Thermofluids analysis of four novel anchor-shaped turbulator and eco-friendly nanofluid (GAGNPs /H2O) in a parabolic trough solar collector: A CFD modeling approach

Abstract

In this paper, four new turbulator models are implemented inside the absorber tube of the Parabolic Trough Solar Collector (PTSC) in a linear arrangement (anchored shape) to regulate and standardize its surface temperature. The study analyzes the impact of parameters such as heat transfer coefficient (h), friction factor (f), Nusselt number (Nu), and outlet temperature (T_out). Moreover, a new type of nanofluid (GAGNPs/H₂O) has been utilized, consisting of gallic acid combined with graphene nanoplatelets (GNPs), known for its environmental friendliness. The solar heat flux (SHF) in the environment is calculated using the Monte Carlo Radiation Transfer Method (MCRT) with C++ code. The key findings indicate that at Reynolds number 25,000, replacing the simple absorber tube with the DEA, DEA-f, FEA, and FEA-f models increases the Nusselt number by $\sim$3.99 %, $\sim$5.40 %, $\sim$14.08 %, and $\sim$16.20 %, respectively. Additionally, increasing fin height from 34 mm to 58 mm at this Reynolds number results in $\sim$ 18.26 % increase in the Nusselt number, while increasing the outlet temperature by $\sim$0.08 %. Increasing the top height from 34 mm to 58 mm can increase efficiency by up to 8.20 %. The efficiency of the PTSC decreased by approximately $\sim$3.04 % when the inlet temperature was increased from 300 K to 345 K in FEA-f turbulator (H: 58 mm). Furthermore, increasing the concentration of GAGNPs/H₂O nanofluid from 0.025 % to 0.1 % in the same FEA-f turbulator (H: 58 mm) resulted in $\sim$ 4.50 % increase in efficiency.