The Heat Transfer Characteristics Of Solar Pyrolysis ZnO/Zn Pairs

With the development of social economy, the demand for energy is growing. Faced with the declining traditional fossil fuels and the polluted environment caused by fossil fuels, it is urgent to develop environment-friendly new energy. Solar thermochemical hydrogen production uses solar energy as a heat source to produce hydrogen through the chemical reactions. Due to the characteristics of low cost、no pollution、high cycle efficiency, it has a great development space.This paper, based on Zn O/Zn redox pair, studies the process of solar two-step thermochemical hydrolysis for hydrogen production. The Zn O decomposition process in solar reactor and hydrolysis process of zinc particles in hydrolysis reactor are studied.It is very important to study the reactor heat transfer characteristics for improving the conversion rate of reactants in reactor, optimizing the design of reactor and promoting the solar energy to chemical energy conversion rate. With the help of CFD, the steady heat transfer model coupling conduction、convection、radiation and chemical reaction is established. With the developed steady heat transfer model, the steady heat transfer characteristics of solar pyrolysis Zn O/Zn pairs for hydrogen production and the effect rules of operation and geometry parameters of solar reactor on conversion rate of Zn O are gotten.Based on the developed steady heat transfer model, the transient heat transfer model of solar reactor is established. The transient heat transfer model is modified with regard to the radiation transfer equation, including the effect of wavelength to radiation transfer equation, the characteristics of spectrum and temperature of ceramic emissivity and Zn O particles’ absorption factor. The temperature of solar reactor is higher than the one gotten by the steady heat transfer model. What’s more, the transient heat transfer characteristics of solar pyrolysis Zn O are obtained.The findings in this paper can contribute to further understand of solar two-step chemical cycles for hydrogen production. It can provide a reference for the selection of operation parameters and the optimal designs of reactor. What’s more, it is the basis of further study of improving conversion rate from solar energy to chemical energy.