Experimental study on heat transfer of supercritical water flowing downward in circular tubes

An experimental study on heat transfer of supercritical water flowing downward in circular tubes with 7.6 mm inner diameter was carried out on the SWAMUP test facility. More than 3500 test data were obtained with the following test conditions: pressure from 23.0 MPa to 26.0 MPa, mass flux from 450 kg/m2 s to 1500 kg/m2 s, heat flux from 0.17 MW/m2 to 1.4 MW/m2 and bulk temperature from 280 °C to 410 °C. Effect of various parameters on heat transfer was investigated. Test data in the present study were also compared with those obtained in tubes with upward flow. In addition, comparison of the test data with available correlations indicates that none of the correlations give an accurate prediction. Based on the test data and sensitivity study of various dimensionless numbers, a new correlation was developed which introduced one additional dimensionless number πB to correct the conventional Dittus-Boelter equation and gives a satisfying agreement with the test data.