Experimental Study of Downward Facing Boiling under IVR-ERVC Conditions

Open Access
Author:
Gorman, Nicolas Stephen
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 15, 2014
Committee Members:
  • Fan Bill B Cheung, Thesis Advisor
  • Gita Talmage, Thesis Advisor
Keywords:
  • IVR
  • ERVC
  • Boiling
  • Two-phase
  • heat transfer
  • nucleate boiling
Abstract:
New correlations are developed to more completely capture the physics of downward facing boiling, especially under nuclear accident conditions requiring In Vessel Retention External Reactor Pressure Vessel Cooling (IVR-ERVC) strategies. Extending the length scale correlations used by Rohsenow to derive the heat ux from a at plate (Reference [16]), a correlation based on bubble size at detachment is obtained for downward facing boiling. To validate this correlation, downward facing boiling data was obtained in the Subscale Boundary Layer Boiling(SBLB) facility, which was refurbished and out tted with a new data acquisition system. In addition to correlating the heat ux to the wall superheat, video was taken of downward facing boiling so that the volumetric ow rate and the ow area may be better understood and observed. In particular, IVR-ERVC strategies require that adequate steam venting be provided. Because the speed of sound is so slow in saturated water, it is possible that for some designs of reactor pressure vessels (RPVs) and their insulation structures, the entrained ow of steam will become choked. If the ow becomes choked, then it will prevent the liquid water from reaching the surface of the RPV, and ERVC will fail. The size and frequency of bubble formation is recorded, and a lower bound on the minimum allowable ow area for an insulation structure is established. The validity of the bubble size correlation is established by using it to back-predict the heat ux. Measurements are made of the wall superheat at various locations on the RPV surface, as well. From these measurements and the extension of the Rohsenow correlation, it was possible to predict the heat ux as a function of location on the RPV and surface temperature. By performing downward facing boiling experiments with di ering levels of subcooling, it was possible to predict the e ect of subcooling on surface temperature, with known heat ux and position. The validity of these correlations is established by using them to accurately predict the superheat at di erent locations for downward facing boiling using both saturated and subcooled liquid.