Experimental and numerical evaluation of heat transfer and pressure drop using acid-functionalized titanium dioxide nanofluids in separation flow passage

Abstract

Nanofluids have progressively gained popularity as thermodynamic fluids due to their intriguing qualities in terms of thermal conductivity. Though the nanofluids have gained greater attention in heat-transfer applications, their suspension stability is still not resolved, especially for the metal oxide nanofluids. Therefore, this study aims to functionalize titanium dioxide (TiO 2 ) nanoparticles for polar and non-polar fluids and investigate their water-based nanofluids for the enhancement of heat transfer and pressure drop in separation flow. For functionalization of TiO 2 nanoparticles to improve its stability in non-polar fluids, Oleic Acid (OA) was utilized as a functional material, while Citric Acid (CA) was used for polar fluids. After functionalization, their functionality was validated via Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (FESEM-EDX), and Thermogravimetric Analysis (TGA). The thermophysical characteristics of CA-functionalized TiO 2 nanofluids at four different concentrations showed that water-based-TiO 2 nanofluids enhanced thermophysical performance compared to the base fluid. Therefore, CA-TiO 2 nanofluids have been utilized in a separation flow tube at 4,000 < Re < 20,000. After experimental validation with distilled water, numerical simulations were performed, which show that the heat-transfer coefficient and pressure drop are enhanced with a rise in the mass percentage of nano additives. The Thermal Performance Factor (TPF) shows the best performance at 0.1 mass% of nanoparticles.