The influence of the operating pressure on the stability of natural circulation systems

Static flow instability, namely reverse flow, in a natural circulation system with two unequally heated riser systems, which are fed by the same unheated downcomer, were numerically investigated. The boiler was analysed under variable operating pressures. The dependence of the critical heat absorption ratio Vcrit from the pressure is discussed. A lower boundary for the part load operation of the analysed natural circulation steam generator was determined. Modifications of the boiler geometry were analysed and the calculation results were presented and discussed.