Thermal efficiency and safety of Generation-IV nuclear-power-reactor concept  SuperCritical Water-cooled Reactor (SCWR) depend on solid knowledge of specifics of SCW thermophysical properties and heat transfer within these conditions, i.e., SC pressures and temperatures, lower mass fluxes compared to those in current PWRs, high heat fluxes, etc.&nbsp;&nbsp;As a preliminary, but conservative approach to uncover these specifics is analysis of experimental data obtained in bare tubes including numerical investigation. Due to conditional restrictions, researchers are less likely to use long circular&nbsp;tubes to conduct experimental and theoretical analysis and there are still contradictions between the data and conclusions of different researchers.&nbsp;Therefore, it is necessary to further combine experiments and the numerical analysis of SCW behavior in tubes. This paper presents the numerical investigation, based on computational fluid dynamics, of the heat-transfer characteristics of SCW flow in a 4-m long circular&nbsp;tube ( ID = 10 mm).&nbsp;A&nbsp;dimensional analysis was conducted to derive the general form of an empirical supercritical water heat-transfer correlation, which was finalized based on the experimental data obtained at the normal and improved heat-transfer regimes.&nbsp;The data were collected at pressures of about 24 MPa, inlet temperatures from 320 to 350℃, mass flux of about 1000 kg/m 2 s and heat fluxes up to 1256 kW/m 2 .&nbsp;Numerical&nbsp;model for SCW was established&nbsp;in this analysis, and forced-convection heat transfer was studied at different operating conditions. The flow and heat-transfer mechanism of SCW in the vertical tube under the influence of buoyancy and flow acceleration were analyzed.&nbsp;Results of numerical simulation predict the experimental data with reasonable accuracy.&nbsp;The results indicated that when q / G &nbsp;&lt; 0.4 kJ/kg, wall-temperature distribution tends to be linear, which represents a normal heat-transfer regime. When T b &lt; T pc &lt; T w , wall temperature distribution shows a nonlinear trend, which corresponds to heat-transfer deterioration, i.e., the tube-wall temperature shows peaks and local heat transfer shows dips in its profile. Meanwhile the position, where the deterioration occurs is continuously moved forward to the inlet as the heat flux increases. Under high heat flux, the average velocity of the flow field is distorted, showing a flat M-shaped distribution change for coupling of buoyancy and thermal acceleration.


ICONE Competition - ICONE28-POWER2020-16456: Numerical Investigation on Heat Transfer to Supercritical Water  Flowing Upward in a 4-M Long Bare Vertical Circular Tube

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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