Evaluation of the Safety of High-Salt Wastewater Treatment in Coal Chemical Industry Based on the AHP Fuzzy Method

Aim. Epichlorohydrin (ECH) is a widely used chemical product. The production of glycerol has its irreplaceable advantages. With the development of biodiesel industry, it will become the main trend of ECH production in the future. Methods. A vacuum evaporation device is built to investigate the effect of evaporation on the treatment of this kind of high-salt wastewater, and the feasibility of the thermodynamic equation of the simulation process is verified. Process. An AHR fuzzy mathematics evaluation algorithm is used to compare experimental values with simulated numerical values in brine. Results and Conclusions. In the multieffect evaporation process simulation with glycerin-containing brine, the amount of salt precipitated by unit steam energy is arranged in order from more to less than that of seven-effect parallel flow evaporation, is greater than five-effect parallel flow evaporation, and is larger than three-effect parallel flow evaporation, which shows that the increase of validity number is beneficial to the utilization of heat.

Numerical Modelling of a Photovoltaic Thermal (PV/T) System Using Nanofluid With Parallel Flow Thermal Absorber

In the present study, a numerical model of photovoltaic thermal (PV/T) system using alumina (Al2O3) nanofluid, and pure water are used as working fluid. The proposed PV/T model consists of parallel riser tubes that are connected to two header tubes and it is attached to an absorber plate to simulate the conduction and convection heat transfer mechanism of a conventional PV/T system. The energy efficiency of the PV/T model is analyzed by varying the solar radiation (Heat Flux), inlet fluid velocity, and the volume percentage of the nanofluids. The numerical simulation is performed by using a conjugate heat transfer method with a computational fluid dynamics (CFD) software. According to the simulation data, the energy efficiency and the heat transfer coefficient of the PV/T system increased by increasing the inlet fluid velocity. In comparison with water, alumina nanofluid showed better thermal and electrical efficiency due to its high thermal conductivity. The thermal efficiency increased by 5.55% for alumina, compared to pure water and the electrical efficiency increased by 0.15% for alumina. Moreover, the effect of inlet fluid velocity ranging from 0.04m/s to 0.2m/s was also evaluated, and the results showed that the increase in thermal efficiency for pure water and alumina are 18.15% and 25.77%, respectively. Subsequently, the electrical efficiency increased by 0.52% and 0.56% for pure water and alumina using the new parallel flow thermal absorber, respectively.

Experimental and CFD Analysis of GW70 based Cu Nanofluids in a Parallel Flow Heat Exchanger

The Nusselt number, overall heat transfer, and convective heat transfer coefficients of glycerol-water-based Cu nanofluids flowing in a parallel flow double pipe heat exchanger are estimated using CFD analysis. Single-phase fluid approach technique is used in the analysis. Ansys 19.0 workbench was used to create the heat exchanger model. Heat transfer tests with nanofluids at three flow rates (680<Re<1900) are carried out in a laminar developing flow zone. For testing, a 500 mm long concentric double pipe heat exchanger with tube dimensions of ID=10.2 mm, OD= 12.7 mm, and annulus dimensions of ID=17.0 mm, OD= 19.5 mm is employed. Copper is utilized for the tube and annulus material. This study employed three-particle volume concentrations of 0.2 percent, 0.6 percent, and 1.0 percent. The mass flow rates of hot water in the tube are 0.2, 0.017, and 0.0085 kg/s, while the mass flow rates of nanofluids in the annulus are 0.03, 0.0255, and 0.017 kg/s. The average temperature of nanofluids is 36°C, whereas hot water is 58°C. In comparison to base liquid, the overall heat transfer coefficient and convective HTC of 1.0 percent copper nanofluids at 0.03 kg/s are raised by 26.2 and 46.2 percent, respectively. The experimental findings are compared to CFD values, and they are in close agreement.

Performance Enhancement of PEM Fuel Cells with an Additional Outlet in the Parallel Flow Field

The design of bipolar plates is critical for improving the performance of proton exchange membrane fuel cells (PEMFCs). In this research, a new additional outlet based on a PEMFC’s parallel flow field was proposed, and three different positions of outlet were designed on the target side of gas flowing in parallel channels. The results revealed that the additional outlets are able to increase the gas speed through channels near the additional outlets, which results in a lower water saturation and a more uniform distribution of oxygen concentration at the interface between the catalyst layer (CL) and gas diffusion layer (GDL). With the variation of the outlet position in the target side, it was found that the additional outlet set in the middle of the target side exhibits the highest increase of peak power density, namely, 13%. Furthermore, the optimal position of the additional outlet was proved to be suitable for PEMFCs with various active surface areas, indicating the universality of the present results in the study.

Analysis of Energy Efficient Scheduling of the Manufacturing Line with Finite Buffer Capacity and Machine Setup and Shutdown Times

The aim of this paper is to present a model of energy efficient scheduling for series production systems during operation, including setup and shutdown activities. The flow shop system together with setup, shutdown times and energy consumption are considered. Production tasks enter the system with exponentially distributed interarrival times and are carried out according to the times assumed as predefined. Tasks arriving from one waiting queue are handled in the order set by the Multi Objective Immune Algorithm. Tasks are stored in a finite-capacity buffer if machines are busy, or setup activities are being performed. Whenever a production system is idle, machines are stopped according to shutdown times in order to save energy. A machine requires setup time before executing the first batch of jobs after the idle time. Scientists agree that turning off an idle machine is a common measure that is appropriate for all types of workshops, but usually requires more steps, such as setup and shutdown. Literature analysis shows that there is a research gap regarding multi-objective algorithms, as minimizing energy consumption is not the only factor affecting the total manufacturing cost—there are other factors, such as late delivery cost or early delivery cost with additional storage cost, which make the optimization of the total cost of the production process more complicated. Another goal is to develop previous scheduling algorithms and research framework for energy efficient scheduling. The impact of the input data on the production system performance and energy consumption for series production is investigated in serial, parallel or serial–parallel flows. Parallel flow of upcoming tasks achieves minimum values of makespan criterion. Serial and serial–parallel flows of arriving tasks ensure minimum cost of energy consumption. Parallel flow of arriving tasks ensures minimum values of the costs of tardiness or premature execution. Parallel flow or serial–parallel flow of incoming tasks allows one to implement schedules with tasks that are not delayed.

Performance of flow distribution in a microchannel parallel flow gas cooler with stepped protrusion depth header

Microchannel parallel flow gas cooler is commonly used in transcritical carbon dioxide automotive air conditioning system. To investigate the influence of the flat tube protrusion depth on fluid distribution, a numerical calculation model of microchannel parallel flow gas cooler with D-shaped header is established. With the object of even flow distribution, a novel stepped protrusion depth header is proposed. The effects of new header on the flow distribution of gas cooler were studied by numerical simulation. The results show that the flow distribution performance of gas cooler can be improved by changing the flat tube protrusion depth. Changing the protrusion depth of three groups of flat tubes simultaneously can achieve a better flow distribution performance of gas cooler than changing the protrusion depth of only one or two groups of flat tubes. When compared with the protrusion depth of all flat tubes is 0, the novel stepped protrusion depth header reduces the total flow distribution nonuniformity of gas cooler by 34–51%. The research in this paper provides a method for improving the flow distribution performance of gas coolers.