This paper presents experimental results for the pressure drop across an annular geometry restriction in a Tube Support Plate (TSP). These restrictions are typical in pressurized water reactor (PWR) steam generators. The pressure drops were experimentally measured for single and two-phase air-water mixture. This research compares the pressure drops for two different geometries (annular and trefoil) with the same hydraulic diameter (0.0906 inch) to determine if the hydraulic diameter is an appropriate geometric modeling parameter for this type of geometry. The loss coefficients were also determined and empirical correlations were developed. A conclusive comparison of the annular with trefoil geometries is provided and recommendations given. It is concluded that the hydraulic diameter is not an appropriate geometric modeling parameter. The annular geometry yields to a lower pressure drop than the trefoil geometry for the same hydraulic diameter. The tests were performed at atmospheric conditions
