The pressure drop for airflow through a column filled with 1-in. ceramic Raschig rings is 0.01 in. water per foot when G_o = 80 lb/ft² - h and 0.9 in./ft water when G_o = 800 lb/ft² . h, all for a mass velocity of the liquid flowing counter currently of 645 lb/ft² - h. Since the change in pressure drop with liquid rate is slight in the range of liquid mass velocities between 645 and 1.980 lb/ft² - h. ignore the liquid holdup and estimate the void fraction if the rings have a wall thickness of 1/8 in. Use this void fraction and the Ergun equation to predict the pressure drop, and discuss the difference between predicted and experimental values.