Download Chapter 2 Basic concept of Cycle

Apparatus models
3.8
Saturator (type 28)
3.8.1 Functioning of the model of the saturator
The model of the saturator is based on a counterflow saturator. It is used to moisturize a gas
with water vapour. The composition of the gas to be moisturized is free to be chosen and can
be defined by the user himself.
The composition of the outgoing gas is calculated with the inlet pressure and inlet
temperature and the relative humidity (RELHUM) specified by the user.
3.8.2 Calculation of the gas composition in the gas outlet pipe
The molar fraction water vapour in the gas outlet pipe can be calculated in three ways.
It can be specified with MLFH2O. The molar fraction water vapour (xout,gas,H2O) is considered
to be equal to MLFH2O. Then the molar fractions of the other components are calculated,
see below.
Or the amount of water to be evaporated can be specified with DELMW. If PIPE is also
specified, DELMW is relative compared to another mass flow. The amount of water to be
evaporated is DELMW × Φm,PIPE.
In order to calculate the molar fraction water vapour in the gas outlet pipe, the number of
moles water to be evaporated are calculated, after which
xout , gas , H 2O =
Φ mol ,in , gas , H 2O + Φ mol , water to be evaporated
Φ mol ,in , gas ,total + Φ mol ,water to be evaporated
(3-48)
The mole flows are calculated by dividing the mass flows by the mole mass.
If MLFH2O nor DELMW are specified, the molar fraction water vapour is calculated out of
the pressure and the temperature in the gas outlet pipe.
In order to calculate the composition of the outgoing gas, first the partial pressure of the
water vapour is determined at the temperature of the outgoing gas:
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