The experimental investigation has been performed with enhancement devices (nozzle-turbulators) for enhancing heat transfer rate in a constant heat flux circular tube. It is found that the insertion of nozzle-turbulators has significant effect on the enhancement of heat transfer which the turbulator is used as a reverse/turbulence flow generator. Correlations for the Nusselt number and the friction factor based on the present experimental data are introduced for practical use. In addition, the heat transfer rate in the test tube can be promoted by fitting with nozzle-turbulators. Despite very high friction, the turbulators can be applied effectively in places where pumping power is not significantly taken into account but the compact size including ease of manufacture installation is required.