Papers by Author: S.K. Pabi

Abstract: A model reported by the present investigators has earlier shown that the extent of heat pick up by a nanoparticle during its collision with the heat source in a given nanofluid would depend on the thermal conductivity (k_p, unit W/m.K), density (ρ, unit kg/m³), elastic modulus (E, unit GPa) and Poissons ratio (μ) of the nanoparticle and heat source. Considering the expression for collision period and thermal conductivity of nanoparticle, a factor χ =k_p(ρ/E)^0.4 is proposed here and examined for the preliminary identification of the potential of a dispersoid in enhancing the thermal conductivity of a nanofluid. The χ-factor for Ag, Cu, CuO, Al₂O₃ and SiO₂ are 2960, 2247, 116, 14.1 and 5.5, respectively. The higher χ-factor of CuO compared to that of Al₂O₃ can explain why water and ethylene glycol (EG) based CuO-nanofluid is reported to show higher enhancement in the thermal conductivity, when compared to similar Al₂O₃-nanofluid. The χ for SiO₂ is much smaller than that for Ag, which also corroborates well with the marginal enhancement in thermal conductivity of water based nanofluid containing SiO₂ nanoparticles. Therefore, a high value of χ of the nanodispersoid can serve as a parameter for the design of nanofluids for heat transfer applications.

Abstract: Recent studies indicate that the existing criteria for amorphous phase formation are not precise. This study emphasizes that the extent of deviation from the linear relationship of the chemical contribution to enthalpy of the solid solution with the enthalpy difference between the amorphous phase and the constituent elements is a measure of tendency to bypass amorphous phase formation. Mechanical alloying experiments on a number of compositions in Al-Ni-Ti system showed that the compositions, not following the aforesaid relation, yield partial or no amorphization.