非等压条件下单相自然循环回路的比例分析

Scaling Analysis of Single-phase Natural Circulation Loop under Non-isobaric Condition

非能动安全设计是第三代核电技术AP1000的显著特点。在非LOCA事故工况下,非能动安全设计中的非能动余热排出系统(PRHRS)自然循环特性直接影响余热排出效果。本文进行了非能动自然循环整体回路一、二次侧热工水力学行为研究。对于上述特性的试验研究通常会在缩比的实验台架上进行,运行压力会低于原型压力以减小工程难度,这使得一些相似性分析中等物性条件难以得到满足。针对上述情况,本文对非能动余热排出系统单相自然循环回路进行非等压条件下的比例分析,通过一维单相自然循环系统控制方程无量纲化分析,获得相似性准则数。基于上述研究,得出以下结论:低压下模拟单相自然循环回路是可行的,其可行性可通过失真度来判断;回路中流体的密度、热膨胀系数对于模拟有重要影响,Richardson数在整体自然循环回路的模拟中最为重要,其失真度可以保持在可接受的范围内;通过对PRHR换热器一二次侧进行相似性分析,发现其一二次侧耦合传热特性对相似性准则数要求相对较为宽松。

The design of passive residual heat removal is one of the most important features in AP1000.Natural circulation has been adopted in the design,and its natural circulation characteristics have become an important research subject.So the characteristics are studied in both the primary and secondary side in the present work.The characteristics are also studied by simulating the process and phenomena in some integral scaling test facilities,but the operating pressure in these facilities is usually lower than that in the prototype.Scaling analysis on the facilities often assume that the operating pressure and physical properties are the same,but this assumption is not satisfied in its application.Scaling analysis and design criteria are discussed on the condition that the operating pressure is non-isobaric and similarity groups can be obtained through non-dimensionalization of the well-established balance and constitutive equations.In the scaling analysis of the single-phase natural circulation loop under non-isobaric condition,it is feasible to scale a single-phase natural circulation loop and its feasibility can be validated by the distortion.Under the simulative test of the whole loop,Richardson number is the most important similarity criterion parameter.The density and coefficient of thermal expansion of fluid in the loop have great influence on it,which should be taken into account.The requirements of the coupled similarity of the primary side and the secondary side of PRHR HX are not high.