Subtopic: Mass of water removed during batch grain drying
Question Statement:
A batch of paddy weighing $1000\text{ kg}$ is dried from an initial moisture content of $24\%$ wet basis to a safe storage moisture content of $14\%$ wet basis. The total mass of water evaporated during drying is ________ $\text{kg}$ (round off to two decimal places).
Answer Key:
116.28
Step-by-Step Solution & Explanation
The bone dry solid mass ($W_s$) remains constant throughout drying:
$W_s = W_1 (1 - M_{w1}) = 1000 \times (1 - 0.24) = 760.0\text{ kg}$
The final total weight of grain $W_2$ at $M_{w2} = 0.14$ is:
$W_2 = \frac{W_s}{1 - M_{w2}} = \frac{760.0}{1 - 0.14} = \frac{760.0}{0.86} = 883.72\text{ kg}$
Water removed:
$\Delta W = W_1 - W_2 = 1000 - 883.72 = 116.28\text{ kg}$