THE OPTIMIZATION OF COMBINED MICROWAVE AND HOT AIR FOR DRYING SYSTEM

Abstract

The objective of this research was to study the optimum conditions of the combined microwave with hot-air drying on drying of turmeric. The prototype designed to use 1,000 watts magnetron and 800 watts heater. This research was dried with three different drying methods: microwave, hot-air and microwave combined with hot-air that using turmeric weighing 100 grams. The microwave drying was carried out in a microwave oven with output power of 300, 400, 500, 600, 700 and 540 W, while the hot-air drying was carried out at drying air temperatures of 60, 70 and 80 ^๐C. The drying time to test is 5, 10, 15, 20, 25 and 30 minutes with air velocity of 0.5 . The results showed that the optimum point of the microwave with hot-air for drying is the microwave power of 800 watts and hot air temperature of 60 ^๐C, which takes 10 minutes. In addition, using microwave with hot air for drying can maintain the color quality of turmeric after drying better than just drying and drying with hot-air. The microwave with the hot air has cost of 15,000 baht. The break-even point of the machine is 134.27 and the payback period is 2 months. It can be concluded that the method of microwave drying combined with hot-air can reduce the drying time and preserve the quality of turmeric after drying.