Experimental investigation on heat transfer characteristics of high pressures water in a vertical upward annular channel

Heat transfer experiments of high-temperature high-pressure water in a vertical upward annulus have been completed at Xi’an Jiaotong University. Particular attention was paid on heat transfer of water at sub-critical pressures with respect to the engineering application of nuclear reactor in this pressure region. Experimental parameters covered the pressures of 11–25 MPa, mass fluxes of 350–1000 kg/m2 s and heat fluxes up to 600 kW/m2. The gap of the annular flow channel was 6.0 mm with an effective heated length on the inner heated rod of 1400 mm. According to the experimental results, it was found that the increase of pressure and heat flux may lead to heat transfer deterioration in the steam-water two-phase region, whereas the increase of mass flux enhances heat transfer significantly. Two types of heat transfer deterioration, DNB and Dryout, were discussed and analyzed in detail. Based on the experimental data, heat transfer correlations were obtained to predict heat transfer in single-phase and two-phase regions. In addition, the present paper compared heat transfer difference of sub-critical pressure water in annulus and circular tube. At similar test parameters, annular channel has a better heat transfer performance in comparison with circular tube. Finally, heat transfer characteristics of water at sub-critical and super-critical pressures in the annulus were compared and discussed, which differed a lot at both normal and deteriorated heat transfer conditions.

► Effects of system parameter on heat transfer of water in annulus were studied.
► DNB heat transfer deterioration was observed.
► Heat transfer correlations were obtained for annular channel.
► Heat transfer of water in different pressure regions differs a lot.