integration of solid oxide fuel cells and ... - Ea Energianalyse

3.1. Introduction
The seven stream are indicated by their corresponding color in the
following list:
1. Flue gas (including atmospheric air and fuel input).
2. External heat transfer loops.
3. Domestic hot water.
4. Atmospheric air.
5. Absorption cycle: Refrigerant.
6. Absorption cycle: Weak solution of LiBr water.
7. Absorption cycle: Strong solution of water-LiBr.
The flue gas stream is used in the components around the SOFC
component (SOFC sub-system) and in the heat exchangers connecting it
to the ABS cycles and Hot Water heating. These components have been
modeled to accept seven different chemical species: C H 4 , CO, CO 2 , H 2 ,
H 2 O, N 2 and O 2 . All seven species are assumed to behave like ideal
gases, i.e. the enthalpy is independent of pressure (and there are no
phase changes). This can be assumed since the pressure change in the
components is relatively small.
The reference pressure and temperature for enthalpy of these gasses
are 100 kPa and 25 ◦ C respectively. The enthalpy of formation is included
in the chemical compounds.
A mixture of the species is assumed to be ideal, which means that the
physical property of a mixture is the sum of properties of each species in
the mixture.
The enthalpy flow rate Ḣ at state point ”j” is calculated as the sum of
mass flow rate times enthalpy of species ”k”:
Ḣ j =
7∑
ṁ j,k h j,k (3.1)
k=1
The fluid in the external heat transferring loops and domestic hot water is
sub cooled water. A real water fluid property function is applied in these
streams. To keep the water sub cooled, an sufficiently high pressure is
applied.
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