Katharine J. Beverley

Evaporation rates of pure liquids measured using a gravimetric technique

We describe a gravimetric method for the determination of evaporation rates. The liquid sample is held in a partially filled, cylindrical open-topped tube within a vertically flowing gas stream. A simple model appropriate to this geometry is found to account for the variation of rate with liquid height within the sample tube and gas flow rate. Evaporation rates for a range of pure liquids with vapour pressures ranging from 0.1 to 500 Torr were determined and showed reasonable agreement with theoretical values estimated using literature values of the vapour pressures and vapour diffusion coefficients in air.

Evaporation rates of structured and non-structured liquid mixtures

We have used a gravimetric technique to measure the rate of evaporation of a volatile liquid in mixtures with a second, involatile component under conditions of controlled gas flow. A range of non-structured and structured mixtures were investigated in order to examine whether the rate limiting step for evaporation may switch from vapour diffusion across the stagnant gas layer above the liquid to mass transfer within the liquid mixture. Evaporation rates of pentane and hexane from mixtures with squalane (involatile) show excellent agreement with rates calculated on the basis that vapour diffusion across a stagnant gas layer is rate limiting and that mass transfer within the liquid mixture is fast. Hexane gelled by the addition of silica particles is found to evaporate at a rate very similar to that for un-gelled hexane because the equilibrium vapour pressure of hexane is unaffected by silica particle addition. Water evaporation rates from mixtures with the non-ionic surfactant n-dodecyl hexaoxyethylene glycol ether (C12E6) were found to be up to 10 times slower than calculated vapour space diffusion controlled rates owing to the slow development of concentration gradients within these highly structured liquid mixtures.

Evaporation rates of water contained within porous silica particles

We have used a gravimetric technique to measure the rate of evaporation of water contained within the pores of powdered silica particles. The experimental conditions are such that the rate is directly proportional to the water vapour pressure. For silica powders of different mean pore sizes, the reduced water evaporation rates are in agreement with the reduction of vapour pressure predicted according to the Kelvin equation. For a particular silica powder, evaporation rates determined from samples with different water contents show the variation in effective pore radius as a function of pore filling volume. Experiments in which a partially water filled powder is overlaid with a dry powder show that the achievement of a homogeneous distribution of water throughout the powder sample takes several hours.

Development of An Ideation Toolkit Supporting Sustainable Fashion Design and Consumption

This paper explores the potential for co-design to link sustainable consumption and production in the fashion industry. We review relevant research and perspectives and propose a co-design platform and an ideation toolkit in which users are encouraged to explore sustainability as a way of thinking at the early stages of the fashion design development process. We explain the rationale behind the ideation toolkit, its structure and demonstrate how to apply the toolkit to fashion design through a case study. Finally, we discuss both opportunities and challenges of co-designing the fashion system and its implementation in sustainable fashion and textile design education.