This paper constructs a heat transfer model for an annular heat pipe. The volum of fluid model in FLUENT software is used to simulate vapor-liquid two-phase flow and phase change. A structured grid (0.5 mm in the evaporation and condensation sections, 1 mm in the adiabatic section) is used, with a convergence residual of 1 ? 10-6) and a computational time of 300 seconds. Experiments using the controlled variable method investigate the effects of working fluid type (distilled water, ethanol, and a 3:1 mixture), filling ratio (30%-70%), heat load (500-2000 W/m2), and tilt angle (0?, 30?, and 60?) on the heat transfer performance. Experimental results show that the mixed refrigerant achieves optimal overall performance, with a heat transfer efficiency of 85%-92% in the stable phase, a startup time of 35 seconds, and a heat transfer coefficient of 986 W/m2K. The heat transfer coefficient reaches its peak at a filling rate of 60%. The heat load and heat transfer rate exhibit a significant linear correlation (Q = 0.92q - 35, R2 = 0.994), and the inclination angle has little effect on heat transfer. Numerical simulations and experimental results show consistent trends, validating the reliability of the model. Inclination angle minimally affects heat transfer because capillary pressure. This results in <2.3% variation in heat transfer coefficient across 0?-60?, confirming the heat pipe?s adaptability to non-horizontal installations without performance degradation.
Chen et al. (Thu,) studied this question.