An enhanced electrical resistance technique for foam drainage measurement

The ability to characterise the drainage behaviour of foams is of direct value to the design of foaming systems and control of foam structures. Traditional electrical resistance methods for characterising foam drainage do not take into consideration the effects of foam inhomogeneity, and in particular the hitherto unnoticed substantial liquid layer established on the wall during drainage. An improved electrical resistance technique has been developed for accurate measurement of foam resistance which includes the liquid layer at the wall. The multi-channel set-up allows measurement of the temporal and vertical variations in the electrical resistance of a standing foam. The liquid holdup in the foam is inferred by calibration against a gamma-ray absorption technique. The capability of the technique is demonstrated through drainage tests performed on different foaming systems. (C) 2001 Elsevier Science B.V. All rights reserved.