Research on the steam–gas pressurizer model with Relap5 code

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Abstract

Steam–gas pressurizers are self-pressurizing, and since steam and noncondensable gas are used to sustain their pressure, they experience very complicated thermal–hydraulic phenomena owing to the presence of the latter. A steam–gas pressurizer model was developed using Relap5 code to investigate such a pressurizer’s thermal–hydraulic characteristics. The important thermal–hydraulic processes occurring in the pressurizer model include bulk flashing, rainout, wall condensation with noncondensable gas, and interfacial heat and mass transfer. The pressurizer model was verified using results from insurge experiments performed at the Massachusetts Institute of Technology. It was found that noncondensable gas was one of the important factors governing the pressure response, and the accuracy of the developed model would change with different mass fractions and types of noncondensable gas.

Keywords

Relap5 code Noncondensable gas Heat and mass transfer Steam–gas pressurizer Condensation 

List of symbols

A

Area (m2)

B

Body force (m/s2)

C

Coefficient of virtual mass

D

Diameter (m)

Di

Energy-dissipation function (W/m3)

F

Drag coefficient (m3/kg s)

fc

Modification factor

H

Volumetric heat-transfer coefficient (W/K m3)

h

Specific enthalpy (J/kg)

hc

Condensation heat-transfer coefficient with noncondensable gas (W/(m2 K))

hl

Dittus–Boelter coefficient assuming all fluid is liquid (W/(m2 K))

hsf

Superficial heat-transfer coefficient (W/(m2 K))

k

Thermal conductivity (W/m K)

M

Mass (kg)

P

Pressure (Pa)

Pr

Prandtl number

Pred

Reduced bulk pressure (Pa)

Q

Volumetric heat rate (W/m3)

Re

Reynolds number

T

Temperature (K)

t

Time (s)

U

Specific internal energy (J/kg)

v

Velocity (m/s)

X

Mass fraction

Z

Two-phase friction correlation factor

Symbols

α

Void fraction

Г

Volumetric mass exchange rate (kg/m3 s)

ε

Coefficient

ρ

Density (kg/m3)

Subscripts

cr

Critical condition

f

Liquid phase

g

Gas phase

h

Hydraulic

i

Interface

liq

Liquid phase

m

Mixture of gas phase and liquid phase

mix

Mixture of vapor and noncondensable gas

n

Noncondensable gas

ref

Reference condition

s

Steam component of gas phase

w

Wall

Superscripts

*

Total derivative of saturation property with respect to pressure

Derivative

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Copyright information

© Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Chinese Nuclear Society, Science Press China and Springer Science+Business Media Singapore 2017

Authors and Affiliations

  1. 1.Institute of Nuclear and New Energy Technology, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijingChina

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