An experimental investigation on a thermosyphon loop performance using water as a working has been carried out. A two-phase loop consisting only of a condenser and an evaporator separated by the liquid and vapor lines is developed. It uses the process of fluid phase change to transfer energy from the heat source to the condenser. The thermosyphon loop's evaporator and condenser heat transfer coefficients are compared with available predictive correlations. The new correlations for thermosyphon evaporation and condensation heat transfer coefficients are proposed. They predicted heat transfer coefficients with ±10% compared to the experimental data. A micro-porous layers are tested as a mean of evaporator heat transfer coefficient enhancement. It shown that the evaporator thermal resistance could be reduced up to 75% compared to a smooth surface evaporator, at low heat flux. In the same conditions, the system thermal resistance could be diminished up to 20%. Moreover, micro-porous layer fastened the loop's start up time.