The Designing and Optimization of Solar Dryers for Improving the Quality of Dates in Khairpur, Pakistan
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Department of Physics, Shah Abdul Latif University, Khairpur, Sindh, Pakistan
Department of Physics, Research Complex, Allama Iqbal Open University Islamabad, Pakistan
Institute of Chemistry, Shah Abdul Latif University, Khairpur, Sindh, Pakistan
Zubeda Bhatti   

Department of Physics, Shah Abdul Latif University, Khairpur, Sindh, Pakistan
Submission date: 2021-12-21
Final revision date: 2022-03-14
Acceptance date: 2022-04-05
Online publication date: 2022-07-13
Publication date: 2022-09-01
Pol. J. Environ. Stud. 2022;31(5):4043–4050
The present work was conducted to develop an efficient solar dryer for improving date fruit quality of Khairpur, Pakistan. Three different dryers were developed i.e., a natural convectional solar dryer, direct solar dryer and an oven solar dryer comprising air velocity of 0.5 m/s, 0.6 m/s and 0.4 m/s respectively. The temperature inside the three dryers significantly increased with the increase in time interval from 2 to 10 hrs. An average temperature ranged from 40.4 to 41.4ºC after 2 hrs which was significantly higher (p<0.0001) than the air temperature outside (36.4ºC) the three dryers. Moreover, increased up to 47.9ºC after 10 hrs of interval. Average highest temperature recorded in oven dryer was 41.4, 41.9, 45.8, 41.8 and 47.9 after a time interval of 2, 4, 6, 8 and 10hrs respectively. The highest solar radiation was observed as 985 W/m2 at 2:30 pm and average solar radiation was found to be 791 W/m2. The highest percentage of total sugar (67.7%), non-reducing sugars (18.1%) and reducing sugars (49.54%), proteins (31%) and calcium quantity (32.59 μg/g) was found in conventional dryers, which was followed by (66.88%) of total sugars,( 49.6%) of reducing sugars and (17.61%) non-reducing sugars in direct dryer and (2.19%) of proteins and (22.76) μg/g of calcium in oven dryer. The results revealed that the drying natural oven solar dryer provided a good quality dates with satisfactory and competitive to enforce convective solar drying process. The drying time found to be approximately 8 hours daily and total 5 days taken to complete process of drying dates presents the advantage of being able to avoid the discontinuity of the treatment and to discard the night conservation problems. Owing to its low cost and green energy use, this study offers an efficient alternative to convectional drying under open sunlight for making quality dates.