Taylor-Series Approximation for the Convective Heat Flux in Thermal-Hydraulic Computer Codes

摘要

A technique for decreasing the computer execution time for convective heat transfer calculations in transient thermal-hydraulic computer codes is investigated. The technique consists of approximating the convective heat flux by the first order terms of a Taylor series expansion with fluid and heat structure conditions as independent variables. The approximation is used until the system state point varies enough to make the approximation inaccurate. The technique was incorporated into RELAP5 and calculations were performed to determine the savings in computer execution time and to verify the accuracy of the approximation. In slowly varying transients, the approximation ran up to 19% faster than the current RELAP5 technique. In rapidly varying transients it ran slower. Investigations show the technique can provide the savings desired and that with future development of criteria of when to use and when not to use the approximation, it represents a significant calculational improvement to the code. (ERA citation 07:054749)