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IEA SHC Task 38 Solar Air Conditioning and Refrigeration Subtask C2-A, November 9, 2009
Figure 5. Comparison of simulated and measured generator outlet temperatures.
Figure 5 shows that the steady-state agreement between measured and simulated values is
reasonably well despite the fact that steady-state accuracy has been incorporated coarsely
only. At simulation start, the simulated temperatures diverge slightly from the initial measured
state towards a different steady-state. In general, the temperature difference between
experiment and simulation is larger after the step which shows that there is a dependency of
the model output on the hot water temperature. This can be related to temperaturedependent
parameters which have been assumed constant for the simulation, such as
evaporation and solution enthalpy, density and specific heat capacity. As steady-state
accuracy is not the focus in this paper this deviation shall not be discussed further.
Much more important is the fact that the dynamic agreement between measured and
simulated output data is very good. Figure 5 shows that the fluctuations of simulated and
measured hot water outlet temperature are well synchronized, although there is a slight delay
of approximately 10 seconds of measured to simulated values. This has to be put into
relation to the 600 seconds or 10 minutes that it takes to reach a steady state in the
generator temperatures again.
The delay between simulation and experiment can – at least to some extent - be explained
with the assumptions of thermal mass for the individual vessels in Table 1 which have not
been verified yet. Another reason for the disagreement is the fact that some time delays
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