Steam Properties and Pipe Velocity Calculator

Saturated steam temperature, specific volume and latent heat from the gauge pressure, and the velocity of the steam in a pipe for a given heat load.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Saturated steam has a fixed temperature for each pressure, and each kilogram carries a large amount of latent heat. From the heat load and the latent heat you can find the steam flow, and from the flow, the specific volume and the inside diameter of the pipe you can find the velocity.

Steam piping is often sized so the velocity stays within about 15 to 40 m/s for saturated steam, depending on the pressure and the allowable pressure drop and noise. The values here are approximate steam table values: use the property tables calculator for interpolated table values.

Formulas used

  • \dot m = \frac{Q}{h_{fg}}
  • v = \frac{\dot m\, v_g}{A}

Worked example

With the default numbers in the calculator above:

  1. Absolute pressure: 11 bar abs
  2. Saturation temperature: 184 °C
  3. Specific volume of dry steam: 0.178 m³/kg
  4. Latent heat: 1999 kJ/kg
  5. Steam needed for the heat load: 900 kg/h
  6. Velocity in the pipe: 8.85 m/s

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

Gauge or absolute pressure?

The calculator asks for gauge pressure, as read on a boiler gauge, and adds atmospheric pressure to look up the table.

What is latent heat?

The heat given up when steam condenses to water at the same temperature. It is most of the heat steam carries.

What velocity is acceptable?

It depends on the line. Saturated steam lines are commonly designed for about 15 to 40 m/s.

Related calculators

Further reading: Cengel and Boles, Thermodynamics: An Engineering Approach; Moran and Shapiro, Fundamentals of Engineering Thermodynamics.

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