Developing Flow With Combined Forced and Free Convection of Nanofluids for Horizontal Semicircular Ducts With the Flat Wall at the Vertical Position

2008 ◽  
Author(s):  
Yousef M. F. El Hasadi
Keyword(s):  
Boundary Condition ◽  
Nusselt Number ◽  
Friction Factor ◽  
Volume Concentration ◽  
Pure Water ◽  
Wall Friction ◽  
Vertical Position ◽  
Flow Conditions ◽  
Grashof Number ◽  
Flat Wall

This study is concerned with the numerical investigation of the developing laminar mixed convection of a nanofluid which consists of water- γAl2O3 in a horizontal semicircular duct with the flat wall at a vertical position. The governing momentum and energy equations are solved numerically using a marching technique with the finite control volume approach following the SIMPLER algorithm. The properties of the nanofluid have been simulated by using a well known models and correlations from the literature. Results are obtained for the thermal boundary condition of uniform heat input axially with uniform wall temperature circumferentially, at any cross section (H1 boundary condition), different values of particles volume concentration and for two values of Grashof number 104 and 106. These results include the velocity and temperature distributions at different axial locations, axial distributions of local Nusselt number, and local average wall friction factor. It was observed that increasing the nanoparticles concentrations at low Gr, has a negligible effect on the developing of Nusselt number and friction factor. However, at high Gr it was found that increasing the particle volume concentration increases the Nusselt number in the developing and fully developed regions and reduces the friction factor at the developing and fully developed regions, if it is compared to the results obtained from the results obtained from the pure water at the same flow conditions. As an example for the case of Grashof number equals to 106 and particles volume concentration equals to 0.1, the enhancement of the Nusselt number and the reduction of wall friction factor at the fully developed region, are 17.5% and 6.4% respectively, if it is compared to that of the base fluid (water), at the same flow conditions.

A Numerical Simulation of Heat Transfer Enhancement Using Al2O3 Nanofluid

2020 ◽  
Vol 10 (5) ◽  
pp. 610-621
Author(s):  
Taliv Hussain ◽  
Mohammad T. Javed
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Volume Concentration ◽  
Numerical Study ◽  
Pure Water ◽  
Maximum Deviation ◽  
Nanoparticle Concentration ◽  
Maximum Increase

Introduction: A numerical study is performed in which the friction factor and forced convection heat transfer is studied for Al2O3 nanoparticle dispersed in water as a base fluid. Methods: Four concentrations of nanofluids in the range of 0-2.5 vol% have been simulated. The Reynolds Number is varied in the range of 100-500 by varying inlet velocity. Cross flow of air is assumed over the pipe with air velocity of 2.2 m/s. Results: The results depict that the friction factor decreases with an increase in flow rate and increases with increase in volume concentration. The maximum deviation for friction factor obtained by simulation from that obtained using Darcy’s relation is about 21.5% for water. Nusselt number increases with increase in Reynolds Number and nanofluid volume concentration with a maximum of 7653.68 W/m2 at a nanoparticle concentration of 2.5% and Reynolds Number of 500. Heat transfer rate enhancement of upto 13.6% is obtained as compared to pure water. The maximum increase in Nusselt Number is about 13.07% for a nanoparticle concentration of 2.5%. Conclusion: The simulation results are compared with established relations obtained by other researchers and there is a good agreement in terms of trends obtained. The deviations from established relations are also depicted.

Laminar Mixed Convection in the Entrance Region of Horizontal Semicircular Ducts With the Flat Wall at the Top

2006 ◽  
Vol 129 (9) ◽  
pp. 1203-1211 ◽  
Author(s):  
Y. M. F. El. Hasadi ◽  
A. A. Busedra ◽  
I. M. Rustum
Keyword(s):  
Nusselt Number ◽  
Mixed Convection ◽  
Friction Factor ◽  
Entrance Region ◽  
Wall Friction ◽  
Flat Wall ◽  
Simpler Algorithm ◽  
Laminar Mixed Convection ◽  
Wide Range ◽  
Semicircular Ducts

Laminar mixed convection in the entrance region for horizontal semicircular ducts with the flat wall on top is investigated theoretically. The governing momentum and energy equations are solved numerically using a marching technique with the finite control volume approach following the SIMPLER algorithm. Results are obtained for the thermal boundary conditions of uniform heat input axially with uniform wall temperature circumferentially at any cross section (H1 boundary condition) with Pr=0.7 and a wide range of Grashof numbers. These results include the velocity and temperature distributions at different axial locations, axial distribution of local Nusselt number, and local average wall friction factor. It is found that Nusselt number values are close to the forced convection values near the entrance region and then decrease to a minimum as the distance from the entrance increases and then rise due to the effect of free convection before reaching constant value (fully developed). As the Grashof number increases the Nusselt number and the average wall friction factor increase in both developing and fully developed regions and the location of the onset of the secondary flow moves upstream.

Effect of Pr on the Development of Upward Laminar Mixed Convection in the Entrance Region of Vertical Quarter Circle Ducts

2007 ◽  
Author(s):  
Yousef M. F. El Hasadi
Keyword(s):  
Boundary Condition ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Friction Factor ◽  
Local Nusselt Number ◽  
Entrance Region ◽  
Wall Friction ◽  
Simpler Algorithm ◽  
Laminar Mixed Convection ◽  
Wide Range

Upward laminar mixed convection in the entrance region for vertical quarter circle ducts is investigated theoretically. The governing momentum and energy equations are solved numerically using a marching technique with finite control volume approach following the SIMPLER algorithm. Results are obtained for the thermal boundary condition of uniform heat input axially with uniform wall temperature circumferentially at any cross section (H1 boundary condition) with Pr = 7.0 and 0.7 which corresponds to water and air respectively, Re = 500 and wide range of Grashof numbers. These results include the velocity and temperature distributions, at different axial locations, axial distribution of local Nusselt number and local average wall friction factor. It is found that the local Nusselt number follows the expected behavior of monotonic decrease along the developing region down to the fully developed region. However, the axial development of the local friction factor follows a different trend than that of local Nusselt number. The effect of Grashof number is to increase the values of local Nusselt number and friction factor in the developing and fully developed regions. The effect of Pr is mainly in the entrance region where the values of Nusselt number and friction factor corresponding to air are higher than those of water; however, the flow in the fully developed region is independent of Pr.

scholarly journals The Effect of Nanofluid Volume Concentration on Heat Transfer and Friction Factor inside a Horizontal Tube

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Adnan M. Hussein ◽  
K. V. Sharma ◽  
R. A. Bakar ◽  
K. Kadirgama
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Thermal Properties ◽  
Friction Factor ◽  
Volume Concentration ◽  
Convection Heat Transfer ◽  
Horizontal Tube ◽  
Maximum Deviation ◽  
Flat Tube

The additives of solid nanoparticles to liquids are significant enhancement of heat transfer and hydrodynamic flow. In this study, the thermal properties of three types of nanoparticles (Al2O3, TiO2, and SiO2) dispersed in water as a base fluid were measured experimentally. Forced convection heat transfer turbulent flow inside heated flat tube was numerically simulated. The heat flux around flat tube is 5000 W/m2and Reynolds number is in the range of5×103to50×103. CFD model by finite volume method used commercial software to find hydrodynamic and heat transfer coefficient. Simulation study concluded that the thermal properties measured and Reynolds number as input and friction factor and Nusselt number as output parameters. Data measured showed that thermal conductivity and viscosity increase with increasing the volume concentration of nanofluids with maximum deviation 19% and 6%, respectively. Simulation results concluded that the friction factor and Nusselt number increase with increasing the volume concentration. On the other hand, the flat tube enhances heat transfer and decreases pressure drop by 6% and −4%, respectively, as compared with circular tube. Comparison of numerical analysis with experimental data available showed good agreement with deviation not more than 2%.

Roughness Effects on Flow and Heat Transfer for Additively Manufactured Channels

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Curtis K. Stimpson ◽  
Jacob C. Snyder ◽  
Karen A. Thole ◽  
Dominic Mongillo
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Flow Conditions ◽  
Roughness Effects ◽  
Flow And Heat Transfer ◽  
Technological Advances ◽  
Rectangular Channels ◽  
Significant Augmentation ◽  
Flow Through

Recent technological advances in the field of additive manufacturing (AM), particularly with direct metal laser sintering (DMLS), have increased the potential for building gas turbine components with AM. Using the DMLS for turbine components broadens the design space and allows for increasingly small and complex geometries to be fabricated with little increase in time or cost. Challenges arise when attempting to evaluate the advantages of the DMLS for specific applications, particularly because of how little is known regarding the effects of surface roughness. This paper presents pressure drop and heat transfer results of flow through small, as produced channels that have been manufactured using the DMLS in an effort to better understand roughness. Ten different coupons made with the DMLS all having multiple rectangular channels were evaluated in this study. Measurements were collected at various flow conditions and reduced to a friction factor and a Nusselt number. Results showed significant augmentation of these parameters compared to smooth channels, particularly with the friction factor for minichannels with small hydraulic diameters. However, augmentation of Nusselt number did not increase proportionally with the augmentation of the friction factor.

Heat Transfer Enhancement in Laminar Graetz and Taylor Flows Using Nanofluids

2018 ◽  
Author(s):  
K. Alrbee ◽  
Y. S. Muzychka ◽  
X. Duan
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Aluminum Oxide ◽  
Heat Transfer Enhancement ◽  
Pure Water ◽  
Flow Conditions ◽  
Transfer Enhancement ◽  
Segmented Flow ◽  
Constant Wall Temperature ◽  
Developing Flow

This paper focuses on heat transfer in mini scale tubes under laminar developing flow conditions for a constant wall temperature boundary condition. An experimental study was preformed using Aluminum Oxide nanoparticles (< 50nm) for continuous and segmented fluid streams. A two step method was employed to prepare several samples of aluminum oxide nanofluid with different concentrations 0.25, 0.5 and 1% by volume. Heat transfer enhancement in mini scale tubes (∼1 mm) was assessed using the dimensionless Graetz parameter L*, dimensionless mean wall heat flux q*, and Nusselt number Nu. In this study we investigate the effect of nanofluid concentration on laminar heat transfer enhancement in mini-scale circular tube under continuous and segmented flow using gas as a segmenting medium. The initial results show a maximum of 10–65% enhancement of Nusselt number as compared with pure water under the same conditions as a function of L*. For the upper limit of concentration of 1% Al2O3 nanofluid, the friction factor was found to be less than 5% greater, which means a small sacrifice on pumping power is to be expected. This study provides new insights on the thermal behaviour of nanofluids under laminar developing flow and segmented flow conditions in straight tubes.

scholarly journals Experimental Investigation of Heat Transfer of Nanofluid in Elliptical and Circular Tubes

2021 ◽  
Vol 8 (4) ◽  
pp. 665-671
Author(s):  
Ammar M. Al-Tajer ◽  
Abdulhassan A. Kramallah ◽  
Ali M. Mohsen ◽  
Nabeel Sameer Mahmoud
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Volume Concentration ◽  
Pressure Change ◽  
Experimental Comparison ◽  
Distilled Water ◽  
Cross Sectional ◽  
Pressure Drops ◽  
Circular Tubes

The paper presents experimental comparison of forced convection for steady state turbulent flow of nanofluid (Al2O3-distilled water) inside circular and elliptical (aspect ratio of 0.75) cross section tubes of identical circumference and tube surface area. Convection coefficient, pressure change, and fiction factor were compared at different Reynolds number (3,000-9,230) with different nanoparticles volume concentration (0.5%, 1.0%, and 1.5%). The results showed that Nusselt number increases with increasing Reynolds number and nanoparticle volume concentration. The pressure drops and friction factor of nanofluid are higher than the distilled water and are increasing as the volume concentration increases. Furthermore, the elliptical tube provided small increase in Nusselt number compared to that of circular cross sectional tube. However, the friction factor in the elliptical tube was slightly higher.

scholarly journals Thermal–Hydraulic Performance in a Microchannel Heat Sink Equipped with Longitudinal Vortex Generators (LVGs) and Nanofluid

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 231
Author(s):  
Basel AL Muallim ◽  
Mazlan A. Wahid ◽  
Hussein A. Mohammed ◽  
Mohammed Kamil ◽  
Daryoush Habibi
Keyword(s):  
Nusselt Number ◽  
Friction Factor ◽  
Heat Sink ◽  
Pure Water ◽  
Hydraulic Performance ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Fanning Friction Factor

In this study, the numerical conjugate heat transfer and hydraulic performance of nanofluids flow in a rectangular microchannel heat sink (RMCHS) with longitudinal vortex generators (LVGs) was investigated at different Reynolds numbers (200–1200). Three-dimensional simulations are performed on a microchannel heated by a constant temperature with five different configurations with different angles of attack for the LVGs under laminar flow conditions. The study uses five different nanofluid combinations of Al2O3 or CuO, containing low volume fractions in the range of 0.5% to 3.0% with various nanoparticle sizes that are dispersed in pure water, PAO (Polyalphaolefin) or ethylene glycol. The results show that for Reynolds number ranging from 100 to 1100, Al2O3–water has the best performance compared with CuO nanofluid with Nusselt number values between 7.67 and 14.7, with an associated increase in Fanning friction factor by values of 0.0219–0.095. For the case of different base fluids, the results show that CuO–PAO has the best performance with Nusselt number values between 9.57 and 15.88, with an associated increase in Fanning friction factor by 0.022–0.096. The overall performance of all configurations of microchannels equipped with LVGs and nanofluid showed higher values than the ones without LVG and water as a working fluid.

TURBULENT-FORCED CONVECTIVE HEAT TRANSFER AND PRESSURE DROP ANALYSIS OF FE3O4 MAGNETIC NANOFLUID IN A CIRCULAR MICROCHANNEL

2015 ◽  
Vol 75 (11) ◽  
Author(s):  
Nor Azwadi Che Sidik ◽  
M.M. Yassin ◽  
M.N. Musa
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Concentration ◽  
Pure Water ◽  
Dimensional Structure ◽  
Outlet Section

A numerical simulation was accomplished in this study that investigated the turbulent force convective heat transfer and pressure drop in straight circular copper pipe with a hydraulic diameter of 0.0005m and 0.1m in length, as given by Lee and Mudawar [11]. The enhancement of heat transfer for water and nanofluids (Fe3O4) under 100 [W/m2] constant heat flux was applied around the wall of the pipe. In this study, standard k-ɛ turbulence model was employed and was performed at a steady state flow, incompressible turbulent flow, and three-dimensional structure. Various volume concentrations of nanoparticles were conducted in the range of 1% to 15% at constant nanoparticle diameter size, which was 32 nm. The heat transfer enhancement was obtained in the range of Reynolds number from 3000 to 10,000. The results displayed an increase in Reynolds number and volume concentrations, as well as an increase in the Nusselt number. The optimum Nusselt number gained was about 5% to 6% of volume concentration at each Reynolds number tested. Besides, with the increase of Reynolds number, the variation pressure saw a dropped for inlet, whereas an increase in the outlet section. Moreover, the  increase in volume concentration also caused a small increment in the pressure drop compared to pure water.

Pressure Drop and Heat Transfer of Nanofluid in Turbulent Pipe Flow Considering Particle Coagulation and Breakage

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Jian-Zhong Lin ◽  
Yi Xia ◽  
Xiao-Ke Ku
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Pipe Flow ◽  
Volume Concentration ◽  
Particle Diameter ◽  
Turbulent Pipe Flow ◽  
Particle Volume ◽  
Friction Factors

Numerical simulations of Al2O3/water nanofluid in turbulent pipe flow are performed with considering the particle convection, diffusion, coagulation, and breakage. The distributions of particle volume concentration, the friction factor, and heat transfer characteristics are obtained. The results show that the initial uniform distributions of particle volume concentration become nonuniform, and increase from the pipe wall to the center. The nonuniformity becomes significant along the flow direction from the entrance and attains a steady state gradually. Friction factors increase with the increase of particle volume concentrations and particle diameter, and with the decrease of Reynolds number. The friction factors increase remarkably at lower volume concentration, while slightly at higher volume concentration. The presence of nanoparticles provides higher heat transfer than pure water. The Nusselt number of nanofluids increases with increasing Reynolds number, particle volume concentration, and particle diameter. The rate increase in Nusselt number at lower particle volume concentration is more than that at higher concentration. For a fixed particle volume concentration, the friction factor is smaller while the Nusselt number is larger for the case with uniform distribution of particle volume concentration than that with nonuniform distribution. In order to effectively enhance the heat transfer using nanofluid and simultaneously save energy, it is necessary to make the particle distribution more uniform. Finally, the expressions of friction factor and Nusselt number as a function of particle volume concentration, particle diameter and Reynolds number are derived based on the numerical data.

Sign in / Sign up

Export Citation Format

Share Document