CONDENSATION ENHANCEMENT BY STEAM PULSATION IN A REFLUX CONDENSER

Reflux condensation in a long vertical tube was experimentally investi gated for both the case in which the inlet mass flow rate was steady a nd the case in which steady controlled pulsation was applied to the in let steam flow. The steam flow rate and heat removal capability of the condenser under steady inlet steam flow were found to be severely lim ited by the formation of a plug of single-phase condensate on top of t he two-phase condensing region, as a result of flooding in the tube. S ubsequently, steady controlled pulsations were applied to the inlet st eam flow with the aim of preventing the formation of a stable water co lumn above the condensing region. Three pulsing frequencies, 0.08 Hz, 0.14 Hz, and 0.25 Hz, were considered. The controlled pulsations were found to have a destabilizing effect on the water column, and led to s everal-fold increase in the condensation capacity and heat removal rat es in the condenser. Further, this improvement in performance was depe ndent on the frequency of pulsation. An analytical model for the limit ing process of countercurrent steam and subcooled-condensate flow, or flooding, which took into account the additional steam condensation ef fects resulting from the subcooled condensate, was compared with the e xperimental data. The theoretical model revealed that flooding will ex hibit a hysteresis effect above a certain level of subcooling, a chara cteristic feature of steady inlet flow reflux condensation that was al so observed experimentally.