ABk

BC cross sectional area (at BC node boundary k)

ANn, AMn

SC cross sectional area (at SC node boundary n, mean value)

ATWMn

Surface area of a (single) tube wall along a node n

C

C0,

-

-

Dimensionless constant

Phase distribution parameter and its slope at α = 0

dHY

m

Hydraulic diameter

f(z, t), fNn, fMn

-

General and nodal (boundary and mean) solution functions

fLIMCA

-

Upper or lower limit of the approx. function f(z,t)

Mass flow

Mass flux

h, hP, cP = hT

Specific enthalpy and its partial derivatives with respect to pressure and temperature (=specific heat)

hSW = h// − h/, h//, h/

Latent heat, saturation steam and water enthalpy

KEYBC

-

Characteristic key number for each channel (BC) within an overall design

LFTYPE = 0, 1, 2 or 3

-

SC with saturated water/steam mixture, sub-cooled water, superheated or supercritical steam

LFTBE (=LFTYPE of 1-st NSC)

LHEATB = 0 or = 1

-

-

LFTYPE of 1-st SC within BC

Non-heated or heated wall

LNOCCF = 0 or = 1

-

Eventual CCF situation allowed or not allowed

NBT = NBCA − NBCE + 1

-

Total number of BC nodes

NBCA = NCT + NBCE − 1, NBCE

-

BC node numbers containing BC outlet or entrance

NCT = NCA − NCE + 1

NCA, NCE, NCT = NCA − NCE + 1

-

Total number of SC nodes BC node number containing SC outlet and entrance and total number of SC nodes

NSC = NSCE, NSCA

-

Characteristic number of each SC, setting NSCE = 1, 2, 3 or 4 if LFTYPE = 0, 1, 2 or 3. Then NSCA = NSCE + NSCT − 1

P, ΔPT = PA − PE

Pressure and pressure difference (in flow direction)

QBT, QBMk

W

Total and nodal power into BC node k

Mean nodal BC power density into the fluid (=volumetric heat transfer rate)

Heat flux from (heated) wall to fluid at BC node k

Linear power along BC node k

Mean nodal SC power density into fluid (=volumetric0 heat transfer rate)

T, t

C, s

Temperature, time

UTW

m

Perimeter of a heated (single) tube wall

m3

Mean nodal SC volume

Water velocity

Steam velocity

-

Steam quality (extended to single-phase flow too)