Heat pipe devices, for their typical working mode, are particularly suitable for zero gravity applications, and have also been considered for applications in space satellites with nuclear generators because of the absence of active systems for the coolant circulation. The present work reports the results of experimental tests carried out on a heat pipe facility designed to investigate the thermal hydraulic performance of a water heat pipe. The device layout, configuration and geometry, simulate a heat pipe working mode utilizable in space applications under zero gravity conditions. The evaporating section, completely lined (covered) with wicks (sintered stainless steel), and nearly plane shaped, is housed in a cylindrical container. The obtained results show that the system can approach steady state conditions, at a pressure of 4 bar and with a heat flux transferred of about 150 W/cm 2, supporting an electric power step of about 1.8 kW.  Heat pipe devices, for their typical working mode, are particularly suitable for zero gravity applications, and have also been considered for applications in space satellites with nuclear generators because of the absence of active systems for the coolant circulation. The present work reports the results of experimental tests carried out on a heat pipe facility designed to investigate the thermal hydraulic performance of a water heat pipe. The device layout, configuration and geometry, simulate a heat pipe working mode utilizable space application under zero gravity conditions. lined (covered) with wicks (sintered stainless steel), and nearly plane shaped, is housed in a cylindrical container. The obtained results show that the system can approach steady state conditions, at a pressure of 4 bar and with a heat flux transferred of about 150 W / cm 2, supporting an electric power step of about 1.8 kW