Question Bank • QB_APE_005 NAT • 2 Marks

Section 6: Agricultural Process Engineering

Engineering Properties of Agriculture Produce

Subtopic: Physical properties

Question Statement:

A bed of cereal grains has a bulk density of $780\text{ kg/m}^3$ and true particle density of $1300\text{ kg/m}^3$. The porosity of the grain bed expressed in percentage is ________ (answer in integer).

Answer Key:

40

Step-by-Step Solution & Explanation

Porosity $\epsilon$ of a granular packed bed is given by: $\epsilon = \left(1 - \frac{\rho_b}{\rho_t}\right) \times 100$ Where: • Bulk density $\rho_b = 780\text{ kg/m}^3$ • True density $\rho_t = 1300\text{ kg/m}^3$ $\epsilon = \left(1 - \frac{780}{1300}\right) \times 100 = (1 - 0.60) \times 100 = 40\%$
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