Mass Transfer and the Washing Process

Abstract

Published soil removal data suggest that the mass transfer process in a washing ma chine (transport of materials between cloth and bath) may influence or even dominate the soil removal process. Therefore, mass transfer is investigated in a small scale washer (Terg-O-Tometer). The process is characterized by the transfer coefficient, which is the inverse of the time constant. It is correlated using dimensional analysis with such variables as the bath volume, the water-holding capacity of the cloth load, the agitation speed, and stroke angle. Actual experiments are conducted with water-soluble substances; their results sup port the theoretical developments set forward. The transfer coefficient is directly proportional to agitation speed and stroke angle, inversey proportional to the water- holding capacity of the cloth load, and independent of the bath volume. Finally the mass transfer process is compared in a full-size machine, a small commer cial washer, and the test device by scale-up experiment. Good agreement is found, thus confirming the full-scale application of the results.