Design and evaluation of a refractance window lab-scale dryer

Purpose Refractance window drying (RWD) has been identified as the method that can give high-quality products at a relatively low production cost. However, knowledge about its use and adoption remains lacking both in academic curricula and industry in the developing world. Design/methodology/approach A lab-scale batch RWD of a closed-loop control system was designed, fabricated and evaluated for drying rates, evaporation rate, the energy of evaporation, energy efficiency and throughput. Testing was done using mango and tomato pulps. Findings Drying rates at 95 degrees C of 1.32 gg(-1)min(-1) and 0.854 gg(-1)min(-1) at 2 and 3 mm, respectively, for tomato, 0.6 gg(-1)min(-1) and 0.33 gg(-1)min(-1) at 2 and 3 mm for mango pulp were obtained. The dryer had an evaporation rate of 4.63 x 10(-4) kg/s and 4.25 x 10(-4) kg/s, the energy of evaporation of 1.05 kW and 0.96 kW and thermal energy efficiency of 25.64% and 21.73% while drying tomato and mango pulps, respectively. Dryer throughput of 0.6 kg/h of dried mango Pulp and 0.47 kg/h of dried tomato pulp was obtained. Originality/value The designed RWD can be adequately used in laboratory experiments on different products to produce powders. This will enable the transfer of knowledge about RWD technology in developing countries.