Fouling effect of lead oxide crystallization on heat transfer in LBE

The fouling of heat exchangers in LBE-cooled systems is normally expected to occur only in a restricted condition that the active control of oxygen in the coolant fails, such as in an accidental condition. However, many practices of numerical system analysis on LBE systems which include the fouling effect given by the lead oxide (PbO) formation appear to be not well grounded on how to simulate the fouling effect given since it has been treated arbitrarily with additional thermal resistance layers and low thermal conductivities. To fill the knowledge gaps, this study aims at the characterization of PbO deposits on a cold surface in terms of its effect on heat transfer. The crystallization fouling by PbO was experimentally simulated with a thin U-shape stainless steel tube cooled by compressed air in a small, heated vessel containing LBE. As a result, the overall thermal resistance of the tube increased over time with the fouling layer buildup, suggesting the formation of PbO shows the fouling effect. Furthermore, an analytical parametric study showed that the actual thermophysical properties of the layer would be far different from what were originally expected from those of pure PbO, indirectly indicating that it consists of not only PbO but other compounds including LBE.