Pressure Drop and Distribution of Moisture Content in Layers of Rayon Staple Dried by Throughflow of Air

Abstract

The drying the falling-rate period of drying is known to be approximately pro-portional to the moisture content W.∂W/∂θ=-KWwhere W: moisture content (kg water/kg dried fiber)θ: time (min)K : proportionality constant (1/min)The author has found that K is a function of the temperature and humidity of drying air; and that ∂K/∂ω decreases at a rate proportional to R/G, where R is the drying rate, ∂W/∂θ and G is the mass velocity of dryingair (kg/m2). This relation is expressible thus by equation : ∂K/∂ω=J/G-∂W/∂θwhere J is a proportionality constant.The two partial differential equations were integrated numerically with results which a greed well with experimental data.The pressure drop across fiber layers cannot be represented by a single coefficient of resistance, becuause fiber layers are compressed in varying degrees by the applied air pressure.The mean solid fraction (1-e) in fiber layers compressed by air pressure was obtained from the compressional characteristics of fiber layers compressed by uniform pressure so as to modify the above-mentioned coefficient of resistance for the pressure drop. The coefficient of friction when divided by a certain power of (1-e) is a relatively constant value.