DISCUSSION In this experiment, food samples such as coarse sugar and vegetable seeds were used to determine their flowability through hopper. For the first experiment, coarse sugar has higher measurement of flow rate compare to vegetable seeds. This result was reliable since the granular diameter of sugar was lower than vegetable seeds thus resulting a lower time consumed by coarse sugar to pass through hopper. However, as the orifice size was decreased, the flow rate was also decrease for both coarse sugar and vegetables seeds.
The results of mass flow rate of experiment was quite tally with the mass of flow rate of equation. It shows decrement of flow rate as the orifice size decreases from 15 mm to 9 mm. Next, coarse sugar has a higher bulk density than vegetable seeds. This is because, coarse sugar has a larger weight with volume almost the same with vegetable seeds, despite its smaller diameter size. Thus, the powder particles will move and usually settle closer together, resulting in a higher bulk density. For measurement of angle of repose, vegetable seeds have a lower value of mean ? han coarse sugar. The conical pile formed was flatter than for coarse sugar. This indicates that coarse sugar was more cohesive, thus more hygroscopic. Hygroscopic materials are materials that have the ability to absorb moisture from its surroundings. As more hygroscopic materials present in powdered food, this will then lead to poor flowing conditions hence causing several flowing problems such as rathole, bridging and segregation. Ratholing occurs when discharge takes place only in a flow channel located above the outlet.
If the material being handled is cohesive, the material outside of this channel will not flow into it and may cake or agglomerate. Once the central flow channel has emptied, all flow from the silo stops. Meanwhile, bridging occurs when an arch-shaped obstruction forms above the hopper outlet and stops flow. It can be an interlocking arch, where large particles mechanically interlock to form an obstruction, or a cohesive arch. A cohesive arch occurs when particles bond together due to effects of moisture, fines concentration, particle shape, temperature, etc.
Next, segregation results when particles separate due to differences in their size, shape, or density. Segregation can result upon handling of a powder blend or material with varied particle size. Common segregation mechanisms include sifting, fluidization, and dusting. To encounter these problems, anti-caking agents are added to allow them to flow and mix evenly during the food production process. In addition, the true values of C, as stated in the result, decrease according to the decrement in orifice size.
