Experimental investigation of nickel-based nanofluid on the performance of evacuated tube solar collector

This paper conducts an experimental investigation of an evacuated tube solar collector type solar collector employing a unique Ni/water nanofluid to assess its exergetic and energy performance. The investigation sheds light on the intricate behavior of nanofluid and their consequential impact on the efficiency, thermal properties, and entropy generation within the framework of evacuated tube solar collector (ETSC). The study reveals that an escalation of nickel nanoparticles volumetric concentration results in a reduction of specific heat capacity, attributed in part to the clustering effect of nanoparticles mixed with working fluid. Nevertheless, higher temperatures counterintuitively lead to an augmentation in specific heat capacity. The study presents the comparative behavior of nanofluid and the parent base fluid. The study further elucidates that augmenting the volumetric concentration of nanoparticles causes a reduction in the temperature difference between the collector's both side inlet and outlet, affecting thermal efficiency positively. Moreover, with mass flow rate contribute and increased volumetric concentration to a diminished outlet temperature, thereby enhancing the efficiency of ETSC. The study also analyzed the thermophysical properties such as thermal conductivity, viscosity, and specific heat of the Ni/water nanofluid across different volumetric concentrations and temperature ranges from 25 °C to 50 °C. Furthermore, the thermal performance of the collector was evaluated at various mass flow rates ranging from 0.0085 kg/s to 0.051 kg/s. The findings revealed a maximum energy efficiency of 73.14% at a volumetric concentration of 1% and a mass flow rate of 0.041 kg/s.