Comparative experimental analysis of potato slice drying using a multiple phase change material cascaded modified indirect solar dryer and conventional indirect solar dryer

Abstract

In the present research, multiple phase change materials (M-PCMs) have been utilized to enhance the performance of conventional indirect solar dryer (ISD). The bheem paraffin and paraffin wax having phase change temperatures of 50–55 °C and 60–62 °C were cascaded in rectangular chambers at beneath of absorber plate at the inlet and outlet side up to nearly half the length of the absorber plate of the solar air heater (SAH), known as a modified ISD. The experiments were carried out on conventional and modified ISD simultaneously under the climate of Valsad (20.61° N, 72.91° E), Gujarat, India. An atmospheric air with a velocity of 15 m/s was flown through conventional and modified ISD. In the first batch, 0.5 kg of pre-processed potato slices were placed in the bottom and top trays of conventional and modified ISD whereas in the second batch, 0.3 kg was placed on each tray. A 2 h and 1 h faster drying of potato slices was achieved in the bottom and top trays for the first batch in modified ISD than in conventional ISD. In the second batch, nearly 92.11% and 54.35% drying of potato slices in the bottom and top trays was achieved in modified ISD, which was 269.92% and 227.41% higher than conventional ISD. During 12 h of the drying operation, a total of 1.13 kg of water evaporated from the potato slices in modified ISD compared to 0.87 kg in conventional ISD. Compared to conventional ISD, an enhancement of 22.29% and 7.92% in SAH efficiency without and with considering blower power, an enhancement of 29.69% in overall drying efficiency, and a reduction of 22.87% in specific energy consumption were achieved for modified ISD. The use of M-PCMs in conventional ISD significantly enhances the drying of potato slices during the sunshine as well as off-shine hours and enhances the performance of conventional ISD.