Experimental Investigation on Heat Transfer of Supercritical Water in Wire-wrapped 2×2 Rod Bundle

The experiment was performed to study the heat transfer of supercritical water in wire-wrapped 2×2 rod bundle under the background of supercritical water-cooled reactor fuel qualification test. The experimental parameters cover the pressure of 23 to 28 MPa, mass flux of 400 to 1 000 kg/(m²•s) and heat flux of 200 to 1 000 kW/m². The circumferential wall temperature distributions of the heated tubes were obtained. In addition, the effects of heat flux, mass flux, pressure and wire-wrapped spacer on wall temperature and heat transfer coefficient were analyzed. It is found that the wall temperatures along the circumferential direction of the heated tube are non-uniform and non-symmetric. The highest wall temperature appears either at the corner sub-channel, or at the location covered by the wrapped wire. The heat transfer coefficient drops considerably with increasing heat flux or decreasing mass flux in the pseudo-critical region, but varies slightly at different pressures. Compared with the bare 2×2 rod bundle, the wire-wrapped spacer not only changes the circumferential wall temperature profiles of the heat tube, but also promotes the average heat transfer coefficient.