Heat exchanger is a tool used to transfer heat from one system to another. The heat exchanger unit consists of air heater and rotary dryer. The purpose of this research is to get the optimum rotary dryer’s rotation in cassava drying in terms of reduction of cassava’s mass, heat accepted by cassava, rotary dryer’s efficiency, and heat exchanger’s efficiency. The variations of rotation used were 26.25 rpm; 30 rpm; 42 rpm; and 70 rpm. This research also has 2 variations of fin number in its air heater, it will be calculated how much heat produced by air heater and efficiency of air heater.
The operation of this heat exchanger is the air flow as the cold fluid produced by the blower enter into the air heater. In the air heater, air receives heat from the hot fluid flowing through the air heater’s shell. The source of the hot fluid comes from the stove under the air heater. After receiving the heat, the hot air goes into the rotary dryer, the place where cassava is placed for the drying process.
The optimum drying result for air heater with 2 rectangular fin tube occurred at rotation of 42 rpm, which has a mass reduction of 0.210 kg, 386623 J heat received by cassava, 5.42% rotary dryer’s efficiency and 3.85% heat exchanger unit’s efficiency. The heat produced by air heater and the air heater’s efficiency is directly proportional to the increase of rotary dryer’s rotation to the peak of 42 rpm. For air heater with 4 rectangular fin tubes the optimum drying occurred at rotation of 70 rpm, which has a mass reduction of 0.260 kg, 487888 J heat received by cassava, 7.40% rotary dryer’s efficiency, and 4.86% heat exchanger’s efficiency. The Heat produced by air heater and the air heater’s efficiency inversely proportional to the increase of rotary dryer’s rotation in the range of rotation 26.25 rpm to 70 rpm.
Keywords: heat exchanger, air heater, rotary dryer, rotation, mass, efficiency
