Question

How much air would be introduced by a practically calm wind through an inlet into a building

• A. \(0.18 \text{ m}^3\) air \(\text{cm}^2\) of inlet
• B. \(0.28 \text{ m}^3\) air \(\text{cm}^2\) of inlet
• C. \(0.38 \text{ m}^3\) air \(\text{cm}^2\) of inlet
• D. \(0.48 \text{ m}^3\) air \(\text{cm}^2\) of inlet

Hint:

Natural ventilation relies on two forces: wind force and stack force (hot air rising). Under calm wind conditions, the ventilation rate is modeled using the standard coefficient of \(0.28 \text{ m}^3/\text{cm}^2\) of inlet area.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Proper ventilation in livestock housing is essential to remove moisture, heat, carbon dioxide, ammonia, and pathogens from the air. In naturally ventilated barns, air exchange is driven by wind-induced pressure differences.

Step 2: Detailed Explanation:
Let us analyze the principles of natural ventilation design:

Natural ventilation systems rely on openings (inlets and outlets) in the walls and ridge of the building.

When designing these systems, agricultural engineers must calculate the volume of air introduced through these inlets under different wind speeds.

Under "practically calm" wind conditions (where wind speed is minimal), air exchange occurs primarily due to thermal buoyancy (the stack effect) and light air currents.

For design calculations, the standard volume of air introduced by a practically calm wind through a wall inlet is estimated to be approximately\(0.28 \text{ m}^3\) of air per \(\text{cm}^2\) of inlet area per hour.

This standard value is used to calculate the total inlet area needed to maintain minimum ventilation rates during calm summer days.
Thus, the standard value is \(0.28 \text{ m}^3\) air \(\text{cm}^2\) of inlet.

Step 3: Final Answer:
The correct option is (B).