Passive thermal spreaders utilizing liquid/vapor phase-change mechanism such as heat pipes, have been widely used in the macro-scale thermal management of electronic devices for many years. Micro fabrication techniques enabled the fabrication of micro-scale grooved heat pipes on semiconductors. Recent advances in fabrication techniques, on the other hand, enabled production of nano- and Angstrom-scale capillaries and cavities, which renders the manufacturing of nanoscale heat pipes possible. In the present study, we have simulated nanoscale heat pipes composed of nano-grooves using molecular dynamics and evaluated their performance based on different operating parameters such as the filling ratio and heat load. Moreover, evaluation of size effect on the thermal performance is made by comparing proportionally scaled heat pipes. Simulation results reveal that efficient operation of nano-grooved heat pipes depends not only on the proper selections of filling ratio and heat load, but also on the geometrical parameters such as cross sectional dimensions and aspect ratio of the groove. The modeling strategy used in this study opens an opportunity for computational experimentation of nanoscale heat pipes. (C) 2018 Elsevier Ltd. All rights reserved.