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Properties of Supercritical Water

Properties of Supercritical WaterA supercritical fluid is a fluid that is at pressures higher than its thermodynamic critical values. At the critical and supercritical pressures, a fluid is considered a single-phase substance, although all thermophysical properties undergo significant changes within the critical and pseudocritical regions.

At pressures above the critical pressure,  properties of water in the reactor change gradually and continuously from those we ordinarily associate with a liquid (high density, small compressibility) to those of a gas (low density, large compressibility) without a phase change. There is no change in the phase of water in the core. On the other hand, physical properties such as density, specific heat, specific enthalpy undergo significant changes, especially in the temperature range of the pseudocritical region (for 25 MPa between 372°C and 392°C). For example, in a typical supercritical water reactor:

  • the density of supercritical water at the inlet and at the outlet is about 777 kg/m3  (for 25MPa and 280°C) and 90 kg/m3 (for 25MPa and 500°C),
  • the specific enthalpy of supercritical water at the inlet and at the outlet is about 1230 kJ/kg (for 25MPa and 280°C) and 3165 kJ/kg (for 25MPa and 500°C)

supercritical-fluid-specific-heat-conductivityThe following figures show the behavior of thermophysical properties of water near the critical (22.1MPa) and pseudocritical (25MPa) points. Near the critical point, these property changes are dramatic. In the vicinity of the pseudocritical point at 25 MPa, these property changes become less significant. At 25 MPa, the most significant property changes occur within ±25◦C around the pseudocritical point (389.4◦C). This region is known as the pseudocritical region. For convenience, fluid properties are considered to show liquid-like behavior below the pseudocritical point, and above the pseudocritical point, they are considered to show gas-like behavior.

 
Steam Tables
Special links:
 www.nist.gov – Steam Tables – Saturation (Temperature)
 www.nist.gov – Steam Tables – Saturation (Pressure)
 www.nist.gov – Steam Tables – Compressed Water – Superheated Steam
 
What is Pseudocritical Line
Pseudocritical line - Pseudocritical pointsPseudocritical line – pseudocritical points. Pseudocritical line consist of pseudocritical points, which are points at a pressure above the critical pressure and at a temperature (Tpc > Tcr) corresponding to the maximum value of the specific heat at this particular pressure.
Characteristics of SCWRs
Typical properties of coolant in SCWR.
 
References:
Reactor Physics and Thermal Hydraulics:
  1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).
  2. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.
  3. W. M. Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1.
  4. Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317
  5. Todreas Neil E., Kazimi Mujid S. Nuclear Systems Volume I: Thermal Hydraulic Fundamentals, Second Edition. CRC Press; 2 edition, 2012, ISBN: 978-0415802871
  6. Zohuri B., McDaniel P. Thermodynamics in Nuclear Power Plant Systems. Springer; 2015, ISBN: 978-3-319-13419-2
  7. Moran Michal J., Shapiro Howard N. Fundamentals of Engineering Thermodynamics, Fifth Edition, John Wiley & Sons, 2006, ISBN: 978-0-470-03037-0
  8. Kleinstreuer C. Modern Fluid Dynamics. Springer, 2010, ISBN 978-1-4020-8670-0.
  9. U.S. Department of Energy, THERMODYNAMICS, HEAT TRANSFER, AND FLUID FLOW. DOE Fundamentals Handbook, Volume 1, 2, and 3. June 1992.

See above:

Supercritical Water