Static Pressures Heating Systems

Overview

Engineering reference data for Static Pressures Heating Systems in material science and properties.

Key Formulas

Stress

$\sigma = \frac{F}{A}$

Force per unit area.

Strain

$\varepsilon = \frac{\Delta L}{L_0}$

Change in length per original length.

Hooke's Law

$\sigma = E \varepsilon$

Stress proportional to strain in elastic region.

Thermal Expansion

$\Delta L = \alpha L_0 \Delta T$

Length change due to temperature.

Variables

Practical Considerations

The static pressure in most HVAC systems results from the height of the building plus a cushion at the top. The cushion typically ranges from:

• 5 - 10 psi (lb/in²), or
• 10 - 20 ft (3 - 6 m) water column

Example Calculation

For a 200 ft tall building with a 20 ft cushion head:

Static head: $h_s = h_b + h_c = 200 + 20 = 220 \text{ ft}$

Static pressure (with water at 60°F, specific weight $\gamma = 62.4 \text{ lb/ft}^3$):

$p_s = h_b + \frac{h_c}{\frac{144}{\gamma}} = 200 + \frac{20}{\frac{144}{62.4}} = 95.3 \text{ psig}$

Note: The factor 144 in the denominator converts from lb/ft² to psi (since 1 ft² = 144 in²).

References

• Original Source