Performance study of solar vacuum tubes type dryer

Abstract

In the present work, a solar vacuum tubes type dryer is designed, fabricated, and tested for drying of different fruit and vegetable samples. The selected fruits and vegetables such as pineapple, apple, banana, guava, beans, brinjal, carrot, lady finger, and potato were dried separately by the open sun drying and by the solar dryer under consideration, and the drying efficiencies of the two methods were compared with each other. While conducting experiments on fruit samples, the solar air heater efficiency varied from 59% to 80% and the corresponding solar dryer efficiency and open sun drying efficiency were found to vary in the range of 55%–78% and 3.0%–5.0%, respectively. Similarly, while conducting experiments on vegetable samples, the solar air heater efficiency varied from 73%–84% and the corresponding solar dryer efficiency and open sun drying efficiency were found to vary in the range of 70%–79% and 3.0%–3.6%, respectively. The solar dryer reduces the average moisture content from 0.32 to 0.85 kg for drying fruits and from 0.36 to 0.71 kg for drying vegetables. The time taken by open sun drying is almost 1.5 times that taken by vacuum tubes type dryer under consideration and the final moisture content of the product in open sun drying is also higher. Therefore, in terms of utilisation of solar energy, solar vacuum tubes type collector dryer may be considered to be the best method for drying fruits and vegetables within a short period of time.