Experimental Tests of the Scaling Laws for Air Clearing in Water-Type Pressure Suppression Systems

Experiments were conducted to test the validity of the scaling laws which have been put forward for the small-scale modeling of the air clearing phase of flow into the condensation pool of a pressure suppression system. Three geometrically similar wetwells (differing in linear dimension by a factor of 4) were used, along with two liquids (differing in density by a factor of 3) and three gases (differing in enthalpy by a factor of 10). When using different pressures, liquids, and gases, the dimensionless pressures were in excellent agreement as long as the four scaling parameters were held constant. The enthalpy flux must be scaled by the use of an orifice to ensure that the pressures will scale. Our tests uncovered two areas where the scaling laws will not hold if the proper precautions are not taken. First, the vapor pressure of the pool liquid must be sufficiently low. Secondly, peak downloads will scale only if the containment walls are rigid and precautions are taken to eliminate small air bubbles in the liquid.