Mass Transfer in a Laboratory Washing Machine

Abstract

Rinsing of loosened soil from textiles into an agitated bath is one of the essential steps in washing. This paper describes a rinsing model, its measurements, and further applications. A textile is an inhomogeneous porous medium. The liquid from the bath easily flows into the large pores. In these regions the soil is dispersed mainly by convection. The small pores are occupied by stagnant liquid. Consequently, the supply of detergents and the transport of loosened soil take place by diffusion. A piece of textile is therefore regarded as a porous slab having diffusion and convective regions. The length of each region depends on agitation, cloth/liquor ratio, textile porosity, and tem perature. Using the diffusion length as a characteristic parameter, the agitation and the influence of detergents in fabric cleaning can be investigated and optimized in washing machines of various types and dimen sions.