Theses and Dissertations Collection

Modeling a system with natural convection being the coolants primary driving force is fre-quently challenging due to the programs governing equations not accounting for pressure difference in calculating the mass flow rate. The objective of this project is to create a pro- gram that can run a model with the only driving force being the natural convection formed from the pressure difference between an energy sink and an energy source. To accomplish this the software RELAP5-3D will be used in the one-dimensional format. The model will not have any pumps within the program to ensure the evaluation is capturing only the mass flow rate from the natural convection forces. The only fluid that will be contained within the system is H2O in both gas and liquid form. The model is divided into four separate executable programs due to complication of the mass flow rate oscillating during initial startup of the program. The results showed that the RELAP program can run a system using the pressure differences as the driving force for the mass flow rate of the coolant fluid. The result had uncharacteristic oscillations in both the mass flow rate and temperature of the coolant. This is most likely due to the one-dimensional format of the model. It is recommended to modify to a two-dimensional model to reduce the oscillations within the system. When comparing to hand calculations there is a considerable difference between the two values. Without the physical models mass flow rate data to compare, the results are inconclusive as to the accuracy of both evaluations data.