We measured the homogeneous nucleation rates of D2O in a supersonic nozzle. Small angle neutron scattering (SANS) experiments characterized the nanodroplet aerosols and yielded the number density N of particles formed. In these new SANS measurements the number densities were in the range of 4×1011<N/cm−3<2×1012. We then determined the characteristic time interval corresponding to the peak nucleation rate ΔtJmax from conventional pressure profile measurements in the nozzle. The sensitive time is typically (11±3) μs. Combining these two pieces of information we obtained the nucleation rate J=NNZ/ΔtJmax, where NNZ is the number density of the aerosol in the nucleation zone. In this nozzle, the peak nucleation rate ranges between 6×1016 and 1.2×1017 cm−3 s−1 and is quite insensitive to the initial conditions of the expansion.
Dimples play a very important role in heat transfer enhancement of electronic cooling systems. In the current paper, the fluid flow and heat transfer characteristics of spherical dimples at different angle of orientation from the centre with apex facing the inlet were investigated. The experiment was carried out for laminar Natural convection conditions with air as a working fluid. The overall Nusselt numbers and heat transfer coefficient at different orientation angle of dimples were obtained. From the obtained results, it was observed that the Nusselt numbers and heat transfer coefficient increases with decrease in the orientation angle of dimples.
Dimples play a very important role in the heat transfer enhancement of electronic cooling systems. In the current paper, the flow and heat transfer characteristics of spherical dimples of non uniform diameter were investigated. The experiment was carried out under laminar forced convection conditions using air as a working fluid. The overall Nusselt number and heat transfer coefficient at different dimple structures were obtained for various inlet air flow rates. From the obtained results, it was observed that the heat transfer coefficient and Nusselt number were high for the plate in which the diameter of dimples increases centrally in the direction of flow as compared to the other cases.
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