The purpose of this study is numerical investigation of the heat transfer and laminar two-phase Nanofluid flow in a rotating U-shaped microtube with hydrophobic surfaces. One of the applications of rotating U-shaped channels is their use in turbine blades for cooling purposes. In addition, in laboratory centrifuge equipment, micro heat exchangers and micropumps U-shaped microtube can be used due to their smaller volume occupancy. Therefore, the study of heat transfer and pressure drop in this type of applications is of vital importance. Utilizing Nanofluid enhances the heat transfer thus providing better cooling for a thermal system, which is usually associated with an increase in pressure drop. Applying hydrophobic surfaces, the flow is considered a slippery flow that causes a pressure drop in a duct. In general, applying Nanofluid and hydrophobic surfaces simultaneously, results in enhanced thermal efficiency and the pressure drop of a thermal system. The initial diameter in this study was selected to be 150 µm. In this research, water and Nanofluid were considered with water acting as the base fluid at 0.5 to 5 vol%. Heat transfer and fluid flow through the microtube were studied via single-phase and two-phase models. Iecting the important parameters on the thermal function of microtube such as Reynolds number (from 100 to 500), rotational speed, the sliding length of the surfaces and the type of the fluid and Nanofluid is one of the objectives of this study. After conducting a thorough literature review it was revealed that this particular geometry has not been studied before. All the simulations are 3-dimensional, steady and laminar and are conducted via ANSYS Fluent using single-phase and two-phase models for hydrophobic/hydrophilic surfaces. The results demonstrate that using ducts with lower radius of curvature will enhance the heat transfer rate. Additionally, with rotating geometry and utilizing Nanofluid instead of distilled water will enhance the heat transfer rate. Although the pressure drop is increased in these circumstances, the thermal efficiency is improved compared to distilled water. Reducing the radius of curvature will increase the centrifugal force and improves the heat transfer rate. The increase in heat transfer rate was 18.6% for distilled water due to reducing the radius of curvature whereas, this enhancement was 26.1% for Nanofluid. Keywords: Numerical investigation, rotating U-shaped Microchannel, hydrophobic surface, Nanofluid, Euler-Lagrange method, Eulerian-Eulerian method, heat transfer, pressure drop, performance coefficient, nanoparticle