Preface - kmutt

16
Worachest Pirompugd, Somchai Wongwises,
Chi-Chuan Wang
Heat Mass Transfer, Vol. 41, No. 8, 2005,
pp. 756-765
This study proposed a new method,
namely a tube-by-tube reduction method to
analyze the performance of fin-and-tube heat
exchangers having plain fin configuration under
dehumidifying conditions. The mass transfer
coefficients which seldom reported in the open
literature, are also presented. For fully wet
conditions, it is found that the reduced results
for both sensible heat transfer performance and
the mass transfer performance by the present
method are insensitive to change of inlet
humidity. Unlike those tested in fully dry
condition, the sensible heat transfer performance
under dehumidification is comparatively
independent of fin pitch. The ratio of the heat
transfer characteristic to mass transfer
characteristic (h c,o /h d,o C p,a ) is in the range of
0.6~1.0, and the ratio is insensitive to change of
fin spacing at low Reynolds number. However, a
slight drop of the ratio of (h c,o /h d,o C p,a ) is seen
with the decrease of fin spacing when the
Reynolds number is sufficient high. This is
associated with the more pronounced influence
due to condensate removal by the vapor shear.
Correlations are proposed to describe the heat
and mass performance for the present plate fin
configurations. These correlations can describe
89% of the Chilton Colburn j-factor of the heat
transfer (j h ) within 15% and can correlate 81%
of the Chilton Colburn j-factor of the mass
transfer (j m ) within 20%.
IJ-041 EFFECT OF THERMAL PROCESSING
ON THE QUALITY LOSS OF PINEAPPLE
JUICE
Marisa Rattanathanalerk, Naphaporn Chiewchan,
Walaiporn Srichumpoung
Journal of Food Engineering, Vol. 66, No. 2,
January 2005, pp. 259-265
Three indexes, namely colorimetric
Hunter parameters (L, a, b and ∆E),
hydroxymethylfurfural (HMF) and brown
pigment formation, were monitored to determine
the quality loss of pineapple juice at
temperatures ranging from 55 to 95 °C. The
changes in a and b values followed first order
kinetics while ∆E fitted well to a combined
model which described both non-enzymatic
KMUTT Annual Research Abstracts 2005
browning reaction and destruction of carotenoid
pigment. For browning indexes, HMF and
brown pigment formation increased linearly with
heating time and could be explained using zero
order reaction kinetics. The results suggested
that processing temperature had a significant
effect on the color change of pineapple juice.
The dependence of the rate constant on
temperature was represented by an Arrhenius
equation.
IJ-042 EFFECTS OF DRYING METHODS AND
CONDITIONS ON DRYING KINETICS AND
QUALITY OF INDIAN GOOSEBERRY FLAKE
Siporn Methakhup, Naphaporn Chiewchan,
Sakamon Devahastin
LWT - Food Science and Technology, Vol. 38,
No. 6, September 2005, pp. 579-587
Vacuum drying and low-pressure
superheated steam drying (LPSSD) of Indian
gooseberry flake (used to prepare Indian
gooseberry tea) were carried out at various
drying conditions to monitor the drying kinetics
and quality degradation of the product during
drying. In terms of drying kinetics, the vacuum
drying took shorter time to dry the product than
LPSSD at every drying condition. In terms of
quality, it was found that only the product
subjected to vacuum drying at 75 °C and
absolute pressure of 7 kPa had similar level of
ascorbic acid retention compared to those
samples of LPSSD at every condition. The total
color difference of this sample was, however,
slightly higher than that of product dried by
LPSSD. Nevertheless, since the color changes
were not of much concern to the consumers of
Indian gooseberry tea, vacuum drying at 75 °C
and 7 kPa was proposed as the most favorable
condition for drying of Indian gooseberry flake
in terms of energy consumption.
IJ-043 EFFECTS OF GEOMETRY AND
OPERATING CONDITIONS ON THE MIXING
BEHAVIOR OF AN IN-LINE IMPINGING
STREAM MIXER
Chalida Niamnuy, Sakamon Devahastin
Chemical Engineering Science, Vol. 60, No. 6,
2005, pp. 1701-1708
The present study investigated
experimentally the effects of various geometric
and operating parameters on the mixing
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