Dry cooled waste heat removal system with direct contact heat exchanger and instability of falling film along vertical strings

Abstract

An innovative dry cooled waste heat removal system using direct contact heat exchanger (DCHE) was designed. The system has high heat removal performance and prevents loss of vacuum in condenser. Heat removal performance and pressure drop of spray, vertical string and horizontal string types of DCHEs were evaluated and system optimization was conducted. Transient analysis of the new system found that the condenser conditions can be within design criteria. The system with vertical string type of DCHE has the highest heat removal performance and has 1/4 of pressure drop of the typical system using fin tubes. The heat removal performance is the highest when surface of the falling film is smooth, therefore analysis of the film flowing down on vertical strings was conducted to find stable film conditions. The existing analysis of Rayleigh-Plateau instability had conducted only for stagnant air, on the other hand a film modeling considering effect of counter-current air flow was conducted in this research and conditions of unstable film were expanded. Moreover, an experiment revealed that the expanded range of the unstable film conditions and falling film in the designed system condition is stable.