Study on the second-order transfer function models for dynamic tests of flat-plate solar collectors Part II: Experimental validation

In order to validate the accuracy levels of three forms of transfer function models (TFMs), dynamic thermal performance tests of a flat-plate solar air collector with louvered fin structure are conducted. Model coefficients in the TFMs are constructed by strict error analysis and the weighed least square (WLS) method. Comparing with the experimental data, it is verified that the three forms of TFMs perform well and have the similar level of accuracy. It is further demonstrated that, the second-order differential TFMs have the same accuracy as the reduced first-order differential models with the present temperature measurement accuracy using thermocouples. Whilst the collector thermal storage quantities of the second-order differential terms in the TFMs are very small. In order for the second-order TFMs to perform better in the dynamic tests, the measured accuracy of temperatures should be improved. Otherwise, the combined standard uncertainties of the second-order differential terms of temperatures could be larger than the second-order differential terms of temperatures and the second-order terms in the three forms of TFMs would become meaningless.