The effect of the Density Wave Oscillations (DWO) on the heat transfer is studied experimentally. A horizontal test section of 5 mm I.D with R134a as working fluid was used for the experiments. The time averaged boiling heat transfer was found to be different under DWO conditions than under steady-state flow. Four different cases were studied considering different inlet pressure, temperature and mass Row rate. It was observed that the occurrence of the DWO can result in a premature dry out and that the impact of the DWO on the heat transfer depends on the particular conditions. However for the studied cases the impact on the heat transfer was not severe. (C) 2015 Elsevier Ltd. All rights reserved.