Visual Observations of Chamber Volume Effect on Ebullience From Submerged Orifice Plates

Effect of chamber volume upstream of the orifice on ebullience from orifice plates is studied experimentally in this paper. Bubble growth from orifice plates submerged in liquid pools is captured using high speed videography. The orifice plate substrate is acrylic glass and 11 different orifice diameters (diameter range: 0.610< D₀< 2.261mm) are utilized. In addition to water, ethanol-water binary mixture with surface tension of 54 mN/m is used to examine the interplay between surface tension and chamber volume effects on bubble characteristics. For an acrylic glass orifice plate with a fixed chamber volume, above a certain transition orifice diameter, the bubbles from the orifice plate are of the same size and shape as those from a capillary tube orifice. However, below this diameter, the bubbles from the orifice plate show significantly different characteristics due to the chamber volume effect. The bubbles are more spherical in shape with the apex being sharper and more pointed. The bubbles also tend to sit closer to the plate due to their abnormally large size while the growth times are much shorter. These differences are highlighted by comparing photographs of bubble growth with and without the chamber volume effect. Additionally, for the medium chamber region, an empirical correlation was proposed to predict bubble departure diameters to within ±15 %. For a fixed chamber volume, variation in surface tension showed no change in the transition orifice diameter.