Heat and Mass Analogy Model for PCCS Condensation Heat Transfer

摘要

Many industrial systems use vertical tube condensers and practice has indicated that, much higher coefficients of heat transfer are obtained when vapors are condensed inside tubes rather than outside. However, in practical operations of the condensers, small amounts of non-condensable gas (NC) may exist in working vapors due to characteristics of the system or dissolution of working vapors. One of the safety systems in the ESBWR is a passive containment cooling system (PCCS) which is composed of a number of vertical heat exchangers [1-2]. During and after a loss of coolant accident, the pressurized steam discharged from the reactor and the NC mixture flows into the PCCS condenser tube. The PCCS condenser must be able to remove sufficient energy from the reactor containment to prevent it from exceeding its design pressure. The efficient performance of the PCCS condenser is thus vital to the safety of the ESBWR. Three different operational modes are possible in the PCCS depending on the non-condensable gas concentration and the pressure difference between the drywell and wetwell. These are bypass or through flow mode, complete condensation mode, and cyclic venting mode. The ID of the PCCS tubes is nominally 5.08 cm . Testing on the condensation heat transfer for PCCS is typically done in scaled tests facilities often with reduced diameter and reduced length [2]. A heat and mass analogy model is developed to simulate condensation heat transfer in PCCS and the predictions from model are compared with experimental data.