Research on Heat Transfer Characteristics of Steam Condensation with Non-Condensable Gas at Low Steam Mass Flux

Steam direct contact condensation plays an essential role in ensuring structural integrity and the safe operation of nuclear reactors. Due to the unsteady and complicated gas-liquid interface of steam condensation with noncondensable gas at low steam mass flux during the containment suppression, the estimation of condensation heat transfer coefficient is an intricate topic. In this work, the heat transfer characteristics of pure steam and mixed gas condensation are experimenally investigated through the single-hole and multi-hole spargers. The evaluation methods of transient gas-liquid interface parameter and the condensation heat transfer coefficient are proposed during steam chugging regime and oscillatory bubble regime. The simplified lumped condensation models are developed based on the gas-liquid interface characteristics and image reconstruction methods. The influence of critical factors on the heat transfer coefficient is discussed and analyzed. The heat transfer coefficient increases with steam mass flux increasing and water temperature decreasing in pure steam condensation. The heat transfer coefficient of mixed gas condensation increases with water temperature increasing, and decreases with the noncondensable gas content, resulting from the increasing the thickness and thermal resistance of boundary layer. Besides the existing heat transfer models of steam condensation are analyzed and evaluated. The predicted models that calculate the heat transfer coefficients of pure steam and mixed gas condensation are obtained, respectively.