Parameters affecting critical heat flux of nanofluids: Heater size, pressure orientation and anti-freeze addition

This research aims at investigating the effect of heater size, pressure, heater orientation and effect of anti-freeze addition on critical heat flux of nanofluids which have shown large potentials as coolants for high power generating uses. Nanofluids have shown about ∼ 180--200% enhancement in critical heat flux values. The effect of heater was carried out using three different sized heaters. Maximum enhancement of ∼190% was achieved for a 1 x 1 cm2 heater. The effect of pressure on critical heat flux was investigated by testing nanofluids at three pressures. Maximum enhancement of ∼ 240% increase in critical heat flux was observed at the lowest pressure tested. Surface orientation effect on critical heat flux carried out for a 2 x 2 cm2 heater at five orientations revealed about ∼120% enhancement over the critical heat flux obtained using Zuber's correlation at an orientation of 150°. Two commercially used antifreezes, ethylene glycol and propylene glycol, were used to study the effect of anti-freeze addition to nanofluids. Alumina-water nanofluid of 0.025 g/L concentration mixed with the antifreezes at five compositions by volume showed a maximum enhancement of ∼120% for ethylene glycol and ∼70% for propylene glycol.