Question Bank • QB_PARAMETRIC_APE_PHY_032NAT • 1 Mark
Section 6: Agricultural Process Engineering
Physical & Geometric Properties of Agro-Produce
Subtopic: Grain bulk porosity from true and bulk density
Question Statement:
A bulk grain bed has a true density of $\rho_t = 1350\text{ kg/m}^3$ and a bulk density of $\rho_b = 800\text{ kg/m}^3$. The porosity of the bulk grain bed is ________ $\%$ (round off to two decimal places). (Variation QB_PARAMETRIC_APE_PHY_032)
Answer Key:
40.74
Step-by-Step Solution & Explanation
The porosity $\epsilon$ of a granular bed is given by:
$\epsilon = \frac{\rho_t - \rho_b}{\rho_t} \times 100$
Given $\rho_t = 1350\text{ kg/m}^3$ and $\rho_b = 800\text{ kg/m}^3$:
$\epsilon = \frac{1350 - 800}{1350} \times 100 = \frac{550}{1350} \times 100 = 40.74\%$