with the modified Rayleigh numbers, the aspect ratio, and area ratio for the laminar and transition regimes. The longitudinal or total averaged heat transfer coefficients are observed to decrease in the laminar region and to increase in the transition region. Laminar regimes are obtained only at very small heat fluxes, otherwise, transitions are observed.

Natural Convection Heat Transfer From Vertical 5 × 5 Rod Bundles in Liquid Sodium

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Tohru Mizuuchi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Liquid Sodium ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Rod Bundles ◽  
Nusselt Numbers

Natural convection heat transfer from vertical 5 × 5 rod bundles in liquid sodium was numerically analyzed for two types of the bundle geometry (equilateral square array (ESA) and equilateral triangle array (ETA)). The unsteady laminar three-dimensional basic equations for natural convection heat transfer caused by a step heat flux were numerically solved until the solution reaches a steady-state. The phoenics code was used for the calculation considering the temperature dependence of thermophysical properties concerned. The 5 × 5 test rods for diameter (D = 7.6 mm), heated length (L = 200 mm), and L/d (=26.32) were used in this work. The surface heat fluxes for each cylinder were equally given for a modified Rayleigh number, (Rf,L)ij and (Rf,L)5×5,S/D, ranging from 3.08 × 104 to 4.19 × 107 (q = 1 × 104–7 × 106 W/m2) in liquid temperature (TL = 673.15 K). The values of S/D, which are ratios of the diameter of flow channel for bundle geometry to the rod diameter, for vertical 5 × 5 rod bundles were ranged from 1.8 to 6 on each bundle geometry. The spatial distribution of local and average Nusselt numbers, (Nuav)ij and (Nuav,B)5×5,S/D, on vertical rods of a bundle was clarified. The average value of Nusselt numbers, (Nuav)ij and (Nuav,B)5×5,S/D, for the two types of the bundle geometry with various values of S/D were calculated to examine the effect of the bundle geometry, S/D, (Rf,L)ij, and (Rf,L)5×5,S/D on heat transfer. The bundle geometry for the higher (Nuav,B)5×5,S/D value under the condition of S/D = constant was examined. The correlations for (Nuav,B)5×5,S/D for two types of bundle geometry above mentioned including the effects of (Rf,L)5×5,S/D and S/D were developed. The correlations can describe the theoretical values of (Nuav,B)5×5,S/D for the two types of the bundle geometry at S/D ranging from 1.8 to 6 within −12.64% to 7.73% difference.

Natural convection of a hybrid nanofluid subjected to non-uniform magnetic field within porous medium including circular heater

2019 ◽  
Vol 29 (4) ◽  
pp. 1211-1231 ◽  
Author(s):  
Mohsen Izadi ◽  
Nemat M. Maleki ◽  
Ioan Pop ◽  
S.A.M. Mehryan
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Hybrid Nanofluid ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Content Type ◽  
Porosity Coefficient

PurposeThis paper aims to numerically investigate the natural convection heat transfer of a hybrid nanofluid into a porous cavity exposed to a variable magnetic field.Design/methodology/approachThe non-linear elliptical governing equations have been solved numerically using control volume based finite element method. The effects of different governing parameters including Rayleigh number (Ra= 103− 106), Hartman number (Ha= 0 − 50), volume fraction of nanoparticles (φ= 0 − 0.02), curvature of horizontal isolated wall (a= 0.85 − 1.15), porosity coefficient (ε= 0.1 − 0.9) and Darcy number (Da= 10−5− 10−1) have been studied.FindingsThe results indicate that at low Darcy numbers close to 0, the average Nusselt numberNuaenhances as porosity coefficient increases. Fora= 1 anda= 1.15 in comparison witha= 0.85, the stretching of the isothermal lines is maintained from the left side to the right side and vice versa, which indicates increased natural convection heat transfer for this configuration of the top and bottom walls. In addition, at higher Rayleigh numbers, by increasing the Hartmann number, a significant decrease is observed in the Nusselt number, which can be attributed to the decreased power of the flow.Originality/valueThe authors believe that all the results, both numerical and asymptotic, are original and have not been published elsewhere.

Laminar Natural Convection Heat Transfer From Vertical 7 × 7 Rod Bundles in Liquid Sodium

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Tohru Mizuuchi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Liquid Sodium ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Rod Bundles ◽  
Nusselt Numbers ◽  
Rod Bundle ◽  
Laminar Natural Convection

Laminar natural convection heat transfer from vertical 7 × 7 rod bundle in liquid sodium was numerically analyzed to optimize the thermal–hydraulic design for the bundle geometry with equilateral square array (ESA). The unsteady laminar three-dimensional basic equations for natural convection heat transfer caused by a step heat flux were numerically solved until the solution reaches a steady-state. The code of the parabolic hyperbolic or elliptic numerical integration code series (PHOENICS) was used for the calculation considering the temperature dependence of thermophysical properties concerned. The 7 × 7 heated rods for diameter (D = 0.0076 m), length (L = 0.2 m) and L/D (=26.32) were used in this work. The surface heat fluxes for each cylinder, which was uniformly heated along the length, were equally given for a modified Rayleigh number, (Raf,L)ij and (Raf,L)Nx×Ny,S/D, ranging from 3.08 × 104 to 4.28 × 107 (q = 1 × 104∼7 × 106 W/m2) in liquid temperature (TL = 673.15 K). The values of ratio of the diagonal center-line distance between rods for bundle geometry to the rod diameter (S/D) for vertical 7 × 7 rod bundle were ranged from 1.8 to 6 on the bundle geometry with ESA. The spatial distribution of average Nusselt numbers for a vertical single cylinder of a rod bundle, (Nuav)ij, and average Nusselt numbers for a vertical rod bundle, (Nuav,B)Nx×Ny,S/D, were clarified. The average values of Nusselt number, (Nuav)ij and (Nuav,B)Nx×Ny,S/D, for the bundle geometry with various values of S/D were calculated to examine the effect of array size, bundle geometry, S/D, (Raf,L)ij and (Raf,L)Nx×Ny,S/D on heat transfer. The bundle geometry for the higher (Nuav,B)Nx×Ny,S/D value under the condition of S/D = constant was examined. The general correlations for natural convection heat transfer from a vertical Nx×Ny rod bundle with the ESA and equilateral triangle array (ETA), including the effects of array size, (Raf,L)Nx×Ny,S/D and S/D were derived. The correlations for vertical Nx×Ny rod bundles can describe the theoretical values of (Nuav,B)Nx×Ny,S/D for each bundle geometry in the wide analytical range of S/D (=1.8–6) and the modified Rayleigh number ((Raf,L)Nx×Ny,S/D = 3.08 × 104 to 4.28 × 107) within −9.49 to 10.6% differences.

Natural Convection From Horizontal Wires to Viscoelastic Fluids

1986 ◽  
Vol 108 (4) ◽  
pp. 790-795 ◽  
Author(s):  
M. L. Ng ◽  
J. P. Hartnett ◽  
E. Y. Kwack
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Shear Rate ◽  
Convection Heat Transfer ◽  
Viscoelastic Liquid ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Nusselt Numbers ◽  
Prandtl Numbers ◽  
Different Diameters

Natural convection heat transfer from horizontal wires of three different diameters (0.0254, 0.0508, and 0.0826 cm) to a pool of viscoelastic liquid was studied. Aqueous solutions of Natrosol and Polyox constituted the viscoelastic test fluids. The experimental Nusselt numbers were found to agree with the correlations recommended by Fand and Brucker for Newtonian fluids if the zero shear rate viscosity is used in the Rayleigh and Prandtl numbers.

ANALYSIS OF NATURAL CONVECTION HEAT TRANSFER BETWEEN TWO HORIZONTAL CYLINDERS AND THEIR ENCLOSURE

1992 ◽  
Vol 16 (1) ◽  
pp. 17-32 ◽  
Author(s):  
M. Lacroix
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Nusselt Numbers ◽  
Horizontal Cylinders ◽  
Rayleigh Numbers

A numerical study has been conducted for natural convection heat transfer for air around two horizontal heated cylinders placed inside a rectangular enclosure cooled from the side. Three cylinder spacings were investigated. The local and overall Nusselt numbers were determined over the range of Rayleigh numbers from 104 to 106. It is found that the thermal performance of the unit is strongly influenced by the Rayleigh number and, to a lesser extent, by the cylinder spacing. A correlation is suggested for the overall Nusselt number.

Natural Convection Heat Transfer From Vertical 7x7 Rod Bundles in Liquid Sodium

2017 ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Tohru Mizuuchi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Liquid Sodium ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Rod Bundles ◽  
Nusselt Numbers ◽  
Rod Bundle ◽  
Square Array

Natural convection heat transfer from vertical 7×7 rod bundle in liquid sodium was numerically analyzed to optimize the thermal-hydraulic design for the bundle geometry with equilateral square array, ESA. The unsteady laminar three dimensional basic equations for natural convection heat transfer caused by a step heat flux were numerically solved until the solution reaches a steady-state. The PHOENICS code was used for the calculation considering the temperature dependence of thermo-physical properties concerned. The 7×7 test rods for diameter (D = 7.6 mm), heated length (L = 200 mm) and L/d (= 26.32) were used in this work. The surface heat fluxes for each cylinder were equally given for a modified Rayleigh number, (Rf,L)ij and (Rf,L)Nx×Ny,S/D, ranging from 3.08×104 to 4.28×107 (q = 1×104∼7×106 W/m2) in liquid temperature (TL = 673.15 K). The values of S/D, which are ratios of the diameter of flow channel for bundle geometry to the rod diameter, for vertical 7×7 rod bundle were ranged from 1.8 to 6 on the bundle geometry with equilateral square array. The spatial distribution of average Nusselt numbers for a vertical single cylinder of a rod bundle, (Nuav)ij, and average Nusselt numbers for a vertical rod bundle, (Nuav,B)Nx×Ny,S/D, were clarified. The average value of Nusselt number, (Nuav)ij and (Nuav,B)Nx×Ny,S/D, for the bundle geometry with various values of S/D were calculated to examine the effect of array size, bundle geometry, S/D, (Rf,L)ij and (Rf,L)Nx×Ny,S/D on heat transfer. The bundle geometry for the higher (Nuav,B)Nx×Ny,S/D value under the condition of S/D = constant was examined. The general correlations for natural convection heat transfer from a vertical Nx×Ny rod bundle with the equilateral square and triangle arrays including the effects of array size, (Rf,L)Nx×Ny,S/D and S/D were derived. The correlations for vertical Nx×Ny rod bundles can describe the theoretical values of (Nuav,B)Nx×Ny,S/D for each bundle geometry in the wide analytical range of S/D (= 1.8 to 6) and the modified Rayleigh number ((Rf,L)Nx×Ny,S/D = 3.08×104 to 4.28×107) within −9.49 to 10.6 % differences.

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