IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration Subtask C2-A, November 9, 2009
Temperature deviation [ C]
3
2.5
2
1.5
1
0.5
0
-0.5
Desiccant wheel
-1
-1.5
T reg =80 C
T reg =70 C
-2
T reg =65 C
T
-2.5
reg =60 C
measurement accuarcy
-3
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2
Humidity ratio deviation [g.kg -1 ]
Figure 8: Deviation of the outlet temperature and outlet humidity ratio in comparison with
measured results for different operating conditions
The maximum error in predicting the temperature at the outlet of the desiccant wheel is 1°C
(a relative error of 2.5%). This error occurs for different regeneration temperatures and for
the same inlet temperature of the wheel, 38°C, whic h is not in the application domain of
desiccant cooling. For the humidity ratio, the maximum error is 0.5 g/kg but it should be
noted that the accuracy of humidity ratio measurement in the air handling unit is 0.4 g/kg (this
accuracy can be tested by comparing the humidity ratio at points 2, 3 and 4 of Figure 1 with
the supply humidifier switched off; in this case the points must have the same humidity ratio),
so the error is in the validity domain of the measurements.
This accuracy of the model is obtained when the model is dynamically parameterized
in function of the operating regeneration temperature; if this is not the case, the
deviation will be more significant when the operating regeneration temperature is
much higher than that of rating conditions used to parameterize the model [1].
The evaporative cooler
For the evaporative cooler model, Figure 9 demonstrates that the enthalpy is constant across
the evaporative cooler and that the constant enthalpy model can thus accurately predict the
outlet temperature of the evaporative cooler.
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