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

5.3. Partial optimization of standard parameters
Figure 5.24: The influence of the Closest Approach Temperature for the Air Pre heater
(GGHEX4) on the COP (STD value is 25 ◦ C). The electrical efficiency remains virtually
constant.
the hot water generation will fall, since there is less energy in the exhaust
gas at point 23.
It appears that GGHEX4 is one of the most important heat exchangers
(when it comes to COP variation). When its ∆T min is decreased 50%
(from 25 ◦ C to 12,5 ◦ C), COP ABS,f uel increases from 45,6% to 48,9%. The
second most important heat exchanger (the evaporator) only increases
the COP ABS,f uel from 45,6% to 46,5% when its ∆T min is decreased 50%
(from 5 ◦ C to 2,5 ◦ C).
So cutting ∆T min in halves will give 3,6 percent points for GGHEX4
and only 0,9 percent point for the evaporator. And if GGHEX4 is made
more efficient, GGHEX3 can be made less efficient, since T 14 must remain
constant.
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