Heat and Mass Transfer During Steam Pressing of Wool Fabrics

Abstract

The temperature and humidity of steam and their effects on the absorption of moisture into wool fabrics during steam pressing are investigated. The temperature of buck steam in a steam press is greatly influenced by the temperature of the buck padding. The physics of heat and moisture transfer between the steam and the padding material is modeled to give predictions of the temperature and humidity of the steam entering the fabric. The calculated steam temperature confirms its dependence on the buck padding temperature, as does the steam relative humidity, which decreases steeply with prolonged steaming. A sharp increase in the fabric moisture content during the first few seconds of steaming is predicted by the model and confirmed by experimental measurements. Subsequent changes in moisture content as the fabric equilibrates to the steam condition will depend on the initial fabric regain and the steam condition. Variations in the temperature and humidity of steams between presses are explained as due mainly to the type and conditions of the padding. The model is also used to simulate vacuum cycles and can predict fabric temperature and regain during different cooling procedures.