MEASUREMENT OF INTERFACIAL RE-EQUILIBRATION DURING HYDROGEN BUBBLE COALESCENCE

A new experimental technique has been developed and tested to measure the interfacial velocities associated with the coalescence of small, e lectrolytically generated gas bubbles. The technique involves measurin g, by means of a linear photodiode array, the rate of deflection of a laser-light sheet caused by the movement of a newly formed boundary be tween coalescing bubbles. Bubble pairs in the 500 to 1000 mum range we re generated at precisely controlled rates between two parallel glass- encased microelectrodes. Correlation of data obtained on the coalescen ce of two hydrogen bubbles of identical size shows that the position o f the interface along the coalescence plane varies with the square-roo t of time, in agreement with the hole expansion model advanced by Char les and Mason.2 Initial interfacial velocities are in the range of 200 to 300 cm/s. Larger numbers of such events occurring simultaneously a t gas evolving electrodes will significantly disturb the fluid immedia tely adjacent to the electrode, thereby improving mass transport rates to and from the surface.