Advanced heat transfer in shell and tube exchangers using TiO2-SiO2 nanofluids

This study experimentally investigated the thermohydraulic performance of TiO 2 –SiO 2 binary nanofluids (BNFs) in a 1-pass shell-and-tube heat exchanger under laminar flow. The nanoparticles were dispersed in a 40:60 (v/v) monoethylene glycol–distilled water mixture at volume fractions ( φ ) of 0.5%, 1.75%, and 3.0%. Hot water flowed through the shell, whereas TiO 2 –SiO 2 BNFs circulated in the tubes at 1–4 L/min, covering Re = 500–2222. The results show that both the heat transfer coefficient (HTC) and overall heat transfer coefficient (OHTC) increased with φ and Re, reaching maximum values of 1908 and 2707 W/m²·K at φ = 3.0%. BNFs with φ = 1.75% achieved an optimal performance evaluation criterion (PEC) of 1.054–1.168. The enhancements in HTC were 8.7%, 29.8%, and 38.1%, corresponding to OHTC increases of 32.4%, 69.3%, and 91.6% for φ = 0.5%, 1.75%, and 3.0%, respectively. These findings demonstrate the significant improvement in convective heat transfer provided by TiO 2 –SiO 2 BNFs and provide experimentally validated thermohydraulic data relevant to the performance range reported for practical heat exchanger applications.