Numerical study on effect of hybrid nanofluid as a passive heat transfer enhancement technique and different climates on thermal performance in a linear Fresnel collector

A notable distinction in this research is the utilization of a new method for calculating critical heat flux (CHF) based on a Look-Up Table. The present study comprehensively investigates the effects of hybrid nanofluid, a type of passive heat transfer enhancement technique, on convection heat transfer coefficients and CHF. The study covers five different climates representing significant climate conditions in Iran, namely Bandar Abbas, Esfahan, Shiraz, Tehran, and Yazd, each with different solar irradiations. The nanoparticles considered in this study include silver, nickel, and aluminum, as well as Ag-Au hybrid nanofluid with volumetric concentrations of 0.1%, 0.3%, 0.5%, 1%, and 2%. The modeling results reveal that the heat transfer coefficient increases with the volumetric concentration of nanoparticles. According to the results, at the CHF point for 2 vol% Ag–Au hybrid nanofluid and Ag, Ni, and Al nanoparticles, the heat transfer coefficient shows an increase of 28%, 11.5%, 10.6%, and 4.9%, respectively, compared to the results for pure water in Shiraz. Despite the acceptable results and effective performance of 2 vol% Ag–Au hybrid nanofluid for a linear Fresnel reflector, economically, 2 vol% nickel nanoparticles are identified as the most suitable choice.