Effect of different carrier gases on productivity enhancement of a novel multi-effect vertical concentric tubular solar brackish water desalination device

A novel multi-effect vertical concentric tubular solar brackish water desalination device is introduced in present study. The device consists of four closely spaced concentric pipes, in which the feed water gets preheated by hot brine water to guarantee the evaporation efficiency. An experimental investigation and analytical analysis were carried out to signify the effect of carrier gas-water vapor mixture on productivity enhancement of the device. Different carrier gases were used in the performance evaluation: carbon dioxide, helium, nitrogen, oxygen, air and argon. The water yield and the top/bottom temperature values of condensation surface of the device with different carrier gases were tested. In addition, the present investigation is presented an approach to predict the theory yield based on the internal heat and mass transfer mechanism. The experimental results indicate that, when the heating temperature is 80 °C and the carrier gas is helium, the water productivity rate can reach to 1.19 kg/h. It is increased by 30.76% than the carrier gas of air. The numerical results had been calculated and a consistent agreement with the experimental results had been obtained of different operation temperatures. The Dv under different heating temperature were obtained according to the experimental results

The mass transfer coefficient assessment and productivity enhancement of a vertical tubular solar brackish water still

This paper presents an experimental investigation of a single-effect vertical tubular solar brackish water desalination device, with an aim to determine the mass transfer coefficient and its enhancement. The device consists of two closely spaced concentric pipes. The outside of the inner pipe is covered with a wicking material and wetted with hot brackish water. The water vapor evaporated from the wicking material condenses on the inside of the outer pipe. The measured productivity and temperatures at various points are given for different wicking materials thickness, water flow rates and chamber pressure under the condition of given heating power. Mass transfer coefficients are calculated from the experimental results and then applied in the prediction of water productivity. The maximum discrepancy between the calculation yield and measurement yield is relatively small compared with previous study. In addition, it was found that the yield of the solar still is 23.9% higher when the chamber pressure is lower by 25 kPa due to the enhanced mass transfer. Similar, doubling the ambient air velocity can increase the water yield by about 17.0%

Effect of Inoculated Fermentation with Different Aspergillus Strains on the Formation of the Umami Taste of Liuyang Douchi

In order to investigate the effect of inoculated fermentation with different Aspergillus strains on the umami taste of Liuyang Douchi, the differences in the umami taste and protein degradation of Liuyang Douchi fermented naturally (NF) or by four dominant Aspergillus flavus strains isolated from Douchi (A. flavus 7214, A. flavus 7622, A. flavus 6112, and A. flavus 5322) alone and their mixture in an equal proportion (M4) were compared. The results showed that the major protease produced by each of the four strains was serine proteases, and A. flavus 5322 had the strongest protease activity, with significantly higher activity of acidic protease than the other three strains. The contents of amino acid nitrogen and water-soluble protein in Aspergillus fermented Douchi were higher than those in NF Douchi after the end of pile-fermentation stage. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the degradation trends of six proteins in Douchi were consistent, all of which exhibited rapid degradation during the pile-fermentation process. Additionally, the results of sensory evaluation and electronic tongue analysis showed that Douchi fermented by A. flavus 5322 showed the strongest umami taste, which significantly increased when compared with NF. Using ultra-high performance liquid chromatography-electrospray/quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) combined with correlation and peptidomics analysis, a total of 43 potential umami peptides were identified. The total peak area of potential umami peptides in Douchi fermented by A. flavus 6112 was the highest, followed by A. flavus 5322 with little difference, significantly greater than that in NF Douchi. In summary, inoculated fermentation, especially with A. flavus 5322, could promote protein degradation and the release of potential umami peptides, thereby enhancing the umami taste of Liuyang Douchi. This study will provide theoretical guidance for improving the umami taste of Liuyang Douchi and development of industrial production strains

Analysis of electric field distribution at air gap defect and its influencing factors in mine-used high-voltage cable insulatio

In order to know influence factors and laws of electric field distribution with air gap defects in cable insulation, taking mine-used high-voltage XLPE cable as research object, ANSYS finite element software was used to establish cable structure model contained air gap defect. Influence of shape, size and location of the air gap and thickness of the insulating layer on electric field distribution in the air gap was simulated and studied based on theoretical analysis of relationship between shape, size and electric field strength of air gap in insulation. Results show that electric field intensity of elliptic cylinder air gap defect is the largest of four different shapes of air gap, and the larger the air gap length in direction of insulation perpendicular to the field strength, the greater the field strength in the air gap. For size of the air gap, the larger the r value, the greater the field strength at the air gap, and change of the air gap size has little influence on the field strength at the air gap. For different radius size of the air gap, the maximum electric field strength at the air gap increases first and then decreases with increasing of distance between the air gap and the conductor shield. For a given size of the air gap, the field strength in the air gap and the insulation increase accordingly with decreasing of thickness of the insulation. These conclusions lay foundation for partial discharge of air gap defects, and also provide technical guidance for cable operation and maintenance

Mechanistic Insight into the 2° Alcohol Oxidation Mediated by an Efficient CuI/L-Proline-TEMPO Catalyst—A Density Functional Theory Study

Density functional theory (DFT) calculations have been performed to investigate the 2° alcohol oxidation to acetophenone catalyzed by the CuI/L-Proline-2,2,6,6- tetramethylpiperidinyloxy (TEMPO) catalyst system. Seven possible pathways (paths A→F) are presented. Our calculations show that two pathways (path A and path B) are the potential mechanisms. Furthermore, by comparing with experimental observation, it is found that path A—in which substrate alcohol provides the proton to −OtBu to produce HOtBu followed by the oxidation of substrate directly to product acetophenone by O2—is favored in the absence of TEMPO. Correspondingly, path B is likely to be favored when TEMPO is involved. In path B, the O–O bond cleavage of CuI–OOH to CuII–OH species occurs, followed by acetophenone formation assisted by ligand (L)2ˉ. It is also found that the cooperation of ligand (L)2ˉ and TEMPO plays an important role in assisting the formation of the product acetophenone in path B