The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of t...The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of the commercial casting simulation package, ProCASTTM, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient values. The simulation results were used to estimate the centerline cooling curve at various locations through the casting. The centerline cooling curves, together with the die temperature and the thermodynamic properties of the alloy, were then used as inputs to compute the solution to the Stefan problem of a moving phase boundary, thereby providing the through-thickness cooling curves at each chosen location of the casting, Finally, the local cooling rate was used to calculate the resulting grain size via previously established relationships. The effects of die temperature, filling time and heat transfer coefficient on the grain structure in skin region and core region were quantitatively characterized. It was observed that the grain size of skin region strongly depends on above three factors whereas the grain size of core region shows dependence on the interracial heat transfer coefficient and thickness of the samples. The grain size distribution from surface to center was estimated from the relationship between grain size and the predicted cooling rate. The prediction of grain size matches well with experimental results. A comparison of the predicted and experimentally determined grain size profiles enables the determination of the apparent interracial heat transfer coefficient for different locations.展开更多
This work is interested in solving the complex problem of understanding mass transfers in biological media. The contribution of the initial sample size is taken into account. Transfers are established more efficiently...This work is interested in solving the complex problem of understanding mass transfers in biological media. The contribution of the initial sample size is taken into account. Transfers are established more efficiently in small samples. Thus, from the first 50 minutes, the cubic sample at 1 cm stop is already at 50% while the sample at 4 cm edge is at about 90% of its initial water content. Likewise the shape is combined with the size. But it is revealed that if we fix similar characteristic dimensions, we can bypass the notion of initial shape. Thus the cubic samples 4 cm of edges. 4 cm diameter of spherical shape, 4 cm × 4 cm height-diameter cylindrical one, all dry identically.展开更多
针对微生物种间电子转移效率低会影响厌氧消化甲烷产量的问题,以餐厨垃圾压榨液为基质,将导电材料生物炭加入厌氧发酵体系中,综合考察生物炭粒径对体系直接种间电子转移(direct interspecies electron transfer,DIET)和产甲烷能力的影...针对微生物种间电子转移效率低会影响厌氧消化甲烷产量的问题,以餐厨垃圾压榨液为基质,将导电材料生物炭加入厌氧发酵体系中,综合考察生物炭粒径对体系直接种间电子转移(direct interspecies electron transfer,DIET)和产甲烷能力的影响。结果表明,随着生物炭粒径的增大,体系的最大产甲烷潜能先增大再减小,40~80目为生物炭最佳粒径,其最大产甲烷潜能和滞后期分别提升17.09%、缩短21.74%。污泥特性分析表明,生物炭能够在厌氧产甲烷过程中建立DIET途径,最佳粒径组的电导率、ETS活性和辅酶F_(420)浓度分别为空白组的1.04、1.46和2.51倍。微生物分析表明,生物炭使得Proteobacteria、Chloroflexi、Methanoculleus和Methanosarcina的相对丰度提高了86.56%、71.62%、27.16%和337.87%,说明生物炭在微生物间成功构建了DIET通道,进而增加了厌氧发酵过程的累积产甲烷量。展开更多
基金jointly supported by Canadian Network for Research and Innovation in Machining TechnologyNatural Sciences and Engineering Research Council of Canada-Automotive Partnership Canada programNRCan’s Office of Energy R&D through the Program on Energy R&D
文摘The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of the commercial casting simulation package, ProCASTTM, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient values. The simulation results were used to estimate the centerline cooling curve at various locations through the casting. The centerline cooling curves, together with the die temperature and the thermodynamic properties of the alloy, were then used as inputs to compute the solution to the Stefan problem of a moving phase boundary, thereby providing the through-thickness cooling curves at each chosen location of the casting, Finally, the local cooling rate was used to calculate the resulting grain size via previously established relationships. The effects of die temperature, filling time and heat transfer coefficient on the grain structure in skin region and core region were quantitatively characterized. It was observed that the grain size of skin region strongly depends on above three factors whereas the grain size of core region shows dependence on the interracial heat transfer coefficient and thickness of the samples. The grain size distribution from surface to center was estimated from the relationship between grain size and the predicted cooling rate. The prediction of grain size matches well with experimental results. A comparison of the predicted and experimentally determined grain size profiles enables the determination of the apparent interracial heat transfer coefficient for different locations.
文摘This work is interested in solving the complex problem of understanding mass transfers in biological media. The contribution of the initial sample size is taken into account. Transfers are established more efficiently in small samples. Thus, from the first 50 minutes, the cubic sample at 1 cm stop is already at 50% while the sample at 4 cm edge is at about 90% of its initial water content. Likewise the shape is combined with the size. But it is revealed that if we fix similar characteristic dimensions, we can bypass the notion of initial shape. Thus the cubic samples 4 cm of edges. 4 cm diameter of spherical shape, 4 cm × 4 cm height-diameter cylindrical one, all dry identically.
文摘针对微生物种间电子转移效率低会影响厌氧消化甲烷产量的问题,以餐厨垃圾压榨液为基质,将导电材料生物炭加入厌氧发酵体系中,综合考察生物炭粒径对体系直接种间电子转移(direct interspecies electron transfer,DIET)和产甲烷能力的影响。结果表明,随着生物炭粒径的增大,体系的最大产甲烷潜能先增大再减小,40~80目为生物炭最佳粒径,其最大产甲烷潜能和滞后期分别提升17.09%、缩短21.74%。污泥特性分析表明,生物炭能够在厌氧产甲烷过程中建立DIET途径,最佳粒径组的电导率、ETS活性和辅酶F_(420)浓度分别为空白组的1.04、1.46和2.51倍。微生物分析表明,生物炭使得Proteobacteria、Chloroflexi、Methanoculleus和Methanosarcina的相对丰度提高了86.56%、71.62%、27.16%和337.87%,说明生物炭在微生物间成功构建了DIET通道,进而增加了厌氧发酵过程的累积产甲烷量。
