3. Results and discussion
3.1Model validation
The heat transfer model is validated with the experimental data [3] considering the cavity
temperature and oxygen molar flow rate through the outlet. The experiments have been carried using
high-flux solar simulator at Paul Scherrer Institute, Switzerland. The cavity temperature has been
measured using Type-B thermocouples at the back of ZnO tiles. The oxygen molar flow rate through the
outlet is one of the indicators of the progress of the reaction. The model cavity temperature was slightly
higher than that of the experimental value by 10 K as shown in Fig. 2 (a). The oxygen molar flow rate
varied with time in a smooth manner as opposed to the transient fluctuations in case of experimental run
due to noise in measurement as shown in Fig. 2 (b). The drop in oxygen flow rate at 3400 s is due to the
formation of CO2 due to the oxidation of carbon impurities present in the ZnO feed. At lower
temperatures i.e, 1500-1700 K the deviation from the experimental value is not substantial but at higher
temperatures the deviation is high which indicates the dependence of the reaction pre-exponential factor
on temperature.