Improving Heat Exchanger Effectiveness in Industrial Applications Through Nanofluid Utilization

Abstract

Low thermal conductivity in conventional heat transfer fluids limits the efficiency and compactness of industrial thermal systems. This study experimentally investigates the convective heat transfer and thermodynamic performance of a 2 m galvanized iron concentric tube-in-tube double-pipe heat exchanger (DPHE) using an Al₂O₃–water nanofluid. The nanofluid was synthesized using a stable two-step method by dispersing 25 g of alumina nanoparticles (20–30 nm) into 25 L of deionized water with polyvinyl alcohol (PVA) surfactant under ultrasonic sonication. Experiments were conducted at fixed inlet temperatures and constant mass flow rates for both parallel-flow and counter-flow configurations. The baseline water-to-water performance was directly compared with the water-to-nanofluid system.

In the parallel-flow configuration, the nanofluid increased the heat transfer rate by 65% (from 0.2283 to 0.3780 kW) and enhanced the overall heat transfer coefficients by approximately 45%, resulting in a 50% improvement in thermal effectiveness (from 0.181 to 0.272). In the counter-flow arrangement, the nanofluid improved the heat transfer rate by 33% (from 0.4496 to 0.5995 kW), increased the overall heat transfer coefficients by 7.8%, and raised the effectiveness to a peak value of 0.363.

The results further demonstrate that incorporating the Al₂O₃ nanofluid in a parallel-flow configuration can achieve thermal performance comparable to that of a conventional water-based counter-flow system. This finding highlights a practical approach for improving compact thermal equipment where counter-current flow arrangements are restricted by spatial or structural limitations.