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[en] This paper analyzed the influence of working fluids selection and operation conditions on the cost-effectiveness performance and net power output of an ORC for low grade heat utilization. A net power output model has been proposed theoretically and compared with the theoretical data calculated from thermodynamic analysis, exhibiting excellent agreements with the theoretical data. The proposed net power output model theoretically indicates that Jacob number and the ratio of evaporating temperature and heat rejected temperature play essential roles in discriminating the net power output among various working fluids at the same operation condition. For a given condensing and evaporating temperature, it can be concluded theoretically that fluid with low Jacob number will show attractive performance in an ORC. The maximum net power output is determined by the heat source rather than working fluids with a low inlet temperature of heat source. Cost-effectiveness performance analysis reveals that the maximum net power output and the best CEP cannot be achieved at the same time and compromise must be made when choosing the most suitable organic working fluids in different ORC designs. -- Highlights: • A net power output model is proposed and compared with theoretical data. • For fixed operation condition, low Ja fluid shows attractive performance in ORC. • The heat source rather than working fluid determines ORC performance at low Ths,in • The peak Wnet and best CEP cannot be achieved at the same time, compromise must be made
[en] In this letter, large-mode-area double-cladding ytterbium-doped photonic crystal fiber was designed in theory and fabricated in practice. This fiber we have fabricated successfully has endless single mode operation performance and large inner-cladding numerical aperture of more than 0.75. The struts width between large air-holes in the outer-cladding is about 0.22 μm. The photonic crystal fiber has a mode-area about 1465.7μm2. Due to the material being pure silica and air, such structures have excellent capacity to with-stand high temperature. The laser light can have very good beam quality, even diffraction-limited beam quality because of the single-mode core. This fabrication technical breakthrough of novelty high performance double-cladding ytterbium-doped photonic crystal fibers will give contributions to the high power fiber lasers and promote the progress of technology in the fields of high power lasers.
[en] Highlights: • The influence of disk configurations on droplets characteristics is investigated. • The droplets size, droplets size distributions, filament mass fraction and particle uniformity were analyzed. • A correlation of dm for four types of disks is presented. • The majority of the droplets size is populated in the range of 0.2–1.0 mm. • The flat/arc-edge disks represent a superior uniformity compared with the other disks. - Abstract: The influence of rotary disk configurations on droplets characteristics in molten slag ligament granulation was investigated by using the high-speed camera visualized system. Rosin/Paraffin mixture was adopted as the analogue of the molten slag according to the similarity theory. Four groups of disks with different configurations were studied. The droplets characteristics, such as droplets size, droplets size distributions, filament mass fraction and particle uniformity were analyzed. Generally, the droplets mean diameters (dm) decreases by increasing the rotary speed (ω) or disk diameter (D), and increases slightly by increasing the liquid flow rate (Q). Based on the experimental data, a simple correlation of dm for four types of disks is presented. The majority of the droplets size is populated in the range of 0.2–1.0 mm for all ω and Q, which accounts for over 70% mass fraction. The ω has significant influence on droplets size distribution and particle uniformity. The flat/arc-edge disk configurations can contribute to produce the narrower size range of droplets and obtain the superior particle uniformity compared to the other two types of disks. In the ligament breakup mode, the filament mass fraction reduces by increasing Q or decreasing ω. Meanwhile, the liquid film breakup mode also has significant impact on the formation of filament.
[en] This research proposes a double organic Rankine cycle for discontinuous waste heat recovery. The optimal operation conditions of several working fluids have been calculated by a procedure employing MATLAB and REFPROP. The influence of outlet temperature of heat source on the net power output, thermal efficiency, power consumption, mass flow rate, expander outlet temperature, cycle irreversibility and exergy efficiency at a given pinch point temperature difference (PPTD) has been analyzed. Pinch point analysis has also been employed to obtain a thermodynamic understanding of the ORC performance. Of all the working fluids investigated, some performances between each working fluid are rather similar. For a fixed low temperature heat source, the optimal operation condition should be mainly determined by the heat carrier of the heat source, and working fluids have limited influence. Lower outlet temperature of heat source does not always mean more efficient energy use. Acetone exhibits the least exergy destruction, while R245fa possesses the maximal exergy efficiency at a fixed PPTD. Wet fluids exhibit lower thermal efficiency than the others with the increasing of PPTD at a fixed outlet temperature of heat source. Dry and isentropic fluids offer attractive performance. - Highlights: ► We propose a double organic Rankine cycle for discontinuous waste heat recovery. ► Performance of organic Rankine cycle (ORC) is analyzed by pinch point analysis. ► The heat carrier of the heat source determines ORC optimal operation condition. ► Design of ORC heat exchangers prefers lower pinch point temperature difference.