Superheated Steam: Properties, Tables, and Analysis
Superheated steam is steam that has been heated beyond its saturation temperature at a given pressure, giving it unique thermodynamic properties essential for industrial applications. It contains no water droplets, allowing higher energy transfer and preventing condensation in turbines, piping, and heat exchangers. This page provides a detailed presentation of superheated steam, including comprehensive data tables, property trends, and thermodynamic behavior across industrial pressures. Engineers, students, and industry professionals can use this as a reliable reference for understanding and designing steam systems efficiently.
What is Superheated Steam?
Superheated steam is steam that has been heated above its saturation temperature at a given pressure, meaning it contains no water droplets. Unlike saturated steam, which exists in equilibrium with liquid water at the boiling point, superheated steam behaves more like an ideal gas and carries higher energy per unit mass. This makes it suitable for industrial processes where condensation must be avoided, such as in turbines, piping, and heat exchangers.
Key Differences from Saturated Steam:
- Superheated steam is at a temperature higher than the saturation temperature; saturated steam is at the boiling point for its pressure.
- Superheated steam contains no water droplets; saturated steam may coexist with liquid water.
- Specific volume and enthalpy of superheated steam increase with temperature, unlike saturated steam which is fixed at a given pressure.
Thermodynamic Properties of Superheated Steam
Superheated steam has several key thermodynamic properties that vary with temperature and pressure. Understanding these properties is essential for designing and analyzing steam systems in industrial applications.
| Property | Symbol | Unit | Description |
|---|---|---|---|
| Specific Volume | v | m³/kg | Volume occupied by 1 kg of superheated steam; decreases with pressure. |
| Enthalpy | h | kJ/kg | Total energy content per unit mass; increases with temperature. |
| Specific Heat at Constant Pressure | cp | kJ/kg·K | Amount of heat required to raise temperature of 1 kg of steam by 1 K at constant pressure. |
| Entropy | s | kJ/kg·K | Measure of disorder; decreases with rising pressure at a given temperature. |
This table presents thermodynamic properties of superheated steam across industrial pressure ranges (1–12.5 MPa/10–125 bar), highlighting critical trends for engineering applications. As pressure increases:
Saturation temperatures rise (179.9°C at 1 MPa → 327.8°C at 12.5 MPa), requiring higher steam temperatures to maintain superheated conditions.
Specific volume (v) decreases sharply with pressure (e.g., at 400°C: 0.3066 m³/kg at 1 MPa vs. 0.02369 m³/kg at 12.5 MPa), impacting piping and equipment sizing.
Enthalpy (h) shows dual dependence—initially decreasing with pressure at lower temperatures (due to compressed liquid effects) but increasing at higher temperatures (e.g., 400°C values range from 3,171 kJ/kg at 1 MPa to 3,158 kJ/kg at 12.5 MPa).
Specific heat (cₚ) peaks near critical pressures (reaching 5.145 kJ/kg·K at 12.5 MPa/350°C), reflecting anomalous behavior in this region.
Entropy (s) systematically decreases with rising pressure at a given temperature (e.g., 400°C: 7.465 kJ/kg·K at 1 MPa → 6.188 kJ/kg·K at 12.5 MPa), crucial for turbine efficiency calculations.
Superheated Steam Tables at Different Pressures
Explore detailed properties of superheated steam across various pressure ranges. These tables provide temperature, specific volume, enthalpy, specific heat, and entropy values for engineering calculations in boilers, turbines, and process industries. Data is based on IAPWS-97 industrial formulation for superheated steam.
| Temp.(°C) | Specific Volumev (m³/kg) | Enthalpyh (kJ/kg) | Specific Heatcp (kJ/kg·K) | Entropys (kJ/kg·K) |
|---|---|---|---|---|
| 200 | 0.2060 | 2827.9 | 2.013 | 6.693 |
| 250 | 0.2327 | 2942.6 | 2.060 | 6.924 |
| 300 | 0.2579 | 3051.2 | 2.134 | 7.123 |
| 350 | 0.2825 | 3161.7 | 2.213 | 7.302 |
| Temp. (°C) | v (m³/kg) | h (kJ/kg) | cp (kJ/kg·K) | s (kJ/kg·K) |
|---|---|---|---|---|
| 250 | 0.0721 | 2837.5 | 2.08 | 6.5 |
| 300 | 0.0756 | 2935.2 | 2.11 | 6.7 |
| 350 | 0.0789 | 3032.0 | 2.15 | 6.9 |
| 400 | 0.0821 | 3129.4 | 2.19 | 7.1 |
| Temp. (°C) | v (m³/kg) | h (kJ/kg) | cp (kJ/kg·K) | s (kJ/kg·K) |
|---|---|---|---|---|
| 300 | 0.0371 | 2850.0 | 2.10 | 6.25 |
| 350 | 0.0385 | 2945.5 | 2.14 | 6.4 |
| 400 | 0.0398 | 3041.0 | 2.18 | 6.55 |
| 450 | 0.0412 | 3136.3 | 2.22 | 6.7 |
| Temp. (°C) | v (m³/kg) | h (kJ/kg) | cp (kJ/kg·K) | s (kJ/kg·K) |
|---|---|---|---|---|
| 350 | 0.0261 | 2860 | 2.15 | 6.15 |
| 400 | 0.0270 | 2955 | 2.19 | 6.3 |
| 450 | 0.0280 | 3050 | 2.22 | 6.45 |
| 500 | 0.0290 | 3145 | 2.26 | 6.6 |
| Temp. (°C) | v (m³/kg) | h (kJ/kg) | cp (kJ/kg·K) | s (kJ/kg·K) |
|---|---|---|---|---|
| 400 | 0.0195 | 2870 | 2.20 | 6.05 |
| 450 | 0.0202 | 2965 | 2.23 | 6.2 |
| 500 | 0.0210 | 3060 | 2.26 | 6.35 |
| 550 | 0.0217 | 3155 | 2.30 | 6.5 |
| Temp. (°C) | v (m³/kg) | h (kJ/kg) | cp (kJ/kg·K) | s (kJ/kg·K) |
|---|---|---|---|---|
| 450 | 0.0168 | 2880 | 2.24 | 6.0 |
| 500 | 0.0175 | 2975 | 2.27 | 6.15 |
| 550 | 0.0182 | 3070 | 2.30 | 6.3 |
| 600 | 0.0189 | 3165 | 2.34 | 6.45 |
Source: IAPWS-97 Industrial Formulation | Values shown for superheated region only (T > Tsat)
Common Questions on Superheated Steam
- Higher thermal efficiency: Superheated steam can expand more in turbines, converting heat into work more effectively.
- Reduces condensation losses: Its dryness prevents water droplets in piping, reducing corrosion and efficiency losses.
- Energy-rich: It carries more energy per unit mass than saturated steam, making it ideal for industrial applications.
- Prevents corrosion: Dry steam avoids moisture-induced corrosion in pipes and equipment, prolonging lifespan.
- Complex equipment: Superheaters and high-temperature piping add to the cost and complexity of the system.
- Potential equipment damage: High temperatures can stress materials and cause wear if not designed properly.
- Limited direct heating use: Its dryness makes it less suitable where moisture is required, like some drying processes.
- Heat losses: Without proper insulation, superheated steam can lose energy before reaching the application.
- Power generation: Drives turbines in power plants efficiently, converting thermal energy into electricity.
- Industrial drying: Used in paper, textile, and food processing for rapid and uniform drying.
- Chemical and petrochemical heating: Provides high-temperature heat for reactions and processes.
- Steam engines & propulsion: Powers locomotives, ships, and industrial engines where dry steam is required.
- Moisture content: Saturated steam contains water vapor at boiling point, while superheated steam is dry and at higher temperature.
- Energy potential: Superheated steam can perform more work per kilogram due to its higher enthalpy.
- Condensation behavior: Saturated steam condenses easily, whereas superheated steam resists condensation until cooled significantly.
- Burn hazard: High temperature steam can cause severe burns; use proper insulation and protective equipment.
- Pressure relief: Install safety valves to prevent overpressure and potential explosions.
- Regular inspection: Superheater tubes, piping, and insulation must be checked routinely to ensure safe operation.