Momentum and heat transfer characteristics from heated spheroids in water based nanofluids

摘要

In this work, the governing field equations describing the momentum and forced convection heat transfer from heated spheroids, including the limiting case of a sphere, in water based nanofluids have been solved numerically in the steady and axisymmetric flow regime over the following ranges of conditions: Reynolds number, 1 ≤ Re ≤ 100; nanoparticle volume fraction, 0 ≤ φ ≤ 0.06 and aspect ratio, 0.2 ≤ e ≤ 5 for two sizes (d_p), namely, 30 nm and 100 nm, of CuO and Al_2O_3 nanoparticles. Over the present range of conditions, a qualitative similar behavior is observed for both CuO and Al_2O_3 nanofluids. The detailed structure of the flow and temperature fields in the vicinity of the spheroid is analyzed in terms of streamline patterns and isotherm contours, respectively. The value of the total drag coefficient for all configurations of the spheroid is always seen to increase with the increasing value of φ for all values of Re, d_p and e. All else being equal, the flow detaches early from the spheroid in nanofluids comprised of 100 nm nanoparticles, whereas the flow separation delays in nanofluids containing 30 nm nanoparticles with reference to that seen in clear water. The rate of heat transfer is seen to be monotonic with φ for nanofluids containing 100 nm nanoparticles, whereas it is seen to be non-monotonic for nanofluids having nanoparticles of 30 nm in size. Finally, the present values of the total drag coefficient and average Nusselt number are correlated using simple analytical forms which facilitate the interpolation of the present results for the intermediate values of the governing parameters.