Presentazioni e Articoli Tecnici

Steam drums of a nuclear power plant separate steam from the steam water mixture and sub cooled incoming feed water returns to the reactor. The entire feed water flow is delivered to the steam drum through the feed water sparger. The feed water sparger is provided with number of inverted ‘j’ type lateral tubes to  distribute the feed water in the drum for proper mixing with the separated saturated water in the steam drum of a nuclear reactor. The flow distribution through these lateral branches is an important aspect of the design of steam drum internal. Non-uniformity in the flow distribution of feed water along the steam drum can cause different enthalpy (different density and hence) of fluid entering into different down-comers. This may lead to thermal hydraulic instability in the Primary Heat Transport (PHT) system of the nuclear  reactor due to variation in the driving head in the down comers which is not desirable from reactor control point of view. Thus an accurate design of feed sparger is required to ensure uniform flow distribution in the steam drum. This paper presents a computer model which has been developed to study the flow distribution in the lateral branches of dividing flow system analytically for accurate prediction of the no. of “j” type tube (lateral branches), spacing between the each lateral branch and the diameter of the lateral branches. Predictions for the flow rates and pressure in the feed sparger are obtained from the solution of two first order differential equations (pressure-flow equation set) which are formulated by using the continuity and momentum equations involving the flow rate and the pressure difference across the feed pipe and a discharge equation for the lateral flows. The approach has been generalized in terms of dimensionless equations and flow coefficient.