A continuous countercurrent drier is used to dry 425.6 kg dry solid / h containing 0.035 kg total moisture / kg dry solid. The granular solid enters at 25 C and leaves at 60C. The heating medium is air which enters at 84.2 C and has a humidity of 0.0175 kg moisture/ kg dry air and leaves at 32.8 C. Calculate the air flow rate and the outlet humidity, assuming the heat losses from the drier to be 9300 kJ/h. The constant heat capacity of the dry solid is 1465 kJ/kg K. (12) (April '98).