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Dryness Calculator

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Dryness Calculator

A “Dryness Calculator” is an essential tool used in thermodynamics and various engineering fields, particularly when dealing with steam systems. This calculator helps determine the dryness fraction of a steam-water mixture, a critical parameter for optimizing the efficiency and safety of steam engines, turbines, and heating systems.

Understanding the Dryness Fraction

The dryness fraction (symbolized as “x”) is a unitless number ranging from 0 to 1. It represents the proportion of mass in a steam-water mixture that exists in the vapor phase. A dryness fraction of 0 means the mixture is all liquid, while a fraction of 1 indicates pure steam.

Formula and Calculation

The formula to calculate the dryness fraction is:



  • x = Dryness fraction (unitless)
  • h = Specific enthalpy of the mixture (kJ/kg)
  • hf​ = Specific enthalpy of saturated liquid (kJ/kg)
  • hfg​ = Specific enthalpy of vaporization, also known as latent heat (kJ/kg)

Inputs Required for Calculation

  1. Specific Enthalpy of the Mixture (ℎh): Total enthalpy per unit mass in the steam-water mixture, measured or calculated based on steam conditions.
  2. Specific Enthalpy of Saturated Liquid (ℎhf​): This value depends on the temperature or pressure and is usually sourced from steam tables.
  3. Specific Enthalpy of Vaporization (hfg​): Also obtained from steam tables, this figure depends on the temperature or pressure.

Step-by-Step Example

Let’s walk through an example calculation using data typically obtained from steam tables:

  • Specific Enthalpy of the Mixture (ℎh): 2700 kJ/kg
  • Specific Enthalpy of Saturated Liquid (ℎhf​): 1000 kJ/kg
  • Specific Enthalpy of Vaporization (ℎhfg​): 2100 kJ/kg

Using the formula:


This result indicates that 81% of the mass in the mixture is in the vapor phase, with the remaining 19% in the liquid phase.

Relevant Information Table

ParameterSymbolValue (kJ/kg)Description
Enthalpy of the Mixtureh2700Total energy per unit mass in the mixture
Enthalpy of Saturated Liquidhf1000Energy of the liquid phase at saturation
Enthalpy of Vaporizationhfg2100Energy required to convert liquid to vapor


The Dryness Calculator provides a simple yet powerful means to determine the dryness fraction of steam-water mixtures, essential for efficient energy use in steam-driven systems. By understanding the proportion of steam to water, engineers and technicians can make informed decisions about equipment design, operation, and maintenance, ensuring optimal performance and safety. This tool’s integration into digital platforms like WordPress allows for easy accessibility and use, making it an invaluable resource in the field of thermodynamics.

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