Experimental study on heat transfer to supercritical water in 2 × 2 rod bundle with wire wraps

Experimental studies on heat transfer to supercritical water in 2 × 2 rod bundle with wire wraps are performed at Shanghai Jiaotong University. The test section consists of two channels separated by a square steel assembly box with round corners. Water flows downward in the first channel and then turns upward in the second channel to cool the 2 × 2 rod bundle with wire wraps installed inside the assembly box. The bundle consists of four heater rods of 10 mm in O.D. and 1.18 in. pitch-to-diameter ratio. Experimental parameter ranges cover pressure from 23.0 MPa to 26.0 MPa, mass flux from 400 kg/m2 s to 1400 kg/m2 s, heat flux from 300 kW/m2 to 1000 kW/m2 and bulk temperature from 280 °C to 500 °C. The fluid enthalpy in the first channel increases due to the heat transfer through the assembly box when flowing downward. Heat transfer deterioration is observed in the bundle. The degree of the deterioration is moderated in the developed region due to the mixing by the wire wraps. Significant non-uniformity of circumferential wall-temperature distribution around the heater rods is observed. Effects of various parameters on heat transfer behavior inside the 2 × 2 rod bundle are similar to those observed in a tube. The heat transfer enhancement due to the wire wraps becomes remarkable under a high mass flux condition. The Jackson and Fewster correlation and Bishop et al. correlation give the best predictions when evaluated against the experimental data.