Simulation of two-phase hybrid nanofluid flow in a flat plate solar collector equipped with spiral absorber tube under the influence of magnetic field: Hydraulic-thermal, energy, and exergy analysis

Abstract

In this research, a flat plate solar collector (FPSC) equipped with a spiral absorber tube is numerically simulated. The aim of using the spiral tube in the FPSC is to enhance the amount of hybrid nanofluid (HN) mixing and turbulence and to improve the thermal efficiency of the FPSC. First, the FPSC geometry was prepared in SolidWorks software, and then the Design Modeler and Meshing module of Ansys software was used to evaluate the computational domain and meshing. MgO-MWCNT/Therminol VP-1 two-phase HN is simulated using a mixture model and the RNG k-ε turbulence model has been used to model the turbulent flow. The range of Reynolds number (Re) is from 9000 to 24,000 and the volume fraction (φ) of MgO and DWCNT nanoparticles changes from zero to 3% when the pitch ratio (α) of the absorber tube is 0.75, 1.50, and 2.25. Finally, the absorber tube of the FPSC is placed under a magnetic field with the Hartmann number (Ha) of 20 to 140. Based on the obtained results, an increment in the Re and φ leads to an increase in the thermal performance and pressure drop (Δp) of the FPSC. When φ = 3% and Re = 24000, the use of a spiral absorber tube with α = 2.25, the average Nusselt number (Nuave) and Δp are enhanced by 121.11% and 309.52% compared to the solar collector (SC) with a simple absorber tube. The energy efficiency is always improved with Re and φ. Also, the maximum energy efficiency corresponds to α = 2.25 for all amounts of Re and φ. The exergy efficiency has increased, increased and decreased with the increase of Re, φ, and α, respectively. In the f FPSC equipped with a spiral absorber tube with α = 0.75, the exergy efficiency is improved by 36.14% when Re increases from 9000 to 24,000 and φ = 3%. The performance evaluation criteria (PEC) index of the FPSC is more than 1 for all cases when the magnetic field is applied. Also, the maximum exergy efficiency occurs when the magnetic field is applied, Re = 14000, and Ha = 150.