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NEA-0362 MEDEA.

MEDEA, Steady-State Pressure and Temperature Distribution in He H2O Steam Generator

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1. NAME OR DESIGNATION OF PROGRAM:  MEDEA.
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2. COMPUTERS
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Program name Package id Status Status date
MEDEA NEA-0362/01 Tested 01-NOV-1974

Machines used:

Package ID Orig. computer Test computer
NEA-0362/01 IBM 370 series IBM 370 series
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3. NATURE OF PHYSICAL PROBLEM SOLVED

MEDEA calculates the time-independent pressure and temperature distribution in a helium-water steam generator. The changing material properties of the fluids with pressure and temperature are treated exactly. The steam generator may consist of economizer, evaporator, superheater and reheater in variable flow patterns. In case of reheating the high-pressure turbine is taken into account. The main control circuits influencing the behaviour of the system are simulated.
These are water spraying of the hot steam, load-dependent control of steam pressure at the HP-turbine inlet and valves before the LP-turbine to ensure constant pressure in the reheater section.
Investigations of hydrodynamic flow stability in single tubes can be performed.
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4. METHOD OF SOLUTION

The steam generator is calculated as a 1-dimensional model, (i.e. all parallel tubes working under equal conditions) and is divided into small heat exchanger elements with helium and water in ideal parallel or counter flow. The material and thermodynamic properties are kept constant within one element.
The calculations start at the cold end of the steam generator and proceed stepwise along the water flow pattern to produce pressure and temperature distributions of helium and water. The gas outlet temperature is changed until convergence is reached with a continuous temperature profile on the gas side. MEDEA chooses the iteration scheme according to flow pattern and other special arrangements in the steam generator. The hydrodynamic stability is calculated for a single tube assuming that all tubes are exposed to the same gas temperature profile and changing the water flow in a single tube will not influence the conditions on the gas side.
Varying the water flow by keeping gas temperature constant and repeating the steam generator calculations yield pressure drop and steam temperature as a function of flow rate.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maximum number of steam generator sections is 4. The steam generator is divided into small heat exchanger elements (or mesh points) not exceeding 300.
MEDEA is restricted to helium and water. Helium could however easily be replaced by any other non-boiling fluid by changing the programmed material properties of helium.
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6. TYPICAL RUNNING TIME

Depends on the complexity of the problem and the initial guess for the gas outlet temperature. A typical case with a steam generator consisting of 4 sections and a HP-turbine, 80 mesh points, takes 30 sec CPU time on a IBM-360/75. The case includes ahydrodynamic stability investigation for 10 different flow rates. Cases with control of steam pressure require about twice the time.
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7. UNUSUAL FEATURES OF THE PROGRAM

The program changes the input parameters of the fluids according to user specifications to investigate whole load ranges of operation. The flow stability and tube temperature are checked for different flow rates at each working point.
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8. RELATED OR AUXILIARY PROGRAMS: RELATED AND AUXILIARY PROGRAMS
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9. STATUS
Package ID Status date Status
NEA-0362/01 01-NOV-1974 Tested at NEADB
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10. REFERENCES
NEA-0362/01, included references:
- Ulf Hansen:
"MEDEA - Modell einer Dampferzeuger-Anlage"
JUEL-698-RG, Kernforschungsanlage Juelich GmbH (Sept. 1970).
- IBM-7090 Programm zur Ermittlung der Zustandsfunktionen des
  Wassers (Wasserdampftafel) IRWDT1, IRWDT2.
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11. HARDWARE REQUIREMENTS

MACHINE REQUIREMENTS. The program was written for the IBM 360/75 with a main storage of at least 160k bytes.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0362/01 FORTRAN-IV
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13. OPERATING SYSTEM OR MONITOR UNDER WHICH PROGRAM IS EXECUTED:  OS release 16.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

ANY OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS
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15. NAME AND ESTABLISHMENT OF AUTHOR:   Ulf Hansen, Kernforschungsanlage, Juelich, Germany.
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16. MATERIAL AVAILABLE
NEA-0362/01
File name File description Records
NEA0362_01.001 SOURCE PROGRAM (F4) 4185
NEA0362_01.002 SAMPLE PROBLEM DATA 487
NEA0362_01.003 SAMPLE PROBLEM PRINTED OUTPUT 763
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17. CATEGORIES
  • H. Heat Transfer and Fluid Flow

Keywords: distribution, hydrodynamics, pressure, steam generators, temperature, turbines.