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Plant Engineering Calculator

Compressed Air Pressure Dew Point Converter — PDP to Atmospheric Dew Point

Convert a pressure dew point at one absolute pressure to the equivalent dew point after expansion or compression using water-vapor partial-pressure scaling.

Inputs

Results

Known vapor partial pressure 0.1258 kPa
Target vapor partial pressure 0.0157 kPa
Equivalent target dew point -41.79 °C
Dew-point shift -21.79 °C

Formula

e1=Psat(T1); e2=e1(P2/P1); T2=MagnusInverse(e2).

Worked example

A -20°C PDP at 8 bar absolute expands to a much lower vapor partial pressure at 1 bar absolute, producing a lower atmospheric dew point.

Assumptions & limits

  • Pressures are absolute, not gauge.
  • Uses a Magnus saturation-pressure approximation; verify very low dew points with dryer/OEM or standards-based property data.

FAQs

What does this Compressed Air Pressure Dew Point Converter calculate?

Convert a pressure dew point at one absolute pressure to the equivalent dew point after expansion or compression using water-vapor partial-pressure scaling.

What should I verify before using the result?

Check units, operating point, measured site data and OEM limits. This calculator is a transparent screening tool, not a substitute for equipment selection or code-required design.

Why are intermediate results included?

Intermediate values expose the engineering chain so you can audit assumptions, compare scenarios and catch unrealistic inputs.

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Last updated: 2026-09-17