Limits...
Scaling analysis for the investigation of slip mechanisms in nanofluids.

Savithiri S, Pattamatta A, Das SK - Nanoscale Res Lett (2011)

Bottom Line: From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles.The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration.The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.

View Article: PubMed Central - HTML - PubMed

Affiliation: Heat Transfer and Thermal Power Laboratory, Department of Mechanical Engineering, Indian Institute of Technology - Madras, Chennai 600 036, India. skdas@iitm.ac.in.

ABSTRACT
The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.

No MeSH data available.


Related in: MedlinePlus

Effect of particle shape. (a) Gravity and thermophoresis forces, (b) lift and rotational forces, (c) drag and Magnus forces, and (d) Brownian force for water-based nanofluids.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211984&req=5

Figure 1: Effect of particle shape. (a) Gravity and thermophoresis forces, (b) lift and rotational forces, (c) drag and Magnus forces, and (d) Brownian force for water-based nanofluids.

Mentions: The result of the scaling analysis on the particle shape is plotted in Figure 1. The results are plotted for water based nanofluids. From this figure, it is observed that all the seven slip mechanisms, namely the drag, rotational, gravity, thermophoresis, Brownian, Saffman lift, and Magnus forces, dominate for cylindrical particles compared to that of sheet and spherical particles. In terms of the order of magnitude, the drag force is the largest with values in the range 10-6 to 10-9, and the Brownian force is the smallest with values in the range 10-25 to 10-27. The results are in agreement with the finding of Lazarus et al. [19] that cylindrical-shaped particles lead to a higher thermal transport over spherical-shaped particles. Gao et al. [20] also concluded that the non-spherical nanoparticle shape is helpful in achieving appreciable enhancement of effective thermal conductivity.


Scaling analysis for the investigation of slip mechanisms in nanofluids.

Savithiri S, Pattamatta A, Das SK - Nanoscale Res Lett (2011)

Effect of particle shape. (a) Gravity and thermophoresis forces, (b) lift and rotational forces, (c) drag and Magnus forces, and (d) Brownian force for water-based nanofluids.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211984&req=5

Figure 1: Effect of particle shape. (a) Gravity and thermophoresis forces, (b) lift and rotational forces, (c) drag and Magnus forces, and (d) Brownian force for water-based nanofluids.
Mentions: The result of the scaling analysis on the particle shape is plotted in Figure 1. The results are plotted for water based nanofluids. From this figure, it is observed that all the seven slip mechanisms, namely the drag, rotational, gravity, thermophoresis, Brownian, Saffman lift, and Magnus forces, dominate for cylindrical particles compared to that of sheet and spherical particles. In terms of the order of magnitude, the drag force is the largest with values in the range 10-6 to 10-9, and the Brownian force is the smallest with values in the range 10-25 to 10-27. The results are in agreement with the finding of Lazarus et al. [19] that cylindrical-shaped particles lead to a higher thermal transport over spherical-shaped particles. Gao et al. [20] also concluded that the non-spherical nanoparticle shape is helpful in achieving appreciable enhancement of effective thermal conductivity.

Bottom Line: From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles.The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration.The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.

View Article: PubMed Central - HTML - PubMed

Affiliation: Heat Transfer and Thermal Power Laboratory, Department of Mechanical Engineering, Indian Institute of Technology - Madras, Chennai 600 036, India. skdas@iitm.ac.in.

ABSTRACT
The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.

No MeSH data available.


Related in: MedlinePlus