ABSTRACT

Natural convection causes a fluid to move at a much lower velocity than forced convection, and consequently, the heat transfer coefficients are much lower than when the flow is forced. If a flow channel becomes partially blocked, and the coolant pumps are turned off, a circulatory flow pattern may develop that sometimes resembles the natural circulation of the coolant in an enclosed space. When the coolant surrounding a stationary surface becomes hot enough to boil, it becomes much more difficult to predict how the flow patterns will behave when the flow rates are low. The air flowing between the steel liner and the outside of the containment building naturally cools the heated steel liner. However, during natural convection, the Rayleigh number is much more reliable indicator to use, and the heat transfer coefficient can be correlated to it more easily.