Evaluation of the thermal performance of a heat pipe using alumina nanofluids

This study demonstrates the enhancement of the thermal performance of a heat pipe charged with nanofluid. The Al ₂O ₃/water nanofluid in this study was produced by the direct-synthesis method using a cationic chitosan dispersant. The Al ₂O ₃/water nanofluid served as the working fluid with three concentrations (0.5, 1.0, and 3.0wt.%) in heat pipes. The heat pipe in this study is a straight copper tube with an outer diameter of 9.52mm and different lengths of 0.3m, 0.45m, and 0.6m. This study presents a discussion on the effects of the charged volume ratio of the working fluid (20%, 40%, 60%, and 80%), tilt angle (10°, 40°, 70°, and 90°), heat pipe length, heating power (20W, 30W, and 40W), and weight fraction of nanoparticles on the overall thermal conductivity of the heat pipe to evaluate the thermal performance. Experimental results show that at a heating power of 40W, the optimal thermal performance for Al ₂O ₃/water nanofluid heat pipes measuring 0.3m, 0.45m, and 0.6m was 22.7%, 56.3%, and 35.1%, respectively, better than that of pipes using distilled water as the working fluid.