Thermal Performance Analysis of a Miniature Loop Heat Pipe with Water-Graphene Working Fluid

Abstract

This paper deals with the three-dimensional modeling of heat and mass transfer in a miniature loop heat pipe operating with water-graphene nanofluid. Different diameters of the liquid and vapor lines are proposed to prevent the vapor from entering the liquid line. Comparison of the numerical outputs with available empirical data shows a good agreement with a reasonable discrepancy. The effects of heat load applied in the range of 20–380 W and nanofluid concentration in the range of 1–3%vf on the thermal performance of the system are investigated and discussed. The results indicate that, by increasing the heat load to 40 W, the average temperatures of the evaporator, vapor line, and condenser increase by 7.5 K, 4.9 K and 3 K, respectively. Also, the evaporation and condensation rates increase by 72.6% and 29.3%, respectively, indicating an improvement in the thermal performance. Using 1% water-graphene nanofluid instead of pure water leads to 1K reduction in the average temperature of evaporator and 4216.4 W/(m2 (Formula presented.) K) increase in its heat transfer coefficient. Moreover, the effective thermal conductivity increased 3.2% with nanoparticles, which indicates again an improvement in the system performance. However, the use of more concentrated nanofluid does not show a significant effect on performance. © 2025 Taylor & Francis Group, LLC.