Pattern Formation in a Bacterial Colony Model

We investigate the spatiotemporal dynamics of a bacterial colony model. Based on the stability analysis, we derive the conditions for Hopf and Turing bifurcations. Furthermore, we present novel numerical evidence of time evolution of patterns controlled by parameters in the model and find that the model dynamics exhibit a diffusion controlled formation growth to spots, holes and stripes pattern replication, which show that the bacterial colony model is useful in revealing the spatial predation dynamics in the real world

Simultaneous Removal of SO2 and NO by O3 Oxidation Combined with Seawater as Absorbent

Aiming at NOx (NO 90%, NO2 10%) and SO2 in simulated vessel emissions, denitration and desulfurization were studied through ozone oxidation combined with seawater as absorbent. Specifically, the different influencing factors of denitration and desulfurization were analyzed. The results indicated that the oxidation efficiency of NO can reach over 90% when the molar ratio of O3/NO is 1.2. Ozone oxidation and seawater washing in the same unit can decrease the temperature of ozone oxidation of NO, avoid high temperature ozone decomposition, and enhance the oxidation efficiency of NO. When NO inlet initial concentration is lower than 800 ppm, the NOx removal efficiency can be improved by increasing NO inlet concentration, and when NO inlet initial concentration is greater than 800 ppm, increasing the concentration of NO would decrease the NOx removal efficiency. Increasing the inlet concentration of SO2 has minor effect on desulfurization, but slightly reduces the absorption efficiency of NOx due to the competition of SO2 and NOx in the absorption solution. Besides, final products (NO2−, NO3−, SO32−, and SO42−) were analyzed by the ion chromatography

Simulation study of heat transfer characteristics of a biomimetic honeycomb CO

CO2 air source heat pumps are widely used because of their advantages of energy saving, high efficiency and clean. Gas cooler is one of the key components of CO2 heat pump system, while its heat transfer effect will affect the energy efficiency of the whole system. In order to improve the heat transfer efficiency, a biomimetic honeycomb gas cooler is proposed in this paper, the steady-state simulation model of the biomimetic honeycomb gas cooler is established by using MATLAB software, and the reliability of the model is verified by literature data. In addition, the heat transfer performance of the biomimetic honeycomb gas cooler is compared with that of the tube-in-tube gas cooler. The results showed that, under the same working condition, compared with the tube-in-tube gas cooler, the outlet temperature of the biomimetic honeycomb gas cooler with 1st, 2nd and 3rd level increased by 9.7°C, 25.4°C and 27.3°C, and heat transfer can be increased by 55.5%, 205.4% and 220.6% respectively. This research is helpful to provide the reference for the design and optimization of this type of gas cooler, and is conducive to the popularization of CO2 air source heat pump

Performance Optimization and Economic Evaluation of CO2 Heat Pump Heating System Coupled with Thermal Energy Storage

CO2 air source heat pump (ASHP), as a kind of clean and efficient heating equipment, is a promising solution for domestic hot water and clean heating. However, the promotion of CO2 ASHP encounters a great resistance when it is used for space heating; namely, the return water temperature is too high that cased higher throttle loss, which decreases the COP of the CO2 ASHP unit. To solve this problem, a heating system of CO2 ASHP coupled with thermal energy storage (TES) is developed in this work. The simulation model of the studied system is established using TRNSYS software, and the model is verified by experimental data. Additionally, the performance of the studied system is optimized, and its economy is analyzed by life cycle cost (LCC). The results showed that, compared with the system before optimization, the cost of the optimized system increased, the annual operating cost of the system was reduced, and the COP of the system (COPsys) increased by 7.4%. This research is helpful in improving the application of the CO2 ASHP unit in cold server and cold areas

Techno-economic evaluation of a frost-free air source heat pump water heater

© 2020 Elsevier Ltd In order to improve the performance of air source heat pumps (AHSPs) when it is operated in winter, a novel frost-free ASHP system has been developed and the thermodynamic characteristics was performed in the previous work. Before it is large-scale promoted and applied, an economic analysis should be conducted. However, there is little research on the economic analysis of the system, which limits the development and application of innovation technologies. Therefore, a techno-economic analysis of the system was evaluated in typical climate zones in China and compared with a conventional ASHP unit in this paper. The results showed that the running cost of the frost-free ASHP system reduced 23.2, 23.6 and 29.0 % in comparison with the conversional ASHP system in Xi\u27an, Shenyang and Hefei cities respectively, also, corresponding to the payback period of the initial cost were 4.2 years, 3.3 years and 4.03 years respectively. It shows that the frost-free ASHP system is a promising economical way for space heating. Conclusion from this work will provide key information for the user in decision making and determining the economic viability of the frost-free ASHP system has been evaluated before it is large-scale promoted and applied

Performance Optimization and Economic Evaluation of CO₂ Heat Pump Heating System Coupled with Thermal Energy Storage

CO2 air source heat pump (ASHP), as a kind of clean and efficient heating equipment, is a promising solution for domestic hot water and clean heating. However, the promotion of CO2 ASHP encounters a great resistance when it is used for space heating; namely, the return water temperature is too high that cased higher throttle loss, which decreases the COP of the CO2 ASHP unit. To solve this problem, a heating system of CO2 ASHP coupled with thermal energy storage (TES) is developed in this work. The simulation model of the studied system is established using TRNSYS software, and the model is verified by experimental data. Additionally, the performance of the studied system is optimized, and its economy is analyzed by life cycle cost (LCC). The results showed that, compared with the system before optimization, the cost of the optimized system increased, the annual operating cost of the system was reduced, and the COP of the system (COPsys) increased by 7.4%. This research is helpful in improving the application of the CO2 ASHP unit in cold server and cold areas

Changing Characteristics of Sandstone Pore Size under Cyclic Loading

The size and distribution of pores in rocks are closely related to their physical and mechanical properties. It is important to study the structure and distribution of pore size inside the rock to assess the risk of damage to a given rock volume. These characteristics were studied under different pressures, pore diameters, and pore throat size distribution laws using a UTM5540 electronic universal testing machine, magnetic resonance imaging scanning, and low field nuclear magnetic resonance spectroscopy with cyclic loading on yellow sandstone. We found the following. (1) Under 0–10 MPa load, the peaks of the sandstone T2 spectrum move left as load increases, and the porosity of the sandstone decreases. The peak area of the middle relaxation spectrum increases as pressure increases from 10 to 20 MPa, and a peak for the long relaxation time spectrum appears. (2) Under 0–10 MPa load, the spectral peak associated with a large pore moves left and decreases in area as pressure increases. Under 10–20 MPa load, the large-pore spectral peak moves right and increases in area as pressure increases. (3) Under the applied 0–10 MPa load, the porosity of water-saturated sandstone gradually decreases, and the sandstone NMR images darken with increasing load. The porosity of saturated sandstone gradually increases under 10–20 MPa pressure, and its NMR image brightens. (4) The number of small pore throats increases with increasing load, but the number of large- and medium-sized pore throats decreases. From 0 to 15 MPa, crack (>1 micron) abundance decreases, and fractures are generated by compaction under a 20 MPa load. The pore interconnectivity is enhanced, as are the number and size of pores in the sandstone. With continuing increasing pressure, the numbers of pores and penetration of cracks increase, which damages the sandstone

Finite-Time Speed Control of Marine Diesel Engine Based on ADRC

In this paper, in order to handle the nonlinear system and the sophisticated disturbance in the marine engine, a finite-time convergence control method is proposed for the diesel engine rotating speed control. First, the mean value model is established for the diesel engine, which can represent response of engine fuel injection to engine speed. Then, in order to deal with parameter perturbation and load disturbance of the marine diesel engine, a finite-time convergence active disturbance rejection control (ADRC) is proposed. At the last, simulation experiments are conducted to verify the effectiveness of the proposed controller under the different load disturbances for the 7RT-Flex60C marine diesel engine. The simulation results demonstrate that the proposed control scheme has better control effect and stronger anti-interference ability than the linear ADRC