Garg, Paritosh (2008-05). An experimental study on the effect of ultrasonication on viscosity and heat transfer performance of aqueous suspensions of multi-walled carbon nanotubes. Master's Thesis. Thesis uri icon


  • Through past research, it is known that carbon nanotubes have the potential of enhancing
    the thermal performance of heat transfer fluids. The research is of importance in
    electronics cooling, defense, space, transportation applications and any other area where
    small and highly efficient heat transfer systems are needed. However, most of the past
    work discusses the experimental results by focusing on the effect of varying
    concentration of carbon nanotubes (CNTs) on the thermal performance of CNT
    nanofluids. Not much work has been done on studying the effect of processing variables.
    In the current experimental work, accurate measurements were carried out in an effort to
    understand the impact of several key variables on laminar flow convective heat transfer.
    The impact of ultrasonication energy on CNT nanofluids processing, and the
    corresponding effects on flow and thermal properties were studied in detail. The
    properties measured were viscosity, thermal conductivity and the convective heat
    transfer under laminar conditions. Four samples of 1 wt % multi walled carbon
    nanotubes (MWCNT) aqueous suspensions with different ultrasonication times were
    prepared for the study. Direct imaging was done using a newly developed wet-TEM technique to assess the dispersion characteristics of CNT nanofluid samples. The results
    obtained were discussed in the context of the CNT nanofluid preparation by
    ultrasonication and its indirect effect on each of the properties.
    It was found that the changes in viscosity and enhancements in thermal conductivity and
    convective heat transfer are affected by ultrasonication time. The maximum
    enhancements in thermal conductivity and convective heat transfer were found to be 20
    % and 32 %, respectively, in the sample processed for 40 minutes. The thermal
    conductivity enhancement increased considerably at temperatures greater than 24 ?C.
    The percentage enhancement in convective heat transfer was found to increase with the
    axial distance in the heat transfer section. Additionally, the suspensions were found to
    exhibit a shear thinning behavior, which followed the Power Law viscosity model.

publication date

  • May 2008