Nitrogen Gas Properties

Overview

Engineering reference data for Nitrogen Gas Properties 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

Key Thermodynamic Properties for Nitrogen (N2)

The chart referenced provides values for three fundamental thermodynamic properties of nitrogen gas (N₂) as functions of temperature, from 0 K to 3000 K:

1. Specific Enthalpy (h): The total heat content of the gas per unit mass.
2. Specific Internal Energy (u): The energy stored within the gas molecules due to their motion and molecular interactions.
3. Specific Absolute Entropy (s): A measure of the disorder or randomness of the gas at a given state.

These properties are critical for calculations involving heating, cooling, work output, and the overall energy balance of systems using nitrogen gas.

Important Note: The entropy values are referenced to a standard reference pressure. For most engineering applications, this is typically 1 atm (101.325 kPa). When comparing or calculating entropy changes at other pressures, you must account for the change using the ideal gas relation.

The fundamental relationships between these properties are defined by the first and second laws of thermodynamics:

First Law (Relationship between u and h): $h = u + Pv$ Where $P$ is pressure and $v$ is specific volume. For an ideal gas, this simplifies to: $h = u + RT$ Where $R$ is the specific gas constant.

Property Relation for Entropy Change: The change in entropy for a simple compressible substance is given by: $s_2 - s_1 = \int_{T_1}^{T_2} \frac{c_p}{T} dT - R \ln\left(\frac{P_2}{P_1}\right)$ Where $c_p$ is the specific heat capacity at constant pressure.

References

• Original Source