Preface - kmutt

KMUTT Annual Research Abstracts 2005
indicated that the two sub-drying systems
(system No. 2) with tempering and ventilation as
elements of each stage yielded higher drying
capacity and thermal efficiency than the single
drying system (system No. 1), in which paddy
was treated with the drying, tempering and
ventilation units only once. The proportion of
full kernels and value of the whiteness obtained
from both drying systems were not significantly
different. System No. 3, where grains after the
first tempering were dried immediately by the
second fluidised-bed dryer with no ventilation
unit, produced poor head-rice yield and colour
and was unacceptable for producing white rice.
IJ-018 COMPARISON OF PERFORMANCES
OF PULSED AND CONVENTIONAL
FLUIDISED-BED DRYERS
Somkiat Prachayawarakorn, Warunee Tia,
Korakot Poopaiboon, Somchart Soponronnarit
Journal of Stored Products Research, Vol. 41,
No. 5, 2005, pp. 479-497
Consumption of energy, outlet moisture
content and quality of the dried commodity
are important parameters of paddy-dryer
performance. The fluidised-bed paddy-dryer has
been commercialised for several years and in
this paper, paddy drying by pulsed and
conventional fluidised-bed dryers are compared.
Experimental results have shown that the
variation of moisture content at the exits of both
dryer types in test runs was very small. Heat
utilisation was more effective when such dryers
were used to dry paddy at moisture contents
above 24% dry basis and up to 50% of the
thermal energy was saved by recycling 70-80%
of the air. Paddy qualities i.e. head-rice yield and
colour of the dried white rice were similar with
both dryers and almost the same as the original
undried values, or slightly higher in the case of
head-rice yield, depending upon the drying
conditions. Below 28% dry basis, it is
recommended that inlet-air temperature should
be lower than 145 °C in order to maintain white
colour. The cooked rice obtained from paddy
dried at a temperature of 145 °C was harder than
naturally dried control samples. A mathematical
model based on energy and mass balance
predicted values in good agreement with
experimental results for both the pulsed and
conventional fluidised-bed dryers. Calculated
thermal and electrical energy consumptions
indicated that the pulsed flow dryer was more
economical than the conventional dryer.
IJ-019 SUPERCRITICAL CO 2 EXTRACTION
OF NIMBIN FROM NEEM SEEDS:
A MODELLING STUDY
Dayin Mongkholkhajornsilp, Supaporn Douglas,
Peter L. Douglas, Ali Elkamel,
Wittaya Teppaitoon, Suwassa Pongamphai
Journal of Food Engineering, Vol. 71, No. 4,
December 2005, pp. 331-340
The extraction of nimbin from neem
seeds using supercritical carbon dioxide is
investigated in this paper. A model that accounts
for intraparticle diffusion (D e ) and external mass
transfer of nimbin (k f ) is presented for the
supercritical extraction process. Mass transfer is
based on local equilibrium adsorption between
solute (nimbin) and solid (neem solid). The
external mass transfer coefficient was
determined by fitting the theoretical extraction
curve to experimental data. The following range
of conditions: 0.24-1.24 cm 3 /min of CO 2 , 10-26
MPa, 308-333 K, 1.0-2.5 g of neem kernel
powder and 0.0575-0.185 cm of particle size of
neem kernel powder, were considered. In
addition, a new correlation for Sherwood
number (Sh) was developed in terms of the
dimensionless groups; Reynolds number (Re)
and Schmidt number (Sc) from optimisation
results. This correlation was compared to
previous correlations and was found to give
superior results when compared to experimental
data.
IJ-020 EFFECT OF FLY ASH FINENESS ON
COMPRESSIVE STRENGTH AND PORE SIZE
OF BLENDED CEMENT PASTE
Prinya Chindaprasirt, Chai Jaturapitakkul,
Theerawat Sinsiri
Cement and Concrete Composites, Vol. 27,
No. 4, April 2005, pp. 425-428
This paper presents an experimental
investigation on the effect of fly ash fineness on
compressive strength, porosity, and pore size
distribution of hardened cement pastes. Class F
fly ash with two fineness, an original fly ash and
a classified fly ash, with median particle size of
19.1 and 6.4 µm respectively were used to
partially replace portland cement at 0%, 20%, and
40% by weight. The water to binder ratio (w/b)
of 0.35 was used for all the blended cement
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