A Comparison between Natural and Solar Drying of Banana Chips and Chilly Drying using Smooth and Artificially Roughened Absorber Plate in Solar Air Heater

The present work compares natural and solar drying technique for drying banana chips and chilly drying. The solar drying method is carried out in two ways using smooth and artificially roughened absorber plate of solar air heater. The solar air heater is having dimensions 1000mm length, 540 mm width and 30 mm height. The width is divided into two equal portions, one fitted with smooth absorber plate and another with artificially roughened absorber plate. Artificial roughness in absorber plate is done by shot peening process. The natural drying process was carried out from 8:00 AM to 5:00 PM under open sunlight. Solar drying technique was used with a solar air heater fitted with smooth and artificially roughened absorber plate. The hot air from solar air heater was passed into a cabinet dryer comprising of four metal drying trays of dimension 41.5 cm *28 cm, consisting of mesh and painted with black board paint to enhance heat absorbing capacity. It took seven days for chill to dry completely naturally. Smooth plate and roughened plate solar drying of chilli completed in four days and three and half days respectively. The maximum temperature difference of 19.2 °C and 21.2 °C was observed for chilli drying using smooth and rough plate respectively. Banana chips dried naturally almost in one day with removal of 670 gm moisture, on second day only 10 gm moisture is removed. The solar drying of banana chips completed in three hours and two hours using smooth plate and roughened plate respectively. The maximum temperature difference using smooth plate and rough plate was 15 °C and 21 °C respectively. It is observed that the drying time is considerably reduced using roughened plate along with better texture of the product.