Evaluation of cooling system reliability of any heat generation system has important impact on system engineering safety during transient conditions. Loss or reduction of flow is the main transient initiating event that leads to reduction in heat transfer ability of the cooling system. The research target is to evaluate the reliability of typical cooling system theoretically based on its success criteria during both steady & transient states. It emphasis on analytical approach to fix the main success criteria of cooling system based on calculated heat transfer parameters during flow reduction transient, while it use the probabilistic approach for evaluating overall system reliability based on this success criteria. Four types of design layout is specified during this study which fulfill cooling system design criteria during postulated cooling deficiency that leads to sequential local or nucleate boiling on heat resource surface and extends to film boiling and boiling crisis later on. System reliability calculations are conducted for two types of success criteria. The first is based on 75% of full cooling capacity, while the second requires 50% of full cooling capacity for each type of design layout which ensures minimum cooling requirements during above mentioned transient conditions. The results show the effect of redundant pumping branches increase on the overall system reliability during steady state operation. It investigates further system reliability versus redundancy percentage based on the number of cooling system branches required for each design type during transient condition based on its success maintain certain acceptable temperature on heat source surface during transient conditions.

Reliability success criteria flow reduction transient nucleate and film boiling.