Rotary driers are most economically designed for the number of heat transfer units (HTU) from _________________? August 23, 2021March 2, 2019 by admin Rotary driers are most economically designed for the number of heat transfer units (HTU) from _________________? A. 0.01 to 1B. 1.5 to 2.5 C. 5 to 10 D. 10 to 20