How to Use Steam Table?

A steam table gives the properties of water (liquid, vapor, and mixture) at different temperatures and pressures. Common properties listed:

 T = Temperature

 P = Pressure (absolute, not gauge)

 v = Specific volume (m³/kg)

 u = Internal energy (kJ/kg)

 h = Enthalpy (kJ/kg)

 s = Entropy (kJ/kg·K)

 x = Quality (mass fraction of vapor, 0 = sat liquid, 1 = sat vapor)

Understand Column Symbols
Every column represents a distinct property or baseline state: 

• Subscript f (v_f,h_f): Properties of saturated liquid (100% liquid water).

• Subscript g (v_g, h_g): Properties of saturated vapor (100% dry steam).

• Subscript fg (h_fg): The latent change during evaporation (h_fg = h_g - h_f)  

Identify Your Region

Water can be in three zones:

• Compressed (subcooled) liquid – Not about to boil, below saturation temp at given pressure.

• Saturated mixture – Liquid and vapor coexist (boiling).

• Superheated vapor – Above saturation temperature at given pressure. 

Which Table to Use?

• Saturated Table (Temperature-Based): Best used when the given variable is a specific temperature.

  

• Saturated Table (Pressure-Based): Best used when the given variable is a specific pressure.

  

• Superheated Steam Table: Used when system temperature exceeds the saturation boiling temperature for its pressure.

  

• Compressed Liquid Table: Used when system pressure exceeds the saturation pressure for its temperature.

Determine Mixture Qualities 

If the system is a mixture of liquid and steam, you must use steam quality (x), which is the mass percentage of vapor ranging from 0 to 1.

Calculate mixed properties with this fundamental equation: 

v = v_f + x (v_g - v_f)

Apply Linear Interpolation

If your exact system parameters fall between two listed rows, you must execute a vertical linear interpolation to isolate the true midpoint value, 

y = y₁ + [(x - x₁)/(x₂ - x₁)] x (y₂ - y₁)

Example (Saturated mixture)

Find the specific enthalpy (h) of a wet steam mixture at a pressure of 10 bar with a steam quality (x) of 0.85. 

• Open the Saturated Steam Pressure Table

• Locate the 10 bar row.

• Extract baseline values:

• h_f = 762.6 kJ/kg

• h_fg = 2014.6 kJ/kg

• Compute final mixture value: 

• h = 762.6 + 0.85 x (2014.6) = 2475.01 kJ/kg 

Example (Superheated steam)

Find the specific volume (u) of steam at 10 bar and 300°C. 

1. Check the saturated table for 10 bar to find the boiling boundary (T_sat = 179.9⁰ C).
2. Because your target 300⁰ C > 179.9⁰ C, flip over to the Superheated Steam Table.
3. Locate the sub-block labeled P= 1.0 MPa (10 bar).
4. Read down to the T = 300⁰ C row, and isolate the value under the u column (v = 0.258 m³/kg). 

Example

1. Find the enthalpy of water at P = 0.5 MPa, T = 200°C.
2. Find saturation temperature at 0.5 MPa from saturation table (Pressure entry) at 0.5 MPa ≈ 151.8°C.
3. Compare: T (200°C) > 151.8°C → Superheated vapor.
4. Go to Superheated steam table at 0.5 MPa.
5. Find row for 200°C → read h (enthalpy) ≈ 2855 kJ/kg.

Example (mixture)

P = 0.5 MPa, x = 0.9. Find h.

1. From sat table at 0.5 MPa: h_f = 640 kJ/kg, hg = 2748 kJ/kg.
2. Formula: h = h_f + x(h_g – h_f) = 640 + 0.9(2108) = 2537 kJ/kg.

Common Mistakes to Avoid

• Using gauge pressure: Steam tables use absolute pressure (P_abs = P_gauge + P_atm).
• Quality outside 0 – 1: If x > 1 → superheated; if x < 0 → compressed liquid. Interpolation required between table entries.

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