Droplet-Induced Heat Transfer Augmentation Downstream of a Spacer Grid During Dispersed Flow Film Boiling
The mechanism of droplet-induced heat transfer augmentation downstream of a spacer grid in the dispersed flow film boiling region of a rod bundle is investigated theoretically. A physical model is developed by considering a dispersed two-phase mixture flowing through a grid spacer whereby shattering and breakup of liquid droplets occur to generate smaller droplets leading to a larger interfacial heat and mass transfer area in the dispersed flow field. This causes an increase in the total rate of droplet evaporation downstream of the grid, which in turn accelerates the flow and de-superheats the steam, thus enhancing convective cooling of the fuel rods. In this study, a droplet breakup model is employed to predict the increase in the interfacial area downstream of a grid spacer and a droplet evaporation model is developed to predict the droplet evaporation rate. The latter accounts for convection heat transfer between the droplets and the continuous phase (I.e., the superheated steam) and radiation heat transfer between the droplets and the rods. Based on the flow acceleration so predicted, the effect of spacer grid on heat transfer augmentation due to evaporation of liquid droplets in superheated steam is quantitatively determined.
Dispersed Flow Film Boiling Spacer Grid Effects Heat Transfer Augmentation
F. B. Cheung S.M. Bajorek S. Goverapet Srinivasan
Department of Mechanical & Nuclear Engineering Pennsylvania State University, University Park, PA 16 Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission, Washington, DC 20555
国际会议
上海
英文
1336-1349
2010-10-10（万方平台首次上网日期，不代表论文的发表时间）