effect of base fluid on pool boiling of silica nanofluids and variation of surface roughness

In this work pool boiling of silica nanofluid by two different base fluids were investigated, experimentally# roughness effects on pool boiling heat transfer of silica nanofluid and characteristics of boiling under di water and mixture of di water/ethylene glycol (70/30 di#w/eg) as base fluid were examined# the mechanism of roughness effects on pool boiling was explained by measuring the roughness of deposition layer on the boiling surface# evaluation of boiling surface roughness showed that the surface roughness increases with increasing concentration for two base fluids# these experiments were carried out in three different concentrations of 0#006, 0#008, and 0#01(%vol)# the enhancement of criticl heat flux (chf) and deterioration of boiling heat transfer coefficient (bhtc) attributed to different roughness of boiling surface# it was observsed that bhtc enhances with nanopartices concentration (<0#01 vol%) and indicated an optimum in 0#008 (vol%)# according to the our results, it was found that nanofluids based on di water as a base fluid, enhances chf and bhtc more than the nanofluids with di#w/eg base fluid due to (i) the higher thermophysical properties of di water base fluid, (ii) surface roughness was higher for nanofluid with di water based fluid# it was found that the surface with higher roughness had better heat transfer rate due to having more active cavities during boiling#