Numerical analysis of control valve open ratio effect on letdown flow

The internal flow and heat transfer in the letdown pipes of Chemical and Volume Control System (RCV) are investigated with numerical simulation, and Flowmaster V7 is employed to achieve these objects. The effect of control valve RCV013VP open ratio on the letdown flowrate and other physical variables is numerically investigated. The results show that the letdown flowrate is sensible when RCV013VP open ratio is less than 60%, while the letdown flowrate seems to be independent with the valve open ratio when it is more than 60%. In the normal operation, even if the RCV013VP is fully open, flashing will not occur in the letdown pipes. As the control valve opens more, coolant pressure in the letdown pipes will be closer to the coolant saturation pressure at the corresponding letdown temperature. (authors)