The modified sigmoidal bacteria growth functions (the modified Gompertz, logistic, and Richards) were used to evaluate the methane production process kinetics of agricultural wastes. The mesophilic anaerobic co-digestion experiments were conducted with various agricultural wastes as feedstocks, including cow manure, corn straw, grape leaves, vines, wine residue, strawberry leaves, and tomato leaves. The results showed that anaerobic co-digestion of cow manure and other agricultural wastes increased the methane yields while it prolonged the lag phase time. Compared with the modified Gompertz and logistic models, the modified Richards model obtained higher correlation coefficients and was able to fit experimental data better. The results of this study were expected to determine a suitable model to simulate and study the kinetic process of anaerobic co-digestion with mixed agricultural wastes as feedstocks.

No abstract

No abstract

In order to decrease the operation costs of air conditioning systems, an evaluation model based on unit thermoeconomic costs of thermoeconomic theory is presented in this paper. By using real components and fictitious components in an air conditioning system, the relationships between the fuel and product are established, and then the operation performances of the air conditioning system can be analyzed and evaluated. The unit thermoeconomic costs can be obtained with the experimental data. The results show that the unit thermoeconomic cost of the system is the lowest when the vaporizing temperature is at 16.3°C, and the unit thermoeconomic cost of the compressor component is the highest. Therefore, the direction and emphases of the technique improvement and performance enhancement are provided.

The kinetics of biogas production on anaerobic fermentation with anionic surfactants added was evaluated using the sigmoidal models (the modified Gompertz and Logistic). The mesophilic anaerobic co-fermentation experiments under different anionic surfactants concentrations were conducted with mixed cow dung and corn straw as feedstocks. The results showed that the anionic surfactants in appropriate concentrations on anaerobic fermentation increased the cumulative biogas yields while prolonged the lag phase time. The modified Logistic model performed better than modified Gompertz model in fitting the experimental results of anaerobic co-fermentation with anionic surfactants added. The results of this study were expected to provide theoretical guidance for studying the impact of anionic surfactants and modelling the kinetic process of anaerobic co-fermentation.