Direct contact condensation with and without noncondensable gas in a water pool
Abstract
Direct contact condensation is widely used in industrial applications due to the required low driving potential and high energy conversion efficiency. It plays an important role in the performance of the suppression pool in the Simplified Boiling Water Reactor. Transport phenomena in the pool start from the initial generation of interfacial structures and gas composition from exhaust devices. In particular for the bubbly regime, the bubble detaching size, gas concentration at the bubble detachment and bubble formation frequency are the boundary conditions for later liquid-gas interactions in the liquid pool. These parameters are coupled together with system operational variables, including system pressure, liquid subcooling, sizes of exhaust devices and gas composition. The bubble formation experiments with and without the presence of noncondensable gas have been conducted in a subcooled water pool with the variations of the liquid subcooling, noncondensable gas concentration, nozzle size, system pressure and gas mass flow rate. The bubble formation device chosen was an up-standing double-walled nozzle. Nitrogen was used as noncondensable gas. The temperature and pressure of fluids and gas flow rates were measured appropriately. The bubble formation behaviors were recorded by using a high speed video camera and the images were stored digitally. A bubble formation hydrodynamic equation was obtained from a constant flow bubble formation model to predict bubble detaching sizes with and without phase change. A linear combination of analytical formulas for static and dynamic regimes was found to be appropriate for both regimes and the transition between them. The condensation at the bubble interface was considered as the flow similarity of film condensation at the surface of a solid sphere including effects of gravitational and interfacial shear forces. Thermodynamic simplifications of interfacial variables allow for analysis of coupled heat and mass transfer without knowing the distributions of the temperature and noncondensable gas in detail. The model equations have been expressed explicitly and compared with the present database in terms of heat transfer at the interface, bubble detachment volume, bubble formation frequency and gas composition at the detachment.
Degree
Ph.D.
Advisors
Ishii, Purdue University.
Subject Area
Nuclear engineering|Nuclear physics
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