Indo - UK: Premature, Oscillation-Induced Critical Heat Flux ("Premature OICHF")

对于核反应堆来说，水是一种很好的冷却剂，但蒸汽却是一种很差的冷却剂。有信心而又不过分保守地预测水冷却转变为蒸汽冷却的时刻，这种能力绝对是至关重要的。发生这种转变时的热传递速率称为“临界热通量”（CHF）。预测CHF会发生的情况（然后确保反应堆的运行条件远离这些情况）是水冷堆热工设计的很大一部分。在一些不寻常的情况下，核反应堆内部的流动可能会变得不稳定和周期性，流速会随着时间的推移而上升和下降。在这种情况下，预测临界热流密度无疑会变得相当复杂和困难。该项目试图建立一个计算机模型，以预测在循环流存在的情况下何时发生临界热通量。本项目的第二部分是进行实验，将测试段置于循环流中，观察临界热流的发生与否。然后，我们开发的模型将根据这些测量进行测试和改进。一个经过验证的、通用的工具，用于预测振荡流条件下的临界热通量，将是反应堆设计人员和安全分析人员可用的有用的附加能力。

Water is an excellent coolant for nuclear reactors, but steam is a very poor one. The ability to predict with confidence, but without excessive conservatism, the point at which cooling by water will turn into cooling by just steam is absolutely vital. The the rate of transfer of heat at which this transition occurs is known as the "critical heat flux" (CHF).Predicting the circumstances under which CHF would occur (and then making sure that reactor operating conditions stay well away from them) is a very large part of the thermal hydraulic design of water cooled reactors.There are some, unusual, circumstances in which the flows inside a nuclear reactor can become unsteady and cyclical, with flow-rates rising and falling with time. Under the circumstances, predicting the critical heat flux not surprisingly becomes rather more complicated and difficult.This project is attempting to build a computer model which will predict when critical heat flux occurs in the presence of cyclical flows. The second strand of this project is to conduct experiments in which a test section is exposed to a cyclical flow, and the occurrence or not of critical heat flux is observed. The model we develop will then be tested and refined against these measurements.A validated, general-purpose tool for predicting critical heat flux under conditions of oscillatory flow will be a useful additional capability available to reactor designers and safety analysts.