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Introduction

Drying is a mass transfer process consisting of the removal of water or another solvent by

evaporation from a solid, semi-solid or liquid (Greensmith, 1998! "his process is often used as a

final production step before selling or pac#aging products! "o be considered $dried$, the final

product must be solid, in the form of a continuous sheet, long pieces, particles or powder! %

source of heat and an agent to remove the vapor produced by the process are often involved! &n

bio products li#e food, grains, and pharmaceuticals li#e vaccines, the solvent to be removed is

almost invariably water! "hus, it is important to have drying process in order to reduce moisture

content in the products! During drying process, two fundamental and simultaneous processes

occur' first is the transfer of energy, mostly as heat from the surrounding environment toevaporate the surface moisture, and second is the transfer of internal moisture to the surface of

the solid and its subsequent evaporation due to the process!

&n industries, there are several type drying units that have been used such as tray dryers,

tunnel dryers, roller or drum dryers, vacuum dryers and freee dryers! )ach have its own pros

and cons! &n this e*periment, tray dryers have been used to reduce moisture content in the rice!

"ray dryers are used for small-scale production or for pilot-scale wor#! +y using this method,

the food (rice is spread out, generally quite thinly, on trays in which the drying ta#es place! "he

trays is heated by an air current sweeping across the trays using hot air that pumped into the

chamber which removes the moist vapors! "he air temperature is usually controlled by a

thermostat which is normally set between and . o/! "he air enters the bottom of the chamber

below the trays and then rises, through the trays of food being dried, and e*its from an opening

in the top of the chamber!

Depending upon the food and the desired final moisture, drying time may be of the order

of 1 or even 0 hours! "ray dryers require low capital and maintenance costs but have relatively

poor control and produces more variable product quality! "hus, in the ractical %ction systems

the trays are designed to force the air to follow a longer igag route which increases the air and

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food contact time and thus improve its efficiency! "his system also reduces bac# pressure which

means that cheaper, smaller fans can be used!

Objective of experiment

"he purpose of this e*periment is

"o determine the drying rate of the sample by drying method using tray dryers!

"o study the drying behavior of a non-porous solid!

Scopes of experiment

"he e*periment is done by using tray dryer! %nalysis of e*perimental data relating

moisture content to time and represented by plotting a drying curves! "he study of drying

behavior can be carried out further by determining the drying rate of the solid and also by

calculating the heat and mass transfer coefficient during the constant rate period!

References

Greensmith, 2! (1998!Practical Dehydration! 3oodhead ublishing, 4td!