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Thermal conductivity of CNT - wated nanofluids: a review

Akhilesh M., Santarao K., Babu M. V. S.

Mechanics and Mechanical Engineering

2018

Vol. 22, nr 1

207--220

In heat transportation applications, water is most commonly used fluid. The efficiency of equipment used in these applications depends on thermal characteristics of water used. The thermal characteristics of water could be upgraded by suspending high thermal conducting solid nanoparticles. In this paper an attempt has been made to know how the use of surfactants and functionalization of carbon nanotube walls can affect the thermal characteristics and stability of nanofluid. A thorough analysis of collected literature revealed that carbon nanotubes have much higher thermal conductivity than any other nanoparticles and hence improve the thermal properties of water when suspended in them. Further it is concluded that suspension of carbon nanotubes in water requires use of surfactant or functionalization of carbon nanotube walls with proper group. By setting optimum pH and better dispersion, better thermal conductivity is possible. Experimental studies in the literature survey reveal that chemical stabilization techniques and physical stabilization techniques together decide the stability of the nanofluid.

Experimental investigation to study the viscosity and dispersion of conductive and non-conductive nanopowders’ blended dielectrics

Santarao K., Prasad C. L. V. R. S. V., Swami Naidu G.

Advances in Science and Technology. Research Journal

2017

Vol. 11, no 1

154--160

Nano fluids are nanotechnology-based colloidal dispersions engineered by stably suspending nanoparticles. The characteristics of nano fluids such as thermal and electrical conductivities, viscosity, specific heat, dispersion etc. were studied and analyzed by earlier researches at different particle concentrations with different nano fluids. It was established that nano fluids have a significant impact on the process due the improvised characteristics. Nano fluid viscosity and dispersion deserve the same attention as thermal conductivity in cases of nano dielectric fluids that are used in EDM as they influence the MRR. In this work, The viscosity and dispersion of the conductive and nonconductive Nano powders blended dielectrics are investigated as a function of volume fraction so as to evaluate the behavior of these nano fluids at different particle volume concentrations. Kerosene and deionized water based nano fluids blended with conductive (SiC) and non-conductive (boric acid) Nano particles are selected for the current study. It is observed that as the percentage volume fraction of nano particles (both SiC and boric acid) increased, the viscosity was found increasing when blended with DI water. But the viscosity behavior with kerosene blended with SiC and boric acid is not same. The existing experimental results about the nano fluids viscosity shows clearly that viscosity have a specific trend in variation with an increase of volume concentration. Boric acid blended with DIW and kerosene shows similar trend in dispersion. However, in case of SiC blended with DIW and kerosene showed some contradictory results giving scope for further investigation. The outcome of these experimental investigations will augment the works that are going on in studying its influence on MRR in EDM processes using nano blended dielectric medium.