experimental investigation of alumina-water nanofluid in solar evacuated tube collector

One of the issues raised today in the processes of heat transfer is the need to increase the heat transfer and minimize the heat transfer equipment# the thermal conductivity of working fluid and the convective heat transfer coefficient play a major role in measuring the efficiency of the heat transfer equipment such as solar evacuated tube collectors( setc)# water, ethylene glycol and oil are among the commonly used working fluids in the thermal equipment#attained results revealed that the collector efficiency had ascending trend with increasing alumina- water nanofluid concentration, and reached 27#2% for the nanofluid 1 %wt from about 15#3% for the base fluid# in general, the efficiency was increased to 67#9% and 77#7% for the nanofluids 0#5 and 1 %wt, respectively, than when water was used as the working fluid# empirical studies demonstrated that the collector efficiency increases for all three samples with an increase in the mean radiation, which was confirmed as a general trend in the collector efficiency# it was noteworthy that the collector efficiency has more fluctuations in cases where the nanofluid was used#