Design Theory of Forced-Air-Curing Facility of Packed Farm Products

Abstract

It was found that the curing of farm products meant a little surface drying operation in constant rate period.
The design formulae which determine the flow rate, the humidity and the temperature of the air were derived by solving the drying equations to satisfy the conditions that the drying was carried out at a given time in accordance with a given average drying ratio within a given range of uneven drying ratio in the facility from the assumption of constant adiabatic saturation temperature of the drying air through the packed products. The formulae are as follows:
Y_L≤α/β
Q=S·γ·K·L/Y_L
HW-H=β/{(K·T/W₀)·(1-exp(-Y_L))/YL)}
where Y_L=dimensionless height(-), α=limit of unevenness(-)
β=directing dried ratio(-), Q=flow rate of air (m³/hr),
S=cross-sectional area of bed (mm2), γ=specific volume of air (m3/kg), K=mass transfer coefficient (kg/m₃·hr·ΔH),
H_W=saturate absolute humidity at wet bulb temperature (kg/kg'),
H=absolute humidity (kg/kg'), T=drying period (hr), W0=observed specific weight of products in bed (kg/m³)
The basic data of Satsuma orange (Citrus unshiu Marc.) are arranged, and an example of design calculation is given for an actual facility.