Heat transfer enhancement in annulus cooling channel subjected to constant heat flux by using Nano-fluid

The research investigates experimentally and theoretically the thermal behavior of Nano-fluid in annulus channel under forced convection at steady state condition. The Nano-fluid which flows in the test section is consisted from alumina Nano powder of 10nm mixed in distilled water as the cooling media. Heat flux density of (q"=20693W/m², q"=27752W/m²) was subjected to the flowing fluid at different Nano particle volume fraction (0.13, 0.24,1, and 1.7%) during the experiments. Preparing the Nano-fluid is ensured by using ultrasonic probe (750W, 20 kHz) and magnetic stirrer for 6hours. The thermal conductivity of Nano-fluid was measured by Decagon KD2-sensor at the average operation temperature (37.87°C, and 44.23°C) at different Nano particle volume fraction. The thermal behavior of the Nano-fluid based on the heat transfer coefficient, thermal conductivity, pressure drop, safety boiling factor, and effectiveness of system with different Nano particle volume fractions, were recorded. The enhancement in the ratio of heat transfer coefficient and thermal conductivity were evaluated and showed an enhancement of about (1.2 - 4.7%) and (0.3 - 4.5%) respectively.