Heat and mass transfer analysis in methanol and ethanol droplet evaporation with film stagnant model

摘要

Food dryers are things that now need to be developed as food aging. One of the drying methods is Spray Drying, where in the drying process mass and heat transfer occurs on the basic elements of Spray Drying, namely Droplets. To show the characteristics of droplets, we have formulated several models of heat transfer and mass equations. The analogy model which is generally used to obtain the heat transfer coefficient and mass values is the analogy model of Ranz W. E. and Marshall W. R. The analogy model must be combined with analytical models. Here we use an analytical model in the form of a stagnant film model. The purpose of this study was to see the results obtained from the analogy model of the Ranz-Marshall equation with a combination of stagnant film models applied to droplets of pure methanol and ethanol, which have Lewis numbers greater than one, with experimental data obtained. The results of the experiment, namely in the form of data that shows changes in temperature that affect the diameter of the droplet, which ranges from 1.5 mm - 3 mm. From the results of the Ranz Marshall analogy model, we get deviations from the values of Nusselt (Nu) and Sherwoods (Sh) numbers which have an impact on the values of C_1 and C_2 which are quite small. Therefore, a more general new equation is needed which is capable of calculating heat transfer and mass of all substances tested at different speeds.