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

D. OTHER
The pressure loss of GGHEX4 have been set to half the pressure loss of
GGHEX3. Because those two heat exchangers experience the same mass
flows, but GGHEX4 transfers much less heat, so it is assumed to be much
shorter (reducing pressure loss in tubes / between plates)
Inlet conditions
The water added in the cooling tower is assumed to be at ambient
temperature.
The air and fuel at the inlet of the SOFC were assumed to be 25 ◦ C
(instead of being equal to the ambient temperature). This way the
ambient temperature could be changed to examine its influence on the
cooling tower without having the results ”polluted” by changes from the
SOFC.
D.2 Spider diagram parameter interval choice
272
• ASR: In reality ASR depends on a number of factors such as
temperature, current density, and oxygen partial pressure. In this
model it only depends on temperature. And in different models
from TOFC the value differs somewhat. So it has been estimated
that it is in reality likely to be within +/-20% of the value in the
model.
• ∆p tower,wet : The pressure loss of the cooling tower has been
estimated by looking at how much fan power small commercially
available cooling towers consume relative to the cooling power and
then calculate the pressure loss from this. But in reality the pressure
loss depends on how big the system is physically build relative to
the amount of cooling to be removed. Also the temperature of the
fluids matters. So this way it can vary a lot, and it is hence estimated
that it can be somewhere between double as large and half as large
as the estimated value.
• T SOFC ,in = 690 ◦ C, T SOFC ,out = 780 ◦ C, and T SOFC ,max is probably a
little over 800 ◦ C. So the average temperature must for sure be over
690 and below 800 ◦ C. At the standard parameter configuration it
is 750 ◦ C (∆T SOFC ,av = 30 ◦ C). And with T SOFC ,max > T SOFC ,out , the
average temperature must be closer to T SOFC ,out than to T SOFC ,in .