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To improve the efficiency of solar flat-plate collectors further, a study had been carried out wherein the conventional working fluid was replaced by nanofluids. A 25-L/day solar flat-plate water heater with collector area of 0.5 has been designed and fabricated. The thermosyphon system of the solar water heater was monitored at 15 locations using T-type thermocouples. Alumina and CuO nanoparticles were synthesized and characterized using Brunauer-Emmett-Teller and X-ray diffraction techniques and dispersed using ultrasonic mechanism. To stabilize the system at an optimum level, the collector is operated with volume fractions of 0.2% and 0.4% of synthesized Al 2O 3 and CuO nanoparticles mixed with distilled water and used in the solar flat-plate collector. The temperature profile was compared with different volume fractions of the nanoparticles in the flowing medium. Enhanced heat transfer was observed in the solar flat-plate collector using nanoparticles, and hence, it is inferred that addition of nanoparticles improves the efficiency of the solar water heaters. This paper details the temperature profile observed in the collectors, variation of insolation over the day, and change in efficiency both on the primary side (collector) and on the secondary side (storage tank) of the solar water heater. [ABSTRACT FROM AUTHOR]

Two collectors with the same area of 945×420mmhave been designed and fabricated: one flat plate collector with internally grooved fins inserted inside the riser tubes and the other one with plain riser tubes. Provisionswere made for inserting the T-type thermocouples at six different locations to monitor temperature variations inside the riser tubes of the collector. The two identical systems of collectors (finned and unfinned tube) were initially run with base working fluid (water) and then with Al2O3 nanoparticles with a size of 40 nm for diffierent weight fractions of 0.2%and 0.4%in incremental order to study the effect on the efficiency of collectors. Mixing of nanoparticles in water thus improves the efficiency of the collector. Results show the efficiency of finned tube collector using the nanoparticles and water is substantially higher when compared to that of unfinned riser tubes collector. [ABSTRACT FROM AUTHOR]