الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
A study was carried out to test and evaluate a portable mechanical date dryer using butane – gas as heat energy source and a forced convection solar dryer with auxiliary electric heater . During the experimental work the temperature of drying air was adjusted to be approximately constant at 40 , 50 , 60 and 70 C and air velocity of 1 ,1.5 and 2 m/s, 0.26 , 0.52 and 0.78 m/sec for a portable mechanical date dryer and a forced convection solar dryer respectively. High moisture hayani date was dried under three different treatments of date (peeled date , peeled treated date and unpeeled date ). Two empirical models (Exponential and Page) were examined to describe the drying behaviour and predict the change in moisture content of date during the drying process. Moisture content of date , thermal efficiency of the dryer and the total sugar and percentage reducing in sugars of the dried date were also determined. The obtained results showed that, both of the empirical models could satisfactorily be described the change in date moisture content during the drying process under specific conditions. On the other hand Page’s model proved that it can predict and describe drying behaviour more adequately than the simple model . The dryer thermal efficiency increased with the increase of drying air temperature and air velocity and it ranged from 32.23 to 75.13% and 16.60 to 55.85 % for a portable mechanical date dryer and a forced convection solar dryer respectively. Also, the total and reducing sugars decreased with the decrease of drying air temperature and air velocity and it ranged from 44.85 to 51.38 % and 40.33 to 44.66 % d.b. for the reducing sugar and from 55.95 to 65.14 % and 49.65 to 56.93 % d.b. for the total soluable sugar for a portable mechanical date dryer and a forced convection solar dryer respectively.