Experimental investigation of thermal and hydraulic 2026 International Jour

Efficient thermal management is essential for high-performance electronic and energy systems, yet the heat transfer capability of conventional heat pipes is limited by the thermal properties of traditional working fluids. This study experimentally investigates the thermal and hydraulic performance of a heat pipe using zinc oxide nanofluids to identify operating conditions that maximize heat transfer while minimizing hydraulic penalties. Two nanoparticle sizes (35 and 55 nm), four nanoparticle concentrations (1, 10, 50, and 100 ppm), and heat inputs ranging from 35 to 65 W were systematically examined. Heat pipe performance was evaluated through measurements of wall temperature, thermal resistance, pressure drop, and effective flow characteristics under steady-state conditions. The results demonstrate that zinc oxide nanofluids significantly enhance heat transfer compared with distilled water. The optimum performance was achieved at a nanoparticle concentration of 50 ppm, where thermal resistance decreased by up to 72% for 35 nm particles and 64% for 55 nm particles. Smaller nanoparticles consistently outperformed larger ones because of their greater effective heat transport capability and improved dispersion characteristics. Although pressure drop increased with nanoparticle concentration, the maximum increase remained within approximately 25 – 30% for the optimal condition, indicating an acceptable hydraulic penalty relative to the thermal benefit. These findings demonstrate that careful optimization of nanoparticle size and concentration is essential to achieve the best balance between thermal enhancement and hydraulic performance.