Fuels Equivalents Calculator

Overview

Engineering reference data for Fuels Equivalents Calculator in combustion engineering.

Key Formulas

Heat Release

$Q = \dot{m} \cdot HV$

Fuel energy release rate.

Air-Fuel Ratio

$AF = \frac{m_{air}}{m_{fuel}}$

Mass of air per mass of fuel.

Excess Air

$EA = \frac{O_2}{21 - O_2} \times 100\%$

From flue gas oxygen measurement.

Variables

Symbol	Description	Unit
$Q$	Heat release rate	W
$\dot{m}$	Mass flow rate	kg/s
$HV$	Heating value	J/kg
$AF$	Air-fuel ratio	—

Example Conversion

The equivalent of 100 Btu energy can be converted to natural gas volume as follows:

Given:

• Natural gas equivalence: $1 \, \text{ft}^3 = 1000 \, \text{Btu}$
• Conversion factor: $1 \, \text{ft}^3 = 0.0283 \, \text{m}^3$

Formula: $V_{\text{gas}} = \frac{E}{CV}$ Where:

• $V_{\text{gas}}$ is the volume of natural gas ($\text{m}^3$)
• $E$ is the energy content (100 Btu)
• $CV$ is the calorific value (1000 Btu/$\text{ft}^3$)

Calculation: $V_{\text{gas}} = \frac{100 \, \text{Btu}}{1000 \, \text{Btu/ft}^3} = 0.1 \, \text{ft}^3$ $0.1 \, \text{ft}^3 \times 0.0283 \, \text{m}^3/\text{ft}^3 = 0.00283 \, \text{m}^3 \approx 0.0025 \, \text{Nm}^3$

Natural Gas Energy Equivalents

Standard reference values for natural gas conversions:

• Volumetric Basis: $1 \, \text{ft}^3 \approx 1000 \, \text{Btu}$ (gross heating value)
• Metric Basis: $1 \, \text{Nm}^3 \approx 9400 \, \text{kcal}$
• SI Basis: $1 \, \text{Nm}^3 \approx 39.4 \, \text{MJ}$

References

• Original Source