(93d) Empirical Correlations for the Heat Transfer Coefficient to Predict Moisture Content in a Fluid Bed Dryer

Drying is a required process in the food and pharmaceutical industry. An efficient drying can make the difference in the quality of a product, especially if people eventually will consume it. That is why the transport phenomena that are involved in drying should be studied in detail to determine their effect in the quality of the products. The transport phenomena include energy and mass transfer. Fluid Bed Drying provides optimum conditions for this phenomenon to occur to the fullest by increasing the area for mass and energy transfer. This in turns decreases the time of drying. This research focuses on obtaining an empirical correlation for the heat transfer coefficient (h) of a pharmaceutical binary mixture in a Fluid Bed Dryer. The binary mixture comprised of lactose monohydrate and pregelatinized starch combined with distilled water. Temperatures of 60°C and 80°C and air flows (m3/hr) of 40, 50, 60, 70 and 80, were used. Surface temperature was measured by a thermocouple that was placed at the bottom of the binary mixture to avoid the interference of air temperature. Then, the value of the surface temperature and air were used in Newton's equation to solve for the heat transfer coefficient. The correlations for (h) occur based on dimensionless numbers Reynolds, Nusselt and Prandtl. These correlations were used to predict the moisture in the two different regions of the drying curve: constant rate and falling rate.