Particle agglomeration and properties of nanofluids

  • Yijun Yang
  • Alparslan Oztekin
  • Sudhakar Neti
  • Satish Mohapatra
Research Paper


The present study demonstrates the importance of actual agglomerated particle size in the nanofluid and its effect on the fluid properties. The current work deals with 5 to 100 nm nanoparticles dispersed in fluids that resulted in 200 to 800 nm agglomerates. Particle size distributions for a range of nanofluids are measured by dynamic light scattering (DLS). Wet scanning electron microscopy method is used to visualize agglomerated particles in the dispersed state and to confirm particle size measurements by DLS. Our results show that a combination of base fluid chemistry and nanoparticle type is very important to create stable nanofluids. Several nanofluids resulted in stable state without any stabilizers, but in the long term had agglomerations of 250 % over a 2 month period. The effects of agglomeration on the thermal and rheological properties are presented for several types of nanoparticle and base fluid chemistries. Despite using nanodiamond particles with high thermal conductivity and a very sensitive laser flash thermal conductivity measurement technique, no anomalous increases of thermal conductivity was measured. The thermal conductivity increases of nanofluid with the particle concentration are as those predicted by Maxwell and Bruggeman models. The level of agglomeration of nanoparticles hardly influenced the thermal conductivity of the nanofluid. The viscosity of nanofluids increased strongly as the concentration of particle is increased; it displays shear thinning and is a strong function of the level of agglomeration. The viscosity increase is significantly above of that predicted by the Einstein model even for very small concentration of nanoparticles.


Nanofluids Thermal conductivity Viscosity Dispersion Particle size 

List of symbols

ke (W m−1 K−1)

Thermal conductivity of nanofluid

kf (W m−1 K−1)

Thermal conductivity of base fluid

kp (W m−1 K−1)

Thermal conductivity of nanoparticle

ϕ (%)

Volume percentage of nanoparticle

γ (s−1)

Shear rate

ρ (kg m−3)

Density of the fluid

μnf (Pa s)

Dynamic viscosity of nanofluid

μf (Pa s)

Dynamic viscosity of base fluid


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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Yijun Yang
    • 1
  • Alparslan Oztekin
    • 1
  • Sudhakar Neti
    • 1
  • Satish Mohapatra
    • 2
  1. 1.Department of Mechanical Engineering and MechanicsLehigh UniversityBethlehemUSA
  2. 2.Dynalene Inc.WhitehallUSA

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