| Author | Martinez, Romualdo C. |
| Call Number | AIT Thesis no.AE-91-24 |
| Subject(s) | Rice--Drying--Simulation methods
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master
of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Two near-equilibrium simulation models (THOMPSON et al., 1968; THOMPSON,
1972) were selected to study the simultaneous drying and rewetting in rice beds. A rewetting
routine was added in the THOMPSON et al. (1968) model to compute the adsorption of
moisture during rewetting. Simulation runs using assumed test conditions were made to
compare the relative performance of the two simulation approaches. A series of experimental
drying tests were carried out with special consideration to the occurrences of simultaneous
drying and rewetting in the grain bed to validate the simulation models. A procedure for
direct estimation of moisture profiles in the grain bed during drying as proposed by
BANJONG (1990) was also verified.
Simulation runs showed that the modified THOMPSON et al. (1968) model performed
satisfactorily, indicating simultaneous drying and rewetting in rice beds. The model was not
very sensitive to the choice of layer thickness and time step taken for the simulation, in
contrast with the THOMPSON (1972) model which was found to be very sensitive to the
layer thickness and time step used. For low-temperature, low-airflow and long- duration
drying, it was possible for the THOMPSON (1972) model to approximate the simulation
result of the THOMPSON et al. (1968) model by proper selection of simulation layer
thickness and time step. For high-temperature, high- airflow and short-duration drying, the
THOMPSON (1972) model would tend to predict narrower drying zones. For rewetting in
grain beds, both models gave consistently different predictions, with the THOMPSON (1972)
model predicting faster rewetting rates.
Comparison of experimental and simulated results indicated that the THOMPSON
(1972) model gave a slightly better overall performance in predicting the moisture changes
ln the grain bed. A mean moisture content difference of 1.3% between experimental and
simulated results was observed as against 1.5% for the THOMPSON et al. (1968) model. The
THOMPSON et al. (1968) model underpredicted the moisture content changes during
rewetting by a mean difference of 1.8%, but predicted the moisture content changes during
drying to within 1.0% on the average. On the other hand, the THOMPSON (1972) model
performed better in predicting the moisture content changes during rewetting with a mean
difference of 1.1 % between experimental and simulated results, but would tend to overpredict
the changes in moisture content during drying. The two models were combined to form a
mixed model which utilized the THOMPSON et al. (1968) approach when the grain
experienced drying and relied on the THOMPSON (1972) approach for moisture absorption.
The mixed model gave better predictions in comparison with either of the two models, with
mean differences between experimental and predicted results of 1.1 % for conditions of drying,
0.9% for conditions of rewetting, and 1.1 % for overall predictions. Comparison of the
predicted moisture profiles using the direct estimation procedure of BANJONG (1990) and
experimental results showed considerable differences in the values of moisture contents and
needs further investigation. |
| Year | 1991 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Jindal, Vinod Kumar; |
| Examination Committee(s) | Athapol Noomhorm;Gupta, C.P.; |
| Scholarship Donor(s) | Government of Australia; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1991 |