Effect of Inclination Angle on Three-Dimensional Combined Convective Heat Transfer of Nanofluids in Rectangular Channels

2013 ◽  
Vol 388 ◽  
pp. 176-184
Author(s):  
Hussein A. Mohammed ◽  
Nur Irmawati Om ◽  
Mazlan A. Wahid
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Inclination Angle ◽  
Pure Water ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Flow And Heat Transfer ◽  
Rectangular Channels ◽  
Energy Equations ◽  
Volume Method

Combined convective nanofluids flow and heat transfer in an inclined rectangular duct is numerically investigated. Three dimensional, laminar Navier-Stokes and energy equations were solved using the finite volume method. Pure water and four types of nanofluids such as Au, CuO, SiO2 and TiO2with volume fractions range of 2% φ 7% are used. This investigation covers the following ranges: 2 × 106 Ra 2 × 107, 100 Re 1000 and 30° Θ 60°. The results revealed that the Nusselt number increased as Rayleigh number increased.SiO2nanofluid has the highest Nusselt number while Au nanofluid has the lowest Nusselt number. An increasing of the duct inclination angle decreases the heat transfer.

Characteristics of Fully Developed Flow and Heat Transfer in Channels With Varying Wall Geometry

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Abhishek G. Ramgadia ◽  
Arun K. Saha
Keyword(s):  
Heat Transfer ◽  
Time Dependent ◽  
Navier Stokes ◽  
Fully Developed Flow ◽  
Flow And Heat Transfer ◽  
Collocated Grid ◽  
Wall Profile ◽  
Energy Equations ◽  
Volume Method ◽  
Wall Geometry

Present study focuses on numerical investigation of fully developed flow and heat transfer through three channels having sine-shaped, triangle-shaped, and arc-shaped wall profiles. All computations are performed at Reynolds number of 600. Finite volume method on collocated grid is used to solve the time-dependent Navier–Stokes and energy equations in primitive variable form. For all the geometries considered in the study, the ratios Hmin/Hmax and L/a are kept fixed to 0.4 and 8.0, respectively. The thermal performances of all the three wall configurations are assessed using integral parameters as well as instantaneous, time-averaged and fluctuating flow fields. The geometry with the sinusoidal-shaped wall profile is found to produce the best thermal properties as compared to the triangle-shaped and the arc-shaped profiles though the obtained heat transfer is the highest for the arc-shaped geometry.

scholarly journals Computations of Flow and Heat Transfer in a Channel With Rows of Hemispherical Cavities

1999 ◽  
Author(s):  
Y.-L. Lin ◽  
T. I-P. Shih ◽  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Wall Functions ◽  
Time Stepping ◽  
Flow And Heat Transfer ◽  
A Cell ◽  
Volume Method

Computations were performed to investigate the three-dimensional flow and heat transfer in a high aspect ratio channel in which one or two wall are lined with four rows of hemispherical cavities arranged in a staggered fashion with two Reynolds numbers (23,000 and 46,000). The focus is on understanding the flow induced by cavities and how that flow affects surface heat transfer. Computed results were compared with available experimental data. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy closed by the low Reynolds number shear-stress transport k-ω turbulence model (wall functions were not used). Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

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.

Convective Heat Transfer in a Circular Annulus With Various Wall Heat Flux Distributions and Heat Generation

1985 ◽  
Vol 107 (2) ◽  
pp. 334-337 ◽  
Author(s):  
O. A. Arnas ◽  
M. A. Ebadian
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Generation ◽  
Navier Stokes ◽  
Circular Pipes ◽  
Negative Effect ◽  
Energy Equations ◽  
Steady Laminar

Convective heat transfer for steady laminar flow between two concentric circular pipes with walls heated and/or cooled independently and subjected to uniform heat generation is presented in analytical closed form utilizing the linearized Navier-Stokes and energy equations. The flow field is hydrodynamically and thermally fully developed. The effect of heat generation is depicted in Fig. 1 where the ratio of the Nusselt number with heat generation to without heat generation is plotted against the radius ratio, the core size ω. It is seen that heat generation may have positive as well as negative effect on the Nusselt number.

Three-Dimensional Simulation of Laminar Rectangular Impinging Jets, Flow Structure, and Heat Transfer

1999 ◽  
Vol 121 (1) ◽  
pp. 50-56 ◽  
Author(s):  
I. Sezai ◽  
A. A. Mohamad
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Streamwise Velocity ◽  
Impinging Jets ◽  
Navier Stokes ◽  
Aspect Ratios ◽  
Laminar Jets ◽  
Nusselt Number Distribution ◽  
Dimensional Simulation ◽  
Energy Equations

The flow and heat transfer characteristics of impinging laminar jets issuing from rectangular slots of different aspect ratios have been investigated numerically through the solution of three-dimensional Navier-Stokes and energy equations in steady state. The three-dimensional simulation reveals the existence of pronounced streamwise velocity off-center peaks near the impingement plate. Furthermore, the effect of these off-center velocity peaks on the Nusselt number distribution is also investigated. Interesting three-dimensional flow structures are detected which cannot be predicted by two-dimensional simulations.

Fluid Flow and Heat Transfer in a Novel Microchannel Heat Sink Partially Filled With Metal Foam Medium

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
E. Farsad ◽  
S. P. Abbasi ◽  
M. S. Zabihi
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Metal Foam ◽  
Three Dimensional ◽  
Numerical Data ◽  
Flow And Heat Transfer ◽  
Cooling Devices ◽  
Volume Method ◽  
Steady Laminar ◽  
Good Agreement

Performance of microchannel heatsink (MCHS) partially filled with foam is investigated numerically. The open cell copper foams have the porosity and pore density in the ranges of 60–90% and 60–100 PPI (pore per inch), respectively. The three-dimensional steady, laminar flow, and heat transfer governing equations are solved using finite volume method. The performance of microchannel heatsink is evaluated in terms of overall thermal resistance, pressure drop, and heat transfer coefficient and temperature distribution. It is found that the results of the surface temperature profile are in good agreement with numerical data. The results show the microchannel heatsink with insert foam appears to be good candidates as the next generation of cooling devices for high power electronic devices. The thermal resistance for all cases decreases with the decrease in porosity. The uniformity of temperature in this heatsink is enhanced compared the heatsink with no foam. The thermal resistance versus the pumping power is depicted, it is found that 80% is the optimal porosity for the foam at 60 PPI with a minimum thermal resistance 0.346 K/W. The results demonstrate the microchannel heatsink partially filled with foam is capable for removing heat generation 100 watt over an area of 9 × 10−6 m2 with the temperature of heat flux surface up to 59 °C.

Heat Transfer Study of Staggered Thin Rectangular Blocks in a Channel Flow

1991 ◽  
Vol 113 (3) ◽  
pp. 294-300 ◽  
Author(s):  
Ching Jen Chen ◽  
Ramiro H. Bravo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Channel Flow ◽  
Vector Fields ◽  
Block Size ◽  
Navier Stokes ◽  
Maximum Heat ◽  
Flow And Heat Transfer ◽  
Maximum Heat Transfer ◽  
Energy Equations

In this study, fluid flow and heat transfer in two-dimensional staggered thin rectangular blocks in a channel flow heat exchanger is analyzed by the Finite Analytic Numerical Method. The heat exchanger consists of four staggered thin rectangular blocks at temperature T1 placed inside a channel which is formed by two plates maintained at constant temperature T0. The fluid is considered to be incompressible and the flow laminar. Flow and heat transfer from the inlet of the heat exchanger to the outlet are simulated by solving Navier-Stokes and energy equations. Results were obtained for different block spacing and different size of the blocks. Computations were made for Reynolds numbers 100, 500, and 1,000, and Prandtl numbers 0.7 and 4.0. The results are presented in the form of velocity vector fields, isotherms, and local and global Nusselt numbers. The characteristics of the heat transfer and pressure drop in different block size and block separation are analyzed. The optimal length of separation between thin blocks and the optimal block length for maximum heat transfer are determined.

Numerical Study of Flow and Heat Transfer Characteristics of Impinging Jets

2010 ◽  
Author(s):  
Tarek M. Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

This study presents results for flow and heat transfer characteristics of two-dimensional rectangular impinging jets and three-dimensional circular impinging jets. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume computational fluid dynamics (CFD) code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results of the three-dimensional cases show that Reynolds number has no effect on the velocity distribution of the center jet. Results of both two-dimensional and three-dimensional cases show that Reynolds number highly affects the heat transfer and values of the Nusselt number. The maximum Nusselt number was always found at the stagnation point of the center jet.

Direct Numerical Simulation of Flow and Heat Transfer From a Sphere in a Uniform Cross-Flow

2000 ◽  
Vol 123 (2) ◽  
pp. 347-358 ◽  
Author(s):  
P. Bagchi ◽  
M. Y. Ha ◽  
S. Balachandar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Vortex Shedding ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Temperature Fields ◽  
Flow And Heat Transfer

Direct numerical solution for flow and heat transfer past a sphere in a uniform flow is obtained using an accurate and efficient Fourier-Chebyshev spectral collocation method for Reynolds numbers up to 500. We investigate the flow and temperature fields over a range of Reynolds numbers, showing steady and axisymmetric flow when the Reynolds number is less than 210, steady and nonaxisymmetric flow without vortex shedding when the Reynolds number is between 210 and 270, and unsteady three-dimensional flow with vortex shedding when the Reynolds number is above 270. Results from three-dimensional simulation are compared with the corresponding axisymmetric simulations for Re>210 in order to see the effect of unsteadiness and three-dimensionality on heat transfer past a sphere. The local Nusselt number distribution obtained from the 3D simulation shows big differences in the wake region compared with axisymmetric one, when there exists strong vortex shedding in the wake. But the differences in surface-average Nusselt number between axisymmetric and three-dimensional simulations are small owing to the smaller surface area associated with the base region. The shedding process is observed to be dominantly one-sided and as a result axisymmetry of the surface heat transfer is broken even after a time-average. The one-sided shedding also results in a time-averaged mean lift force on the sphere.

Sign in / Sign up

Export Citation Format

Share Document