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A bed and furnace integrated model of biomass briquette chain boilers was built on basis of theories of computational fluid mechanics, heat transfer, thermodynamics, and chemical reaction kinetics. The combustion in the biomass briquette chain boilers was characterized under five working parameters (air-preheating temperature, fuel bed thickness, grate advancing speed, particle diameter, air supply mode) through experimental design, numerical simulation, and mathematical programming. Finally, these parameters were optimized with the ant colony algorithm. It was found that the combustion efficiency and economic benefits were both optimized at the air-preheating temperature of 553.22 K, fuel bed thickness of 0.16 m, particle diameter of 0.02 m, and uniform centered air supply. This study offers some theoretical basis and method for the optimized design and operation of biomass briquette chain boilers. [ABSTRACT FROM AUTHOR]

Serials of Mn doping by substituting Cd sites on Cu2CdSnSe4 are prepared by the melting method and the spark plasma sintering (SPS) technique to form Cu2Cd1-xMnxSnSe4. Our experimental and theoretical studies show that the moderate Mn doping by substituting Cd sites is an effective method to improve the thermoelectric performance of Cu2CdSnSe4. The electrical resistivity is decreased by about a factor of 4 at 723 K after replacing Cd with Mn, but the seebeck coefficient decreases only slightly from 356 to 289 μV/K, resulting in the significant increase of the power factor. Although the thermal conductivity increases with the doping content of Mn, the figure of merit (ZT) is still increased from 0.06 (x = 0) to 0.16 (x = 0.10) at 723 K, by a factor of 2.6. To explore the mechanisms behind the experimental results, we have performed an ab initio study on the Mn doping effect and find that the Fermi level of Cu2CdSnSe4 is shifted downward to the valence band, thus improving the hole concentration and enhancing the electrical conductivity at the low level doping content. Optimizing the synthesis process and scaling Cu2Cd1-xMnxSnSe4 to nanoparticles may further improve the ZT value significantly by improving the electrical conductivity and enhancing the phonon scattering to decrease the thermal conductivity. [ABSTRACT FROM AUTHOR]