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 Al2O3/water nanofluid in this study was produced by the direct-synthesis method using a cationic chitosan dispersant. The Al2O3/water nanofluid served as the working fluid with three concentrations (0.5, 1.0, and 3.0 wt.%) in heat pipes. The heat pipe in this study is a straight copper tube with an outer diameter of 9.52 mm and different lengths of 0.3 m, 0.45 m, and 0.6 m. 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 (20 W, 30 W, and 40 W), 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 40 W, the optimal thermal performance for Al2O3/water nanofluid heat pipes measuring 0.3 m, 0.45 m, and 0.6 m was 22.7%, 56.3%, and 35.1%, respectively, better than that of pipes using distilled water as the working fluid.

► The Al2O3/water nanofluid is employed as the working fluid of heat pipe. ► The chitosan as a dispersant to keep good suspension for nanofluids. ► The CVR, θ, L  , Q˙, and ω to effect thermal performance of heat pipe are discussed. ► Using the kHP to assess the thermal performance of heat pipe. ► The higher concentrations of nanofluids may not be able to improve the thermal performance of heat pipe.