Question Bank • QB_APE_EXP_002 NAT • 2 Marks

Section 6: Agricultural Process Engineering

Engineering Properties of Agriculture Produce

Subtopic: Physical properties

Question Statement:

A bulk grain sample has a true particle density of $1350\text{ kg/m}^3$ and bulk density of $780\text{ kg/m}^3$. The porosity ($ϵ$) of the grain bed in percentage is ________ (round off to 2 decimal places).

Answer Key:

42.22

Step-by-Step Solution & Explanation

Porosity $ϵ$ of a granular packed bed is given by: $ϵ = \left(1 - \frac{\rho_b}{\rho_t}\right) \times 100$ Given: • Bulk density $\rho_b = 780\text{ kg/m}^3$ • True density $\rho_t = 1350\text{ kg/m}^3$ $ϵ = \left(1 - \frac{780}{1350}\right) \times 100 = \left(1 - 0.57778\right) \times 100 = 42.222\% \approx 42.22\%$
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