Flat-plate solar collectors (FPSC) heaters are widely utilized for heating water in residential buildings and other commercial and industrial applications. The main disadvantage of solar water heater is their low efficiency. Improving the thermal characteristics of the working fluid in solar water heater can dramatically increase its thermal efficiency. The aim of present experimental investigation is to study the effect of using Alumina nanofluids as a working fluid for the solar water heater on its efficiency. Triton X-100 (Iso-Octyl Phenoxy Polyethxy Ethanol) was used as a surfactant and its stability and aggregation of suspension was investigated. Outdoor experiments have been carried out in New Borg El-Arab city, Alexandria, Egypt according to ASHRAE Standard 86-93. Two similar water heaters systems using pure water and the nanofluids were tested at the same time, locations and similar conditions. The results showed that using nanofluid of 0.15% Alumina particles improves the FPSC thermal efficiency by 18%. More than concentration of surfactant were tested and the results showed that more stable nanofluid could be prepared employing suitable surfactant concentration and by sophisticating preparation protocol. Keywords-component; Flat plate solar collector (FPSC); solar water heaters performance; AL2O3 nanofluid Nomenclature Ac Surface area of solar collector (m 2) (Cp)np Heat capacity of nanoparticles (J/kg K) (Cp)bf Heat capacity of base fluid (water) (J/kg K) (Cp)nf Heat capacity of nanofluid (J/kg K) FR Heat removal factor Gt Global solar radiation (W/m 2) m° Mass flow rate of fluid flow (kg/s) Qu Rate of useful energy gained (W) Ul Combined measurement and scatter uncertainties of each parameter (%) Um° Uncertainty of mass flow rate (%) UGt Uncertainty of GT (%) Ut Uncertainty of ∆To,i (%) Uɳi Uncertainty of ɳi (%) Ui,s Random uncertainty of the ith component (%) Ui,u Systematic uncertainty of the i th component (%) t Time (s) Ta Ambient temperature (K) Ti Inlet fluid temperature of solar collector (K) To Outlet fluid temperature of solar collector (K) To.init Collector outlet initial fluid temperature (K) To,t Collector outlet fluid temperature after time t (K) Ul Overall loss coefficient of solar collector (W/m 2 K) Greek symbols Absorptance-transmittance product Time constant for solar collector (min) ɳi Instantaneous collector efficiency Ф Volume fraction of nanoparticles in nanofluid ∆Toi Temperature rise across the collector (= To-Ti) Subscripts TEM transmission electronmicroscopy PV Polypropylene FPSC Flat plate solar collector IEP Isoelectric point DDW Double distilled water |
