Modeling of hot vapor flow in cylinder of drum dryer by using finite element method for drying of Aloe vera gel.

Aloe vera plant (Aloe vera) from Liliaceae family is one of the high valuable medicinal plants. One of the usage the gel of the crop is to use the dried powder. In this research, drum dryer was used to dry the product. Finite element method was used to examine the heat transfer in the cylinder of a drum dryer. Four cylindrical models were used to study the uniformity and maximum heat transfer of steam flow to the dryer cylinder wall. Two parameters were considered for controlling the flow of hot steam inside the cylinder, i.e. the conical barrier at input and the output (narrow and wide). The A and B models are narrow and broad output respectively, both without conical barrier and the C and D models, are similar to the A and B models but including conical barrier. The effect of two mass flow rates of intake water vapor (1 and 2 kg/s) was also investigated on the models. The results were important in terms of uniformity and maximum heat transfer on the cylinder surface. The results showed that the installation of a conical barrier in the drum dryer causes to direct the hot steam to the drum walls immediately and causes to have the highest heat transfer, so that the temperature increase above 485 K. The barrier caused to move the steam near the drum wall from the beginning to the end. Meanwhile the temperature was cooled uniformly about 10 K. The lowest variation of temperature (6 K) on the cylinder wall was for the model B and mass flow rate of 1 kg/s, which the highest temperature (476 K) was at the middle of the cylinder, and the lowest temperature (470 K) was at the beginning as well as at the end of the cylinder.