Dry Air Properties at Temperatures and Pressures

Overview

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Thermodynamic and transport properties of dry air at atmospheric pressure (1 atm / 101.325 kPa) as a function of absolute temperature. Data span 175 K to 1900 K and cover specific heats, viscosity, thermal conductivity, Prandtl number, kinematic viscosity, density, and thermal diffusivity. Dry air is treated as an ideal gas mixture (approximately 78% N₂, 21% O₂, 1% Ar by volume) with a specific gas constant of 287.058 J/(kg·K).

The original source describes thermal conductivity as a measure of how quickly a material can absorb heat from its surroundings, and presents dry-air properties at one atmosphere from 175 K to 1900 K. It also calls out related viscosity references: Air - Absolute and Kinematic Viscosity - SI & Imperial Units and Air - Absolute and Kinematic Viscosity - Imperial Units.

For the full table with ratio of specific heats, thermal conductivity, Prandtl number, kinematic viscosity, density and diffusivity, the original page notes: rotate the screen. The restored source table below preserves those columns in the migrated page.

Key Formulas

Ideal Gas Density

$\rho = \frac{P}{R_{\text{air}} \cdot T}$

Density of dry air from pressure and absolute temperature, where $R_{\text{air}} = 287.058\;\text{J/(kg·K)}$.

Enthalpy Change

$\Delta h = c_p \cdot \Delta T$

Enthalpy change over a temperature interval, using the specific heat at constant pressure.

Specific Heat Ratio

$k = \frac{c_p}{c_v}$

Ratio of specific heats; approaches 1.4 at low temperatures and decreases with increasing temperature as internal energy modes activate.

Sutherland's Law for Viscosity

$\mu = \mu_0 \left(\frac{T}{T_0}\right)^{1.5} \frac{T_0 + S}{T + S}$

Approximate dynamic viscosity of air, with reference viscosity $\mu_0$ at temperature $T_0$ and Sutherland constant $S \approx 110.4\;\text{K}$.

Variables

Dry Air Properties at 1 atm

Property Trends

Air Density Calculator

Use the ideal gas law to compute density at any pressure and temperature.

Restored Original Source Tables

The following tables are restored from the original source page to preserve the complete reference data.

Dry Air - Thermodynamic and Physical Properties

Engineering Notes

• Pressure dependence. The tabulated values assume 1 atm. At elevated pressures, density scales linearly with pressure (ideal gas), but viscosity and thermal conductivity are nearly independent of pressure for moderate ranges.
• Humidity effects. Moist air is less dense than dry air at the same temperature and pressure because water vapor (M = 18.015 g/mol) is lighter than the average air molecule (M ≈ 28.97 g/mol). Use humidity-corrected properties for HVAC and psychrometric calculations.
• Specific heat increase. At low temperatures only translational and rotational modes contribute. Above ~500 K, vibrational modes progressively activate, raising both $c_p$ and $c_v$ and reducing the ratio $k$.
• Prandtl number plateau. For air, Pr stays in the narrow range 0.68–0.73 across the full temperature span, making it a convenient constant in many convective heat transfer correlations.
• Kinematic viscosity. Values marked with superscript 1 in the source are at atmospheric pressure. Because $\nu = \mu/\rho$, it increases strongly with temperature as density drops.
• High-temperature dissociation. Above roughly 2000 K, O₂ and N₂ begin to dissociate and the ideal gas property tables become unreliable. Use thermochemical equilibrium codes for combustion and plasma applications.

References

• Original source: Engineering ToolBox — Dry Air Properties