Heat transfer of supercritical water in annuli with spacers

Experimental investigations on heat transfer of supercritical water in vertical annular channel equipped with spacers have been carried out at the SWAMUP-II facility in Shanghai Jiao Tong University. The test section consists of a heated outer rod of 15.0 mm inner diameter and a concentric unheated inner rod of 7.41 mm outer diameter. The simplified spacers with blockage ratio of 0.2 and 0.3 are equipped into the annular channel. The water flows upward cooling the heated tube. The pressure and mass flux ranges are 23-25 MPa and 450-1200 kg/(m2·s), respectively. Moreover, the heat flux ranges from 400 to 1000 kW/m2, and the fluid temperature is in the range of 240-450 °C. The heat transfer behaviors downstream from the spacers are analyzed. The effects of seven parameters on the heat transfer enhancement downstream from the spacer are presented. At a certain location downstream from the spacer, the further heat transfer impairment may occur on the basis of the previous deterioration. Conventional heat transfer enhancement prediction methods are compared with the experimental data. The correlations based on the subcritical conditions show the limitations at the supercritical pressure. An improved correlation has been derived.