Abstract:
Over-reliance on limited fossil resources to meet the ever-increasing energy demand has several consequences such as high prices, unpredictable supply, and adverse environmental and ecological impact. It
is the need of the current time to explore sustainable renewable energy sources in order to mitigate the
environmental consequences and match the increasing demand economically. Out of various sustainable
renewable energy sources, solar energy stands out as one of the exemplary candidates. It is a clean
energy source with no greenhouse gas (GHG) emissions and is available in abundance at many parts of
the world. Prevailing studies corroborate the merit of nanofluids in harnessing solar energy. In this
experimental study, thermal analysis of a novel spiral-shaped collector is conducted with both hybrid
nanofluid-based volumetric absorption system (VAS) and surface-based absorption system (SAS). In the
case of hybrid VAS, homogenous mixture of Al2O3 and Co3O4 with de-ionized water as base fluid is
employed. The experimental results reveal that the maximum temperature rise and thermal efficiency of
9.8 C and 50%, respectively, is obtained at nanoparticle mass fraction of 100 mg/L Al2O3 þ100 mg/L
Co3O4 which is the optimum mass fraction. Whereas, in the case of SAS, volumetric flow rate of 100 mL/h
is the optimum volumetric flow rate at which the maximum temperature rise of 8.5 C is achieved.
Further, the effect of variation in volumetric flow rate and the incident flux on the thermal performance
of both VAS and SAS is also presented. On comparing the performance of VAS with SAS under a similar
condition a temperature rise and thermal efficiency of about 15.3% and 15%, higher is achieved in VAS
than SAS (at optimum volumetric flow rate)
