Comparative evaluation of heat conduction and radiation models for CFD simulation of heat transfer in packed beds

The existing major heat conduction and radiation models for packed bed of particles are reviewed and evaluated by comparing the predicted results with experimental data. For low-temperature condition, it is found that the Zehner-Bauer-Schlfinder (ZBS) model is less sensitive to the effect of contact area and is thus recommended for the calculation of effective thermal conductivity of packed bed. For high temperature condition, although numbers of models can be used to calculate the radiative heat transfer behavior in packed bed, the Breitbach and Barthels (B-B) correlation is the optimal method applicable for different particle diameters, emissivities and voidages. The results of CFD simulations using the identified optimal heat transfer models agree well with the thermal measurements by thermocouple in four coal pyrolysis fixed-bed reactors mounted with or without particularly designed internals. (C) 2018 Elsevier Ltd. All rights reserved.</p

Evolution of Volatile Aroma Compounds and Amino Acids in Cabernet Gernischt Grape Berries (Vitis vinifera L.): Comparison of Different Training Systems for Mechanical Soil Burial

Soil burial is a survival strategy for grapevines that can safely overwinter in north-western regions of China. A suitable training system was beneficial for soil burial to provide winter protection. Moreover, the training system can also significantly affect fruit quality during the development of grape berries, such as primary and secondary metabolites. In this study, four-year-old Cabernet Gernischt grapevines were used as experimental material and exposed to four training systems, including the Ningxia traditional vertical trunk (control, CK); the gobelet (T1); single guyot (T2); slant trunk with vertical shoot positioning (STVSP) (T3). The results showed that total soluble solid total phenol content was 12.69%, 57% higher under T3 training systems than in the control, and T3 alleviated the canopy density, leading to improving the leaf photosynthetic efficiency gas chromatography-mass spectrometry (GC-MS) assay used to detect the aroma compounds. The results indicated that the T3 training system enhanced the accumulation of alcohols, carbonyl compounds, C6/C9 and esters, which account for the largest proportion of volatile compounds, and the qRT-PCR reveals that VvEcar, Vvter, VvCCD1, and VvLis were raised under T3 at the transcriptional level. Moreover, T3 contributes to most free amino acid synthesis. Additionally, the PCA reveals the correlation of free amino acids under four training systems, which reflected the mostly amino acid related to T3, and thus, we could speculate that T3 enhances the overall aroma. These results may lead to new strategies to select a new, short trunk training system to achieve mechanized buried soil, to prevent cold and produce high-quality wine in this area

Secondary cracking of volatile and its avoidance in infrared-heating pyrolysis reactor

This study aims to compare the pyrolysis behavior of Huadian oil shale in two infrared heating fixed bed reactors with different directions of infrared beam. Our previous work has shown that fast pyrolysis of oil shale conducted in the shallow fixed bed infrared heating reactor (co-current) presented the massive secondary reactions, which lowered the shale oil production (Siramard et al., 2017). Conversely, the cross-current infrared achieved shale oil yields higher than the Fischer Assay oil yield (13.07 wt% of dry basis), such as 117.7% of the Fischer Assay yield at our realized highest heating rate of 7 °C/s under a specified pyrolysis temperature of 550 °C. The shale oil from the cross-current infrared heating reactor was obviously heavier than the oil obtained from the co-current heating reactor. Thus, the infrared cross heating evidently suppressed the secondary reactions toward volatile. Our realized shale oil yield could reach 13.67 wt% or 122.5% of the Fischer Assay yield under reducing pyrolysis pressure of 0.6 atm, indicating that lower pressure is also beneficial to the release of volatile and reduction of the secondary cracking reactions. This work shows essentially that the infrared cross heating provides an effective merge of the advantages from quick heating and minimization of secondary cracking reactions to enable the shale oil yields being higher than the Fischer Assay oil yield. Keywords: Pyrolysis, Secondary cracking, Volatile, Infrared heating, Oil shal

Oil shale pyrolysis in a moving bed with internals enhanced by rapid preheating in a heated drop tube

The enhanced oil shale pyrolysis in a moving bed with internals (MBI) by rapid preheating in a drop tube was developed to improve the quality of shale oil through reaction regulation in stages. Initially rapid preheating of oil shale in the upper drop tube endowed the generation of massive free radical fragments and volatile precursors, which would simultaneously restrict the remarkable release of volatiles from particles to minimize the gas-phase secondary reactions. The preheated oil shale subsequently fell into the lower MBI to shape a granular bed with the cocurrent flow of heat and volatiles. In the MBI, the oil shale pyrolysis and volatiles reactions were directed and regulated by matching the flow and temperature fields to realize the selective cracking of heavy fraction in shale oil. The granular bed also served as a filter for the in-situ removal of dust entrained by the volatiles. The shale oil yield reached 83.0% of Fischer Assay oil yield, its light fraction was as high as 89.2 wt% and dust content was as low as 0.6 wt%. The advantages of pyrolysis in the MBI enhanced by rapid preheating were further justified by comparison with other pyrolysis processes

Mitochondrial impairment and downregulation of Drp1 phosphorylation underlie the antiproliferative and proapoptotic effects of alantolactone on oral squamous cell carcinoma cells

Abstract Background Oral squamous cell carcinoma (OSCC) is one of the most prevalent and fatal oral cancers. Mitochondria-targeting therapies represent promising strategies against various cancers, but their applications in treating OSCC are limited. Alantolactone (ALT) possesses anticancer properties and also regulates mitochondrial events. In this study, we explored the effects of ALT on OSCC and the related mechanisms. Methods The OSCC cells were treated with varying concentrations and duration of ALT and N-Acetyl-l-cysteine (NAC). The cell viability and colony formation were assessed. The apoptotic rate was evaluated by flow cytometry with Annexin V-FITC/PI double staining. We used DCFH-DA and flow cytometry to detect reactive oxygen species (ROS) production and DAF-FM DA to investigate reactive nitrogen species (RNS) level. Mitochondrial function was reflected by mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and ATP levels. KEGG enrichment analyses determined the mitochondrial-related hub genes involved in OSCC progression. Dynamin-related protein 1 (Drp1) overexpression plasmids were further transfected into the cells to analyze the role of Drp1 in OSCC progression. Immunohistochemistry staining and western blot verified the expression of the protein. Results ALT exerted anti-proliferative and pro-apoptosis effects on OSCC cells. Mechanistically, ALT elicited cell injury by promoting ROS production, mitochondrial membrane depolarization, and ATP depletion, which were reversed by NAC. Bioinformatics analysis showed that Drp1 played a crucial role in OSCC progression. OSCC patients with low Drp1 expression had a higher survival rate. The OSCC cancer tissues presented higher phosphorylated-Drp1 and Drp1 levels than the normal tissues. The results further showed that ALT suppressed Drp1 phosphorylation in OSCC cells. Moreover, Drp1 overexpression abolished the reduced Drp1 phosphorylation by ALT and promoted the cell viability of ALT-treated cells. Drp1 overexpression also reversed the mitochondrial dysfunction induced by ALT, with decreased ROS production, and increased mitochondrial membrane potential and ATP level. Conclusions ALT inhibited proliferation and promoted apoptosis of oral squamous cell carcinoma cells via impairment of mitochondrial homeostasis and regulation of Drp1. The results provide a solid basis for ALT as a therapeutic candidate for treating OSCC, with Drp1 being a novel therapeutic target in treating OSCC