Experimental Studies for the Effects of the Spacer Grid on Two-phase Flow Regime Transition
Open Access
- Author:
- Nedwidek, Frank Maurin
- Graduate Program:
- Nuclear Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Seungjin Kim, Thesis Advisor/Co-Advisor
Seungjin Kim, Thesis Advisor/Co-Advisor - Keywords:
- flow regime
spacer grid
two-phase flow - Abstract:
- This study investigates the effect of the spacer grid flow restriction on flow regime transition and additional loss in pressure in an air-water spacer grid separate-effects scaled test facility at the Advanced Multiphase Flow Laboratory of the Pennsylvania State University. To preserve two-phase flow conditions as well as relative geometric dimensions of the spacer grid and bubble size, a scaling study was performed based on a reference four-loop Pressurized Water Reactor (PWR). In this scaling study, important two-phase flow parameters included bubble sizes, bubble Reynolds number, channel Reynolds number, and bubble Weber number, while key geometric dimensions included rod diameter, spacer grid pitch and wall thickness. The test section consists of four sections, namely; a 60.96 cm (2 ft) section upstream of the spacer grid section, a 20.32 cm (8 in) spacer grid section, and two 121.92 cm (4 ft) downstream sections. The inlet test section features a measurement port at an L/D of 19 after the two-phase injectors, while the two downstream test sections combine for six measurement ports located axially at L/D's of 6, 15, 30, 45, 70 and 100 after the grid. In the present study, the local gauge pressure is measured for a variety of single-phase liquid flow conditions at each measurement port in order to characterize the test facility bundle friction factor and the spacer grid minor loss coefficient. Additionally, detailed flow visualization studies are performed for over 100 two-phase flow conditions at three locations - upstream of the spacer grid, at the spacer grid, and downstream of the spacer grid - in order to establish a flow regime map specific to the present study and understand the effect of the spacer grid flow restriction on flow regime transition.