Determination Of Effective Parameters For Drying Of Apples

DETERMINATION OF EFFECTIVE
PARAMETERS FOR DRYING OF APPLES

A Thesis Submitted to
the Graduate School of Engineering and Sciences of
İzmir Institute of Technology
In Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE
in Energy Engineering

by
Tarık DİKBASAN

December 2007
İZMİR

We approve the thesis of Tarık DİKBASAN

____________________________Assoc.Prof.Dr. Gülden GÖKÇEN AKKURT
Supervisor

_____________________________
Prof.Dr. Sacide ALSOY ALTINKAYA
Co-Supervisor

_____________________________
Prof.Dr. Necdet ÖZBALTA
Committee Member

_____________________________
Prof.Dr. Ahmet YEMENİCİOĞLU
Committee Member

_____________________________
Asst.Prof.Dr. Sevgi KILIÇ ÖZDEMİR
Committee Member

26 December 2007
Date_________________________
Asst.Prof.Dr. Ünver ÖZKOL
Head of the Energy Engineering Program

_______________________
Prof.Dr. Hasan BÖKE
Dean of the Graduate School of
Engineering and Science

ACKNOWLEDGEMENTS

I would like to express my sincere gratitude to my supervisor Assoc.Prof.Dr.
Gülden Gökçen Akkurt and co-supervisor Prof.Dr. Sacide Alsoy Altınkaya for their
support and guidance.I also wish to thank to Prof.Dr. Necdet Özbalta, Prof. Dr. Ahmet
Yemenicioğlu and Assist.Prof.Dr. Sevgi Kılıç Özdemir for their valuable suggestions
and comments which helped to improve the Thesis.
I express my special thanks to Assoc.Prof.Dr. Metin Tanoğlu and Assist.Prof.Dr.
Figen Korel for giving me the opportunity to use their laboratory equipment.
I am grateful to the Scientific ResearchFund of IYTE for substantial support in
realizing this study.
Special thanks to my colleagues for their friendship and support during my hard
times.
Finally I would like to thank to my family for their excellent support and try to
keep me high-spirited throughout the MSc. Programme.

ABSTRACT
DETERMINATION OF EFFECTIVE PARAMETERS FOR DRYING OF
APPLES

Drying is one of the oldestmethods for the preservation of agricultural products
such as fruits and vegetables. Apple has a significant share in fruit production both in
the World and in Turkey. It is also an important raw material for many food products.
Temperature, velocity and relative humidity of drying air are important
parameters for hot air drying process. To determine the drying kinetic of agricultural
products,drying and drying rate curves should be plotted.
Experiments are conducted in a tunnel dryer using cubic shaped (10x10x10mm)
red delicious (Malus Domestica) apple for various drying air temperature (40.1-65.3oC),
velocity (1.1, 1.4, 1.9, 2.3 and 2.5 m/s) and relative humidity (4.6-20.5%) values. The
temperature and relative humidity are measured and recorded every 1 min. at fan inlet,
upstreamand downstream of the tray, the velocity is measured only at the tunnel exit.
The measured data is used to obtain drying and drying rate curves. The curves indicate
that drying process takes place in the falling rate period except very short unsteady-state
initial and constant rate periods. Thus, effective diffusion coefficients are calculated
using the data collected during the falling rateperiod and the experimental data are
fitted to fourteen thin layer drying models which are found in the literature. Rehydration
time and colour are used as parameters for the dried apple quality.
The effective diffusion coefficients are obtained within the range of 0.486x10-9 5.63x10-9 m2/s Regarding with drying time, rehydration time and colour data, the best
results are obtained at 2.5 m/svelocity, 20.5% relative humidity and a temperature
range of 53.5-65.3oC under experimental conditions. Midilli and Kucuk model is the
best fitted model with a minimum R2 of 0.9991 and a maximum RMSE of 0.0087976.

iv

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