Experiments showed that 10 hours were required to reduce the total moisture content of a granular sample from 60% to 10% in a batch drier. Critical and equilibrium free moisture contents of the sample are 14% and 2%, respectively. Drying rate of the falling rate period is directly proportional to free moisture content.

The same sample having a total moisture content of 60% is to be dried in the same batch drier to a total moisture content of 30%. Then the drying is to be continued, in a continuous countercurrent flow tunnel drier to a total moisture content of 5%. The sample enters the continuous drier at 20 ⁰C and exits at 50 ^oC. The heat capacity of the dry solid is 3.52kJ/kg.K which is assumed constant. 2000 kg dry air/hr. enters the drier at 80 ⁰C with a wet bulb temperature of 32.5 ⁰C and exits at 40 ^oC. The surface area available for drying is 0.0266 m²/kg dry solid. k_yM_B is determined as 393 kg dry air/hr.m². Calculate:

1. the time necessary to dry the sample in the batch drier
2. the time necessary to dry the sample in the tunnel drier
3. the total time to dry the sample in batch-tunnel drier combination