Improving thermal efficiency using vibration monitoring and nanofluids in solar evacuated tube collectors
T. Sathish, R. Saravanan
Abstract
• Investigated nanofluids and vibration effects to boost solar collector efficiency. • Efficiency increased by 83 % with sio 2 /acetone at 82 hz mechanical vibration. • Efficiency improved by 75 % with tio 2 /acetone under mechanical vibrations. • Vibration frequency from 22 to 82 hz enhanced convective heat transfer efficiency. • Pure acetone showed 83 % EHTC improvement, SiO 2 reached 100 % boost in CHTC. Numerous researches have been carried out developing different strategies, including alternative occupied fluids, concentrators, and absorber design adjustments, to enhance the efficiency of thermal evacuated tube collectors of solar thermal. This work proposes the parametric investigation to use several types of nanofluids and controlled vibrations to improve the efficiency of the thermal-based on a solar-evacuated tube collector surrounded with heat pipe (SETC–HP). SETC HPs having six operating under similar conditions of an experiment; as a reference of one arrangement contained acetone only. Acetone based on Silicon dioxide (SiO 2 ) (0.5 % vol) and titanium oxide (TiO 2 ) (0.5 % vol) were used to fill the next two arrangements, respectively. To examine the vibration effects of thermal efficiency of the remaining three arrangements were rehabilitated by applying mechanical excitation controlled at different frequencies (22–82 Hz). A finding showed that the frequency at 82 Hz mechanical vibration pulses fashioned the best boost, efficiency has increased by 83 % and 75 % with SiO 2 /based acetone and TiO 2 /based acetone, respectively. With respect to solar intensity and vibration, the enhancement percentage of the effective heat transfer coefficient (EHTC) and convective heat transfer coefficient (CHTC) varied. For pure acetone, the improvements ranged from 83 % and 52 %; for SiO 2 (0.5 % vol.) and TiO 2 (0.5 vol%) acetone-based nanofluids were obtained by 100 % and 48 % and 80 % and 46 %, respectively.