Effects of Discharge Fan on the Drying Efficiency in Flat-bed type Dryer
— The study of interaction among the grain, moisture, and the surrounding space (air) is key to understanding the grain-drying process. In Iran, rice (mostly Indica type) is dried by flat bed type dryer until the final MC reaches to 6 to 8%. The experiments were conducted to examine the effect of application of discharge fan with different heights of paddy on the drying efficiency. Experiments were designed based on two different configurations of the drying methods; with and without discharge fan with three different heights of paddy including; 5, 10, and 15 cm. The humid heated air will be going out immediately by the suction of discharge fan. The drying time is established upon the average final MC to achieve about 8%. To save energy and reduce the drying time, the distribution of temperature between layers should be fast and uniform with minimum difference; otherwise the difference of MC gradient between layers will be high and will induce grain breakage. The difference of final MC between layers in the two methods was 48-73%. The steady state of temperature between the two methods has saved time in the range of 10-20%, and the efficiency of temperature distribution increased 17-26% by the use of discharge fan.
THIN LAYER SOLAR DRYING CHARACTERISTICS OF ROUGH RICE UNDER NATURAL CONVECTION
Abstract Thin-layer solar drying experiments were conducted at Matsuyama, Japan, with medium grain rough rice. The range of average drying air temperature was 22.3–34.9°C, and the relative humidities were between 34.5% and 57.9%. The initial moisture contents were in the range of 37.07–37.69% dry-basis. A mixed-mode natural convection solar grain dryer was used for this experiment. The data of sample weight and dry- and wet-bulb temperatures of the drying air were recorded continuously from morning to evening for each test. The drying data were then fitted to the Page model, based on the ratios of the differences between the initial and final moisture contents and the equilibrium moisture content (EMC). The model gave a good fit for the moisture content with an average standard error of 0.00387 dry-basis. Both the drying parameters N and K are linear functions of temperature and relative humidity. This single-layer drying equation can be used for the simulation of deep bed drying of rough rice in mixed-mode type natural convection solar dryers.
Prediction of net pressure on pressure equalized cavities
Abstract A numerical model has been developed for prediction of net pressure on pressure equalized cavities. The results based on this model show good agreement with those obtained from mock-up tests. Parametric studies verify that reductions in cladding load are possible, with proper design of curtain walls.