Calculate compressed-air outlet temperature or pressure using absolute/gauge pressures, isentropic efficiency or a polytropic exponent, and °C/°F/K.

Ideal-gas, constant-property, single-stage estimate without intercooling. Match inlet/outlet pressure definitions. Real compressor temperatures and safe operating limits require manufacturer data.

1.4 is an editable dry-air approximation; must exceed 1.

Compressed Air Temperature Formula

For constant-property ideal-gas compression, first estimate the isentropic outlet temperature, then apply the compressor’s isentropic efficiency. The polytropic option instead uses a supplied exponent n. All temperature ratios use kelvin and pressure ratios use absolute pressure.

T2s = T1 × (P2 / P1)⁽(gamma - 1) / gamma); T2 = T1 + (T2s - T1) / eta
  • T2 is the estimated outlet temperature in kelvin; T2s is the isentropic benchmark
  • P1 and P2 are inlet and outlet absolute pressures in matching units; T1 is inlet temperature in kelvin
  • gamma is the specific-heat ratio and eta is isentropic efficiency as a decimal. For the polytropic option use T2 = T1(P2/P1)^((n-1)/n).

Choose a model, enter inlet temperature and pressures, and supply efficiency or polytropic exponent. Gauge readings require local ambient pressure to obtain absolute pressures. The inverse modes solve outlet pressure from a higher target temperature.

Air is approximated as an ideal gas with constant properties in a single stage without intercooling. Actual equipment conditions can depart from this model; verify temperatures and operating limits with the manufacturer.

What is a Compressed Air Temperature?

Definition:

A compressed air temperature is the temperature of a body of air after it has been compressed to a different volume and temperature.

How to Calculate Compressed Air Temperature?

Example Problem:

The following example outlines the steps and information needed to calculate Compressed Air Temperature.

For example, choose the efficiency model with inlet temperature 26.85 °C (300 K), inlet absolute pressure 1 bar and outlet absolute pressure 2 bar.

Use gamma = 1.4 and 100% efficiency for an isentropic benchmark; lower efficiency gives a greater temperature rise at the same pressure ratio.

Finally, calculate the compressed air temperature using the formula above:

T2s = 300 × (2/1)^((1.4−1)/1.4)

T2 = 365.7041 K at 100% efficiency

T2 ≈ 92.55 °C