Experimental evaluation of low head oxygenators

Abstract

The overall mass transfer coefficient, G20, for a single hole orifice plate was evaluated in a series of experiments as affected by four geometric variables: orifice plate hole diameter (5, 10, 14, 19, and 22 mm), hydraulic head on the flooded plate (2.5, 5, and 13 cm), water fall height from the orifice to the receiving pool of water (30, 61, 91, and 122 cm), and the collection pool depth (2.5, 8, 13, 25, and 41 cm). This is, in essence, the simplest form of a low head oxygenator (LHO). A regression equation was developed to predict G20 as a function of these variables, their interactions, and squared terms. The hydraulic head above the flooded plate had no significant effect (P<0.10) on the overall mass transfer coefficient. It was determined that the contribution of the orifice hole solely to overall gas transfer was much less than previously assumed, suggesting that a much larger percentage of gas transfer is due to the splashing and subsequent entrainment as water droplets fall into the receiving pool of water. Practical implications of the results are discussed.