An experimental investigation on flow boiling heat transfer enhancement using spray pyrolysed alumina porous coatings

In this work, flow boiling heat transfer experiments were conducted to investigate the effect of a spray pyrolysed porous alumina coatings over a copper substrates. Two different porous alumina coatings were produced by varying the deposition temperature of the spray pyrolysis technique. The heat transfer experiments were conducted in a mini-channel of dimensions 30 × 20 × 0.4 mm, with de-mineralized water as the working fluid. The coated samples were tested repeatedly for three different mass fluxes and two subcooled temperatures, to investigate their effect on the heat flux, surface temperature and average heat transfer coefficient. An appreciable enhancement in heat flux was observed for the 300 °C spray pyrolysed alumina coated sample, when compared to the bare Cu and 350 °C spray pyrolysed alumina coated sample. An enhancement of 28.3% in the heat flux was observed for the 300 °C spray pyrolysed alumina coated sample compared to the bare Cu sample, for a lower mass flux of 88 kg/m2s.