Gravity Heating Systems

Overview

Engineering reference data for Gravity 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

Symbol	Description	Unit
$\sigma$	Stress	Pa
$\varepsilon$	Strain	—
$E$	Young's modulus	Pa
$\alpha$	Thermal expansion coefficient	1/°C
$\Delta T$	Temperature change	°C

Gravity Circulating Pressure Data

The circulating pressure in a self-circulation heating system depends on both the flow and return temperatures. The following table shows the available pressure (in Pa per meter of circulating elevation) for various temperature combinations.

System Properties

Thermal Expansion: The thermal expansion of water is approximately 4.2% when heated from 4°C to 100°C. This density difference is the driving force behind gravity circulation systems.

Operating Principles:

• Self-circulation systems rely on natural density differences between hot supply water and cooler return water
• No mechanical pump is required; circulation is driven by the "stack effect"
• Greater temperature differences and greater radiator elevation above the boiler increase the circulating pressure and flow rate

Design Considerations:

• Typical operating temperature range: 50°C to 95°C
• Circulating pressure increases with larger temperature differentials (ΔT)
• System performance is sensitive to pipe sizing and circuit resistance

Interactive Charts

References

• Original Source