Abstract A single stage experimental flashing unit operating on water was erected and a correlation, and curves were obtained showing the effect of varying the flow rate (from 4.7 to 8.16m 3/hr.m of chamber width), the liquid inlet temperature (from 98 to 102°C), the liquid level in the flashing chamber (from 28 to 40 cm) , and the flashing range (from 7.5 to 2.5°C) as well as the presence of a baffle on the thermodynamic efficiency of the flashing process. It was found (within the experimental range used) that the efficiency increased with increase of the liquid inlet temperature , the flashing range and the chamber length. Increasing the flow rate and the liquid level in the flashing chamber resulted in a decrease of efficiency. The effect of the baffle was to increase the efficiency. This effect was most marked. Other conclusions are summarised towards the end of the paper.