

Articles
by
A.O. Ashraf 
Total Records (
3 ) for
A.O. Ashraf 





A. S. Mokhtar
,
K. A. Abbas
,
M. M. H. Megat Ahmad
,
S. M. Sapuan
,
A.O. Ashraf
,
M.A. Wan
and
B. Jamilah


The present work aims at finding an optimized explicit finite difference scheme
for the
solution of problems involving pure heat transfer from surfaces of Pangasius
Sutchi fish samples
suddenly exposed to a cooling environment. Regular shaped packages in the form
of infinite slab were
considered and a generalized mathematical model was written in dimensionless form.
An accurate
sample of data set was chosen from the experimental work and was used to seek
an optimized scheme
of solutions. A fully explicit finite difference scheme has been thoroughly studied
from the viewpoint
of stability, the required time for execution and precision. The characteristic
dimension (half
thickness) was divided into a number of divisions; n = 5, 10, 20, 50 and 100 respectively.
All the
possible options of dimensionless time (the Fourier number) increments were taken
one by one to give
the best convergence and truncation error criteria. The simplest explicit finite
difference scheme with
n = (10) and stability factor ( (δX )^{2} /δτ = 2) was found to be reliable and
accurate for prediction
purposes. 




F. A. Ansari
,
K.A. Abbas
,
J. Bakar
,
A.O. Ashraf
,
A.S. Mokhtar
and
S.M. Sapuan


In an earlier study, it was demonstrated that the empirical approach used to calculate
surface film conductance resulted into a higher value compared to those obtained from the other
methods available in the literature. During further investigations, surface film conductance values
were found to gradually decrease with a fall in temperature. When this nonlinear variation was used
to develop a correlation and it was used to calculate temperatures by the same empirical correlation,
a remarkably excellent improvement in the calculated temperature resulted. 




K.A. Abbas
,
F.A. Ansari
,
A.S. Mokhtar
,
A.O. Ashraf
,
M.A. Wan
and
S.M. Sapuan


The present work aims at finding an optimized finite difference scheme for the solution of
problems involving pure convection heat transfer in slab shaped fresh water fish pieces. A generalized
mathematical model was written in dimensionless form and an optimized scheme of solutions was
worked out. A fully explicit finite difference scheme, an implicit finite difference scheme and different
combination of the two, with varying values of weighing factor were thoroughly studied. All the
possible options of temperaturetime grid sizes were considered. It was found that the simplest explicit
finite difference scheme with ten characteristic length division and Fourier number increments one
sixth of the square of the space division size gives best convergence and minimal truncation error.
Numerically computed and measured temperaturetime variations were found to have excellent
agreement. 





