Dynamic simulation of natural circulation steam generators with the use of finite-volume-algorithms – A comparison of four algorithms

The paper reports the results of a comparison of the four finite-volume-algorithms SIMPLE, SIMPLEC, SIMPLER and PISO. The analysis has been done to explore and compare the suitability of the algorithms for the dynamic simulation of natural circulation steam generators based on a so called tube-header-model. The suitability of the algorithms was tested with the results of two simulation examples – a heat recovery steam generator with a horizontal tube bank (Fig. 3a) and a two-drum steam generator with a vertical tube bank (Fig. 3b). The calculations are done at low system pressure and under hot start-up conditions for the boilers. The results of the computations demonstrate that the SIMPLER algorithm should be preferred for dynamic simulations which are based on the tube-header-model. The algorithm shows a high stability, an extended field of variability of the under-relaxation factors as well as small required under-relaxation. The strong dependence of the calculation time on the number of control volumes is the only unfavourable characteristic of the SIMPLER algorithm.