Multi-phase And Multi-scale Mechanism Research Of Heat And Mass Transfer Coupling With Chemical Reaction In Porous Media

Waste heat recovery is an important way to improve energy efficiency and reduce emissions, one effective means is to enhance the quality of low-temperature energy to high-temperature. Isopropanol-Acetone-Hydrogen chemical heat pump (IAH-CHP) is a competitive alternative in 1view of its advantages of energy upgrading and effective energy storage. The key components of IAH-CHP are catalytic reactors,whose performance play a decisive procedure in the system.This paper using both experimental and theoretical methods to studied the single/multi-phase catalytic reactor on multi-scales. Research focued on improving the reaction performance under steady state conditions and optimizing the design of the reactor to meet efficient chemical heat pump system. By revealing the multiphase reaction mechanism, establishing the multicomponent multiphase heat and mass transfer theory in porous media system, building efficient circulatory system, to provide an important scientific basis and technical support for improving and optimizing the design of chemical heat pump systems,In chapter 2, the kinetics of the liquid-phase dehydrogenation of isopropanol over Raney nickel and rapidly quenched Raney nickel catalysts were studied experimentally. The results showed that the rapidly quenched Raney nickel catalyst is much more active than Raney nickel. The reaction kinetics of liquid-phase isopropanol dehydrogenation with the two different catalysts was obtained respectively.Then,we investigated the application of ultrasound irradiation to enhance catalytic dehydrogenation rate of isopropanol.The dehydrogenation rate of isopropanol with ultrasound and stirrer is also compared. When the ultrasonic power dissipated is larger than 26.87 W for reactant of 300 ml, the apparent dehydrogenation rates with ultrasound irradiation are significantly improved in comparison to that with agitation. The activation energy when using ultrasound is smaller than that when using stirrer, and it decreases with the increase of the ultrasonic power dissipated. The quantitative relationship between the dehydrogenation rate and ultrasonic power density is identified.In chapter 3, the lattice Boltzmann method (LBM) is developed to simulate the characteristics of fluid flow, heat and mass transfer coupling with exothermic reaction of acetone hydrogenation in the exothermic reactor. Fractal theory is used to structure a porous media. The effects of the process variables including mole ratio,inlet velocity, and porosity on the heat transfer characteristics are studied. The results show that the heat and mass transfer characteristics in porous media are strongly influenced by the flow behavior. Its complex mechanism lies in the coupled effect of diffusion and convection effect on mass transport process.In chapter 4, a modified pseudo potential model for multi-phase flows is used to improve numerical stability; the Carnahan-Starling real-gas equation of state is incorporated into the proposed model to simulate the liquid-vapor phase change process. We demonstrated and discussed the qualitative simulation results. The simulation results show that the LBM can be developed to simulate the multi-component flow, heat and mass transfer coupling with the chemical reaction with approximately satisfaction.We investigated the application of reactive distillation to enhance the thermodynamic performance of the IAH-CHP system in chapter 5. First, experiments regarding liquid-phase dehydrogenation of isopropanol has been investigated by using a reactive distillation column. It was found that the liquid phase dehydrogenation of isopropanol using reactive distillation needed less energy and was much more efficient. A further discussion about the performance of reactive distillation demonstrated the effect of the catalyst amount, the temperature of the heat source and the reflux ratio. On the basis of experimental result, the operating performances between an IAH-CHP system with and without reactive distillation part were compared numerically. The results indicate that the COP and exergy efficiency of an IAH-CHP system with reactive distillation part increase by 19.2% and 16.7% at most, respectively, compared with an IAH-CHP without reactive distillation part.