Gross Net Heating Values

Overview

Engineering reference data for Gross Net Heating Values 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

Key Relationship

The difference between the gross and net heating value is the latent heat of vaporization of the water produced during combustion. This relationship can be expressed as: $H_{gross} = H_{net} + m_{H_2O} \cdot h_{fg}$ where:

• $m_{H_2O}$ is the mass of water produced per unit mass/volume of fuel.
• $h_{fg}$ is the specific latent heat of vaporization of water (approximately 580 kcal/kg or 2,260 kJ/kg at 100°C).

Practical Implications

• Net Heating Value (LHV) is the standard used for most boiler and engine calculations, as water vapor in the flue gas is not condensed and its latent heat is not recovered.
• Gross Heating Value (HHV) is relevant when designing systems with high-efficiency condensing heat exchangers that can recover the latent heat from the water vapor.

Unit Conversion

• 1 kJ/kg = 1 J/g = 0.4299 BTU/lb = 0.23884 kcal/kg

Interactive Charts

References

• Original Source