Complete condensation analysis of a multi-tube passive condenser for an economic simplified boiling water reactor

Gavin Henderson, Purdue University

Abstract

The Economic Simplified Boiling Water Reactor is General Electric's latest boiling water reactor design. It offers improved and simplified designs utilizing passive features to reduce overall cost and achieve the highest levels of safety. One of the safety features for the reactor is the Passive Containment Cooling System (PCCS). The PCCS removes core decay heat, by the method of condensation heat transfer, during accident conditions that cause the containment to fill with steam. In an accident, such as a loss of coolant accident, the containment will begin filling up with steam. To prevent the containment from reaching the maximum design pressure, the PCCS condenses steam passively through a water pool, thus depressurizing the containment. The PCCS has three main operating conditions, including complete condensation, through flow, and cyclic venting mode. A detailed knowledge of the heat transfer characteristics is necessary in assessing the PCCS capabilities. An experimental study of heat removal capabilities in a multi-tube condenser during complete condensation mode of a passive condenser was performed. Previous experiments have been carried out to simulate PCCS operations with a single tube. A four tube test facility, with full scale height and diameter condenser tubes, was designed and constructed to investigate the effect of a tube bundle on PCCS capabilities. Experiments were run using pure steam with flow rates ranging from 1 to 50 g/s and pressures from 100 to 300 kPa. Results showed that the system pressure was directly determined by the steam flow rate to the tube bundle condenser. Higher system pressures resulted in a higher condensate mass flow rate. Condensation, secondary, and overall heat transfer coefficients were calculated for each of the experimental runs. Experimental results were then compared to data obtained from single tube analysis. The tube bundle results showed a slightly higher condensate mass flux than the results recorded with a single tube. The finding was shown to be caused by an increased secondary heat transfer coefficient in the tube bundle experiments. This result can be explained by a turbulent mixing effect created in the tube bundle. As opposed to a single condensing tube, the boil off interactions from the four tubes in the water pool is more violent causing turbulent mixing. This turbulent mixing effect increased the secondary heat transfer capabilities in the water pool, resulting in high condensation rates. A heat and mass transfer analogy model was used to compare with the experimental results and obtain axial profiles for heat transfer properties. The model slightly under predicted the condensate mass flow rates for most of the experiments. This is due to the fact that only a single tube is analyzed in the model, and turbulent mixing in the water pool is not taken into account. The model was also used to help predict local condensation heat transfer coefficients for the experiment. Local heat transfer coefficients can not be directly recorded from experiments due to the inability to measure local condensate mass flow rates. The model was used to develop axial condensate mass flow rates to then predict axial condensation heat transfer coefficient profiles in experiments. Axial profiles were also produced for heat flux, bulk Reynolds number, and film resistance from the model.

Degree

M.S.

Advisors

Revankar, Purdue University.

Subject Area

Nuclear engineering

COinS