Prediction of in-house constant rate drying of chicken excreta by dimensional analysis

摘要

Results from a study simulating in-house drying of chicken excreta were used to develop a drying rate prediction equation using dimensional analysis. The study recorded drying rates of ninety-five samples of excreta dried in a controlled environmentchamber. The samples were dried under typical values of temperature, humidity, and air velocity found in a poultry house, and one third of the samples was heated by conduction. Consideration of the physical system determined nine pertinent quantities; drying rate, specific gas constant, temperature of body, pressure difference, velocity of air, viscosity of air, density of air, volumetric diffusivity, and characteristic dimension. Dimensional analysis of these variables revealed three dimensionless groups; a dimensionless drying rate, the Schmidt number, and the Reynolds' number. A correlation of these groups was able to adequately predict drying rate in the unheated samples, but not in the heated ones. Inclusion of an additional quantity, the latentheat of vaporization of water, permitted the creation of a fourth dimensionless group, the ratio of the latent heat of vaporization at the heated body temperature and the unheated body (wet bulb) temperature. Another correlation including the fourth dimensionless group was able to adequately predict the drying rate of all samples.