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

5.1. Basic absorption cooling
geous seems to be the following:
When the desorber temperature is 72 ◦ C (optimum) the concentration
of the strong solution is only slightly higher than that of the weak
solution so the mass flow of the two flows is almost identical. This means
that the heat capacity flow (Ċ = ṁ · c p ) becomes almost equal as seen in
figure 5.3B
Now that Ċ is almost the same for both flows, ∆T min,SHE X will be
around zero in both ends of the SHEX as seen in figure 5.3B. This means
that when the weak solution comes out of the SHEX and enters the
desorber, it is already at the same temperature as the rest of the desorber
(72 ◦ C). This way all of the heat supplied to the desorber can be used to
evaporate refrigerant (water) from the solution instead of ”wasting” part
of it on heating up the weak solution entering the desorber.
If the desorber temperature was now increased to 80 ◦ C the weak
solution would only be 75 ◦ C when entering the desorber since the ∆T min
at the strong solution inlet would be 5 ◦ C even though the ∆T min at the
weak solution inlet is 0 ◦ C. So in that case some of the heat supplied to
the desorber would be needed for heating up the incoming solution to
80 ◦ C before evaporation could begin. Hence the desorber temperature
should not be too high.
Conclusion on Desorber Temperature
The investigations show that when the SHEX is omitted, a high desorber
temperature is an advantage since it minimizes the energy required for
heating up refrigerant into the desorber before evaporation can begin.
But the better the SHEX is, the more advantageous it becomes to use
a lower desorber temperature, since the SHEX can then do all of the ”pre
heating” of the weak solution whereby all energy input into the desorber
can be used for evaporating the refrigerant.
5.1.2 Changing condenser temperature
When the temperature of the condenser increases, the pressure increases
as well because the condensation mainly takes place in the two phase
region where pressure and temperature are dependent, see figure 5.4.
Since the temperature of the desorber is kept constant and the
pressure is equal to the condenser pressure, the concentration of the
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