带定位格架的类三角形堆芯通道超临界水传热试验研究

针对带定位格架的超临界水冷堆堆芯垂直上升类三角形子通道，开展超临界水的流动传热试验研究。反应堆堆芯类三角形子通道棒束直径为8 mm、栅距比为1.4，试验参数范围为:热流密度q=200~600 kW/m2、压力P=23~28 MPa、质量流速G=700~1300 kg/(m2·s)。分析了热流密度、压力和质量流速等热工参数对超临界水传热特性的影响。试验结果表明:定位格架处质量流速升高，流体扰动性增强，换热系数提升显著；在超临界压力下，提高压力会导致内壁温度上升，换热系数峰值降低；过高的热流密度会导致换热系数峰值降低，适当减小热流密度可提高换热性能；提高质量流速会导致内壁温度降低，换热系数峰值上升，能够显著提高换热性能。压力变化对定位格架区域传热特性影响较小，适当提升压力可提高系统安全性。 

Experiemental Study on Heat Transfer of Supercritical Water in Triangular Channel of Reactor Core with Spacer Grid

The experimental study on supercritical water flow heat transfer is carried out for the vertical upward triangular sub-channels in the supercritical water cooled reactor core with spacer grid. The fuel bundle diameter and pitch ratio of this sub-channel used are 8 mm and 1.4 respectively. The parameters adopted in the research include heat flux (q) ranging from 600 kW/m2, pressure (P) ranging from 23-28 MPa, and mass flow rate (G) ranging from 700-1,300 kg/(m2·s). This study analyzes the effect of such thermal parameters as heat flux, pressure and mass flow rate on the heat transfer characteristics of supercritical water. According to the experimental results, with the mass flow rate at the spacer grid increasing, the fluid disturbance increases and the heat transfer coefficient rises significantly; under the supercritical pressure, the inner surface temperature increases with the increasing pressure, and consequently, the peak heat transfer coefficient decreases; as the peak heat transfer coefficient reduces at an excessively high heat flux, the heat transfer performance can be improved when the heat flux is reduced properly; increasing the mass flow rate causes the drop of inner surface temperature and the increase of peak heat transfer coefficient, and thus can significantly improve the heat transfer performance; and the pressure change has little effect on the heat transfer characteristics in the vicinity of spacer grid, and however, the system safety can be improved by increasing the pressure properly.